Q & A of the Day – Is earth bonding required for this building that has lots of old pipes?

Question: I'm re-wiring an old listed building (Grade 2) that has old, disused and partly dismantled iron heating pipes throughout - which will remain. On the ground floor, sections of these are buried in concrete, although I believe that they remain within the footprint of the building. There are many old metal water pipes (about 300mm long) capped off in the cellar, which were probably originally intended for outside taps etc.

I intended to earth bond all of these as they bring an (earth) potential into the building, but owner says 'no'. I want to be certain of the requirements and will say 'no earthing - no installation' if necessary. So I need to confirm whether the bonding is absolutely required, or advisable, or indeed is not needed.

If I can prove the continuity of the heating pipes (would this have to be <0.05 ohms?), could I earth bond these at one point rather than each pipe as it emerges from the floor?

Answer: BS 7671: 2008 (17th Edition) states that all incoming services should be earth bonded at the point of entry back to the main earth terminal. All other heating pipework or bits of isolated pipework - if continuous - could be bonded at one location only and cross-bonded together.

You could also carry out a risk assessment for any pipework that cannot/is unlikely to become live under fault conditions. These may not need to be earth bonded at all.

To see many more Q & A in Voltimum UK's Experts Area, please click on the link:

www.voltimum.co.uk/consult.php?universe=consult.index.questions