***Cont../ Useful Information for Electricians & Apprentices***

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RCD– is the Generic Term applied . :20:

RCCB:- Residual Current Breaker .
RCBO:- Residual Current Breaker withOver-current protection .

An RCCB differs from an RCBO in thatthe RCBO will additionally respond to over-current conditions whereas the RCCBwill NOT respond to such conditions .

Apprentices : RCDs

The magnitude of thecurrent flowing to the Load will equal the magnitude ofthe current returning from the Load back to the supply .
Any difference in the current flowing to the Load &returning from the Load is known as a ( Residual Current ) – Dual / Two / Line & Neutral :svengo:

 

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Apprentices : RCDs

Values of Rated ResidualCurrent ( I∆n )

RCDs– can be provided with any value of Residual Current Operating Current ( I∆n ) .
10mA: 30mA : 100mA : 300mA : 500mA : ↔ 704.4.1.1.3.2.1. :20:

30mA : isthe maximum value permissible for additional protection & 300mAis the maximum value permissible for fire protection.
Non-standard values may be Used . BUT the Additional Protection & Fire must NOT beexceeded . :svengo:

 

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Apprentices : RCDs :hurray:

OperatingTimes .

RCDsfall in to two categories in terms of the time taken to respond to & clearResidual Currents’ .

Regulation table - 3A . Appendix 3 – Informative . p/243

General Type :- These RCDs have no specified minimum responsetime but have specified maximum response times as follows .
I∆n ≤ 300mS ↔ Note:- BS-EN
I∆n ≤ 40mS

S Type :- These RCDs have no specifiedminimum response times but have specified maximum response times .
I∆n ≤ 130 – 500mS
5 . I∆n ≤ 50 – 150mS

Delayedresponse ( S – Type ) RCDs are commonly fitted Upstream of general type RCDsbut general type RCDs should never be fitted Upstream of Delayed Types .
The “ Term “ Upstream. refers to proximity to the origin of the Installation & “ Downstream “ refersto proximity to the Load .

 

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Apprentices : RCDs :bulb2:

Maycomprise One or Two poles for use on Single-phase supplies . ( Two currentpaths ) . Three-poles for use on Three-phase supplies . ( Three-current paths ) or
Four-polesfor use on Three-phase & Neutral supplies( Four-current paths )

 

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Inspection& Testing of an installation should be completed by . A competent person

ByDefinition . RCDs :17:

A.C.current comprises of Positive & Negative half cycles with respect to a Zero reference point . & an A.C. fault current canstart to flow to Earth at any point during either half cycle . An A.C. type RCDwill only trip in response to either the Positive &Negative half cycles of the A.C. Earth faultcurrent .
Whereasas ( A ) type RCDwill respond to both half cycles . As the A.C. type RCD is Blind to either the Positive & Negative halfcycles of the A.C. fault current .
Thefault current could flow for up to 10mS before the RCD will see the faultcurrent .

This10mS will be added to the response time of the device .
RCDtesters are usually provided with a button to enable the user to start the flowof the test current at ( 0 degrees / 180degrees ) starting on a Positive goingor a Negative going half cycle respectively .

Bystarting the testing of the RCD at both settings of the test current conductionangle . The user will be able to determine the maximum trip time of the RCD .
Thiscan be done at different test current levels .

 

[shill]

Thank you for all the easy to read info... you made it easy to follow, thank you

 

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Calculationof Earth Fault Loop Impedance :speechless:

The most commonly used measure . Automatic Disconnectionof supply either the Overcurrent protective devices - Which also provideprotection against “ Overload &Short circuit Currents for the circuit Concerned .

ResidualCurrent Devices . RCDs or combined devices RCBOs . Whichever type of device ischosen .

TheEarth Loop Impedance that has to be considered is that which comprises the Impedance of the Source .
TheLine conductor up to the Fault plus the Protective Conductor from the fault to the Source .

Whys& How’s .

Note:- That when an RCD or RCBO is used to provide Automatic Disconnection of thesupply in a ( TN- system ) the calculation of ( Zs ) is normally “ Unnecessary “ provided that “ Continuity“ of the EarthLoop has been Established . ◄◄

Anotherreason for calculating the Earth Loop Impedance is to check that the “ Circuit Protective conductors are adequatelyprotected thermally . & That they comply with the “ Adiabatic Equation givenin Regulation . 543.1.3. – Subject ofChapter 4 .

 

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BS-7671:2008– Bottom of . Table 41.3 – NOTE.

ContainsNO requirements in relation to the Conductor Temperatureat which the Earth Loop Impedance iscalculated .
Note :- The notes to the tables of Maximum Earth FaultLoop Impedance . – Table 41.2. – to 41.4. . States . that the Tabulated Valuesshould NOT be exceeded when the conductors’ are at their Normal Operating Temperature.

ifthe conductors’ are at a different temperature when tested . The reading should be Adjusted Accordingly – Appendix 14.

 

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Current – Carrying Capacity . ofa Conductor . :speechless:

TheMaximum Current which can be carried by aconductor under Specified Conditions without itssteady state temperature exceeding a specified value.

 

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Apprentices.

Namethree types of “ Diagram “used in the Electrical Industry . & explain – ThereUse . :icon_bs:

Anythree from Wiring diagram . Circuit diagram . Block diagram . Layout drawing .Installation drawing . Schematic drawing . Site plan .

A wiringdiagram provides a pictorial representation of an Electrical Circuit . showing arepresentation of the components .
A blockdiagram typically shows the flow of aprocess . each function being represented by a block .
A schematicdiagram uses symbols to show the arrangement of a system clearly .
Whereasa layout diagram shows the physical arrangement of the wires & components .

 

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:45:2392-10: ▼
Q) The main switch in a “ Single – Phase “ domestic Installation interrupt’s how many “ Live Conductors “

-&-s: BS-7671 – Regulation 537.1.4. The main switch should interrupt both LiveConductors on a Single/Phase Supply .

A MainSwitch intended for operation by “ Ordinary Person“ of a Household or similar Installation . shall Interruptboth Live Conductors of a Single-phase supply .

Q) How many poles would the main switch on aThree-phase & Neutral – TN-S supply have .

Threepoles - BS-7671 – Regulation 537.1.2. The Neutral neednot be Switched . ( TN-S or TN-C-S )

2392-10: ▼

Q) State: Two precautions that must be takenbefore carrying out Insulation Résistance Testing .

i) Remove sensitive equipment – Dimmers .Programmers . P.I.R.
ii) Remove equipment that “ GIVES “ falsereadings – Lamps . Neon’s . Motors .
iii)Check it is Safe to continue with the Test . When applying – 250 / 500V .

-&-s: Make sureNo-one else is in contact with any part of the Circuit .

 

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2392-10: ▼

Inrelation to Electrical Installations . :waving:

Whatis meant by Maximum Demand :- This is an Assessment of the current demand of an Installation.
Whatis meant by Discrimination :- The co-ordination ofprotective device(s) so that the device nearest to the load . being of a lowerrating . operates before the device futher up the line . Thereby minimisingloss of supply when a fault occurs .
Whatis meant by Diversity :- An allowance given when calculating maximum demand . due tothe fact that not all of the appliances . will be Used at the Same Time .

 

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2392-10:

FunctionalTesting ?? :waving:

Testing of Switches . Disconnections. Controls . RCDs . to check that they FunctionCorrectly .

 

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2392-10:

ApprovedVoltage Tester . To - GN-38 . :waving:
State:- Three of the requirements for Test Leads .
i) Retractable tips . or not more than ( 4mm) prefer 2mm . Fingers guards . Robustleads . coloured or identified . long enough for the purpose . Fused probes .

State:- the method of Ensuring it is working Effectively .
ii) By the use of an Approved Proving Unit .Testing the voltage tester . Before & After testing the equipment . or Circuit .

 

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Definitions’/ p/23 . EarthingConductor

A protectiveconductor connecting the main Earthing Terminal of an Installation to an EarthElectrode or to other means of Earthing .

Connectsthe main Earthing Terminal to the source of Earth . either an Electrode ( TT ) or means ( TN-S or TN-C-S ) :95:

 

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2392-10: ( T )

Howis Discrimination achieved when Using RCDs . :- Byusing Time-delayed RCDs . :79:

 

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Insight to the working of 17[SUP]TH[/SUP] Edition . “ Examples “

BS-7671:2008. Section 708 – Caravan & Camping Parks .

Thisis accommodated by the provision of suitably placed socket outlets . supplied via distribution circuits .

External Influences .
Equipmentshould have at least the following protection codes .
Impactrésistance . 708.512.2.
IPX4– for the presence of Splashes – ( AD4 ) in accordance with BS-EN 60529.
IP3X– for presence of small objects - ( AE2 ) in accordance with BS-EN 60529.
IK08- for presence of high severity mechanical stress ( AG3) in accordance with BS-EN 62262 .
(The ( IK ) codes are for Impact & ( 0.8 ) is an Impact of ( 5-Joules ) ImpactRésistance .
( Environment – p/324 . AG3 – High Severity . Reinforced Protection . IK08 )

British Standards to whichReference is made in the Regulations . Appendix1 – “ Normative “ p/228 – ( Requirement )

BS-EN 62262:1992 . – 2004 . Specification for degrees’ ofprotection provided by enclosures ( IP Code )
527.2.6.– (i) the system satisfies the test of BS-EN 62262 for ( IP33 )
527.2.6.– (ii) any termination of the system in one of the compartments , separated bythe building construction being penetrated . satisfies the test of BS-EN 62262for ( IP33 )
702.512.2.: External Influences . Electrical equipment shall have at least the following degree of protection according to BS-EN 62262. ( IP ???? )
708.512.2.- (i) & (ii)
708.553.1.8.each socket-outlet & its enclosure forming part of a caravan pitch electricalsupply equipment shall comply with ( BS-EN 60309-2 ) & meet the degree of protection of at least( IP44 ) accordance with BS-EN 60529 .
A721.55.6.- p/218. Terminal blocks .
A721.55.10.- p/218. External lights .

Note : Section 721 : tells us . p/209 – Wording . Yeah :96:
Inorder not to ►► MIX ◄◄ Regulationson different Subjects such as those for Electrical Installation ofcaravan parks with those for Electrical InstallationINSIDE caravans .
Section– 708 . concerns Electrical Installations ( IN ) caravanparks . camping parks & similar locations & . Outside.
Section– 721 . concerns Electrical Installations ( IN ) caravans& motor caravans . Inside

WiringSystems .
Thedistribution circuits are erected either Underground or Overhead .
708.521.1.1.- i) Underground cable ( Preferred )should be suitably protected against Mechanical damage . tent pegs . steelspikes . & at a depth of NO less than ( 0.6m )
708.521.1.2.- ii) Overhead . if overhead . Then ( 6m) above ground where there is Vehicle movement ( 3.5m ) elsewhere .

Switchgear& Socket outlets .
708.530.3.- Supply equipment should be adjacent to . or within ( 20m ) of the pitch .
708.553.1.8.– Socket-outlets should be :- BS-EN 60309-2– ( IP44 )
708.553.1.9.- at between ( 0.5m to 1.5m ) aboveground .
708.553.1.10.- rated not less than ( 16A )
708.553.1.13.– each socket-outlet shall be protected individual by an ( 30mA ) RCD protection. ( The device shall disconnect all LIVE CONDUCTORS including the NEUTRAL.
708.553.1.14.– if the supply is ( TN-C-S ) the protective conductor of each socket-outletneeds to be connected to an ( Earth Rod ) Regulation – 411.5. TT System .

 

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AdditionalProtection . :hurray:

703.411.3.3.Sauna heater .
Allcircuits in the location should have “ Additional Protection “ against shock by30mA RCD .
Except Sauna heater circuits unless Recommended by the Manufacturer . :svengo:

 

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External :- Earth Fault Impedance . ( Ze )

The Importance of this Test . To establish that a good Earthexists at the installation in order for the Remainingtests to go ahead . :svengo:

 

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Additions & Alterations to anInstallation . :waving:

General :

Many existing electrical installations require one or moreAdditions or Alterations during their lifetime . An Addition or Alteration maybe minor ( such as the Addition of a point to a final circuit . or therepositioning of a point ) or major ( such as the Addition of a new finalcircuits . distribution circuits . distribution boards & an upgrade to thesupply .

Where an Addition or Alteration ( which temporary or permanent) is to be made to an installation . the relevant requirements of BS-7671 .have to be met such that both the Addition or Alteration is Safe . & thesafety of the Existing Installation is not Impaired.

In order to be meet the requirements of BS-7671 . Followingmust be undertaken .

• Assessment ofthe existing installation to establish that the parts upon which the Additionor Alteration will rely for safety are both present & suitable for thealtered circumstances . & will continue to be so . & that the supply issuitable .
• Upgrading of parts of the existing installation . where foundnecessary to safely accommodate the Addition or Alteration . as a result of theabove Assessment .
The electricity distributor will need to upgrade thesupply . if Necessary .
• Design & construction of the Addition or Alteration inaccordance with the requirements of BS-7671 .
(T) • Inspection &Testing of any upgrading of the existing installation . & of the Addition or Alteration . as requiredby chapter 63 of BS-7671:2008
• Certification of any upgrading of the existing installation . & of the Addition or Alteration . as requiredby chapter 63 of BS-7671:2008

Assessment of an Existing Installation .
Regulation ( 131.8.) requires an Assessmentto be made of the relevant parts of an existing installation which is tobe Added to or Altered of the Supply .

Regulation ( 131.8.) No Addition orAlteration . temporaryor permanent shall be made to an existing installation . unless it has been ascertained thatthe rating & the condition of any existing equipment . including that ofthe distributor . will be Adequate for the Altered circumstances . furthermore . The Earthing & Bonding arrangements . if necessary for theprotective measured applied for the safety of the Addition or Alteration . shall beAdequate .