Bonding Boilers

[kasper]

BS7671 411.3.1.2 states various situations where main protective bonding is required. (iv) states; Central heating and air conditioning sytems. Does this mean that Boilers need to be bonded via 10mm back to the board? If not what does it mean? Is cross bonding of the pipes necessary, since they are all bonded via the metal connection plate to the boiler?

[akaboosi]

This regs book interpretation is different for everyone. Why can't they just write it in plain english.

I'm at college just now and am sure a lecturer says that he does cross bond boilers. My boss does it too.

I suppose it's incase a pipe may be disconnected from the boiler therefore would loose earth continuity.

[amooramin]

I belive no. The central heathing that needs bondig has to come from outside of building. If Boiler inside property has conecction to gas pipe and/or water pipe and those have bonding where entering property, there is no need for bonding to boiler.

[davron11]

no you dont need a main bond this goes to gas and water you need cross bonding across the pipes at boiler unless it is on an rcd circuit this is no longer needed

[Greg]

no you dont need a main bond this goes to gas and water you need cross bonding across the pipes at boiler unless it is on an rcd circuit this is no longer needed

Agreed, as long as the consumer unit is dual RCD protected or split load with RCBO's then you wont need to do your cross bonding.

[Central Scrutinizer]

Main protective bonding is applied to extraneous conductive paths - that is metallic paths not forming part of the electrical system liable to intruduce a potential, generally earth potential - so the systems being discussed are, for example aircondition/heating ducts which come in from outside

by 'cross bonding' i presume you are discussing supplementary bonding - well there has NEVER been a requirement in BS7671 (any edition) to my knowledge that has specifically required bonding (main or supplementary) at boiler pipes - it has nothing to do with RCD's. split load boards or the 17th edition

this is part of the same batch of old wives tales that saw kitchen sinks, radiators in kitchens, radiators in toilets/cloakrooms and any spare bit of copper pipe subjected to green/yelow cable

quite often, there would be no path to earth, however unknowing 'sparks' introduce them with their 'safety measure' of 'cross bonding' - a little knowledge can be dangerous!