Main Earth Bonding

[dolland]

I appear to have a 10mm Earth Cable running from the CU and clamped to the Incoming Water Pipe just above the stop cock. So far, so good. However, neither the gas supply or oil supply are earthed.

The copper gas pipe feeding the cooker and a gas fire enters through the backwall of the kitchen from outside and is fed by two 47kg cylinders standing on slabs three or four metres away. A 'T' routes a second copper pipe around two sides of the house externally above ground level (except for a short distance where it is buried to allow a patio door to open) to a second fire.

The oil supply feeds the gravity hot water/pumped central heating system through copper pipe which also enters the boiler from through the backwall of the kitchen from outside and is fed from a plastic tank standing on slabs also a few metres away. The pipework exits the tank and is immediately buried a few inches deep for about two metres until it reaches the outside wall of the house. The boiler is linked to the central heating system and has electronic ignition.

Could someone please confirm that the gas and oil supplies need main bonding, or are any other earthing arrangement required for bottled gas or oil supplied from the plastic tank. Also, if bonding is required, is it notifiable?

 

[RF Lighting]

Yes, they can introduce a potential from outside into your equipotential zone, so they must be main bonded to your main earthing terminal.

Installation / upgrading main bonding does not require notification to your LABC.

The usual rules for bonding apply. Within 600mm / before any tee's etc.

 

[dolland]

Thanks very much for the reply RF, I thought that would be the case.

I think I know what the answer will be for this next question, but could you/someone also confirm whether I MUST run the new main bonding cables direct from the earth block next to the CU, or can I somehow attach/splice the new cables on from the clamp at the water main. It will be a doddle to complete the bonding if this were possible, otherwise it will be extremely difficult and inconvenient to route a cable from CU to gas and oil pipes without clearing out rooms, ripping up laminate flooring and causing a lot of disruption.

 

[bongos]

could you/someone also confirm whether I MUST run the new main bonding cables direct from the earth block next to the CU, or can I somehow attach/splice the new cables on from the clamp at the water main

The protective earth bond has to be unbroken throughout.

If it is easier than running separate cable from each service back to the earth terminal, you could replace the existing cable with a longer piece which allows you to connect water/gas/oil together in one go then back to your earth terminal. You would need to remove a small section of insulation from the cable, where you would use a BS951 clamp to connect it to the incoming service and continue the cable onto the next service.

 

[rebuke]

I believe (but don't quote me on it - check the regs etc) you're allowed to crimp main earth bonding, so you could simply cut the current bit next to the water pipe, and crimp on a much longer bit that you then run through the water pipe and your other services as suggested in the previous post...

 

[RF Lighting]

Main bonding cables can be jointed if using a permanant joint. This is basically either by crimping or soldering.

I really don't like to see it, and if you can replace the existing cable then this is of course favorite, but as an absoloute last resort, sometimes needs must.

You need to ensure the bonding still has an overall resistance of less than 0.05 ohms end to end.

You must not break the bonding at any point, i.e. it needs to be looped round each clamp without beinbg cut.

 

[dolland]

I will see if the existing cable can be pulled back without too much friction through the joist space (only about 4 metres). If so, I will attach a new earth cable and pull that through with it. If no movement is possible, it looks like crimping or soldering an extension to the existing cable.

Thank you to RF Lighting, Bongos and Rebuke for your helpful and informative replies.

 

[BS3036]

You need to ensure the bonding still has an overall resistance of less than 0.05 ohms end to end.

Is this actually specified somewhere? I always wondered as I never came across any max length spec. in the red book.

 

[Spark123]

It is in GN3, iirc it is derived from the current required to disconnect a 100A BS1361 II within 5s and the 50V rule.

 

[BS3036]

It is in GN3, iirc it is derived from the current required to disconnect a 100A BS1361 II within 5s and the 50V rule.

Thanks for that.