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Unusual voltage measurements

vantech

Hi, 

Just moved into a new build and have 2 questions which have me scratching my head. 

The electrician has used through crimps (so he says on the phone), to join a 25mm armoured and meter tails in a metal junction box. He stated this was inside of the meter cupboard on the outside wall, but it isn‘t. I think this is OK as a setup, however the builder has whacked the joint into the cavity of the wall behind the built in meter cupboard so it isn’t accessible - this of course isn’t acceptable. 

The second finding is that, if the main switch in the DB is turned off, I can measure 230V between L&N and L&E (as expected, PME system) on the input side of the isolator. 

What i am unsure of, is that a measurement between the live side of the isolator and the Neutral (output side of the isolator), shows a voltage of 230V. This neutral output, should be isolated by the main switch. My thought is that perhaps voltage is flowing back to earth through electronic devices that naturally leak to earth?  

The isolator is absolutely working as it should, so no issues there. The voltage must be running back somewhere else . 

I haven’t seen this before, so before I call the original installer i wanted to raise it here first. 

Thanks. 

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  • 0

    Maybe they won’t guarantee it this I appreciate. 

    I suspect that's more of the issue. A generation ago most houses had 60A fuses - after which 100A and 80A got more common. What's likely to happen in the lifetime of current services? An even bigger upgrade (to cope with EVs and heat pumps) or perhaps a change from fuses to some kind of circuit breaker (like they usually have in France) - which may or may not have the same Zs requirement as the original HBC fuse. I guess the DNOs have enough foresight not to want to be in the position of having to ensure that things will still be safe if they're faced with an unknown length of an unknown type of cable with an unknown Zs at the end of it. 

       - Andy.

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  • 0

    Maybe they won’t guarantee it this I appreciate. 

    I suspect that's more of the issue. A generation ago most houses had 60A fuses - after which 100A and 80A got more common. What's likely to happen in the lifetime of current services? An even bigger upgrade (to cope with EVs and heat pumps) or perhaps a change from fuses to some kind of circuit breaker (like they usually have in France) - which may or may not have the same Zs requirement as the original HBC fuse. I guess the DNOs have enough foresight not to want to be in the position of having to ensure that things will still be safe if they're faced with an unknown length of an unknown type of cable with an unknown Zs at the end of it. 

       - Andy.

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