Electrical Bonding

[PaulSB]

During our annual boiler service the BG engineer gave me an advisory because there is no electrical bonding to the gas meter.

I was surprised by this as I was sure our house is bonded. A bit of rooting about quickly confirmed the earth bond is attached to the incoming water main.

Is this good enough or should the bond be to the gas meter?

It seems to me both the incoming gas and water supply would earth an electrical issue.

 

[Drago]

Is your incoming gas supply via a metal or plastic pipe?

If its the latter, no.

 

[PaulSB]

Is your incoming gas supply via a metal or plastic pipe?

If its the latter, no.

I will have to check. I get your point.

 

[Drago]

Aye, no great expertise on my part. I only know that bit because im im a new buid and all the incoming pipes are plastic. When the chap came to fit the electric car charge he was scratching his head over the total absence of bonding until he had a light bulb moment.

 

[Tenkaykev]

On a related note we have a home battery which switches over seamlessly if there’s a power cut. Because of this the installers hammered an earth rod several feet into the ground to act as an earthing point when there's no grid connection

 

[presta]

All the services are supposed to be bonded as close as possible to the point of entry.

It seems to me both the incoming gas and water supply would earth an electrical issue.

On a TN-C-S supply, your electrical "earth" is provided by the electrode at the substation via the neutral conductor in the service cable, you can't necessarily rely on gas & water pipes to do the job, because they're commonly plastic.

The problem with a TN-C-S system arises if and when the neutral gets broken, because then all the "earthed" metalwork in the electrical system can become live. The purpose of bonding lies in its full name, equipotential bonding: it's to make sure that no potential can exist between one lot of exposed metal and another. If one piece of exposed metal becomes live you can't get electrocuted if every other bit of metal you can find to touch is also live as well:

Twice I've been picked up on my bonding, once by the boiler man from Worcester Bosch, and again recently by Cadent, I think they're obliged to tell you so that it's your fault if you do nothing about it, not theirs. The problem is that mine was installed back in the days when the point of entry was next to the gas meter in the cupboard under the stairs, and now the point of entry could be construed as being in the porch next to the front door. It depends on whether you view the underfloor space from porch to cupboard as outside the point of entry, or inside, as Cadent recently said. If anyone makes a fuss, I could point out that it was British Gas who moved the meter out of the cupboard, so if the bonding needed moving as well, they should have done it at the time. After all, if British Gas hadn't bodged the job of moving the meter from cupboard to porch in the first place, Cadent wouldn't have had to come and sort it all out last June.

 

[oxoman]

Technically BG like to see a bonding point within 1metre of the meter itself. Technically your protecting the copper gas pipes within the property should a fault arise, the same.applys to copper water pipes. Your main earth is provided by the electricity board at the main supply point. There are some anomalies that may require earth stakes, this isnt very often in my experience. As an electrician i have always run a bonding wire to the gas meter and also to the incoming water supply, however as new houses tend to be plumbed in plastic nowadays its a pointless exercise. Luckily I no longer do domestic installs so dont have worry about it.

 

[PaulSB]

Thanks all. Apologies, I've been a bit preoccupied of late. I had a look round and found it difficult to tell if the incoming gas supply is metal or plastic. The supply into the meter is white plastic in appearance but when tapped doesn't sound like plastic. The supply pipe out of the gas meter into the property is definitely copper.

@oxoman our incoming water and gas supply are within 2' of each other. There is electrical bonding internally to the incoming water supply. This is +/- 2' from the combi boiler with a brick wall between them.

Again @oxoman when you say the "main earth is provided by the electricity board at the main supply point" do you mean the point of entry into my property? Your comment prompted me to take a look and I think we have this.

I say think. We live in a 180 year old terraced cottage. The supply to each cottage runs along the front wall! The cables run directly to the consumer unit which is located internally behind the stone lintel.

 

[oxoman]

Looks like they've given you an earth of sorts. Back in the day you would probably have had 2 cables ELCB and an earth stake with this kind of arrangement, now they give you an earth and expect you to have RCD protection on your consumer unit. Even though your gas and water are within a few feet, historically you'd still take individual cables to each one. Practically if all your water within the cottage is plastic then you could just bond to the gas supply as that will be copper within the cottage itself. If any copper or metal pipework and this technically includes metal waste pipe from sinks you need to bond it. Please note when bonding a gas pipe, you put the clamp on your side of the meter not the incoming supply side. If your not 100% just let a proper electrician do it not a FB warrior.

 

[PaulSB]

@oxoman. Thanks. I wouldn't dream of attempting the bonding myself. I'm the person who, quite literally, switches off the relevant ring before changing a light bulb. I leave a light on, switch off the ring at the consumer unit, if the light goes off I know I have the correct ring!!!!! Electricity scares the living daylights out of me..................you can't see it until it bites!