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6mm bonding - new build and Type C RCBOs

vantech

Hi, 

I am in the process of buying a new house (new build), and of course checked out the electrical supply. 
 

The gas and water both have what looks like a 6mm bond on a supply clearly marked PME. I would expect that the gas and water are both plastic to the point of entry. 

I have also noticed that the consumer unit has a mixture of type B and type C MCBs. 
 

Kitchen ring = 32A C 

Down sockets 1 = 20A B 

Down sockets 2 = 20A C 

First sockets = 20A B

Down lights = C10 

Up lights = C10 

All RCBOs. 

I know there is nothing inherently wrong with type C in domestic, as long as the ZS is within limits, but I haven’t seen this done before.

Any suggestions or feedback? 

Obviously I haven’t been able to strip the system back and see how it’s been installed, quality etc, but the water/gas bond has thrown me a bit. The vendor said it’s been signed off by a contractor. The install does look very tidy. 
 

Thank you. 

 

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    So, how can the water affect the result?

    Clean water is a half decent insulator of course, but the water running around most central heating systems is far from clean - having either picked up a decent amount of metal oxide particles or is dosed with inhibitor (or both). Even with that a metre or two of plastic pipe will still likely provide at least many tens of k Ohms of resistance - but a much shorter length - say a push-fit aleration on otherwise copper pipework might not be enough to provide the requried 20-odd k Ohms.

        - Andy.

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  • 0

    So, how can the water affect the result?

    Clean water is a half decent insulator of course, but the water running around most central heating systems is far from clean - having either picked up a decent amount of metal oxide particles or is dosed with inhibitor (or both). Even with that a metre or two of plastic pipe will still likely provide at least many tens of k Ohms of resistance - but a much shorter length - say a push-fit aleration on otherwise copper pipework might not be enough to provide the requried 20-odd k Ohms.

        - Andy.

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