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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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  • 0

    There was an IET video on YouTube filmed in a meter operative training school showing the dangers of thinking that because you have “isolated” an installation using a double pole switch or even by removing the tails it is safe.

    The last time I looked for the video I couldn’t find it, which is a shame because it was one of the best electrical training videos available on the internet.

  • 0 in reply to Sparkingchip

    It may also stem from the fact that many of our continental cousins do not really consider L-N  reversal to be a serious fault on single phase equipment, and so for them double pole disconnection for things like changing a light bulb is a useful thing. Less so here I think, but our regs are to a degree sychronised if we like it or not. (though not our distribution practices)

    However DP isolation  is also important if you wish to isolate faulty sections from an RCD protected part of an installation - RCBOs that break the neutral as well as the live (wylex crabtree etc) are a very useful improvement in this regard.

    I suggest the DP isolator has its merits, but I agree especially on PME set-ups the neutral is never far away from touch. 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....

    Mike.

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  • 0 in reply to Sparkingchip

    It may also stem from the fact that many of our continental cousins do not really consider L-N  reversal to be a serious fault on single phase equipment, and so for them double pole disconnection for things like changing a light bulb is a useful thing. Less so here I think, but our regs are to a degree sychronised if we like it or not. (though not our distribution practices)

    However DP isolation  is also important if you wish to isolate faulty sections from an RCD protected part of an installation - RCBOs that break the neutral as well as the live (wylex crabtree etc) are a very useful improvement in this regard.

    I suggest the DP isolator has its merits, but I agree especially on PME set-ups the neutral is never far away from touch. 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....

    Mike.

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