***Useful Information for Apprentices***

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;) Electrical Appliances

Earthed Equipment
In Practice, the Most Common Instances of Faulty Earthing are:-
1) Earth connections broken accidentally or corroded through age.
2) Earth connections incorrectly made.
3) Earth connections not made at all.
4) Earth connections removed for some specific purpose and not reinstated.
 
2330 – level 3 Unit 1 . 301 / paper 3 :- some old papers ;) 8 Flemings left hand rule can be used to determine the :-
a) emf generated in a conductor within a magnetic field.
b) movement of a conductor within a magnetic field.
c) current flowing in a conductor within a magnetic field.
d) angle of the conductor within a magnetic field.
9 Shunt wound d.c. motors and generators have shunt field coils :-
a) connected across the supply terminals.
b) connected in parallel with the armature.
c) connected in series with the armature.
d) connected in parallel with the rotor.
10 The résistance of a 2.5mm2 copper conductor of length 8m and resistivity p = 1.72 x 10-8 Ωm is :-
a) 0.055 Ω. B) 0.55 Ω. C) 0.12 Ω. D) 5.56 Ω.
11 A circuit consisting of an inductance of 0.35H connected to a 50Hz has an inductive reactance of :-
A) 9.1 mΩ. b) 0.09 Ω. C) 109.9 Ω. D) 1.099 kΩ.
12 When carrying out volt drop calculations the symbol ( Iz ) represents the :-
a) design current.
b) current rating of the protective device.
c) overload current for the circuit.
D) current carrying capacity of the cable.
13 the Star rotor windings of a three-phase wound rotor induction motor are connected to a bank of external resistors by :-
a) slip rings.
b) a commutator and slip rings.
c) slip rings and brushes.
d) an armature and brushes.
14 A series a.c. circuit of 12Ω résistance , 6Ω inductive reactance and capacitive reactance of 3Ω . the impedance is :-
a) 13 Ω. B) 3.6 Ω. C) 153 Ω. D) 12.37 Ω.
15 An eight pole-motor operating on a 50Hz supply would have a synchronous speed of :-
a) 750 rpm. b) 3000 rpm. c) 1500 rpm. d) 2400 rpm.
16 The junction voltages for silicon diodes is approximately :-
a) 0.6V. b) 0.3V. c) 0.7V. d) 0.2V.
17 A short circuit occurring in the primary winding of an auto-transformer could cause :-
a) the supply voltage to be developed across the secondary.
b) a reduced secondary voltage.
c) a reduction of the secondary current.
d) oscillations in the output voltage.
18 The formula for calculating power dissipated in a resistor is :-
A_ P = I/R. b) P = V²R. c) P = l²R. d) P = IR².
19 Fires in the workplace may be caused by :-
a) waste disposal systems.
b) an accumulation of rubbish.
c) storing materials and packaging in designated areas.
d) preventive maintenance practices.
20 Semiconductor devices are sometimes described as :-
a) accessories. B) electronic components. C) resistors. D) devices.
21 MCBs operate on which of the following principles :-
a) thermal and magnetic.
b) thermal.
c) either thermal or magnetic.
d) magnetic.
22 Whilst working in confined spaces you :-
a) should bring a fire extinguisher.
b) use low voltage equipment.
c) use amplification equipment.
d) should be accompanied.
23 Transformers are rated in :-
kWh. B) kVA. C) kW. D) kVAr.
24 Supplies connected to the stator windings in three-phase induction motors create :-
a) opposing magnetic fields.
b) stationary magnetic fields.
c) in phase magnetic fields.
d) rotating magnetic fields.
 
:) The Electricity at Work Regulations 1989 came into force on 1st April 1990; their purpose is to require precautions to be taken against the risk of death or personal injury from electricity, in work activities.

In the main, the Regulations are concerned with the prevention of danger from electric shock, electric burn, electrical explosion or arcing or from fire or explosion initiated by electric energy.

All places of work covered by the Health and Safety at Work Act (shops, offices, factories, workshops, farms, garages, sports and entertainment centres, etc.) are covered under these Electricity at Work Regulations.

Electricity at Work Regulations 1989
Safe Working Practices

WHAT THE REGULATIONS COVER

Some of the regulations are absolute (see * below), which means they must be complied with regardless of costs or other considerations. If you utilise electricity in the workplace you will be affected.

Systems, work activities and protective equipment (Reg 4) (4.4)*
Strength and capability of electrical equipment (Reg 5)*
Adverse or hazardous environments (Reg 6)
Insulation, protection and placing of conductors (Reg 7)
Earthing or other suitable precautions (Reg 8)
Integrity of referenced conductors (Reg 9)
Connections (Reg 10)*
Means for protecting from excess current (Reg 11)*
Means of cutting off the supply and for isolation (Reg 12)*
Precautions for work on equipment made dead (Reg 13)*
Work on or near live conductors (Reg 14)*
Working space, access and lighting (Reg 15)*
Competence to prevent danger and injury (Reg 16)*

The regulations convey principles of electrical safety, as applied to any electrical equipment, any work activity having a bearing on electrical safety - in other words they all apply to all electrical systems and equipment, in connection with work activities, whenever manufactured, purchased, installed or taken into use, even if its manufacture or installation pre-dates the regulations.

► FIXED AND PORTABLE ELECTRICAL INSTALLATION

The Electricity at Work Regulations 1989 place a duty on the employer to maintain and conduct tests of all fixed and portable electrical equipment at reasonable intervals. Records of maintenance and electrical testing must be retained for inspection.
 
8. Cable surrounded by thermal insulation for 400 mm or more has a derating factor of :-
a) 0.63
* b) 0.51 (Table 52.2) p/104
c) 0.55
d) 0.5

9. When automatic disconnection of supply is used as a measure of protection, additional protection by RCD shall be provided for :-
a) Mobile equipment having a rating of greater than 32A
b) Socket outlets in commercial and industrial locations
c) Only for sockets rated at 32A or less where it is reasonable to expect they may be used to supply equipment for use outdoors
* d) (i) Socket outlets with a rated current Not exceeding 20A that are for use by ordinary persons and are intended for general use , and (411.3.3) p/47

10. The maximum disconnection time for a lighting circuit in a commercial premises protected by a ( TT ) system is
0.07
0.4s
5.0s
* 0.2s (Table 41.1) ◄►( 120V < Uo ≤ 230V ) p/46

11. Socket outlets are allowed in a location containing a bath, providing
Located outside of zone 2
Located outside of zone 3
Located outside of zone 2 and protected by a 30 ma RCD
Located 3 metres from the edge of the bath and protected by 30mA RCD (701.512.3)

12. All circuits in a location containing a bath or shower shall have
a) A disconnection time of 0.4s
b) Be installed at a depth of at least 50mm
c) Be installed using earthed conduit
* d) Additional protection by a 30mA RCD (701.411.3.3) p/166

13. When considering if supplementary bonding can be omitted from a location containing a bath or shower, the maximum resistance of extraneous conductive parts connected to the Main Earth Terminal is :-
* a) 1.44[FONT=Times+New+Roman1253]Ω[FONT=Times+New+Roman+Bold1253] 41.3 [/FONT](415.2.2) [/FONT]
b) 0.05[FONT=Times+New+Roman1253]Ω[/FONT]
c) 0.5[FONT=Times+New+Roman1253]Ω[/FONT]
d) 7.6[FONT=Times+New+Roman1253]Ω[/FONT]

[FONT=Times+New+Roman1253]I picked at random ( Amps ) [/FONT]

► R ≤ 50 V/Ia ( 50 ÷ 160 = 0.3 ( I2 / trip sec : ( Type B / MCB . 32A ÷ 160A = 0.2sec ) ◄ R ≤ 50 V/Ia in A.C. ◄◄◄ systems :
► R ≤ 120 V/Ia ( in D.C. ◄◄◄ systems : p/59 !! watch for this

Max loop Impedance : ( Ief )
Zs ≤ Uo / Ia : Zs ≤ 230 ÷ 160A = ( Zs ≤ 1.437Ω )
( Formula : calculating Earth Loop Impedance > ( Zs = Ze + R1 + R2 ) -&-s

435 : Overload Current ( Fault Current Protection / p77
435.1 : Protection afforded by One Device ( RCD/MCB ) p77 ( If ◄ : Short Circuit / Current Protection ) Equal to or Greater than PSCC .
 
;) 1) 75% of 140 ?
a. 110
b. 115
►c. 105
d. 125

2) Output from a single phase alternator is via..?
►a. Slip Rings
b. Commutator
c. Rotor
d. Field windings

3) Temperature increase on copper has the effect of[FONT=Arial+Bold1252]…[/FONT]?
a. expands length ways
b. expands in thickness
► c. expands in all directions
d. decreases in all directions

4) A poor conductor is[FONT=Arial+Bold1252]…[/FONT]?
a. copper
b. salt water
►c. glass
d. gold

5) If power in is 100watts and power out is 75watts, What is the efficiency ?
a. 25%
► b. 75%
c. 33%
d. 100%

6) One application of the chemical effect is ?
a. magnets
►b. battery
c. lighting
d. Carbon

7) one transmission voltage ?
a. 100kV
b. 200kV
► c. 400kV
d. 500kV

8) Which materials resistance decreases when temperature increases ?
a. copper
► b. carbon
c. aluminium
d. tungsten

9) why do we use the colour yellow for extension leads on-site?
a. Good visibility
► b. denotes voltage
c. it’s a pretty colour
d. denotes length

10) In order to prove a circuit is safely isolated we[FONT=Arial+Bold1252]…[/FONT]..?
a. ask someone if its ok to start work
► b. use approved volt tester to check supply
c. check current flow by switching on
d. look for the red or green light
 
11) The flow of electrons is basically[FONT=Arial+Bold1252]………[/FONT]..?
a. voltage
►b. current
c. resistance
d. water flow

12) The insulation [FONT=Arial+Bold1252]“[/FONT]Magnesium Oxide[FONT=Arial+Bold1252]” [/FONT]does not work well ?
a. in high ambient temperatures
b. at high operating temperatures
► c. when ingress of moisture has occurred
d. in damp conditions
 
:) Remember !

Delta = 3 phase, 3 wire system ◄
Star = 3 phase, 4 wire system ( 3 phase + Neutral ) ◄

Math’s of star and delta systems

The voltages and currents that exist within a three phase system have particular relationships.

Voltages measured across any phase winding are known as ‘Phase Voltages’ and are symbolised VP.

Voltages measured between any pair of lines are known as ‘Line voltages’ and are symbolised VL.

Currents measured through any phase winding are known as ‘Phase Currents’ and are symbolised IP.

Currents flowing along any line are known as ‘Line currents’ and are symbolised IL. Indicate all line and phase voltages and all line and phase currents in the diagrams below.

Delta systems
Voltage Relationships ( VL = VP Therefore ( VP = VL

Current Relationships : IL = 1.732 x IP& IP = IL ►1.732 ◄

Star Systems
Voltage Relationships ( VL = 1.732 x VP & VP = VL ►1.732 ◄

Current Relationships ( IL = IP Therefore IP = IL

You must remember these relationships

[FONT=Comic+Sans+MS0]►Note! Rather than use 1.732 many texts 3 will use the square root of 3 which equates to 1.732. ( √3 ) ◄◄[/FONT]

Progress :
[FONT=Comic+Sans+MS0]►[/FONT]A star connected system has phase voltages of 300v and phase currents of 12A. Calculate line voltages and currents. !! now ask your tutor :rolleyes:

[FONT=Comic+Sans+MS0]►[/FONT]If the system above was a delta connected system, calculate the line voltages and currents. !! now ask your tutor :rolleyes:

Balanced and unbalanced systems
* Star and delta systems can also be connected as loads. Many three phase motors will be connected in delta since only three wires are required to make the connection

* Star connections are often used as a means of connecting single phase loads to a 3 phase supply, such as in the case of a street of domestic dwellings.

A delta connected load will have identical phase impedances. The impedance of each phase will therefore be identical both in terms of it’s magnitude AND phase angle. When this is the case the current that flows in each phase will be identical and the sum of the currents will be zero. The system is said to be balanced and there is no need for a 4th wire (neutral conductor ).

It is also possible to have a star connected load where the impedance of each phase is identical in terms of it’s magnitude and phase angle. As with the delta system this will lead to identical phase currents and no excess current to flow back to neutral. Again, the system is said to be balanced and there is no need for a 4th wire(neutral conductor).

It is more usual however, to connect dissimilar loads to each phase of a star system. This will result in differences in phase currents which in turn will create some ‘leftover’ current which will flow back along the 4th wire (neutral) to the star point of the supply origin. Such a system is known as an unbalanced system and usually arises as a result of connecting separate single phase loads to each phase of a three phase star connection.

Progress :
What is meant by a 3 phase balanced system ?
Is there any need for a 4th wire (neutral) in such a system ?
How does an unbalanced system differ ?
What function does the 4th wire serve in an unbalanced system.
Which type of 3 phase system is more likely to be found with an unbalanced load ?
 
Power in three phase systems.
Each phase of a 3 phase system will result in some power consumption.

If the system you are dealing with is balanced there will be an equal power dissipation per phase and therefore it is necessary only to calculate the power dissipated in one phase and multiply the result by 3 (for the 3 phases).

When doing this however you must remember that each phase is an a.c system and as such the power factor is required in addition to phase voltage and current.

Power/phase = VpIp Cos[FONT=Arial+Bold1253]Ø[/FONT]
If the system is balanced :Total Power = 3VpIp Cos[FONT=Arial+Bold1253]Ø[/FONT]

For an unbalanced system it is necessary to calculate each phase power in turn and add them in order to find total power.

An alternative power formula exists which utilises the line voltages and currents:
Total Power = 1.732 x VLIL Cos[FONT=Arial+Bold1253]Ø [/FONT]

These formula apply to both Star and Delta connected systems equally.

Progress :
A star connected balanced load has a phase voltage of 230v and line current of 9A. The system power factor is 0.65. Calculate the total power for the system using both total power formulae. Once you have calculated total power calculate the power per phase.

A delta connected load has a phase voltage of 180v, a phase current of 22A and a phase angle per phase of 25° . Calculate the total power dissipated in the load.

Delta : L1 L2 L3 ,
Star : L1 L2 L3 ( N ◄

Stringbags , I hope this will help your apprentices , something to go on , I knock this up !!
amberleaf :)
 
;) Three Phase Electricity Supplies and Systems
The generation and supply of electricity within the U.K is achieved through the use of a 3-phase system.

Voltage – Time !!!!!!

This consists of 3 separate phase conductors along with a neutral conductor transmitting supplies to a given destination

If we took three of these generators (A,B & C) and positioned them equidistantly (120° ) apart) around a rotating magnet we would generate three separate a.c. waveforms each with a phase displacement of ( 120° ) from each other.

* A * / * B * / * C *
Such an arrangement would provide us with a 3 phase supply but we would need 6 conductors in order for it to function. However if we take each coil and interconnect it with the other coils in particular ways we can achieve a three phase supply in either a 3 wire (Delta) system, or a 4 wire (Star) system.

Delta Connection (3-phase, 3 wire system)
Using this method of connection each of the three coil windings are wound in such a way so they each have a start and a finish to their winding.

Then the finish of winding 1 is connected to the start of winding 2. The finish of winding 2 is connected to the start of winding 3. The start of winding 3 is connected to the start of winding 1.

each winding, A,B or C, then mark their starts and finishes.
The supply is then taken from the interconnection of each winding combination as shown above. This means we can achieve a 3-phase system using only 3 wires.

There is an alternative connection that may be made for the provision of a three phase supply which is known as ‘Star’ connection.

Star Connection (3-phase, 4 wire system)
The three coils are also wound so that each has a definite start and finish to their winding.

However to provide a star connection the starts of each winding are connected together at a common point known as the star point. The phase supplies are then taken from the finish of each winding to the point of utilisation. The star point may also have a fourth wire connected to it (known as the neutral conductor) which is then fed along with the three phase conductors to the point of utilisation.

Balanced and unbalanced systems
Star and delta systems can also be connected as loads. Many three phase motors will be connected in delta since only three wires are required to make the connection.

Star connections are often used as a means of connecting single phase loads to a 3 phase supply, such as in the case of a street of domestic dwellings.

A delta connected load will have identical phase impedances. The impedance of each phase will therefore be identical both in terms of it’s magnitude AND phase angle. When this is the case the current that flows in each phase will be identical and the sum of the currents will be zero. The system is said to be balanced and there is no need for a 4th wire (neutral conductor).

It is also possible to have a star connected load where the impedance of each phase is identical in terms of it’s magnitude and phase angle. As with the delta system this will lead to identical phase currents and no excess current to flow back to neutral. Again, the system is said to be balanced ◄◄and there is no need for a 4th wire(neutral conductor).

It is more usual however, to connect dissimilar loads to each phase of a star system. This will result in differences in phase currents which in turn will create some ‘leftover’ current which will flow back along the 4th wire (neutral) to the star point of the supply origin. Such a system is known as an unbalanced system and usually arises as a result of connecting separate single phase loads to each phase of a three phase star connection.

* What is meant by a 3 phase balanced system ?
* Is there any need for a 4th wire (neutral) in such a system ?
* How does an unbalanced system differ ?
* What function does the 4th wire serve in an unbalanced system.

* Which type of 3 phase system is more likely to be found with an unbalanced load ?
 
[FONT=Arial+Black0]Resistivity ;) [/FONT]
The basis of Ohms Law, of which the Ohmic Triangle we are all so familiar with is derived, is in part derived from these two simple rules…
The resistance of a conductor is Directly Proportional to it[FONT=Arial+Bold1252]’[/FONT]s length ...

i.e. If we double it[FONT=Arial+Bold1252]’[/FONT]s length we will double it[FONT=Arial+Bold1252]’[/FONT]s resistance.
If we half it[FONT=Arial+Bold1252]’[/FONT]s length we will half it[FONT=Arial+Bold1252]’[/FONT]s resistance.
And
The resistance of a conductor is inversely proportional to it[FONT=Arial+Bold1252]’[/FONT]s Cross- Sectional Area[FONT=Arial+Bold1252]…[/FONT].

i.e. If we double the C.S.A we will half the resistance.
If we half the C.S.A we will double the resistance

[FONT=Arial+Bold1252]…[/FONT]at a given temperature.

Note1 - Temperature:
This is an important factor when we consider resistance, as if the Temperature of a conductor increases the resistance increases quite dramatically. All Current Carrying Capacities of cables given in BS7671: 2008 are taken at 30°C. Reasons for an increase in temperature could include Thermal Insulation surrounding a conductor (Ci), Grouping of a number of cables together, all dissipating their heat against each other (Cg), and the Ambient Temperature they are installed in (Ca).

Note2 - Math’s:
Doubling the C.S.A is NOT the same thing as doubling the diameter. Since if the diameter of a cable is doubled it’s C.S.A will increase by a factor of 4 ! Similarly if we half the diameter of the cable it’s C.S.A will fall to a quarter of it’s original value.

Hence if we double the diameter (or radius) of a conductor it’s resistance will fall to one quarter (1/4) of its original value.

If we halve the diameter (or radius) of a conductor it’s resistance will increase by a factor of 4.
 
;) Lighting Control (Automatic/Manual :-

The main lighting controls are:-
Switch (Manual)
Contactor (Manual or Automatic)
PIR (Automatic)
Photocell (Automatic)
Timer (Automatic)

Firstly it is important to consider the reason for your lighting & the amount of lighting required. The answers to those two main questions will effect the control equipment used, and is when possibly all aspects of the above could come into play. Remember, larger loads will nearly always require a contactor instead of a switch.

some installation methods are what could be described as ‘acknowledged cable management systems’
These could include :-

Domestic : PVC/PVC Twin
Outdoor Lighting & Power : SWA
Churches : MICC/MIMS
Small Industrial Workshop : Steel Trunking & Metal Conduit drops
Large Industrial Workshop : Bus-Bar Trunking and metal conduit drops
Industrial Kitchens : Galvanised Conduit
Medical Centres : Conduit Drops fixed with Hospital Saddles
Agricultural Buildings : High Impact PVC Conduit
High Explosive Areas : Seamless Conduit
Multi-Story Accommodation : Rising Main (Bus Bar) – or Rising Tray with SWA.
 
;) Earth-Fault Loop Impedance :
Earth fault loop impedance is the impedance of the earth fault-current loop starting and ending at the point of earth fault. It comprises the following starting at the point of fault :-

(i) The Circuit Protective Conductor :
(ii) The Consumer’s Earthing Terminal & Earthing Conductor :
(iii) The Earth return Path ( for TT System ) :
(iv) The Path through the Earthed Neutral Point of the Transformer and the Transformer Winding :
(v) The Line Conductor from the Transformer to the Point of Fault :

Path for Earth Fault Current :
Earth Fault Loop Impedance > This is Only a EXAMPLE ‼
The significance of earth fault loop impedance is that a fast disconnection time of the protective device means that a ►high fault current ◄ is required to blow the fuse or to trip the circuit breaker. In order to allow sufficient fault current to flow in order to trip the protective device, the earth fault loop impedance must have a low value. ◄◄

If it exceeds the recommended figure, the circuit must be investigated to find out the underlying reason. The reading obtained should also be compared with the reading of the previous test ► (if this information is available) ◄ to see whether the Zs value is on the increase, which might indicate a potential dangerous condition appearing in the circuit. ► EXAMPLE , if the maximum ( Zs ) was ( 2Ω ) and the test reading was ( 1.2Ω ) on a previous test but is now ( 1.8Ω ) this indicates that the next would produce an unacceptable reading with the possibility that an earth fault occurring in the circuit would not produce enough fault current to operate the overcurrent protective device in either ( 0.4 ) second and ( 5 ) seconds, thus increasing the risk of electric shock to persons using the installation.

* the type of overcurrent protective device and its current rating : and
* whether the circuit feeding socket-outlets or equipment. :
 
(1) The “ Line “ > Earth Loop Impedance' Tester is plugged into the 13A Socket Outlet :-
Press the Button. The Digital Meter , give a reading directly in Ohms. This is the Line/Earth Loop Impedance.
Repeat procedure (1) for the ( 4 ) number . 13A socket outlets. ► If the Digital Meter give a reading, record the results. ( each One )

If the Digital Meter does not read ‼ ( Houston we have a problem ) :confused:

By measurement, the Earth Fault Loop Résistance = __________ Ωs

1st 13A S/O : Response of the Impedance Tester ( P-N LED ) ↔ (ON/OFF)↔ ( P-E LED ) Movement of Digital Meter ‼ Reading (Ω s)
2nd 13A S/O ?
3rd 13A S/O ?
4th 13A S/O ?

► Minimum values of the test results to be acceptable. ?
►What is the potential problem if the equipment/cable fails the insulation test ?
► Does all the earth fault loop impedance measured for the functional socket outlets : comply with the requirement as laid down ?
 
;) Insulation resistance :
The object of the test is to verify that the quality of the insulation is satisfactory and has not deteriorated or short circuited.

In the event of any test indicating failure to comply, that test and those preceding, the results of which may have been influenced by the fault indicated, should be repeated after the fault has been rectified. ◄◄
Among these tests, items (iv) and (vi)

(iv) Insulation Résistance ,
(vi) Earth Fault Loop Impedance,
Principles of the Inspection & Testing of Electrical Installations.
 
:) Q) The standard supply voltage in UK domestic premises is .. ? ( you will find . a lot of this comes under Pat / Testing ) CoP .
250V AC .
240V AC .
230V AC . ◄
115V AC .

A) The UK domestic supply has been 230V AC ( RMS ) since 1 January 1995. This has a tolerance of + 10% - 6% ( 216.2 – 253.0V
The old standard was 240V ± 6% / - 6% ( 225.6 – 254.4V ) ► Regs p/242

Q ) The Core Colours for the Phase, Neutral and Protective Conductors of a 3-Core Appliance cord are .. ?
Phase ( Line ) = Brown :
Neutral = Blue :
Earth = Green & Yellow :

Q) Electrical Current is Measured in .. ?
Amperes : ◄
Coulombs :
Volts :
Watts :
A) Electrical Current is Measured in Amperes, Usually shortened to Amps .

Q) Electrical Power is Measured in .. ?
Volts :
Ohms :
Coulombs :
Watts : ◄
A) Electrical Power is Measured in Watts . One Watt is Equivalent ( 1 ) Joule of Power Per-Second ,

Q) 100mA is the same as .. ?
10A :
1A ;
0.1A ◄
0.01A :
A) The Correct Answer is 0.1A : 1mA ( milliamp ) 0.001A , therefore 100mA is the same as ► 0.1A

2.5kW ( kilowatts ) is Equivalent to .. ?
25W :
250W :
2500W : ◄
25000W :
A) The Correct Answer is 2500W , 1kW is equivalent to 1,000W . Therefore 2.5kW = 2,500W

Q) A 230V Kettle rated at 2.3kW draws how much Current .. ?
1A :
10A : ◄
0.1A :
100A :
A) The Correct Answer is 10A ,
Power = Current x Voltage . in this case we know the Power is ( 2.3kW ) and the Voltage is ( 230V ) Therefore the Current = ( 2300W ) ÷ ( 230V ) = 10A

Q) How many 2.3kW heaters can be Safely Connected to a 230V Extension Lead rated at 13A .. ?
A) A 2.3kW heater draws 10A , Therefore Only ( 1 ) heater can be Connected to a 13A Socket .

Q) The Units Used to Measure Résistance are .. ?
Volts :
Ohms : ◄
Amps :
Watts :
A) Electrical Résistance is Measured in Ohms .

Q) When a Fuse is rated 13A , it Means .. ?
It will blow quicker than a 3A fuse if a Fault Occurs .
It can be Used in Any 13A plug .
It will Melt if the Current Exceeds 13A ◄ -&-s
It will blow if the Current falls Below 13A
A) it will Melt if the Current Exceeds 13A . ( The Wire in the Fuse is Designed to Melt if the Current Exceeds 13A )
 
The Danger of Electrical Shock : ( Class 1 , must have an Earth )

Electric Power does a Tremendous Amount of Work . but because it,s such a Powerful Force , :-

1) Understanding how Electricity Works . ◄
2) Recognizing Potential Electrical Hazards . ◄
3) Learning about Safety Devices that Prevent Shock ◄

How Shocks Occur :
Electricity travels in closed circuits, normally through a conductor. Shock results when the body becomes part of the electrical circuit; current enters the body at one point and leaves at another. Typically, shock occurs when a person contacts:

1) Both wires of an energized circuit ,touching two ends of cables . 2) One wire of an energized circuit and to ground, touching one cable . 3) A metallic part in contact with an energized wire while the person is also in contact with the ground.

Metallic parts of electric tools and machines can become energized if there is a break in the insulation of their wiring. A low-resistance wire between the metallic case of the tool/machine and the ground – an equipment earthing conductor – provides a path for the unwanted current to pass directly to the ground. This greatly reduces the amount of current passing through the body of the person in contact with the tool or machine. Properly installed, the earthing conductor provides protection from electric shock.
 
25 – when a four band resistor has only three band assumed tolerance will be ? a) 2% : b) 5% : c) 10% : d) 20% :
26 – H.R.C fuses can distinguish between ?
a) short circuit and starting currents .
b) high starting currents and short duration overload.
c) high fault currents and short term overloads.
d) starting currents and overloads.
27 – Exposed to radioactive material can lead to :
a) skin burns.
b) respiratory problems.
c) carcinogenic symptoms.
d) mild aching.
28- Heath & Safety Executive inspectors are primarily concerned with ?
a) skills levels within the workforce.
b) workplace safety standards and practices.
c) companies health and safety policies.
d) accidents of all types.
29 – The reactance created by a 4.5 µF capacitor in a circuit connected to a 50Hz supply is ? a) 708 Ω. b) 1.08 kΩ. c) 0.0014 Ω. d) 14 kΩ.

1) A - P = √3VL x IL cosθ . 2) C - slip .
3) C - raise the alarm, call for help or get someone to go for help . 4) B - gate . 5) A - break all phases .
6) A - allow current to flow in one direction only . 7) A - Z = √ [R2 + (XL - XC)2] .
8) B - movement of a conductor within a magnetic field . 9) B - connected in parallel with the armature .
10) A - 0.055 Ω . 11) - 109.9 Ω .. 12) D - current carrying capacity of the cable .
13) C - slip rings and brushes . 14) D - 12.37 Ω . 15) A - 750 rpm . 16) A - 0.6V .
17) A - the supply voltage to be developed across the 18) C - P = l²R .
19) B - an accumulation of rubbish . 20) B - electronic components .
21) A - thermal and magnetic . 22) D - should be accompanied . 23) B - kVA .
24) D - rotating magnetic fields . 25) D - 20% . 26) C - high fault currents and short term overloads .
27) C - carcinogenic symptoms . 28) B - workplace safety standards and practices . 29) A - 708 Ω .
2330 level 3 unit 1 , 301 paper 3 ( Q/A s )
 
amberleaf said:
This is Something I knocked Up ;)

Instruments and Testing
Installation Testing

REMEMBER
Visual inspection must precede all testing
→→ Remember →→→ Dead testing precedes

LIVE Testing :

Dead Testing
Isolate before carrying out dead tests ( A Must ) ←←←
* Approved voltage indicator to GS-38
* Maximum of 4mm on exposed prods
* Preferably not more than 2mm
* Fused leads
* Finger guards


Continuity Testing ( Low-Resistance ohmmeter ) ps. You may be asked this on P.Testing )
Battery operated instrument Low voltage d.c.
200mA / 4 – 24V ( 612.2.1 )
Verifying Continuity ( Method 1 ) Caution Supply must be isolated :
( Temporary Link / Instrument Measures ( R1 + R2 )
Along with verification of the cpc, state the Two other tests which are automatically undertaken when carrying out this test
( The value of (R1 + R2) ↔ ( Polarity ) -&-s
***** { Unacceptable practice of connecting c.p.c. to outgoing side of fuse or circuit breaker } *****
Why is it unacceptable ? :-
Unacceptable practiceof connecting c.p.c. tooutgoing fuse orcircuit breaker way

Verifying ContinuityMethod 2
Caution Supply must be isolated :
( Meter Lead on MET ↔ Meter Lead on Pendent or at the Switch )

State Two disadvantages of using Method 2, as compared to Method 1

Use of long wander leadValue of ( R2 ) only obtained
* What consideration should be given to the long wander lead ?
* Its Résistance must be measured anddeducted from the measured value of ( R2 )

Continuity of bondingconductors

Why is it necessary to remove one endof a bonding conductor when verifyingits continuity ?

To avoid the possibility of parallelearth paths ) ←←←←← -&-s
( Break in c.p.c.Parallel path )

Continuity of ferrous enclosures
* visual inspection
* low resistance ohmmeter

Insulation Testing
Instrument must be capable of producing a short-circuit current of 1mA
( you are looking for ! -&-s No Breakdown of the Conductor Insulation )

Caution Supply must be isolated :

Prior to insulation resistance testing :- close main switch if testing from tails
fuses in circuit breakers closed
local switches closed/operate two-way
switches during test
neon's/capacitors disconnected
remove voltage sensitive equipment

Insulation resistance testing between live conductors ( Live & Neutral ) ↔ Neutral is a Live Conductor ←←←← -&-s
Insulation resistance testing between live conductors and earth ( 2 – Leads , one on Earth / one on Brown/Blue Together )

BS 7671 Table 61 - Page 158

State the test voltage and minimum value of insulation permitted for the following circuits :-
* 230V domestic lighting circuit ? 500V – ≥ 1.0MΩ
* 3 phase, 400V motor circuit ? 500V - ≥ 1.0MΩ
* 12V SELV circuit ? 250V ≥ 0.5MΩ
* 750V discharge lighting circuit ? ≥ 1000V - 1.0MΩ
* 50V FELV circuit ? 250V ≥ 0.5MΩ

Live Testing :
Measurement of external impedance ( Ze )
* Main switch open
* Earthing conductordisconnected
* impedance tester ( .35Ω ) ↔ This is Mock Reading

WHY MUST the supply be isolatedbefore disconnecting the earthing conductor ?
Because if you don’t you could possibly kill somebody. If there is a defect with the insulation, and line touches exposed metalwork, the whole of the installation earthing could become live

*** State THREE other instances whereearth-fault loop impedance testing wouldbe required.
* At the furthest point in every final circuit
* At every distribution board
* At every socket outlet

What precautions should be observedwhen undertaking impedance tests withina circuit ?
( Ensure that persons or livestock are not in contact with exposed metalwork )

Measurement of prospective earth fault current
* Prospective faultcurrent tester
* Bonding conductorsconnected

Measurement of prospective short circuit fault current
* Prospective fault current tester

Why is it necessary to verify the valueof prospective fault current at the originof an electrical installation ?
To ensure the rated breaking capacity of the main switch and overcurrent devicesare capable of breaking the prospective fault current level

;) * State the effect on insulation resistance of an installation if :-

a. additional circuits are added
b. circuits were disconnected/removed
c. the length of a 6A lighting circuit was extended

a. insulation resistance decreases
b. insulation resistance increases
c. insulation resistance decreases

* State FOUR external influences that you would need to consider during the inspection process :-
• corrosion (corrosive atmospheres)
• mechanical damage
• vandalism
• extremes of temperature
• ingress of moisture or water
• extremes of temperature
• explosive atmospheres
Click to expand...



cheers mate for always taking time to post all this info i have read a lot of your posts and found them extremely helpful
I am doing the 2391 course at college for 8 week evenings and i am half way through exam is june 3rd. I have been revising everyday for last 16 week as at the minute i am not working as i am a full time carer for the misses at minute
I am doing all this studying to hopefully pass first time so if you have any more info and advice for 2391 i would be grateful is the any chance you could tell me best way to explain test procedures if asked in exam any help cheers
 
;) Non-statutory Requirements
Within BS 7671:2008, the following are of particular relevance in terms of safe isolation:

Regulation 132.15.1
contains the following fundamental principle:

Effective means, suitably placed for ready operation, shall be provided so that all voltage may be cut off from every installation, from every part thereof and from all equipment, as may be necessary to prevent or remove danger.

Regulation group 537.2
contains the requirements relating to isolation

Regulation group 537.3
contains the requirements for switching off for mechanical maintenance.

Table 53.2 summarises the suitability of particular protective, isolation and switching devices to be used as an isolator, an emergency switch, or a functional switch

Basic Safe isolation procedure :-
The following steps are the minimum that would be expected in terms of confirming safe isolation of a circuit or item of equipment.

Locate / positively identify correct isolation point or device

Check condition of voltage indicating device

Confirm that voltage indication device is functioning correctly

Switch off installation / circuit to be isolated

Verify with voltage indicating device that no voltage is present

Re-confirm that voltage indicating device functions correctly on known supply / proving unit

Lock-off or otherwise secure device used to isolate installation / circuit

Post warning notice(s)

( Any current will travel along the path to earth offering the least resistance. )

Electrical test equipment for use by electricians (GS 38) HSE

Statutory Requirements
requirement concerning work The most important statutory requirement concerning work carried out on or near electrical installations is the Electricity at Work Regulations (EWR) 1989. Those regulations within EWR of particular relevance to safe isolation are numbers 12 (Means for cutting off the supply and for isolation) and supply and for isolation) and equipment made dead). Regulation 12 (1) (b) states that where necessary to prevent danger, suitable
means shall be available for the isolation of any electrical equipment, where isolation means the disconnection and separation of the electrical equipment from every source in such a way that the disconnection and separation is secure
 
Fitting Downlights :- ;)

Once you have decided that you wish to install Downlighters in your room it is important for you to decide several things :- 1. How many Downlights do I want ? Or need ? 2. Should the Downlights be 12V or 230V ? 3. Do the Downlights need to be Fire rated ?
4. Can the existing lighting circuit support the extra light fittings ?

Should the Downlights be 12v or 230v?
Low voltage (LV or 12v) downlights are wired to a transformer, which is then wired to the mains supply. Although the transformer wastes approximately 10% of the power through stepping down the voltage to 12v this is more than compensated by the improved performance of low voltage downlights.
Due to a thicker filament, the halogen 12v bulbs (size MR16) are more efficient than the halogen 230v (size GU10) equivalent. The thicker filament also means that the bulbs are more robust.
Another advantage of 12v is that low voltage bulbs use halogen gas, which provides a much whiter and brighter light with higher clarity than the more traditional mains voltage incandescent bulbs.

Mains voltage downlights are wired directly to the mains without the need for a transformer.
The mains voltage (230v) downlights are generally cheaper, and can be simpler to install, as there is no need to install a transformer.

Ceilings provide an important barrier that helps to prevent the spread of fire and noise between the floors of a building. Installing recessed downlights punctures this barrier and can reduce the effectiveness of this safety barrier.

Can the existing lighting circuit support the extra light fittings? Lighting circuits are usually on 6 amp circuit breakers .To calculate how many Amps are loaded onto the lighting circuit a simple calculation is made. 230 volts, now assume that each light on the circuit is 100 watts, and you have got 12 lights on the circuit.

The calculation would be: So taking the above information the calculation would be: ( 1200 watts ÷ 230 volts = 5.22 amps )
So now we can see that the above described lighting circuit is using 5.22 amps meaning that the circuit breaker of 6 amps is not being overloaded.


Now to confuse things a little but very helpful on lighting circuits when you are wishing to add more lights. On lighting circuits once you have worked out the amps you can now apply a thing called Diversity, which for lighting circuits is 66% of the total load. So to work out this calculation we can do the following sum: ( 5.22amps ÷ 100 x 66 = 3.45 amps )
​

So now we can see that we are able to add more lights to the circuit now that diversity has been applied to it.

Remember to carry out your calculations before you start any work!
 
2330 Level 2 Unit 4 / Updated to BS7671:2008 ( some old notes ) ;)

SINGLE PHASE:- Brown – Live Blue – Neutral Green/Yellow – Earth (protective conductor)


OLD COLOURS WERE:- Red – live Black - neutral


THREE-PHASE:-

Brown – Line one

Black – Line two

Grey – Line three

Blue – Neutral

Green/yellow – Earth (protective conductor) OLD COLOURS WERE:- Red – phase one

Yellow – phase two

Blue – phase three

Single and 3-phase supplies :

Star Point , L1 230V N , L2 400V L3 :


* Single phase supplies (230v AC 50Hz) are used for DOMESTIC PREMISES and ‘standard’ circuits within Industrial and Commercial premises (sockets, lights etc).


* 230v AC is acquired from ANY ONE phase and Neutral connection of a 3-phase supply.


* The supply transformer in a residential street is a 3-phase DELTA/STAR arrangement – supplying EACH house with a LIVE and NEUTRAL connection. ( Line )


Each house is supplied with a different phase (brown, black, grey, brown, black, grey, brown etc) and the SAME neutral.

3-phase supplies :


* 3-phase supplies are used for Commercial and Industrial installations.

* Because these premises have lots of electrical equipment – it can be more efficiently supplied when balanced across 3 ‘mains’ supplies rather than just one.

* 400v is acquired between ANY TWO phases (lives).

* Larger electrical equipment requires less current when supplied at 400v 3-phase AC – which is acquires using ALL THREE phases ( and sometimes the Neutral as well ).
* Switchgear and Cable designs are available for both single and 3- phase systems.

Lighting control :

* Lighting circuits can utilise different switch configurations and 2 and 3-core cable (+ cpc) – depending on the type of circuit required;

* One-way control

* Two-way control

* Intermediate two way control

Lighting – one way control :

Example : a light in a bathroom ,
- A ‘live’ feed cable supplies a single-pole switch .

- A ‘switched live’ conductor (blue with a brown marker) connects to the lamp .

- Neutral always connects directly to the lamp in lighting circuits.

- A cpc (circuit protective conductor – earth) connects the main earth at the supply to EACH accessory point in the circuit.
 
Lighting – two way control :

* Example: upstairs/downstairs control of a landing light.

- A 3-core cable connects two, 2-way switches together .

- A two core cable connects the supply to the lamp.

- A cpc is connected to each accessory in the circuit.

- This circuit allows ANY one of the switches to turn the lamp on or off, from any position.

Power circuits :

* Available as RADIAL or RING circuit configuration.

* Radial is the simplest; sockets installed one after the other.

* Ring is more complicated; circuit is installed as a ring so TWO cables supply EACH socket.

Radial and Ring socket circuits :

* Use BS1363 ‘standard’ 13A socket outlets – single gang, twin-gang or ‘multiple-gang’.

* Either can have the following installed onto them – but regulations WILL apply!;

* Fused spurs

* Non-fused spurs

* Permanently connected equipment

A1 ring circuit :-

- Maximum 32A rating for circuit.

* Installed using 2 x 2.5mm² cables in a ring.

* Maximum 100m² floor area for EACH ring circuit.

* Unlimited number of sockets allowed on each circuit.

* ONLY a single non-fused spur is allowed – per number of sockets on the ring. Must be same size cable.

* Unlimited number of sockets allowed on a ‘fused spur’ (minimum 1.5mm² cable size).

* Radial circuits MUST NOT be ‘interconnected’ in a ring so as to form a ‘ring within a ring’

A2 Radial circuit :-

* Maximum 32A rating for circuit when wired in 4mm² cable.

* Maximum 75m² floor area for EACH A2 circuit.

* Unlimited number of sockets allowed on each circuit.

* ONLY a single non-fused spur is allowed – per number of sockets on the radial circuit.

* Unlimited number of sockets allowed on a ‘fused spur’

A3 Radial circuit :-

* Maximum 20A rating for circuit when wired in 2.5mm² cable.

* Maximum 50m² floor area for EACH A3 circuit.

* Unlimited number of sockets allowed on each circuit.

* ONLY a single non-fused spur is allowed – per number of sockets on the radial circuit (same size cable)

* Unlimited number of sockets allowed on a ‘fused spur’ (minimum 1.5mm² cable)

Permanently connected equipment :-

* Should have ‘local’ protection close to the equipment (maximum 13A fuse or 16A mcb) – see chapter 46 in BS7671:2008

* A switch connection unit can do this

* Items include certain types of heater, items of equipment that are not generally moved around (freezer or washing machine etc).


Q) Voltage drop can be evaluated by using Which one of the following Test Values ?
A) VD. Final Circuit Earth Fault Loop Impedance ( Zs )

Regs .p/361 : Zs ( m ) ≤ 0.8 x Uo / Ia , ( 230 ÷ 24A = 9.58 ( Ze – 0.8 x Zs – 9.58 = 7.66 )

( am trying to get my head around this Windows Vista Ultimate . my comp has a mind of it own )
 
:) Special Installations : 2330 Level 2 Unit 4
Contents - Special Installations ,

* Caravan and Caravan Site Installations ,
* Temporary Installations ( Construction Sites )
* Rooms that contain a Bath or Shower ,

Regulation Requirements for Caravans :-
1) Caravan and Caravan Site MUST comply with Electrical Wiring Regulations in the same way that Buildings must – if they are to Utilize a Mains” Electric Supply
2) Section 721 of BS-7671:2008 details Requirements ,
3) “ Hook up “ cable must be NO longer than 25Metres ( +/ - 2m ) Regs p/213 : ► 721.55.2.6 / ( ii )
( Regs p/192 Note : Typical Requirements for Cord Extension Sets !!!! ) worth a Look , Note : Table 51 , Identification of Conductors’ . p/92
4) Electrical Wiring or Accessories MUST NOT be Installed in any Fuel Storage : Compartment(s) in a Caravan or Motorhome UNLESS
Regulation ( 721.528.3.5. ) is Adhered to :

* Section 721 of BS-7671:2008 details Requirements for Caravans ( Including Motorhome – Known as Motor- Caravan ) and Caravan Park Installations .
* Fuel Storage Compartment refers to Gas Cylinder Storage Compartments , ► Risk of Explosion and Fire may Result ,
* A “ Hook up “ cable is the Power Lead that connects the Caravan to the “ Provided “ power “ Hook Up “ point at the Caravan Park ,

Specific Regulations :-
BS-EN 60309-2 Plug and Socket ,
►( Remember to wire Up : ►Female ◄ / to the Supply First !!!!! ( Male , ◄ Connected to the Load Side ) Female ↔ Male / Unique Keyway ‼‼‼
708.530.3 / Caravan/Pitch – Electrical Supply ! “ Blue Flex Cable “ 20 m from ?

* Because caravans are used intermittently, recommended inspection and test intervals should be between 1 and 3 years (max) – see Fig 721 in BS7671:2008

* Extra-low voltage circuits (i.e.12v DC) MUST NOT come into contact with ‘mains’ voltage circuits in caravans and motorhomes – regulation 721.528.3.5

* Because caravans flex when being towed, wiring must be installed with either flexible or stranded conductors (minimum 1.5 mm/sq). regulation 721.524.1

* Conductors must be supported at least every 25cm within a caravan or motorhome/*. regulation 721.522.8.1.3

* Any metalwork within the caravan or motorhome, including the chassis must be bonded. regulation 721.411.3.2.1


Caravan Site Power Supplies :-
* Caravans must be supplied via a ‘Blue’ 16A BS4343 socket outlet adjacent to caravan pitch.

* Sockets are to be protected by an RCD

* RCD rating is 30mA . ◄

* Each socket outlet must be BSEN60309-2 (minimum IP44)

* No caravan should be more than 27 metres from a socket outlet (maximum).

* Connecting cable should be 2.5mm/sq minimum OR comply with table 721. ► p/213 Min/ CSA ????


Caravan Site Power Supplies :-
* Notices regarding the voltage supply and maximum loading MUST be displayed at the supply source.

* A caravan MUST be supplied with a mains disconnector as detailed by regulations 721.537.2.1.1

* A notice MUST also be displayed stating ‘how to connect and disconnect the supply safely’ – for the benefit of holidaymakers.

* Buried supply cables (SWA type) to power outlet points on a caravan site MUST be run outside the pitch area and buried to a depth so they are unlikely to be damaged by awning pegs.


 
FibreOptics Systems – Precautions :-

* Light source is usually via LASER – so beware of damage to eyes (special glasses).

* Do NOT bend fibreOptic cable ‘too sharply’ – this will affect its ability to transmit light effectively.

* Beware of breaking a fibreOptic cable – sharp shards may cut you!.

* Well installed fibreOptic systems can transmit light for many kilometres with virtually NO LOSS in signal strength.

( Transmitted Light / 99.99% Output ) 100km

Other Data Cable System – Cat 5 /

* CAT 5 is a ‘standard’ data cable systems found in many IT applications (home pc networks, office IT networks).

* Special tools are required for BOTH FibreOptic and CAT 5 cable systems.

Summary :
* Section 543.7 of BS7671:2008 regulations detail ‘leakage circuit recommendations’ for circuits with high protective conductor currents.

* IT equipment ‘leaks current to earth – normally.

* IT systems require special precautions (data loss).

* Networks use lasers and fibreoptics – so care and safety is required.


( Remember , CSCS Signs ► Yellow/Black Means ?? ► Hazard or Danger ) Laser Sign !!! )
 
Uo – voltage to earth for TN systems
Ia - current causing operation of overcurrent device
Zs - impedance measures in ohms at the point in the circuit, which is furthest most the origin of the supply
 
Q) The Four Most Common Voltages at which Soldering Irons Operate as follows ?
a) 230V AC. For Workshop Use .
b) 110V AC . for Site Work .
c) 50V AC. For Production Work and Motor Vehicle Repair Workshops .
d) 12/24V DC. For Field Tasks ( where there is No Mains Electricity )
 
;) Confirmation of the Effectiveness of the Integral Test Facility : -

RCDs have an integral test device to Simulate the passing through the detecting device of a Residual Current . This makes possible Periodic Testing of the Ability of the Residual Current device to Operate . However , it should be remembered that operation of the Integral Test button merely confirms the continuing functioning of the Electrical and Mechanical Components of the RCD . it Does Not Confirm that the Device is capable of operating in Accordance with the Specification of the Relevant product standard or , indeed the Requirements of BS-7671 ,

Test Procedure :- With the Supply to the RCD Switched On and with the RCD in the “ ON : Position the Button marked “ T “ or the RCD is pressed . The RCD should switch off ( 514.12.2 ) recommends’ that the Integral Test Button of an RCD is pressed Quarterly ( Every 3 Months ) ◄ -&-s / 17th Edition

Summary :- RCDs should be Tested at ( 50% , 100% ) and, if ► Providing Additional Protection ◄► 500% of their Residual Operating Current ( I∆n ) in Addition . the integral Test Device should be Operated Quarterly . Where an RCD is Employed to Achieve the Disconnection Time ◄► Required by Table 41.1 ( Regs p/ 46 ) it is Necessary to Confirm that the Maximum Earth Fault Loop Impedances ( Zs ) stated for a Particular Sensitivity of the RCD in Table 41.5 ( Regs p/ 50 ) are Not Exceeded in the Circuit to which they Protection . ( you are Using the Calculations’ of the Touch Current ) “ Circuit Protective Conductor “ Does NOT rise above Earth Potential More Than ( 50V ) ◄ P/50 – R ≤ 50V ÷ 30mA = 1667Ω : ) Zs x Ia ≤ Uo ? ( Zs = Ia ÷ Uo = 32A ÷ 230 = 0.13Ω )
 
;) 17TH Edition ( 1 )
Test your self

1 . what colour is the 17th edition ?
a. yellow / b. green / c . brown / ► d . red :

2 . after what date in 2008 must you use the 17th edition :-
a. January 31st / ► b . june30th / c . july31st / d . December 31st :

3 . General use sockets-outlets in bathrooms ?
a . are not allowed
b . must be at least 0.6m from the bath
► c . must be at least 3m from bath :
d . must be un-switched

4 . the type of protection against electric shock under fault-free conditions is :-
a . safety / ► b . basic / c . fault / d . indirect :

5 . the type of protection against electric shock under single-fault conditions is :-
a . safety / b . basic / ► c . fault / d . direct / answer :

6 . which of the following is new to the testing sequence ?
a . continuity / ► b . phase sequence / c . functional testing / d . polarity :

7 . all circuits in a bathroom must ?
a. disconnect in 0.4s / ► b . be RCD protected / c . be MCB protected / d . be run as a radial :

8 . an RCD provided for fire protection on a farm must have an In not exceeding ?
a . 30mA / b . 100mA / ► c . 300mA / d . 500mA :

9 . in the 17th which of the following has a new Section in Part 7 ?
a . petrol filling station b . rooms containing a sauna ► c . floor and ceiling heating systems
d . mine or quarry

10 . The maximum recommended voltage drop for a standard domestic lighting circuit is ?
► a . 3% b . 4% c . 5% d . 6% :

11 . water utility supply pipes can be used as earth electrodes ?
► a . under no circumstances .
b . if their CSA is larger than 6mm2 .
c . if they are metallic .
d . if precautions are taken against removal :

12 . a socket-outlet in a domestic lounge should be ?
► a . protected by a 30mA RCD
b . arranged as part of a ring final circuit
c . switched
d . protected by a 32A circuit-breaker

13 . Supplementary bonding in a bathroom ?
a . is always required
b . is never required
► c . may be omitted if certain conditions met
d . must be at least 4mm2

14 . Twin and earth, cables shallow-chased into a wall in a domestic installation should be ?
a . run in the form of a ring
► b . installed in safe zones and protected by a 30mA - RCD
c . installed in safe zones only
d . protected by a 30mA – RCD only

15 . MI cable shallow-chased into a wall in a domestic installation ?
a . should be installed in safe zones and protected by a 30mA – RCD
b . should be installed in safe zones only
c . should be protected by a 30mA –RCD only
► d . can be installed outside safe zones without RCD protection

16 . the maximum permitted Zs values for low voltage circuits are based on nominal voltage of ?
► a . 230%V b . 240V c . 250V d . 400V

17 . PV stands for ?
a . Preferred voltage
► b . Solar photovoltaic
c . Protective voltage
d . Phase voltage
 
:rolleyes: 17th final score ( 2 )

10 . answer : A appendix 12 now gives a recommendation of 3% for lighting and 5% for other uses.
The figure in the 16th for all users was 4% for LV installations fed from private
LV supplies the figures are 6% and 8% respectively

11 . answer : A Supply pipes may not be used. Other metallic water supply pipes may be used as long as they are suitable and precautions are taken against removal .

12 . answer : A all socket-outlets for general use must be protected by a 30mA RCD they are two exceptions : ( i ) if the socket-outlet is under the supervision of a skilled or instructed person. However this would not apply to a domestic installation .
( ii ) if a socket-outlet is specifically labelled or identified for connection to a particular item
Of equipment , eg .c a fridge .

13 . answer : C Supplementary bonding may be omitted if all of the following conditions are met :
( i ) Disconnection times of all circuit in the bathroom are satisfactory
( ii ) All final circuits in the bathroom have 30mA RCD protection
( iii ) All extraneous parts are effectively connected to the protective equipotential bonding

14 . answer : B This is as for the 16th , but with the added requirement that 30mA RCD protection is required even where cables are installed in safe zones ..

15 . answer : D
The regulations allow cables in earthed conduit / trunking ,with an earthed metallic covering or
Mechanically protected to prevent penetration by nails , screws, drills etc, to be run outside
Safe zones without RCD protection ( the cables ,trunking and conduit used must meet the appropriate standards listed in the regulations ) . it would not be recognized as good practice to do this with MI and similar cables as they would still be susceptible to penetration ,
Albeit not presenting a shock risk .

16 . answer : A
Now 230V, previously 240V. This means that the maximum permissible Zs values given
In tables 41.2,41.3 and 41.4 are slightly lower than in the 16th .

17 . answer : B
Solar photovoltaic systems and other means of micro-generation are becoming increasingly common . in the 17th there are fifteen new definitions relating to PV systems . Section 712 is new and concentrates on PV supply systems .
 
;) Short-Circuit Currents & Interrupting Rating :-
To better Understand Interrupting Rating and the Importance of Compliance , ( Consider these Analogies )

* Normal Current Operation :
Flood Gates > Analogous to Overcurrent Protective Device ,
Reservoir Capacity Analogous to Available Fault Current .
Load > Current ( 100 Gallons per Minute )
Load / Overcurrent Protective Device )
► Available Fault Current / e.g. 50.00 Amps )

* Short-Circuit Operation with Inadequate Interrupting Rating :
Flood Gates > Are Destroyed because of Inadequate Interrupting Rating .
Dam / Breaks and Reservoir Releases Short-Circuit Current of ( 50.000 Gallons per Minute )
Load > Overcurrent Protective Device with Inadequate Interrupting Rating . in Violation of Overcurrent Protective Device is Destroyed .
► Available Fault Current / e.g. 50.00 Amps )

* Short-Current Operation with Adequate Interrupting Rating :
Flood Gates > Have Adequate Interrupting Rating . Fault Current Safely Interrupted .
Load > Overcurrent Protective Device with Adequate Interrupting Rating in Compliance / is Undamaged .
► Available Fault Current / e.g. 50.00 Amps )
► Short-Circuit Current Safely Cleared ,
 
;) Basic Electrical Theory Revision :-
Résistance .
This is the Opposition to the flow of current in a conductor determined by its length, Cross Sectional Area and Temperature .

Power :-
This is the product of current and voltage , hence P = I X V :
Relationship between voltage, current and Résistance :-
Voltage = Current x Résistance V = I x R or ,
Current = Voltage / Résistance I = V/R or ,
Résistance = Voltage / Current R= V/I ,

Common Multiples of Units :-
Current I amperes kA ( kilo-Amperes , 1000 Amperes :- mA ( milli-Amperes , 1/1000 of an Ampere ,
Voltage V volts kV ( kilovolts 1000 volts :- mV millivolts 1/1000 of a volt ,
Résistance R Ohms MΩ . megohms 1.000.000Ω :- mΩ milli-ohms 1/1000 of an Ohm ,
Power P Watts MW megawatt 1.000.000 watts :- kW kilowatt 1000 watts ,

R total = R1 + R2 + R3 + R4 , R1/1Ω : R2/2Ω : R3/10Ω : R4/4Ω ( R total = 1 + 2 + 10 + 4 = 17Ω )

1) 85m of 1.0mm2 Conductor ,
2) 1m of 6.0mm2 Conductor ,
3) 25m of 4.0mm2 Conductor ,
4) 12m of 0.75mm2 Conductor ,

1) 1.0mm2 is 19.5 mΩ/m . so , 85m would be ( 19.5 x 85 ÷ 1000 = 1.65Ω :
2) a 6.0mm2 Conductor would have a résistance 6 times less than a 1.0mm2 Conductor . i.e. ( 19.5/6 = 3.25mΩ :
3) 25m of 4.0mm2 would be 19.5 x 25/4 x 1000 = 0.12Ω :
4) 12m of 0.75mm2 would be 19.5 x 12/0.75 x 1000 = 0.312Ω :
 
;) Verification and Certification
The quality of visual inspection is dependent on the experience and knowledge of the person carrying out the inspection. It is vitally important that this person understands the Regulations .

Visual inspection should precede testing with instruments and must of course be prior to the installation being made live. It may be necessary to inspect some parts of an installation during the construction phase as these parts may be concealed later. A checklist for a Domestic Installation might read as follows:

1. Correct type.
2. Correct voltage rating.
3. Correct current rating.
4. Correct colour coding.
5. Diversity correctly applied.
6. Permitted volt-drop not exceeded.
7. Protected against mechanical damage and abrasion.
8. Not exposed to direct sunlight or, if so exposed, of a suitable type.
9. Correctly selected and installed for use on exterior walls etc.
10. Internal radii of bends in accordance .
11. Correctly supported in accordance .
12. Not used for connection of equipment which can be moved.
 
;) 2.1 Unit 201 Working effectively and safely in the electrotechnical environment (Stage 1)
Q1 Which of the following documents is non-statutory
a Health and Safety at Work Act
b Electricity at Work Regulations
c COSHH
d BS 7671 Requirements for Electrical Installations.
Q2 Prior to using an electric saw on a construction site, a user check finds that the insulation on the supply flex is damaged. The correct procedure would be to
a replace the cord with a new one
b report the damage to a supervisor after use
c repair the cord with insulation tape
d report the damage to a supervisor before use.
Q3 When carrying out repairs to the base of a street lighting column it is essential to wear
a a safety harness
b high visibility clothes
c gauntlets
d high voltage clothing.
Q4 First aid points are indicated using signs bearing a white cross on a
a yellow background
b blue background
c red background
d green background.
Q5 The type of fire extinguisher which would not be suitable for flammable liquids is
a dry powder
b water
c carbon dioxide
d foam.
Q6 CO2 fire extinguishers are indicated by the colour code
a black
b red
c beige
d blue.
Q7 An independent regulatory body responsible for monitoring standards of electrical installation contractors is the
a Electrical Institute Council
b Institute of Electrical Engineers
c National Electrical Contractors Institute Inspection Council
d National Inspection Council for Electrical Installation Contractors.
Q8 To ensure that a particular item of electrotechnical equipment meets a particular British Standard or BSEN Harmonised Standard, the best source of information would be the
a manufacturer of the equipment
b British Standards Institute
c Institute of Electrical Engineers
d supplier of the equipment.
 
Q9 Using a scale of 1:50, a 10 mm measurement taken from a plan would be equal to an actual measurement of
a 5 mm
b 5 cm
c 0.5 m
d 5 m.
Q10
Figure 1 shows the BS EN 60617 symbol for a
a one gang switch with arrow indicator
b one gang one way pull cord switch
c two way switch with on down d fireman’s switch.
Unit 201
Q1 – D
Q2 – D
Q3 – B
Q4 – D
Q5 – B
Q6 – A
Q7 – D
Q8 – A
Q9 – C
Q10 – B
 
;) 2.2 Unit 202 Principles of electrotechnology (Stage 1)
Q1 The Tesla is the unit of
a magnetic flux
b molecular flux
c magnetic flux density
d molecular flux density.
Q2 A single rotation of an alternator, intended to provide a 50 Hz supply frequency, will take
a 2 ms
b 20 ms
c 50 ms
d 5000 ms.
Q3 An increase in current through a conductor will lead to
a a decrease in conductor temperature
b a decrease in conductor resistance
c an increase in insulation resistance
d an increase in conductor temperature.
Q4 Four resistors having values of 2 Ω, 2 Ω, 5 Ω and 20 Ω are connected in a parallel circuit arrangement. The total resistance of this circuit is
a 0.8 Ω
b 1.25 Ω
c 29 Ω
d 400 Ω.
Q5 Where P = V I. The value V can be determined using
a ) V = I / P
b ) V = P I
c V = P - I
d V = P/I
Q6 A mass of 20 kg is to be raised by a hoist 2 m in 30 seconds. Assuming no losses, the power required to raise this load is
a 13.08 Watts
b 196.2 Watts
c 392.4 Watts
d 1200 Watts.
Q7 The white or grey pvc outer layer of a twin and cpc flat thermoplastic (pvc) cable is the
a conductor
b insulation
c conductor
d sheath.
Q8 The purpose of a bonding conductor is to provide
a an earth fault path
b an equal potential zone
c short circuit protection
d overload protection.
Q9 A 110 V, centre tapped earth, reduced low voltage supply for power tools provides a voltage of
a 25 V between live conductors
b 55 V to earth
c 110 V to earth
d 12 V SELV.
Q10 A particular extension lead used on a construction site is coloured yellow to
a indicate its mechanical stress properties
b enable it to be seen in the dark
c indicate the supply voltage to it d enable it to be to be identified as suitable for site use.
Unit 202
Q1 – C
Q2 – B
Q3 – D
Q4 – A
Q5 – D
Q6 – A
Q7 – D
Q8 – B
Q9 – B
Q10 – C
 
;) Q / Basic protection offers protection against :- A / Direct contact with live parts ,
Q / Fault protection offers protection against :- A / protection against electric shock under fault conditions due to indirect contact ,
Q / A single phase-socket outlet ring circuit supply would have :- A / Four live conductors ,
Q / The abbreviation PV stands for :- A / Photo Voltaic ,
Q / A system with a combined natural and earth within both the supply arrangement and installation is known as a :- A / TN-C : Regs p/30 / 32
Q / A system with a separate neutral and earth within the supply arrangement is know as :- A / TN-S : Regs p/30 / 33
Q / A system with a combined natural and earth within the supply arrangement and separate and earth within the installation is know as :- A / TN-C-S ,
Q / A system whose return path is via earth electrodes is known as a :- A / TT system ,
Q / A voltage band 1 covers :- A / Extra low , voltage , Regs p/31
Q / A voltage band 11 covers :- A / low voltage , Regs p/31
Q / The abbreviation cpc stands for :- A / Circuit protective conductor ,
Q / Class 1 equipment would be :- A / Exposed metalwork earthed ,
Q / Class 11 equipment would be :- A / No earth arrangement ,
Q / The abbreviation SELV stands for :- A / Separated extra low voltage ,
Q / Class 111 equipment would have :- A / An SELV supply , regs p/21
 
;) Test Procedures for Electrical Installations :-
( Continuity and Insulation Résistance )

Sequence of Tests ( 612 )
* Continuity of Protective Conductors ( including main and supplementary bonding ). 612.2.1.

* Continuity of Ring Final Conductors. 612.2.2

* Insulation Résistance Tests. 612.3.

* Protection by SELV, PELV or electrical separation. 612.4.

* Basic Protection by barrier or an enclosure provided during erection. 612.4.5.

* Insulation resistance/impedance of floors and walls. 612.5

* Polarity. 612.6

* Earth electrode resistance. 612.7

* Earth loop impedance. 612.9

* Prospective fault current. 612.11

* Check of Phase sequence (for multiphase systems). 612.12

* Functional tests. 612.8, 612.10 and 612.13

ALL TESTS UP TO AND INCLUDING POLARITY are carried out with the ‘mains’ ISOLATED, Earth electrode resistance (if conducted with a Loop Tester) and subsequent tests are carried out with the ‘mains’ ON. If earth electrode resistance is measured using dedicated tester – this is a ‘dead’ test – so ISOLATE. Functional tests also relate to RCD testing.

Continuity of Earth ,
* There are TWO methods available – (R1+R2) or (R2).

* (R1+R2) is often the easier test to carry out for ‘normal circuits’.

* (R2) is used for Bonding conductor tests.


* POINTS TO NOTE:

* Null test leads first – why?

* The test instrument will have a voltage supply of between 4 – 24v (ac or dc) and test current of at least 200mA – why?


1 ) To deduct the resistance of the test leads (and long trailing test lead if used) from the results, when conducting circuit resistance tests.

2 ) This applies electrical ‘pressure’ to the circuit under test – this will identify whether a poor ‘loose’ or ‘dirty’ connection exists. Normal ‘multimeter type’ resistance meters do not apply adequate electrical ‘ pressure’ during a test, so poor connections can go unnoticed!!

( R1 + R2 ) Test
Mains OFF – Temporary Link between Line and CPC in the Consumer Unit ,
Operate ALL Switches , between Line ( Switched ) and CPC at ALL points ( Including Switches ) ↔ ( R1 + R2 ) Test can be Used to Confirm Polarity ,
Note: TEMPORARY LINK IN CONSUMER UNIT CAN BE MADE WITHOUT REMOVING THE CONDUCTORS FROM THEIR TERMINALS.

disconnected here for clarity.Simply connect temporary ‘shorting lead’ between circuit breaker ‘busbar rail’ and CPC block. Then turn on MCB for circuit under test. Measure between any switched live and CPC at end of the circuit under test. Repeat for other circuits. REMEMBER to operate switches to PROVE polarity during test.

Continuity of the Bonding Conductors
Avoid Parallel Paths ◄► Test Each bonding Conductors in Turn , Remember the Disconnected it from the MET ( Main Earthing Terminal )before Testing and Re-Connecting it after Testing

Main Switch in Consumers Unit is OFF , all MCBs OFF , Remember – the Main Earthing Conductor is Removed for this Test , Remember to Reconnect IT Afterwards ,
* Main Earthing Conductor → : Main Earthing Terminal → ( MET ) Gas Meter / 600mm < ( Test Lead on Copper Pipe Water → : Other Lead on Main Earthing Terminal → ( MET ) 0.01Ω

R2 ) test shown here. REMEMBER to NULL test leads due to relatively low values of BONDING conductor resistance being adversely affected if resistance of test leads was added to final readings inadvertently. Record the measured equipotential bonding conductor reading onto the Schedule of Test Results sheet.

Ring Circuit , ( R1 + R2 )
Mains OFF – Shower “ Pull/Cord “ Switch ON .
Shower itself Switched OFF .
Test between Line and CPC . ( R1 + R2 ) Test at Ends of Shower “ Radial Circuit ◄
Operate Pull-Cord to Confirm Polarity !!!!!
Line and CPC “ Temporally Linked “ in Consumer Unit
( One Lead on Con/ Block in Shower Brown ◄► Other Lead on Con/ Block in Shower CPC ) 0.21Ω
 
Continuity of Earth ( Including Bonding Conductor s )

* (R1+R2) or (R2) readings will be dependent on LENGTH and CSA of Live and Earth (or just earth) conductor(s) used .

* Tables in ‘On-site guide’ give comparative values.

* Measured (R1+R2) or (R2) impedance values MUST be LOW ohms readings.

* Bonding conductors MUST be 0.05 ohms or less.

* These readings are recorded on ‘Schedule of test results form’.

* (R1+R2) test can also be used to check POLARITY (so is a preferred test here)


Completing the Test Results Sheet : ( this is just to give you an idea when you go onto : Schedule of Test Results ) Testing

Schedule of Test Results ,
Method of Fault Protection ( Automatic Disconnection of Supply )
Equipment Vulnerable to Testing !! Timer in Bathroom Fan ◄◄
Description of Work !! Periodic Inspection and Test
Circuit Description :-
Overcurrent Device / Short-Circuit Capacity 6 kA ◄
Shower : Type MCB ( B ) : Rating 40 Amp : Wiring Conductors 6mm2 ◄►Wiring Conductors 2.5mm2 ( Continuity – R1 + R2 / 0.21Ω
Remember Polarity ◄
Ring Circuit : Type MCB ( B ) : Rating 32 Amp : Wiring Conductors 2.5mm2 ◄►Wiring Conductors 1.5mm2 ( Continuity – R1 + R2 / !!!!! Ω
Garage : Type MCB ( B ) : Rating 32 Amp : Wiring Conductors 4.0mm2 ◄►Wiring Conductors 2.5mm2 ( Continuity – R1 + R2 / !!!!! Ω
Lights : Type MCB ( B ) : Rating 6 Amp : Wiring Conductors 1.5mm2 ◄►Wiring Conductors 1.0mm2 ( Continuity – R1 + R2 / !!!!! Ω
Gas Bonding ( Equipotential ) Wiring Conductors : 10mm2 ( Continuity – R2 0.01Ω

Continuity of Ring Final Conductors
* This is the ‘trickiest’ of the ‘dead-tests’ that electricians often find difficult to understand.

* The test has TWO purposes.

* 1) To check that the circuit is in a RING configuration (end-to-end).

* 2) To check that NO interconnects exist within the ‘RING’ which could give rise to danger.

* The tests are carried out in THREE stages….


Continuity of Ring Final Conductors Stage 1 – End / to / End Readings ,
Measure Continuity of each pair of Live,s – Neutral,s and CPC,s this will Confirm a Ring Circuit . Live and Neutrals should have same readings
Cpc,s will be approx 1.67x Greater .

Measure open end live-to-live and make a note of reading, do same for neutrals and CPC ’s. These readings are your basis for calculating EXPECTED VALUES for subsequent tests on the RING CIRCUIT.

Continuity of Ring Final Conductors Stage 2 – Line and Neutral Readings ,
Ensure Socket Under Test is Switched ON ! Lines and Neutrals ( Crossed-Linked in Consumer Unit )

All Sockets Outlets will have very similar Readings if Connected on a “ Ring Circuit “
Test between Line / Neutral at Each Socket Outlet ( Note Earth Test Lead is Used for this Test )
( PS you are looking for : Equal Readings from Sockets Outlets !!

A 1.5 MM SQ CPC WILL HAVE APPROX. 1.67X MORE RESISTANCE THAN A 2.5 MMSQ LIVE CONDUCTOR OF THE SAME LENGTH, hence the CPC-CPC reading being 0.55 ohms (1.67x the 0.33 ohms for the live conductor end-to-end reading).
When ring conductors are cross linked as shown (Live – neutral and Neutral – live cross-linking) TOTAL resistance reading is 0.165 ohms. This is R1 (live end-to-end) + RN (neutral-to-neutral)/4 OR, as both Live and Neutral end-to-end readings were identical, EITHER one divided by 2 (i.e. 0.33/2 = 0.165 ohms). This IS THE EXPECTED READING AT EACH SOCKET OUTLET ON THE RING. A substantially different reading may indicate that ‘that’ outlet is a spur (or interconnect) and should be investigated further. Values from this test are NOT recorded on the Schedule of Test Results – but only used as a reference to each socket.

Continuity of Ring Final Conductors Stage 3 – Line and CPC Readings
( R1 + R2 ) Test Ensure Sock Outlet Under Test is Switched ON !
Lives and CPCs are “ Cross-Linked “ in Consumer Unit
All Socket Outlets will have Very Similar Readings if Connected on a “ Ring Circuit “
( PS you are looking for : Equal Readings from Sockets Outlets !!

If live-to-live open end readings = 0.33 ohms and CPC-to-CPC open end readings = 0.55 ohms, then when cross linked as shown reading should be 0.22 ohms at position shown and each socket outlet on the ring. This is the EXPECTED READING AT EACH SOCKET OUTLET ON THE RING. A substantially different reading may indicate that ‘that’ outlet is a spur (or interconnect) and should be investigated further.

0.33 (R1) + 0.55 ( R2) /4 = approx. 0.22 ohms.
R2 value is 0.53 / 2 = approx. 0.27 ohms.
Record EITHER value onto the Schedule of Test Results.
 
“ Interconnection’s” and “ Spurs” on a Ring Circuit ,
( R1 + R2 ) Test Ensure Socket Outlets under Test is Switched ON !
Lives and CPCs are Crossed – Linked in Consumer Unit ,

Test between Live and CPC at Socket Outlets ( Note Neutral Test Lead is Unused for this Test .
► these Two Sockets are “ Spurred “ from the “ Ring “ Circuit – so Reading is “ Substantially “ Different from expected Ring Value ,
Not :- Equal Readings , 0.22Ω / 0.52Ω

As shown here, a substantially different reading is obtained at an outlet. Here, if the last ‘good’ (i.e. 0.22 ohm reading) socket front were to be removed for closer inspection, THREE 2.5mmsq conductors would be seen. Subsequent sockets with increasing resistance values are the indication of an ‘illegal’ spur.

Continuity of Ring Final Conductors Re-Cap :-

* Measure between EACH end of PHASE, NEUTRAL and CPC conductors (note; phase and neutral should be the same reading, cpc may be slightly higher if its CSA is smaller). Record the results.

* Cross-link PHASES and NEUTRALS and measure the resistance at EACH outlet. Total resistance should be (R1+Rn)/4. Check for the same reading at EACH socket outlet on the ring circuit.

* Cross-link PHASES and CPC’s and measure the resistance. Total resistance should be (R1+R2)/4. Check for the same reading at EACH socket outlet on the ring circuit.

* Any SUBSTANTIALLY different readings and any outlet is an indication of an SPUR or INTERCONNECT at that outlet – investigate further.

RECORD the (R1+R2) measured value onto the Schedule of Test Results sheet.
 
;) Typical BS-1362 :- 3A Cartridge fuse in a BS-1363 plug connected to Class 1 Equipment , ( just to show you two different BS-No 1362 / 1363

BS-1362 Cartridge Fuse have a Rated Voltage of 240V and are suitable for use in Circuits’ where the A.C. system Voltage does Not Exceed 110%
Of that Voltage ( that is 264V )
The Rated Frequency of BS-1362 Cartridge Fuse is 50Hz , however the Standard Conditions of Service for such Fuses permit their Use in Circuits having a Frequency within the Range 45 to 62Hz ,

The Rated Current ( In ) allocated by the Manufacturer may be any Value up to and including 13A , although the Values preferred by BS-1362 are 3A and 13A , Other Values of Rated Current Used for BS-1362 Cartridge Fuses are 2A / 5A / and 10A .
Cartridge Fuses Complying with BS-1362 are Required to be Colour Coded According to their Rated Current , and be Marked with their Rated Current Value ,

The Rated Current of BS-1362 Cartridge Fuse is Applicable to Specific Ambient Temperature Conditions . if it is Intended to Use a BS-1362 Fuse where the Ambient Temperature Conditions Differ from the Service Conditions of BS-1362, the Manufacturer should be Consulted Prior to such Use .

Where a Fuse is Used to Provide Fault Current Protection Only , for Example to protect an Appliance with Integral Overload Protection , the Fault Clearance Time Under both Short-Circuit and Earth-Fault Conditions has to meet the Requirements of Regulation 434.5.2 .

For Overload Current Protection , the Rated Current of a Fuse is to be Selected to meet the Requirements of Section 433 of BS-7671 .

Where Overload Current Protection is Afforded by a BS-1362 Cartridge Fuse , there tends to be a need for the Circuit-Conductors to be of a Larger Cross-Sectional Area than Required by most Other Types of Overcurrent Protective Device Used . this is because of the need to Comply with Condition ( iii ) of Regulation 433.1.1 . which Requires that ( I2 ) the Current Causing Effective Operation of the Protective Device , does Not Exceed 1.45 times the Lowest of the Current-Carrying Capacities ( Iz ) of any of the Conductors of the Circuit ,

BS-1362 Cartridge Fuses are Required to be Indelibly Marked with the Following Information .
* Manufacturers Name or Identifying Mark .
* British Standard Number BS-1362 .
* Rated Current in Amperes .
 
Cartridge Fuse to BS-1362 :-
Cartridge Fuses Conforming to BS-1362 are for Use in Low-Voltage Single-Phase A.C circuits of Nominal Frequency 50 or 60Hz .they are General-Purpose Fuses intended for Domestic and Similar Purposes , Primarily in Plugs Complying with BS-1363 although Not Exclusively so , BS-1362 Cartridge Fuses are , for Example Commonly Used in Fused Connection Units .

Where it is intended to Use a BS-1362 Cartridge Fuse in a D.C. circuit , the Fuse Manufacturer should be Consulted prior to its Use .
The Rated Values and Characteristics given in BS-1362 are Applicable to Alternating Current ( A.C. ) the Suitability of BS-1362 Fuses for D.C. Applications Needs to be Established , and the Rated Values and Characteristics Obtained for such Applications .
 
;) Assessment Questions : ( Some Old Notes to play around with ) some are still Active with -&-s ,
2) The main reason for incorporating the wiring Regulations into British Standards BS-7671 was to harmonistion with European Standards , ( True ) *
3) A cable sheath earth supply or TN-S System of supply is one of the most common types of underground supply in the UK ( True ) *
4) A Delivery Note : is a standard form completed by most electrical trainees to inform an employer of how much time has been spent working on a particular job ( False )
5) When materials are delivered to site , the person receiving the goods is required to sign the drivers Time-Sheet to prove that the supplier has delivered the goods as requested ( False ) *
6) A radial socket circuit is wired from the source of supply to each socket in turn and the last socket is wired back to the source of supply ( False )
8) Industrial installations use robust cable enclosures such as conduits and trunking , A conduit is a square or rectangular section from mild steel plate , A trunking is a tube , or pipe in which insulated conductors are contained , ( False ) *
9) Individual cables or accessories may be fixed directly to a surface with a suitable nail , screw or bolt , A spring toggle bolt provides a good method of fixing to concrete or masonry , a Rawbolt provides a good method of fixing to hollow partition walls ( False )
10) The “ Waste Regulations “ tell us that we have a “ Duty of Care “ to handle , recover and dispose of waste responsibly , you company is responsible for the waste that it produces , so always make sure that waste material is put into the proper skip and taken away only by “ Authorised “ companies ( True ) *

Multiple Choice Assessment Questions :-
Tick the correct answer , NOTE that more than ONE answer may be correct ,

11) The Electricity at Work Regulations are :
a) Non-Statutory Regulations ,
b) Statutory Regulations ◄
c) a Code of Practice ,
d) a British Standard ,
12) The IEE Regulations are :
a) Non-Statutory Regulations , ◄
b) Statutory Regulations ,
c) a Code of Practice , ◄
d) a British Standard , ◄
13) A British Standard having a BS number is a :
a) Statutory Regulations ,
b) Non-Statutory Regulations ,
c) British compliant Standard , ◄
d) European harmonised Standard ,
14) A British Standard having a BS-EN number is a :
a) Statutory Regulations ,
b) Non-Statutory Regulations ,
c) British compliant Standard ,
d) European harmonised Standard , ◄
15) part 5 of the IEE Regulations deals with :
a) Protection for Safety ,
b) Selection and Erection of Equipment , ◄
c) Special Installations ,
d) Inspection and Testing ,
16) Part 6 of the of the IEE Regulations deals with :
a) Protection for Safety ,
b) Selection and Erection of Equipment ,
c) Special Installations ,
d) Inspection and Testing , ◄
17) A scale drawing showing the position of equipment by graphical symbols is a description of a :
a) Block diagram ,
b) Wiring diagram ,
c) Circuit diagram ,
d) Layout diagram or site plan , ◄
18) A diagram which shows the detailed connections between individual items of equipment is a description of a :
a) Block diagram ,
b) Wiring diagram , ◄
c) Circuit diagram ,
d) Layout diagram or site plan ,
19) A diagram which shows very clearly how a circuit works , where all components are represented by a graphical symbol is a description of a :
a) Block diagram ,
b) Wiring diagram ,
c) Circuit diagram , ◄
d) Layout diagram or site plan ,
20) A Time Sheet show’s :
a) a Record of goods delivered by a supplier ,
b) a Record of work done which is outside the original contact ,
c) Information about work to be done usually a small job ,
d) the actual time spent working on a particular job or site , ◄
 
21) A job Sheet or Job Card shows :
a) a record of goods delivered by a supplier ,
b) a record of work done which is outside the original contact ,
c) information about work to be done , usually a small job , ◄
d) the actual time spent working on a particular job or site ,
22) A Day Work Sheet shows :
a) a record of goods delivered by a supplier ,
b) a record of work done which is outside the original contract , ◄
c) information about work to be done, usually a small job ,
d) the actual time spent working on a particular job or site ,
23) A Delivery Note shows :
a) a Record of goods delivered by a supplier , ◄
b) a Record of work done which is outside the original contract ,
c) Information about work to be done , usually a small job ;
d) the actual time spent working on a particular job or site ,
24) A cable sheath earth supply is also called a :
a) TN-S system , ◄ ( Regs p/32 /33/34 )
b) TN-C-S system ,
c) TT system ,
d) Standby System ,
25 ) A PME supply is also called a :
a) TN-S system ,
b) TN-C-S system , ◄ ( Regs p/32 /33/34 )
c) TT system ,
d) Standby System ,
26) a No earth provided supply is also called a :
a) TN-S system ,
b) TN-C-S system ,
c) TT system , ◄ ( Regs p/32 /33/34 )
d) Standby System ,
27) The electricity supply to a domestic consumer is usually protected at the incoming service position by a :
a) Meter ,
b) Double pole switch ,
c) 100A MCB ,
d) 100A HBC fuse , ◄
28) The assumed current demand for each lighting point in a domestic installation should be based upon the equivalent of :
a) 5 amps per lampholder ,
b) 6 amps per lampholder ,
c) 100 watt per lampholder , ◄
d) 3kW per lampholder ,
29 The protective Type B MCB for lighting circuit fed from a consumer unit in 1.0mm2 or 1.5mm2 cable should be rated at :
a) 6A or 10A , ◄
b) 10A or 16A ,
c) 16A or 32A ,
d) 32A or 40A ,
30) The protective Type B MCB for Ring circuit fed from a consumer unit in 2.5mm2 cable should be rated at :
a) 6A or 10A ,
b) 10A or 16A ,
c) 16A or 32A ,
d) 32A only , ◄
31) Each ring circuit of 13A sockets must cover a floor area of no more than :
a) 50m2 ,
b) 75m2 ,
c) 100m2 , ◄ ( O.S.G. p/158 )
d) unlimited ,
32) A radial circuit of 13A sockets wired in 2.5mm2 / 1.5mm2 PVC cable must cover a floor area of no more than :
a) 50m2 , ◄ ( O.S.G. p/158 )
b) 75m2 ,
c) 100m2 ,
d) unlimited ,
33) A radial circuit of 13A sockets wired in 4.0mm2 / 2.5mm2 PVC must cover a floor area of no more than :
a) 50m2 ,
b) 75m2 , ◄ ( O.S.G. p/158 )
c) 100m2 ,
d) unlimited ,
34) an MI cable is especially suited to :
a) domestic installations ,
b) fire alarm installations , ◄
c) burying underground ,
d) industrial installations , ◄
 
35) a PVC/SWA cable is especially suited to :
a) domestic installations ,
b) fire alarm installations ,
c) burying underground , ◄
d) industrial installations ,
36) a PVC Insulated and sheathed cable is especially suited to :
a) domestic installations , ◄
b) fire alarm installations ,
c) burying underground ,
d) industrial installations ,
37) FP 200 cables are especially suited to :
a) domestic installations ,
b) fire alarm installations , ◄ ( can be used for Emergency Lighting )
c) burying underground ,
d) industrial installations ,
38) A steel conduit installation is especially suited to :
a) domestic installations ,
b) fire alarm installations ,
c) burying underground ,
d) industrial installations , ◄
39) A metal trunking installation is especially suited to :
a) domestic installations ,
b) fire alarm installations ,
c) burying underground ,
d) industrial installations , ◄
40) Cable tray installations are especially suited to :
a) domestic installations ,
b) fire alarm installations , ◄
c) burying underground ,
d) industrial installations , ◄
41) bathroom installations receive special consideration in the IEE Regulations :
a) electricity and flammable liquids ,
b) electricity and water , ◄
c) the presence of corrosive substances ,
d) the potential for mechanical damage ,
42) Construction sites receive special consideration in the IEE Regulations :
a) electricity and flammable liquids ,
b) electricity and water , ◄
c) exposure to wind and rain , ◄
d) presence of livestock and vermin ,
43) Agricultural installations receive consideration in the IEE Regulations because of the hazard associated with :
a) electricity and water , ◄
b) presence of livestock and vermin , ◄
c) potential for mechanical damage , ◄
d) electricity and flammable liquids ,
44) Petrol pump installations receive special consideration from may Statutory Regulations because of the hazard associated with :
a) electricity and water ,
b) electricity and flammable liquids , ◄
c) exposure to wind and rain ,
d) the temporary nature of the supply
45) Locations containing a bath or shower are divided into zones or separate areas . the most dangerous zone is classified as :
a) Zone 0 , ◄
b) Zone 1 ,
c) Zone 2 ,
d) Zone 10 ,
46) The permissible colours of 230V Single-Phase wiring , up to 30th march 2006 was :
a) brown , blue , green/yellow ,
b) brown , black , gray ,
c) red , black , green/yellow , ◄ ( you’ll never get this )
d) red , yellow , green /yellow ,
48) PVC insulated and sheathed cables are very likely to be fixed and supported by :
a) wood screws and plastic plugs ,
b) a PVC clip and hardened nail , ◄
c) an expansion bolt ,
d) a clip on girder fixing ,
49) A lightweight piece of electrical equipment is very likely to be fixed to a plasterboard by :
a) wood screws and plastic plugs ,
b) a PVC clip and hardened nail ,
c) an expansion bolt ,
d) a spring toggle bolt , ◄
 
50) a heavy electric motor is very likely to be fixed to a concrete floor by :
a) wood screws and plastic plugs ,
b) a clip on girder fixing ,
c) an expansion bolt , ◄
d) a spring toggle bolt ,
51) A run of trunking suspended in an industrial installation is very likely to be fixed to the main structure of the building by :
a) wood screws and plastic plugs ,
b) a clip on girder fixing , ◄
c) an expansion bolt ,
d) a spring toggle bolt ,
52) A run of cable tray suspended in a modern Supermarket building is very likely to be attached to the main structure of the :
a) wood screws and plastic plugs ,
b) a clip on girder fixing , ◄
c) an expansion bolt ,
d) a spring toggle bolt ,
53) what action is necessary to produce a “ secure electrical isolation “ :
a) isolate the supply and observe that the voltage indicator reads zero ,
b) First connect a test device such as a voltage indicator to the supply ,
c) Larger pieces of equipment may require isolating at a local isolator switch ,
d) The isolated supply must be locked off or secured with a small padlock , ◄
54) A voltage proving unit :
a) is used for transmitting data along optical fibre cables ,
b) provides a secure computer supply ,
c) shows a voltage indicator to be working correctly , ◄
d) tests for the presence of a mains voltage supply ,
55) for working even a short distance above ground level periods , the safest piece of access equipment would be :
a) a stepladder ,
b) a platform tower , ◄
c) an extension ladder ,
d) a hard hat ,
56) an example of “ special waste : is :
a) sheets of asbestos , ◄
b) old fibre-glass roof insulation ,
c) old fluorescent tubes , ◄
d) part coils of PVC insulated cables ,
57) Special Waste must be disposed of :
a) in the general site skips ,
b) in the general site skips by someone , designated to have a “ Duty of Care “
c) at the “ Household Waste “ re-cycling centre ,
d) by an “ Authorised Company “ using a system of waste transfer notes , ◄
58) the Heath & Safety at Work Act places the responsibility at work on :
a) the Employer ,
b) the Employee ,
c) both the Employer and Employee ,
d) the Main Contactor ,
59) Under the Heath & Safety at Work Act an Employer must ensure that :
a) the working conditions are appropriate and safety equipment is provided , ◄
b) Employees take reasonable care of themselves and others as a result of work activities ,
c) employees co-operate with an employer and do not interfere with or misuse safety equipment ,
d) that plant and equipment is properly maintained , ◄
60) Under the Heath & Safety at Work Act Employees must ensure that :
a) the working conditions are appropriate and safety equipment is provided ,
b) they take reasonable care of themselves and others as a result of work activities , ◄
c) they co-operate with an Employer and do not interfere with or misuse safety equipment , ◄
d) plant and equipment is properly maintained ,
 
;) Proving Unit :-

Switch ON ,
Insert probe ends of Testing Device into A.C./D.C. Outlet Sockets and while holding Testing device apply a light pressure in direction of Sockets ,
Switch OFF ,
Withdrawal of Testing Device instantly De-Energises ( form the Proving Unit )
Proof Testing ,
With Probes of Testing Device Inserted into Sockets APPLY SUFICIENT PRESURE for Good Electrical Contact ,
CHECK ∆ INDICATES AT ALL TIMES During Testing , Replace Battery if , in Normal Use , it Does NOT Iluminate , ◄

Check ALL NEON LAMPS Located within the Testing Device Iluminate for Duration of PROOF TESTING ,◄

( Remember that -&-s will ask about : Read Instructions Before Use/Operating )
 
;) Proving Unit :-

To Deter ANYONE from RECNNECTING the Supply , a NOTICE must be FIXED on the Isolating SAYING “ Danger – Electrician at Work
Which you should Practice in the Workshop Under the Guidance of your Tutor or at Work Under the Guidance of your Supervisor , Electrical Isolation is an Important Safety Procedure ,

Select an Approved Test lamp or Voltage Indicating device , ▼
Verify that the Device is Functioning Correctly on a Known Supply or Proving Unit , ▼
▼ Satisfactory ? →→ No ► ( Replace or Repair )
Yes :
Locate and Identify Circuit or Equipment to be Worked Upon
Is the Circuit or Equipment in Service ? →→ No ►( Establish where and why it was De Energised )
Yes :
Identify Means of Isolation ▼
Ensure Isolation of the Circuit or Equipment by ▼
- Switching Off .
- Withdrawing Fuses .
- Locking off Isolating Switches or MCBs , ▼
Verify that the Circuit or Equipment to be Worked Upon is DEAD Using a Voltage Indicating Device Testing between :- ▼
Line / and Earth ,
Line / and Neutral ,
Neutral and Earth , ▼
Yes :
Satisfactory ? →→ DEAD ► Fit WARNING Signs , Recheck that the Voltage Indicating Device is Functioning Correctly on a Know Supply or Proving Unit , ▼
▼ Satisfactory ? Yes ( Begin Work ) No ► Replace or Repair and go Through the Procedure Again :
LIVE ~ ~ ~
Discover why with CARE and go Though the Procedure Again ,
 
;) Circuit Diagram :
A Circuit Diagram shows most Cleary how a Circuit Works, All the Essential Parts and Connections are Rep-resented by their Graphical Symbols . The Purpose of a Circuit Diagram is to Help our Understanding of the Circuit , it will be Laid Out as Clearly as Possible , without regards to Physical Layout of the Actual Components and , Therefore , it may Not Indicate the most Convenient way to Wire-a-Circuit ,

;) Symbols and Multiples for Use with SI Units :
Prefix : Mega , Symbol : M , Multiplication Factor : x 10/6 or x 1000000 ,
Prefix : Kilo , Symbol : k , Multiplication Factor : x 10/3 or x 1000 ,
Prefix : Hecto , Symbol : h , Multiplication Factor : x 10/3 or 100 ,
Prefix : Decca , Symbol : da , Multiplication Factor : x 10 or x 10 ,
Prefix : Deci , Symbol : d , Multiplication Factor : x 10_1 or ÷ 10 ,
Prefix : Centi , c , Multiplication Factor : x 10_2 or ÷ 100 ,
Prefix : Milli , m , Multiplication Factor : x 10_3 or ÷ 1000 ,
Prefix : Micro , m , Multiplication Factor : x 10_6 or ÷ 1000000 ,

An Electric Fan-Heater was found to Take 10A when Connected to the 230V Mains Supply , Calculate the Résistance of the Heater Element :- ??
From ( R ) = V/I ( Ω ) ◄► ( R = 230 ÷ 10A = 23Ω ) The Heater Element Résistance is 23Ω

Calculate the Current Flowing in a Disco “ Sound and Light “ Unit having a Résistance of ( 57.5Ω ) when it is Connected to the 230V Electrical Mains ,
From ( I ) = V/R ( A ) ◄► ( I = 230V ÷ 57.5Ω = 4A ( The “ Sound and Light “ Unit takes 4 Amps ,

Resistivity :
“ Remember “ ► The Résistance or Opposition to Current Flow Varies , Depending Upon the Type of Material being Used to Carry the Electric Current ,

Using these Values we can Calculate the Résistance of Different Materials Using the Formulae !!!
Résistance ( R ) = pL / a ( Ω )
Where ( p ) ( the Greek Letter rho ) is the Resistivity Value for the Mater , ( l ) is the Length and ( a ) is the Cross-Sectional Area ,
( just for talk sake ) Copper : Resistivity ( Ωm ) 17.5 x 10-9
( just for talk sake ) Aluminum : Resistivity ( Ωm ) 28.5 x 10-9

* Calculate the Résistance of 100m of 2.5mm2 Copper Cable Using the Resistivity Values ,
We know that ( R ) = pL / a . Ω
Therefore ( R ) = 17.5 x 10-9 x 100 ……. 2.5 x 10-6
Therefore R = 700 x 10-3 ( Ω ) or
R = 700 ( mΩ )

Note : the Cross-Section of the Cable is in mm2 ( mm = 10-3 so, ) mm x mm = 10-6
* Calculate the Résistance of 100m of 2.5mm2 Aluminum Cable Using the Resistivity Values ,
We know that ( R ) = pL / a . Ω
Therefore ( R ) 28.5 x 10-9 x 100 ……. 2.5 x 10-6
Therefore R = 1140 x 10-3 ( Ω ) or
R = 1140 ( mΩ )
 
;) So , if -&- Ask you about :-
Syllabus : Consider Weight , Mass , Force and Work done by a Force so let us Define some of these Scientific Term ,
Mass : this is a Measure of the Amount of Material in a Substance such as Wood or Metal ,
Weight : this is a Measure of Force which the Mass Exerts , it Exerts this Force because it is being Attracted towards the Earth by Gravity ,
Force : The Presence of a Force can Only be Detected by its Effect on an Object , A Force may Cause a Stationary Object to Move or a Moving Object to Stop ,
Gravity : The Force of Gravity Acts toward the Centre of the Earth and Causes Objects to Fall to the Ground at a Rate of ( 9.81 m/s )
Work Done : the Work done by Force is a Measure of the Force Exerted Time the Distance Moved in the Direction of the Force ,

Suppose a Broken-Down Car was to be Pushed along a Road ; Work would be Done on the Car by Applying the Force Necessary to Move it Along the Road , Heavy Breathing and Perspiration would be Evidence of Work Done !!!!!!!!!

Work Done = Force x Distance Moved in the Direction of the Force ( J )
The SI Unit of Work Done is the Newton Metre or Joule ( Symbol J )
Example ;
A Building Hoist Lift ten 50kg bags of Cement through a Vertical Distance of 30m to the Top of a High Rise Building , Calculate the Work Done by the Hoist , Assuming the Acceleration due to Gravity to be 9.81 m/s-2 ,
Work done = Force x Distance moved ( J )
But, Force = Mass x Acceleration ( N )
Therefore : Work done = Mass x Acceleration
x Distance Moved ( J )

work done = 10 x 50kg x 9.81m/s-2 x 30m
work done = 147.15kJ ,
 
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