bonding a boiler

[ashm]

hello and thanks to all that answer,
i've asked the leccies about bonding requirements however can't seem to get an answer on whether a combi boiler needs bonding back to the MET, the gas and water supplies are all ready bonded to the MET at there stop cocks. all pipes at the boiler are cross bonded but do they need returning to the MET. thanks again.

 

[JohnD]

No.

 

[ChrisR]

Some leccies say they don't need to be cross bonded at all, at the boiler itself

 

[ashm]

okay,thanks for the replies.

 

[JohnD]

I've never found an Electrical regulation calling for bonding at a boiler (it isn't Main Bonding; and unless it's in a bathroom or special location, it doesn't need Supplementary Bonding). It may be in the Manufacturer's Instructions for the boiler.

However the Corgis like to see them cross bonded, so all the metal pipes (including the gas) bonded to the carcase of the boiler, and to the CPC of the supply, should give them protection against shocks when they have a pipe in each hand.

Since it isn't Main Bonding it doesn't go back to the MET.

 

[baxpoti]

Assuming you are working in a domestic dwelling with a TN-C-S supply

With ref to IEE publication

'Electrician Guide to the Building Regulations' and 'BS7671 reg 413-02-02 (iv)'

Along with water, gas and other service pipes. Central heating and air conditioning systems are required to connect to the main earthing terminal with main equipotential bonding conductors.

Definition of central heating?
I would take that to be the boiler.

So with 'Part P' all boilers should be bonded back to the main earthing terminal!
With copper gas and water pipes your central heating is already bonded to the main earthing terminal!

There is no requirement to supplementary bond pipes, unless the pipes are in a special location, a bathroom for example.

Contradiction? (memories of doing my 236). Post in electrics UK and see what the bright sparks there say.

 

[namsag]

Seemingly all bonding regs are changing this year and there will be no need to bond boilers, rads in bathrooms etc. Don`t know the full spec but mate has just done part P and they where told on that.

 

[croydoncorgi]

IMHO, the festoons of 'cross bonding' underneath wall-mounted boilers has ALWAYS been pretty-much a waste of time, considering that immediately above the earth clamps there's most likely a large chunk of sheet metal which electrically links all the pipes anyway, or solid metal/metal connections on the boiler itself, with thesame effect.

From other comments here, it appears this futility has at last been recognised.
BUT NOTE that this is NOT the same situation as with Supplementary Bonding requirements which may apply to boilers (although then I'd comment that in that case the boiler would be better soemwhere else!).

 

[Paul Barker]

I hold the view that the onsite guide is wrong on this matter, also corgi also manufacturers.

The way I understand the intent of 7671 2 2002 is central heating which introduces a potential from outside the equupotential zone should be main bonded.

I therefore only bond it as suplementary if in a location where that's requured and cage it to the cpc of the boiler feed.

I hope they have someone intelligent writing 17th edition.

 

[Agile]

If the gas pipe is bonded as it should be then if the boiler has a metal chassis and the system has copper pipes then I dont see any need to cross bond under the boiler.

If, however, the boiler is one with plastic insides like Glowworm and Saunier Duval, then I feel that for safety reasons the pipes MUST be bonded together.

I am not interested in what badly worded regulations may say, only what needs to be done for safety!

Tony

 

[Paul Barker]

I quite agree.

Bye the way just noticed an interesting line BES are doing to make boiler bonding a doddle. Look at Part No 17472 and the next parts to it. I'm going to order one.

Along with cooker hoses £4.65 plus vat or so, £19 in bnq 15p less in merchants.

Syncronos motors, I bought three this week from merchants at £13 plus vat, less than a fiver at bes.

Time to stick in another order.