Figure 3 CIRCUIT DETAILS Wiring details No. Circuit description No. of points


Type (see code below) Ref. method


1 2


3 4 5


Type 2 SPD Shower


Ring final circuit - Kitchen


Central Heating Upstairs lighting Spare


NA 1


9 1 5 NA


providing the circuit details and test results for the final circuit.


SPD status indication In most SPDs, a visual indicator window is typically incorporated and would either normally be transparent or show a green status indication when initially installed. Where the indication is red, this means that either the device has operated or that it is defective and requires to be replaced.


Some SPD manufacturers also may


provide for remote status indicating facilities, such as connections for an audible alarm. A check should be made on each SPD installed that the status indicator is showing correctly for normal operation and as per the manufacturer’s information. This should then be recorded, and the


NA A


A


A A


NA


NA 101


101


101 101 NA


NA 10


2.5


1.5 1.5


NA


‘Remarks’ column is again the most appropriate place for this.


SPDs and testing As mentioned earlier, there is no specific test that can be performed to verify SPDs are operating correctly. However, with regard to testing, where they are present, care should be taken when conducting insulation resistance testing. If carried out at 500V DC with an SPD connected, the SPD will operate and conduct what it sees as a surge current to earth as the value of its continuous operating voltage will have been exceeded. Regulation 643.3.2 allows for this and advises that where the SPD is likely to influence the test result and where it is not reasonable to disconnect the device a test can be conducted with the SPD connected but using a reduced test voltage of 250V DC.


TEST RESULTS


Insulation resistance (Lowest values measured)


MΩ L-L 299+ L-E 299+ ( ) 0.45 RCD protection Z3 Polarity (Max


measured values)


Ω 30 I ∞ mA


(500% test for RCDs rated at 30 mA or less only)


Time (ms) 100% 300 40 CABLEtalk AUGUST/SEPTEMBER 2021 39 500%


Functional tests of


switch gear etc.


( ) Remarks


Indicate points of note e.g.: ● Additional outlets or equipment supplied ● Provision of AFDD for circuit ● Reduce IR test voltage


SPD protection not provided


Conductor csa mm2


Live


NA 4


1.5


1 1


NA Te future


This information should hopefully be useful in raising awareness of what to check and where to record relevant information regarding overvoltage protection. However, it should be noted that work is currently progressing on Amendment 2 to BS 7671:2018 and this is likely to include a review of the requirements given in Chapter 42, as well as the model forms given in Appendix 6. The requirements for overvoltage protection in Chapter 42 may be altered and include the recording of information relating to SPDs within the model forms provided in Appendix 6. This is something that those responsible for verifying compliance of electrical installations should be mindful of in the future.


cpc


1361 B


B


B B


NA


100 40


32


6 6


NA


Protective device (Lowest breaking capacity = 6kA)


Type Amps


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