Too bond or Not too bond

[wmb1973]

Hi guys,

Just after opinions if you bond in 10mm to M.E.T. (same as gas/water) an external oil line. Said oil line goes from oil tank, under ground and then up into external boiler ? Flow/Return and cold feed come from inside the property.

Cheers.

 

[Deleted member 9648]

Main bond metallic pipework coming in from outside only....so flow/return/cold feed bonded as close as possible to the point of entry...If the oil line doesnt come inside dont bond it.

 

[wmb1973]

What about if we get a fault to earth on the boiler, surely the oil line would become live if not bonded ?

 

[Deleted member 9648]

THe reason for main bonding is to ensure there can be no potential difference between conductive parts of the installation connected to the earthing system,and metallic services entering the equipotential zone which introduce an earth potential from outside. It's got nothing to do with preventing pipework from becoming live. Thats taken care of by the protective device which should disconnect an earth fault within 0.4 seconds . Outside of the equipotential zone you are surrounded by lots of different earth potentials so i'ts pointless bonding anything.

 

[sparks1234]

Also as a note on this. I had an NIC assessment yesterday and we had a discussion about bonding.
the property we wer in was a block of old peoples flats, each had its own PME supply, its own stopcock but was on a shared heating system. The pipes coming into that property should be bonded to that MET as it should be in each of the other flats.

 

[Deleted member 9648]

They are a metallic service likely to introduce an earth potential coming into an equipotential zone...each flat is a separate equipotential zone....so yes main bond in each flat.