Useful information

[amberleaf]

3% of 230v = 6.9v
5% of 230v = 11.5v
5 x 230 ÷ 100 = 11.5v

● Tables 41.2 , 41.3 , 41.4 , Zs if the Measured Zs value exceeds 80% of the given values , a more precise measurement may have to be made to satisfy the Requirements BS-7671, p - 361
Uo 230
Zs ( m ) ≤ 0.8 x ------ Ze Zs
Ia 24A = 9.59Ω ( 0.8 x 9.59 = 7.6
The Maximum circuit length is then the smallest of 2 to 4 Regs , 4D5 18mV assuming Ib 32A
Lvd = 4 x 11.5 x 1000 ÷ 32 ÷ 18 ÷ 79.9m

Lvd = 2 x 11.5 x 1000 / 20A / 18mV = 63.8m Lvd = 4 x 11.5 x 1000 / 20A / 18mV = 127.7m
The following values are for T&E cable p282 1.0mm = 44 (mV/A/m)
1.5mm = 29 ( mV/A/m )
2.5mm = 18 ( mV/A/m )
433.2.1 ( Ib ) in each leg of cable is not to exceed ( 20A ) current will not be the same all round Ring , ← ← Assumed to be 20A at far end Additional – 12A evenly Distributed , ( 32A + 20A + 52A ÷ 2 = 26A
Lvd = 4 x 11.5 x 1000 ÷ 26A ÷ 18mV = 98.3m 433.1.5 , ring final circuit , 2.5mm2 & 1.5mm2 ( cable double , cable length to farthest point ) some home work ,

● BS-7671 does not give maximum Zs values for BS 3871 mcb's. ● if the maximum Zs value for a circuit in a TN system cannot be met, the circuit may be protected by a 30mA RCD . 531.3.1 : ● If the maximum Ze value for a TN system cannot be met, the installation may be protected by a 100mA RCD and treated as a TT systems 531.3.1 , 411.5.1 , 411.5.2 , 411.5.3 :
Maximum Ze values for TN-S & TN-C-S systems Typical maximum values published by Public Electricity Suppliers are ↔TN-S : 0.80 ohms ↔ TN-C-S : 0.35 ohms
● Ze Test Sequence ● Turn off the supply to the ccu , ● Disconnect the main earthing conductor from the main earthing terminal , ● Using an earth fault loop impedance tester connect the earth lead to the main earthing conductor, the phase lead to the phase conductor of the incoming supply and the neutral lead to the neutral of the incoming supply and perform a test , ● Reconnect the main earthing conductor , ● Re-instate the supply , ● Zs Test Procedure , ● The Zs value must be measured at the furthest point on each circuit , ● Direct measurement of Zs can only be made on a live installation. The main earth and bonding earth and conductors are not disconnected. At the furthest point on the circuit from the ccu perform an earth fault loop impedance test. The reading given by the loop impedance tester will usually be less than Ze + ( R1+R2 ) because of parallel earth return paths provided by any bonded extraneous conductive parts ,

IT ,
This is for the Cowboy ← that put Singles Cables Plastered in the Wall tapped off a Spur on Ring
For Computers , I feel public is just not aware of the difference of a professional Electrician and a Cowboy still Money ,
Ps , he left his horse tied up in the garden , where’s John Wane

Mr Cowboys if you can READ this , you can put other people at Danger ,

543.7
● Earthing requirements’ for the Installation of equipment having High Protective Conductor currents ,

● Leakage current is approx 2-3 mA Per Computer , if to many computers are installed on One Ring “
Or Radial “ circuit – Protected by RCD , then the RCD may disconnect due to the Aggravate of the
Leakage currents Exceeding the rating of the Ring of the RCD ,
If this is the case – Less Computers on each circuit should be considered
● Clean Supplies ,
Computer supplies to Computer and other IT equipment must be “ Clean “ and Secure ,
● Clean Supplies can be provided by installing Ring or Radial circuit from as close to
The Main intake of the CCU as possible ,
● If you are using a SWA at all use 3 – core
● A clean Earth will be a Copper-core of an Armoured cable rather than using Armour itself ,
Copper cable has a Lower Resistance than Steel of the size ,

● An alternative to this is the use of “ Special Mains Filters “ for IT circuits ,
● Clean Supply – not subject to “ Interference “ on the mains supply secure , -
Not likely to “ Trip Out , unexpectedly or be turned off by Accident ,
● run a 10.0mm2 single with your 2.5mm2 Use a bigger Earth on Domestic ,
IT , 16A , 2.5mm2 – 10.0mm2 earth
Most people are turning one room to there Office ,
543.7.1.3 Equipment having a protective conductor current exceeding 10mA ,
If you have 10mA , you do Not Spur off a Ring if more that 10mA

 

[samjustus88]

when conducting insulation resistance tests on new household electrical appliances to BS 3456 Class 1 insulation,the minimum value would be

 

[samjustus88]

if a standard 13a plug become overheated the most likely cause would be

 

[amberleaf]

[h=1]Samjustus88 . They have a section in the forum for CoP . Q/As . [/h][h=1]Useful information[/h][h=1]Page 1 : Q & As arethere . 2009 . [/h]when conductinginsulation resistance tests on new household electrical appliances to BS 3456Class 1 insulation, the minimum value would be


( 8 ) Whencarrying out an insulation resistance test on a Class I household portableappliance to BS 3456 using the earth leakage method , the maximum acceptablevalue is ,
A – 0.5mA B – 0.75mA C – 0.1mA D – 1.25mA

23 - If a standard13 A plug became overheated the probability is that :
A – There is a loose connection at one of the terminals ,
B – There are poor earthing connection ,
C – An incorrectly rated cartridge fuse is being used ,
D – Reversed polarity of the phase and earth conductors has occurred ,

Sub-Forums: PAT Testing 2009/10

 

[morph]

Sample Questions – C&G 2392-10 Paper 1 Books out Boys & Girls !!!!

( 1) On completion of a new installation , the Electrical Installation Certificate would “ NOT “ be signed by the ,
A – Design Engineer ,
B – Client ,
C – Person who constructed the installation ,
D – inspection and testing engineer ,

( 2 ) Before inspection the condition of electrical equipment installed in a New unoccupied building ,
The inspector should ,
A – Ask the builders if they are aware of any faults , ( ps bloody foreigners would )
B – Disconnect all fluorescent luminaires ,
B – Test run the equipment to ascertain its condition ,
D – Check for components that may be susceptible to damage during testing ,

( 3 ) Any addition to an existing installation should ,
A – Have a similar wiring system to used in the existing installation ,
B – Be inspected & tested separate from the existing installation ,
C – Not impair the safety of the existing installation ,
D – Have its own energy meter separate from that of the existing installation ,

( 4 ) Which of the following duties is “ not “ the responsibility of the inspector ,
A – To carry out maintenance and repairs on the installation ,
B – To compare the test results with the design criteria ,
C – To advise on remedial works ,
D – To recommend the immediate isolation of defective parts ,

( 5 ) Records of inspections and test results should be kept during the life of an installation , this will enable ,
A – Identification of defective parts ,
B – Deterioration to be identified ,
C – Landlords to carry out repairs ,
D – Correct selection of equipment ,

( 6 ) According to BS 7671 , no additions or alterations should be made to an existing installation unless ,
A – The completion certificate can be produced for the existing installation ,
B – A Minor Works Certificate can be produced ,
C – The permission of the supply company has be obtained ,
D – The existing installation conforms to current Regulations ,

( 7 ) Which of the following is not a requirement of the inspection check list ,
A – Availability of customer user instructions ,
B – Presence of a BS mark or other suitable certification ,
C – Correct selection of cable and protection devices ,
D – No visible damage ,

( 8 ) Inspection of fully enclosed domestic consumer unit would not need verification for ,
A – Identification of conductors ,
B – Rating and type of protective devices ,
C – IP rating ,
D – Correct connection of single – poles devices ,

( 9 ) When inspecting for adequate protection against direct contact which of the following
Does not require inspection , Presence and condition of ,
A – Insulation ,
B – Enclosures’ ,
C – Barriers ,
D – Connection of cpcs ,

( 10 ) A visual inspection of a new installation must be carried out ,
A – After completion of the installation ,
B – After testing ,
C – After erection and before testing ,
D – During erection and before testing ,

( 11 ) Which one of the following tests can only be carried out after the supply is connected ,
A – Prospective fault current ,
B – Insulation resistance ,
C – Polarity ,
D – Continuity of protective conductors ,

( 12 ) Which one of the following procedures would be correct , if permission to disconnect information technology
Equipment has not been received ,
A – Apply insulation an earth continuity test only ,
B – Disconnect equipment momentarily and apply tests ,
C – Do not apply to any tests ,
D – Apply rcd test only ,

( 13 ) The test voltage that should be applied when testing the insulation resistance of a domestic ring circuit is ,
A – 500v dc B – 500v ac C – 250v dc D – 250v ac

( 14 ) Which of the following is the most suitable instrument to conduct a polarity test ,
A – A high resistance ohmmeter ,
B – A bell set ,
C – An insulation resistance tester ,
D – A low resistance ohmmeter ,

( 15 ) A continuity test at each socket-outlet of a ring circuit is carried out to make sure that ,
A – All readings are within the maximum Ze values required ,
B – No multiple loop exist ,
C – All conductors are correctly insulated ,
D – The polarity of all the sockets is correct ,

( 16 ) The following tests are to be carried out on a circuit : 1 polarity : 2 , continuity of protective conductors : 3 , Earth fault loop impedance : 4 , insulation resistance , which of the following is correct sequence in Which the tests should be carried out ,
A – 1,2,3,4, B – 1,3,2,4, C – 2,4,1,3, D – 4,2,1,3,

( 17 ) When carrying out an insulation resistance test between conductors on a one-way lighting circuit , have the ,
A – Switch closed and lamp out ,
B – Switch open and lamp in ,
C – Switch open and lamp out ,
D – Switch closed and lamp in ,

( 18 ) The insulation resistance of two circuits is of 40MΩ an 36MΩ respectively , when tested together what would be approximately the total insulation resistance ,
A – 1440MΩ B – 76MΩ C – 19MΩ D – 4MΩ

( 19 ) The outer contact of a centre-contact ( ES ) lampholder , must be connected to the ,
A – Phase conductor B – Neutral conductor , C – Switch wire , D – Earth conductor

( 20 ) A 30mA rcd is used to provide supplementary protection against electric shock , when tested with a current of 150mA , the operating time should not exceed ,
A – 40mS B – 200mS C – 0.4s D – 5.0s

( 21 ) Where electrical accessories have neon indicator lamps inaccurate readings can occur when tests are carried out to determine the resistance between ,
A – Insulation between phase & neutral conductors ,
B – Phase & cpcs ,
C – Neutral & earth conductors’ ,
D – Live conductors’ & earth ,

( 22 ) A legible diagram , chart or table relating to an installation must be provided to indicate ,
A – Any equipment vulnerable to a test ,
B – The location of all socket-outlets ,
C – The expected life of the installation ,
D – Any modifications made to the installation ,

( 23 ) An insulation test carried out on insulated cables should be in the range ,
A – milliΩ B – micro Ω C – ohms D – megohms

( 24 ) The maximum earth loop impedance to BS 7671 : 2008 for a circuit protected by a 32A type C mcb with a disconnection time of 0.4 sec is ,
A – 1.44Ω B – 0.72Ω C – 0.36Ω D – 1.04Ω

( 25 )When carrying out a prospective short circuit fault current test on a three phase system the approximate fault current between phases should be ,
A – Equal to the fault current between one phase and neutral
B - Equal to the fault current between two phase and neutral
C - Equal to the fault current between one phase and earth ,
D – Double the fault current between one phase and neutral ,

( 26 ) Which of the following tests would be carried out on a “ dead “ circuit ,
A – Earth fault loop impedance ,
B – Prospective fault current ,
C – Rcd functional testing ,
D – Continuity of ring circuit conductors ,

( 27 ) The maximum disconnection time allowed for a TN system with a nominal voltage of ,
A – 0.2 sec , B – 0.4 sec , C – 1 sec , D – 5 sec ,

( 28 ) A insulation resistance test is carried out on a three-phase 400V circuit , the minimum acceptable reading and test voltage should be ,
A – 0.5MΩ and 250v dc , B – 0.5MΩ and 500v dc , C – 1.0MΩ and 500v dc , D – 2.0MΩ and 500v dc ,

( 29 ) What is the maximum earth fault loop impedance allowed when using a 20A type C breaker giving a disconnection time of 5 sec, the nominal voltage to earth ( Uo ) is 55v : ↔ regs 41.6
A – 0.55Ω B – 0.22Ω C – 0.28Ω D – 0.14Ω

( 30 ) The commissioning process takes place ,
A – If a fault is reported ,
B – When requested by the client ,
C – After an installation has been inspected and tested ,
D – Before an installation is inspected and tested ,

1 – ( B ) 2 – ( D ) 3 – ( C ) 4 – ( A ) 5 – ( B ) 6 – ( D ) 7 – ( A ) 8 – ( C ) 9 – ( D ) 10 – ( D ) 11 – ( A ) 12 – ( C ) 13 – ( A )
14 – ( D ) 15 – ( B ) 16 – ( C ) 17 – ( A ) 18 – ( C ) 19 – ( B ) 20 – ( A ) 21 – ( A ) 22 – ( A ) 23 – ( D ) 24 – ( B ) 25 – ( D )
26 – ( D ) 27 – ( B ) 28 – ( C ) 29 – ( C ) 30 – ( C )

question 27 is pony.. does not state type of circuit

 

[amberleaf]

CoP: 3[SUP]rd[/SUP]

-&-s. Test probes& Leads . “ Important“ p/45.

-&-s. The product standard for test probes &leads is [ BS-EN-61010-031 ]

-&-s. Test probes & leads for use in conjunctionwith a . Voltmeter . Multimeter . Electricians test lamp : Voltage indicator .
In addition to the requirements of [ BS-EN-61010-031 ] Safety requirements for electrical equipmentfor measurements . control . &laboratory use . test probes & leads should comply with the recommendations given in HSE . GN-38

Testinstruments :

Alltest instruments should be safe . the current safety standard is BS-EN-61010 : Safetyrequirements for electrical equipment for measuring . control . &laboratory use . All new equipment should comply with this . or an equivalentstandard . Equipment pre-dating this standard is not necessarily unsafe .

 

[Deleted member 26818]

question 27 is pony.. does not state type of circuit

Doesn't need to. In fact the question doesn't even need to qualify the earthing system, technically, the answer is the same in all cases.
Now question 6, that's pony.
According to that answer, you would not be able to bring an installation up to the current Regulations, unless it already comformed.

 

[amberleaf]

Classes of Equipment .

CoP :
17[SUP]th[/SUP] Edition .

Definitions : p/25 Class 1 :Class 11 : Class 111 :

p/287 : BS-EN-61140 : 2002 . Protection against electric shock .Common aspects for installation & equipment . Part . 2

Class 1 . equipment . Equipment in which protection againstelectric shock does not rely on “ Basic Insulation Only “ but which includes means for the connection of exposed-conductive-partsto a protective conductor in the fixed wiring of the installation – BS-EN-61140 .

The safety earthing terminal of a Class 1 equipment . which is connected to the exposed-conductive-parts . is normally indicated by the symbol .

Safety earthing terminal of Class 1 equipment .



Symbol for safety earthing terminal

Exposed-conductive-parts . must be connected to the ( MET) of the electrical installation be means of the . circuit protective conductor. of the circuit supplying equipment . BS-7671:2011 Section – 411 .

In . addition it is essential that within the installationthere is . co-ordination between the characteristics of the relevant protectivedevice which affords fault protection & the Earth Fault LoopImpedance ( Ze ) of the circuit .

 

[amberleaf]

Classes of Equipment .

Class II1 . Equipment. p/25
In which protection against shock relies on . supply at (SELV ) & in which voltages higher than those higher than of ( SELV ) arenot generated – BS-EN-61140 .

Construction forClass 111 equipment are less stringentthan for Classes 1 . & 11 . as protection against electric shock isprovided by a reduction in . supply voltage to . Extra-low . & by a high degree of separation fromhigher voltage circuits from Earth .

If Class 111 equipment is fitted with a flexible cord & a plug for connection tothe ( SELV ) supply source . the plugmust not be [ dimensionally ] compatiblewith those used for any other system in the same premises . & must not havea protective conductor contact - Regulation 414.4.3. refers .

CoP :
Class 111 equipment should bear the construction mark . & safety transformer symbol .

 

[samjustus88]

when conducting a formal visual inspection on equipment used outdoor,it is important that the equipment has a suitable