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Do I need to do anything about single pole Isolator owned by DNO

Alan B

I was changing a consumer unit today on a property where there was an isolator supplied by the DNO (owned by _______ molded in to it) but it was only single pole. The supply was TNCS and the consumer unit has a double pole isolator. The property is about to be put on to the rental market.

My initial thought is that the double pole isolator switch in the CU provides the isolation function and its a TNCS supply with limited risk of dangerous voltages on the Neutral. Therefore the single pole isolator upstream of the CU isn't ideal but not immediately dangerous and I should just note it on the installation certificate.

Or should I be highlighting the problem to the owner and suggesting they contact their DNO to request a change and what is the likely response from the DNO?

Looking forward to your views and advice.

Thanks

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    Personally I'd argue on that basis we ought to permit split concetric to be routed like SWA in TN-x' settings, the regs disagree....

    Although in BS 7671 land the N might not be quite so reliably connected to Earth as a PEN - it could well be fed through a DP switch, a N switching RCBO or even a plug and socket - all of which are somewhat less reliable than a simple joint and even when working correctly might not offer any reassurance that N makes first and breaks last. Which then leaves the broken-PEN like problem of the N occasionally being at line voltage due to connected loads (perhaps a concern for insulation withstand for lightly covered N strands as well as from a shock perspective).

       - Andy.

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    Personally I'd argue on that basis we ought to permit split concetric to be routed like SWA in TN-x' settings, the regs disagree....

    Although in BS 7671 land the N might not be quite so reliably connected to Earth as a PEN - it could well be fed through a DP switch, a N switching RCBO or even a plug and socket - all of which are somewhat less reliable than a simple joint and even when working correctly might not offer any reassurance that N makes first and breaks last. Which then leaves the broken-PEN like problem of the N occasionally being at line voltage due to connected loads (perhaps a concern for insulation withstand for lightly covered N strands as well as from a shock perspective).

       - Andy.

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