Earth bonding to water & gas pipes

[miketurner]

Hi
I have metal gas and water pipes with an Earth bonding cable going from my consumer unit to my copper gas pipe near the gas meter. The same Earth wire comes off the gas pipe to my copper water pipe.

My water stop cock in the kitchen does not have any earth bonding cable. It looks difficult to try and run a new cable to the kitchen as all tiled floor etc.

If the earth cable running onto my gas pipe then continuing to my water pipe ok and doing it’s job or do I need to get my kitchen stop cock fitted with one too ?

or is there any other way of earthing the water stop cock in the kitchen, maybe running from a junction box behind the fridge or somewhere in the kitchen where I can find an earth cable ?

pse see photo (gas pipe on the right and water pipe on the left)

any help and advice appreciated thanks

 

[sparkwright]

How far is the section of water pipe with the earth clamp away from the stop cock for the water?

Are you certain that the section of water pipe with the earth clamp is the same pipe as the one where the stop cock is?

Can you remove the kitchen plinths to run cables?

What is the incoming pipe from the road made of?

If the pipe with the earth clamp really is the same pipe from the stopcock, I probably wouldn't worry about it, if wiring access is difficult.

 

[miketurner]

Hi. It’s about 10 feet away. The gas meter is in the hall near the front door.

I don’t know if it’s the same pipe as the stop cock. It’s nearer the front door where the water supply probably enters the house, I can’t see it though.

I have wood floors everywhere on top of the existing floor boards.

I think all pipes are copper, can’t see any plastic.

The house was renovated around 10 years ago with new boiler system and wiring etc. To earth the kitchen I would have to run a cable through the ceiling and drop down somewhere in the kitchen. Maybe a bit difficult.

If I was to run a cable to the kitchen would it come off the earth cable by the gas meter? I’m assuming it wouldn’t need a new earth cable from the consumer unit.

 

[sparkwright]

If you were to do, you could come from the gas meter, no need to go to the consumer unit.

Worth checking if the water pipe in the hall is the same as the stopcock one.

IF you need to do this, and I repeat IF, don't forget you can run the cable outside the house.

 

[ericmark]

The whole idea is not to earth, but to bond so ensuring all metal parts have the same voltage to any common point. If the gas or water pipe is isolated from true earth i.e. plastic main or isolation piece then then it is unlikely to end up different to other metal within the home.

Water pipes are clearly water cooled so no real problem, gas pipes one has to be careful the earth with a TN-C-S supply is correct side of the isolating block or the pipe under fault conditions may not be able to take the current.

To ensure there is no isolating part within the home that would result in part of the metalwork being at true ground potential rather than the potential of whole house, we have rules as to how close to where the supply comes into the house the bonding should be. However with RCD protection once in the house bonding is not so important, the worry was a fault in once area of the house, say for example the dog knocked over a standard lamp which smashed the bulb and resulted in a live part touching the radiator could result in the radiator pipes becoming live and some one in another room touching a radiator could get a shock. But the amount of current required to trip a RCD is very small, less than 30 mA, so today that is not really a valid worry, so the bonding requirements are not as strict any more, at one point in the early 70's it went daft to point of earthing metal window frames, but that is no longer the case.

If you touch a live part, but are not also touching other voltages like the birds on the power lines, you get no shock, so too much bonding can be as bad as not enough.

 

[miketurner]

Thanks, that’s a good idea. Would I just try and follow the pipes to see if the hallway pipe is the same as the kitchen one or is there some way of using a electric meter on the hallway and seeing if it’s shows on the kitchen pipe ?

 

[miketurner]

The whole idea is not to earth, but to bond so ensuring all metal parts have the same voltage to any common point. If the gas or water pipe is isolated from true earth i.e. plastic main or isolation piece then then it is unlikely to end up different to other metal within the home.

Water pipes are clearly water cooled so no real problem, gas pipes one has to be careful the earth with a TN-C-S supply is correct side of the isolating block or the pipe under fault conditions may not be able to take the current.

To ensure there is no isolating part within the home that would result in part of the metalwork being at true ground potential rather than the potential of whole house, we have rules as to how close to where the supply comes into the house the bonding should be. However with RCD protection once in the house bonding is not so important, the worry was a fault in once area of the house, say for example the dog knocked over a standard lamp which smashed the bulb and resulted in a live part touching the radiator could result in the radiator pipes becoming live and some one in another room touching a radiator could get a shock. But the amount of current required to trip a RCD is very small, less than 30 mA, so today that is not really a valid worry, so the bonding requirements are not as strict any more, at one point in the early 70's it went daft to point of earthing metal window frames, but that is no longer the case.

If you touch a live part, but are not also touching other voltages like the birds on the power lines, you get no shock, so too much bonding can be as bad as not enough.

thanks I will bear that in mind. It’s all because of British Gas fitting an EV charger in my garage. Hopefully they won’t think it’s an issue.

many thanks for your help.

 

[ericmark]

EV charging points are very different. But in the garage since inside the building no real problem, the problems arise when being charged outside the building.

 

[miketurner]

That’s all great. Many thanks.

 

[ericmark]

The problem was an earth rod (TT) would not allow enough current to flow to rupture a fuse, so having a supplier supplied earth was better, (TN) at first a TN-S was used, where the earth and neutral were independent, but to save money they started to use a TN-C-S where over part of the supply the neutral and earth are combined this is called the PEN.

With PME there are multiple earths, but TN-C-S not always that many, and if the PEN is lost with a poly-phase supply the voltage line to neutral can vary, and the supply earth can raise up to 230 volts above true earth, as with bird on supply wire this is not a danger if all items are bonded, it may damage equipment, but not a danger. Only when the supply is taken out of the home is there a danger.

So most garden equipment is what we call class II, it does not have an earth, so no danger. But for some reason which I don't understand it seems many EV's are class I, they are earthed, so clearly you don't want a car at 100 volt and the street at zero volt, you can get a nasty shock, with caravans, narrow boats and petrol stations TN-C-S is banned, and a caravan due to fire regulations must be at least 2.7 meters from a building, so touching a caravan at real earth potential and some metal on a building at the TN-C-S earth potential is not possible.

As long as the car is either charged inside the building, or if outside either not using a TN-C-S supply or has some auto-disconnection device which will disconnect first line and neutral then earth should the PEN be lost it is considered safe. Not sure why but it seems 50 volt is the normal safe voltage for touching, but allowed 70 volt with an EV, seems EV people can stand more electric through them? So the EV charging points either have a TT supply, or a reference electrode to detect loss of PEN or rely on the voltage going under or over 207 to 253 volt range if the PEN is lost, and if voltage out of range it auto switches off line, neutral and earth. I don't think it is permitted for it to auto reconnect, think it has to be manual reset, so any brown out can result in EV not charging. Also a problem with some RCD's this applies to both solar panels and EV charging points. Both need special protective measures.

The problem is some one can have a socket fitted for a welder

and the same socket can be used to charge a car at 7 kW with a simple plug in lead,

without any of the protections required for normal EV charge points. So they get whole set up for around £250 but anyone touching their car under fault conditions could get a nasty shock. The same applies for the so called granny charger with a 13 amp plug, so any law to stop the 7 kW version would also include the granny charger.

Lucky loss of PEN is rare, it seems around 250 per year in UK and only 10% cause injury, but often the results are blamed on copper theft. So we get reports of fires due to copper theft, rather than fire due to using a TN-C-S supply.

Charging an EV inside the garage however the only worry is the battery going on fire, the TN-C-S supply is not a problem, where I live I can export a TT supply to where I park my car, and no one other than my wife and I have any reason to go near the car. However where the car is parked in front of the house, post man, milk man and a whole host of others walk past the car.

 

[miketurner]

The problem was an earth rod (TT) would not allow enough current to flow to rupture a fuse, so having a supplier supplied earth was better, (TN) at first a TN-S was used, where the earth and neutral were independent, but to save money they started to use a TN-C-S where over part of the supply the neutral and earth are combined this is called the PEN.

With PME there are multiple earths, but TN-C-S not always that many, and if the PEN is lost with a poly-phase supply the voltage line to neutral can vary, and the supply earth can raise up to 230 volts above true earth, as with bird on supply wire this is not a danger if all items are bonded, it may damage equipment, but not a danger. Only when the supply is taken out of the home is there a danger.

So most garden equipment is what we call class II, it does not have an earth, so no danger. But for some reason which I don't understand it seems many EV's are class I, they are earthed, so clearly you don't want a car at 100 volt and the street at zero volt, you can get a nasty shock, with caravans, narrow boats and petrol stations TN-C-S is banned, and a caravan due to fire regulations must be at least 2.7 meters from a building, so touching a caravan at real earth potential and some metal on a building at the TN-C-S earth potential is not possible.

As long as the car is either charged inside the building, or if outside either not using a TN-C-S supply or has some auto-disconnection device which will disconnect first line and neutral then earth should the PEN be lost it is considered safe. Not sure why but it seems 50 volt is the normal safe voltage for touching, but allowed 70 volt with an EV, seems EV people can stand more electric through them? So the EV charging points either have a TT supply, or a reference electrode to detect loss of PEN or rely on the voltage going under or over 207 to 253 volt range if the PEN is lost, and if voltage out of range it auto switches off line, neutral and earth. I don't think it is permitted for it to auto reconnect, think it has to be manual reset, so any brown out can result in EV not charging. Also a problem with some RCD's this applies to both solar panels and EV charging points. Both need special protective measures.

The problem is some one can have a socket fitted for a welder

and the same socket can be used to charge a car at 7 kW with a simple plug in lead,

without any of the protections required for normal EV charge points. So they get whole set up for around £250 but anyone touching their car under fault conditions could get a nasty shock. The same applies for the so called granny charger with a 13 amp plug, so any law to stop the 7 kW version would also include the granny charger.

Lucky loss of PEN is rare, it seems around 250 per year in UK and only 10% cause injury, but often the results are blamed on copper theft. So we get reports of fires due to copper theft, rather than fire due to using a TN-C-S supply.

Charging an EV inside the garage however the only worry is the battery going on fire, the TN-C-S supply is not a problem, where I live I can export a TT supply to where I park my car, and no one other than my wife and I have any reason to go near the car. However where the car is parked in front of the house, post man, milk man and a whole host of others walk past the car.

Many thanks for the very comprehensive info. Mine will only be charged inside the garage and a new smoke alarm fitted also. Thanks again.

 

[JohnW2]

Water pipes are clearly water cooled so no real problem, gas pipes one has to be careful the earth with a TN-C-S supply is correct side of the isolating block or the pipe under fault conditions may not be able to take the current.

If you're talking about an 'isolating block' in the gas pipe, then (ignoring the regulations, which appear stupid), electrically speaking there is no point in bonding (hence no need to bond) the pipe on the consumer's side of that 'isolating block'.

Again electrically speaking (and possibly in violation of the regulations, depending on where one imagines commas should be!), the place where a metal gas pipe entering the property should be bonded (if bonding is required) is on the supply (not consumer's) side of any 'isolating block' in the pipe - the side which you seem to be suggesting is 'incorrect' (and, by implication, potentially dangerous?).

Kind Regards, John

 

[miketurner]

If you're talking about an 'isolating block' in the gas pipe, then (ignoring the regulations, which appear stupid), electrically speaking there is no point in bonding (hence no need to bond) the pipe on the consumer's side of that 'isolating block'.

Again electrically speaking (and possibly in violation of the regulations, depending on where one imagines commas should be!), the place where a metal gas pipe entering the property should be bonded (if bonding is required) is on the supply (not consumer's) side of any 'isolating block' in the pipe - the side which you seem to be suggesting is 'incorrect' (and, by implication, potentially dangerous?).

Kind Regards, John

many thanks for the info.

 

[JohnW2]

many thanks for the info.

You're welcome but, as you can probably see from what I wrote, there is a bit of a 'problem'.

The Wiring Regs (or, least least, the way in which many people interpret them) appear to be inconsistent with 'electrical common sense', to the extent that some could argue that to comply with the regs (as many interpret them) could actually be potentially 'dangerous'.

Kind Regards, John