1st fix earth bonding query Ask questions and find answers to many subjects relating to electrics and electrical work

[gifford4671]

It’s been a while since I did electrical work, 30yrs as I had a career change.
We are building an extension that will have a bathroom and kitchen. I have a question about earth bonding.

Lost on my head is the memory of running a 10mm earth cable from the distribution board Earth and connecting it to any exposed metal such as water, gas ect at the point of entry into the building. Is that still the case?

2nd - supplementary bonding for the kitchen/bathroom. Is that a seperate run of 10mm earth to the kitchen and connect to pipes and exposed metal and then continue to the bathroom and connect to exposed metal, pipes ect? The shower will be electric

Thanks for the advice in advance. I just need to know enough to do the first fix as my spark can’t be here for 4 weeks so trying to do what I can and then he can check it all

[ericmark]

All changed in 2008 with the 17th edition BS 7671:2008, The requirement for earth bonding was relaxed as long as you have RCD protection. The incoming services depend on material, clearly no need to bond a plastic water pipe, or gas.

However, where and how to bond metallic pipes has to consider under fault conditions how much current will flow, A TT supply is no problem, but a TN-C-S water pipes are by their very nature water cooled, and even if 200 amp in the case of a lost PEN should flow, there is unlikely to be a problem, and if you did melt a water pipe, well things will just get wet.

Gas however tends to burn, and also flexible gas pipes are unlikely to be able to handle 200 amps, so somewhere there should be an isolating part, so the house can be bonded, but should there be a loss of PEN there will not be a huge current through the gas pipe.

We do see reports of fires caused by copper theft, which has resulted in loss of PEN, and in turn gas pipe melting.

However, loss of PEN is rare. And in the main as electricians, we provide an earth wire for the gas installer to fit, we could use our loop impedance tester and see what the potential fault current would be. It is simply common sense.