The only thing I've been able to imagine so far is some deliberate impedance in R2 - perhaps some misguided attempt to avoid problems with earth loops with audio or radio equipment - and then still attempting to claim compliance with BS 7671. (A bit like IT systems, but with the impedance within the consumer's installation, rather than at the star point). It does seem a bit odd that the regs treat TN differently to TT but then (theoretically at least) allow similar loop impedances.

- Andy.

Given 411.4.2 (2nd paragraph) I think it unlikely that any circuit would comply with an impedance that high, or even as high as allowed by 41.5.

IMO this regulation is not at all useful - even after the proposed modifications in the DPC.

Regards

Geoff Blackwell

If your R1 + R2 are ok, and Ze, the the difference is between your ccts and the tails, this would be you consumer unit. Try checking the obviouse, tightening the manufactured terminals, you could also give them a ring.