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Can Zs at DB ever be less than the Zs of the feeding circuit?

Former Community Member
Former Community Member
I am reviewing an EICR recently issued for a building with several Distribution Boards feeding sub-Distribution Boards.

I have noted that in some instances, the figure recorded for 'Zs at this board' is significantly less than the Maximum Measured Zs for the circuit recorded on the feeding DB.

e.g. DB FF4 is recorded as being fed from DB FF1.  The feeding circuit to DB FF4 is recorded as having a Maximum measured Zs of 0.4 Ohm, but the 'Zs at this board' for FF4 is recorded as 0.05 Ohm - which is less than the 'Zs at this board' recorded for FF1 (0.08 Ohm) - and which, is in fact, in turn itself less than the 'Maximum measured Zs' for the circuit feeding it.  Can this be true or are there errors in the report?  I thought that cascaded Zs can only get larger due to the added impedance of the feeding circuits? This is not my primary area of expertise, but I am concerned that the EICR is being used to justify the upgrade of several circuits which have passed previous inspections with no problem (hope the resolution of the extracts from the EICR below are sufficient resolution to read)...

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Many thanks if anyone is able to confirm my concerns or otherwise put me straight...
Parents
  • 0
    Do not worry UKPN, the chances of being served with an N20 due to comments made on here are very slim - perhaps more likely if we were witnesses of fact - that is to say we had accompanied the chap on his  apparently ill fated inspection visit. As it is we are commenting only on information presented. A written deposition in a civil case at most.

    But I agree - in general in a case like this the redaction needs to be good, as we need to discuss matters 'in principle'. If a case like this arose this is the opinion.
Reply
  • 0
    Do not worry UKPN, the chances of being served with an N20 due to comments made on here are very slim - perhaps more likely if we were witnesses of fact - that is to say we had accompanied the chap on his  apparently ill fated inspection visit. As it is we are commenting only on information presented. A written deposition in a civil case at most.

    But I agree - in general in a case like this the redaction needs to be good, as we need to discuss matters 'in principle'. If a case like this arose this is the opinion.
Children
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