Is this earth wire a problem?

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I don't know - but I have read (somewhere) that the gas people do not want voltages on the supply pipe so prevent the bonding conductor being connected to it, although, unless there is an insulating joint on the meter, there is nothing they can do to prevent it.
Quite. If the supply pipe is metal and the gas people "don't want" the possibility of 'voltages on it', then, if the meter is external, they should either use a meter which does not have electrical continuity or put some electrically insulating 'section' in the meter's outlet pipe before it goes into the property. If the meter is internal, they could only satisfy their desire by putting in an 'insulating section' in their (metal) supply pipe before it entered the property, since otherwise BS7671 would require the pipe entering the house (hence their metal supply pipe) to be bonded.

Kind Regards, John
 
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IF something metal enters the outhouse from underground (whether gas pipe, water pipe, structural metal or anything else) then it must be bonded to the earthing system used in the outhouse. If that earthing system is the one exported from the main house, then that bonding has to be back to the MET of the house, and, say, the armour of SWA feeding the outhouse may (but might not) be adequate as the bonding conductor.
Agreed - so far, but:

If the outhouse has its own TT earthing system, and is 'isolated' from the house's earth, then the bonding must be to the local TT system/electrode.
Such a pipe running from the main house to the outhouse underground, it would have to be bonded to the house MET, so would TT at the outhouse be impossible?
 
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Agreed - so far, but: .... Such a pipe running from the main house to the outhouse underground, it would have to be bonded to the house MET, so would TT at the outhouse be impossible?
I did consider that complication, but then wondered how far one can sensibly take such thinking.

It's really very similar to my house. As you know, I have always described and considered it as TT, and hence, for example, have never relied on OPDs for ADS. However, as you know, with bonding connected, my Ze is no more than about 0.3Ω, at most, I assume due to water pipes between houses which are bonded to my neighbours TN-C-S system. One might therefore argue that my house "cannot possibly be TT" - and it's certainly true that if the supply to my neighbour suffered from a 'lost PEN' the potential of my MET/CPCs/earth electrode could rise to considerably above true earth potential.

What do you think?

Kind Regards, John
 
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Gas wise what's important is the correct sealing/sleeving at the pipe exit from the box through the cavity.
We need another picture @Wilseus
 
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I did consider that complication, but then wondered how far one can sensibly take such thinking.
Of course, I omitted to say that the pipe might also be earthed because of connections to the boiler and appliances.

It's really very similar to my house. As you know, I have always described and considered it as TT, and hence, for example, have never relied on OPDs for ADS. However, as you know, with bonding connected, my Ze is no more than about 0.3Ω, at most, I assume due to water pipes between houses which are bonded to my neighbours TN-C-S system. One might therefore argue that my house "cannot possibly be TT" - and it's certainly true that if the supply to my neighbour suffered from a 'lost PEN' the potential of my MET/CPCs/earth electrode could rise to considerably above true earth potential.
Yes, I remember.

What do you think?
Just that it would be impossible to separate the outhouse earth from the house earth, therefore there has to be a correctly sized bonding conductor between outhouse and house. As previously said, a water pipe (metal of course) could be used as that bonding conductor but not a gas pipe.
An earth electrode at the outhouse would simply be an unnecessary intentionally added extraneous-conductive-part.

I have never thought about 'exporting' a gas supply before.
Is it allowed just to connect and bury a gas pipe to wherever someone wants?
Having said that, I suppose a properly installed gas supply - by the supplier - to an outhouse is still likely to be electrically connected.
 
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Just that it would be impossible to separate the outhouse earth from the house earth, therefore there has to be a correctly sized bonding conductor between outhouse and house. As previously said, a water pipe (metal of course) could be used as that bonding conductor but not a gas pipe.
As you say, in the case of a water pipe, that is 'self-fulfilling', in that every part of the water pipe (including the bit that enters the outhouse) will automatically be 'adequately bonded' (by itself) to the house's MET, and that would remain true even if it didn't "need to be".

In view of that inevitable 'automatic bonding' (whether one wants/needs it or not), the question of whether it "needs to be" (adequately bonded to the house earth) cannot be sensibly discussed. However, although, like you, I cannot recall having seen a gas pipe going from a house to an outhouse, I imagine that it occasionally happens (and is probably 'allowed', provided it was installed by someone 'allowed' so to do), so we can discuss the matter in relation to such a gas pipe.

On that basis, and reaching for my 'electrical common sense' hat (rather than a 'regs' one), I have to ask Why it would be necessary to have "a correctly sized bonding conductor between outhouse and house".

As you know, the (only) reason for main ("equipotential") bonding is to turn a space into an equipotential zone, so as to prevent dangerous potentials existing between simultaneously-touchable parts - and, in the case we are talking about, the relevant 'space' is the interior of the outhouse. That can be achieved by bonding together all simultaneously-touchable parts within the outhouse (if, say, it was TTd), without any need for 'bonding' to the house's earth.

We're really talking about the opposite of the normal situation, particularly with a TN-C-S installation. The concern is usually that an extraneous-c-p will introduce 'earth potential' and that this could (under very rare fault conditions) be very different from the TN-C-S 'earth' connected to exposed-c-ps within the property. However, with a TTd outhouse, the greatest concern would probably be that the extraneous-c-p might (under those rare fault conditions) introduce a potential considerably higher than the local (TT) earth to which exposed-c-ps were connected.
An earth electrode at the outhouse would simply be an unnecessary intentionally added extraneous-conductive-part.
As I've said in relation to SB in bathrooms, the most foolproof (and, sometimes, only) way of ensuring that there cannot be dangerous PDs between simultaneously touchable parts is to have local bonding connecting them together (i.e. 'SB'). If, rather than TTing it, one uses (only) an exported TN earth in an outhouse, then bernard would probably point out that the greatest 'risk' (under extremely rare circumstances) is to someone who has 'one foot/hand inside, and one foot/.hand outside' the outbuilding.

In passing, I often wonder about the oft-seen assertion that if one connects an earth electrode to a TN earth, that electrode constitutes an extraneous-c-p. However, I'm reminded of the last clause of the BS7671 definition of extraneous-c-p, which is "...and not forming part of the electrical installation". Is an earth electrode not 'part of the electrical installation'??

Kind Regards, John
 
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As you say, in the case of a water pipe, that is 'self-fulfilling', in that every part of the water pipe (including the bit that enters the outhouse) will automatically be 'adequately bonded' (by itself) to the house's MET, and that would remain true even if it didn't "need to be".
Is that not the same for the gas even though it is not allowed and must have a separate bonding conductor?

In view of that inevitable 'automatic bonding' (whether one wants/needs it or not), the question of whether it "needs to be" (adequately bonded to the house earth) cannot be sensibly discussed.
Ok.

On that basis, and reaching for my 'electrical common sense' hat (rather than a 'regs' one), I have to ask Why it would be necessary to have "a correctly sized bonding conductor between outhouse and house".
Them's the rules to bond any other e-c-ps.

As you know, the (only) reason for main ("equipotential") bonding is to turn a space into an equipotential zone, so as to prevent dangerous potentials existing between simultaneously-touchable parts - and, in the case we are talking about, the relevant 'space' is the interior of the outhouse. That can be achieved by bonding together all simultaneously-touchable parts within the outhouse (if, say, it was TTd), without any need for 'bonding' to the house's earth.
Then why stipulate that a TT outhouse must be separated from the house earthing?

We're really talking about the opposite of the normal situation, particularly with a TN-C-S installation. The concern is usually that an extraneous-c-p will introduce 'earth potential' and that this could (under very rare fault conditions) be very different from the TN-C-S 'earth' connected to exposed-c-ps within the property. However, with a TTd outhouse, the greatest concern would probably be that the extraneous-c-p might (under those rare fault conditions) introduce a potential considerably higher than the local (TT) earth to which exposed-c-ps were connected.
Ok.

As I've said in relation to SB in bathrooms, the most foolproof (and, sometimes, only) way of ensuring that there cannot be dangerous PDs between simultaneously touchable parts is to have local bonding connecting them together (i.e. 'SB'). If, rather than TTing it, one uses (only) an exported TN earth in an outhouse, then bernard would probably point out that the greatest 'risk' (under extremely rare circumstances) is to someone who has 'one foot/hand inside, and one foot/.hand outside' the outbuilding.
Would an additional (unnecessary) electrode remove that risk?

In passing, I often wonder about the oft-seen assertion that if one connects an earth electrode to a TN earth, that electrode constitutes an extraneous-c-p. However, I'm reminded of the last clause of the BS7671 definition of extraneous-c-p, which is "...and not forming part of the electrical installation". Is an earth electrode not 'part of the electrical installation'??
Presumably not until it is connected.

Presumably extraneous-c-ps become part of the electrical installation when bonded?

Isn't all this like your bonded water pipe? Is it just an extraneous-c-p or actually your earth - even though not allowed to be depended on as such?
If you and your neighbour had new plastic water supplies installed, the existing pipe would still be better than an electrode.
 

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upload_2022-2-14_16-23-8.jpeg


Oops, looks like I did :eek:
 
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Is that not the same for the gas even though it is not allowed and must have a separate bonding conductor?
Indeed, electrically identical. It's just the daftness of the regs which says that a pipe carrying water is allowed to 'auto-bond', whereas the same pipe carrying gas 'is not allowed to', such that the latter has to have a substantial G/Y conductor run alongside it!
Them's the rules to bond any other e-c-ps.
Are they? The problem with the regs is that they only talk about 'installations' and do not really give any consideration to 'outhouses'. In electrical terms, there's really no reason why one 'building' and another have to be part of the same equipotential zone. By virtue of the reason for their existence, an equipotential zone is only relevant within one building.
Then why stipulate that a TT outhouse must be separated from the house earthing?
Who 'stipulated' that? It is surely just 'an option'?
Would an additional (unnecessary) electrode remove that risk?
In the 'usual' situiation (i.e. without the complication of a 'house-bonded' metal pipe entering the outbuilding), TTing the outbuilding would totally eliminate that risk, since (if done properly!) the TN-C-S earth would have no 'presence' within the outbuilding. In that situation the earth electrode is not 'unnecessary', since it is required to give (RCD) fault protection within the outbuilding.

When there is the complication (pipe bonded to both TN-C-S 'earth' and the TT electrode), bernard would probably argue that an earth electrode would at least reduce the risk, particularly if the electrode were close to the doorof the outbuilding, since a high TN-C-S 'earth' potential would then raise the potential of the ground outside of the outbuilding to some extent.
Presumably not until it is connected.
Presumably not - but I would say that once is is connected, it becomes (a 'deliberate') 'part of the electrical installation', wouldn't you?
Presumably extraneous-c-ps become part of the electrical installation when bonded?
Dunno. It's not quite as 'deliberate' as an earth electrode. The latter is deliberately installed as part of the installation, whereas an extraneous--c-p has to be dealt with 'because it's already there'.
Isn't all this like your bonded water pipe? Is it just an extraneous-c-p or actually your earth - even though not allowed to be depended on as such? .... If you and your neighbour had new plastic water supplies installed, the existing pipe would still be better than an electrode.
Indeed. However, if it were a gas pipe, I don't think that anyone would seriously suggest that I should run a G/Y conductor from where it enters my house to my neighbour's MET, would they? ... However, if I understand you correctly, if the OP's pipe were a gas one, you would be suggesting that he had to run a G/Y bonding conductor from the outhouse to the MET in 'another building' (albeit his own house, rather than the neighbours'), wouldn't you?

Kind Regards, John
 
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Indeed, electrically identical. It's just the daftness of the regs which says that a pipe carrying water is allowed to 'auto-bond', whereas the same pipe carrying gas 'is not allowed to', such that the latter has to have a substantial G/Y conductor run alongside it!
Precisely.

Are they? The problem with the regs is that they only talk about 'installations' and do not really give any consideration to 'outhouses'. In electrical terms, there's really no reason why one 'building' and another have to be part of the same equipotential zone. By virtue of the reason for their existence, an equipotential zone is only relevant within one building.
Yes, but if the outhouse uses the house TN-C-S MET, e-cps in the outhouse must be bonded to the MET with a 10mm² conductor - according to the regulations.

Who 'stipulated' that? It is surely just 'an option'?
Yes, an option to negate the need for said conductor.

In the 'usual' situiation (i.e. without the complication of a 'house-bonded' metal pipe entering the outbuilding), TTing the outbuilding would totally eliminate that risk, since (if done properly!) the TN-C-S earth would have no 'presence' within the outbuilding. In that situation the earth electrode is not 'unnecessary', since it is required to give (RCD) fault protection within the outbuilding.
Yes but we are discussing a gas pipe earthed and bonded at the house and where there is overcurrent protection in the outhouse using the house earth.

When there is the complication (pipe bonded to both TN-C-S 'earth' and the TT electrode), bernard would probably argue that an earth electrode would at least reduce the risk, particularly if the electrode were close to the doorof the outbuilding, since a high TN-C-S 'earth' potential would then raise the potential of the ground outside of the outbuilding to some extent.
Yes, to some extent in the very close proximity of the electrode.

Presumably not - but I would say that once is is connected, it becomes (a 'deliberate') 'part of the electrical installation', wouldn't you?
Yes, but equally by your reasoning, it is no longer an e-c-p when bonded?

Dunno. It's not quite as 'deliberate' as an earth electrode. The latter is deliberately installed as part of the installation, whereas an extraneous--c-p has to be dealt with 'because it's already there'.
So what?

Indeed. However, if it were a gas pipe, I don't think that anyone would seriously suggest that I should run a G/Y conductor from where it enters my house to my neighbour's MET, would they?
No, because ... However, if I understand you correctly, if the OP's pipe were a gas one, you would be suggesting that he had to run a G/Y bonding conductor from the outhouse to the MET in 'another building' (albeit his own house, rather than the neighbours'), wouldn't you?
Perhaps the difference is that there there is not a separate electrical supply with its own MET in the outhouse.
 
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Yes, but if the outhouse uses the house TN-C-S MET, e-cps in the outhouse must be bonded to the MET with a 10mm² conductor - according to the regulations.
As I said, I think the problem is that the regs have not considered the possibility that one 'installation' (supplied by the same L+N, DNO fuse and usually meter) may serve more than one building.

When it does serve more than one building (far enough apart for the insides not to be 'simultaneously-touchable'!) then, as I said, I see no rational electrical reason why the insides of both buildings have to be within the same equipotential zone. Each building can therefore have its own MET (at the potential of the building's equipotential zone). That's precisely the situation one has if one has a TTd outhouse in which nothing connected to the main house's MET is accessible. I'll leave others to decide whether they want to call that one 'installation' or two :)
Yes but we are discussing a gas pipe earthed and bonded at the house and where there is overcurrent protection in the outhouse using the house earth.
If you're talking about (the earth part of the 'earth fault path' of) fault protection, then that's effectively true (since any local TT electrode would have little effect on the overall EFLI),whether the protective device is in the house or the outhouse, but that would be 'unintentional' if one had (for whatever reason) installed a TT electrode and RCD.

I think we are discussing a pretty rare situation (an underground metal pipe from the house supplying water, let alone gas, to an outhouse) and I'm not sure what I would do if I had that situation. My first inclination, like yours, would be not to bother with the TT electrode. However, that would be fairly analogous to my 'not bothering' with the TT electrode in my actual house. In both situations, that would be fine so long as the metal pipe remained in situ, but I certainly would not feel it appropriate to rely on that for my house, so I wonder whether I would be happy with it for an outhouse. ... and, before you 'try to be clever', one might have to consider that most/all of the metal pipe might one day be removed (and replaced with plastic), leaving my installation with little/no connection to earth at all!
Perhaps the difference is that there there is not a separate electrical supply with its own MET in the outhouse.
As above, I don't think it is the fact that two separate building have the same L+N supply (and DNO fuse, and probably meter) that matters. It is the 'earth' that counts and, as above, I see no reason why two separate buildings cannot have their own (separate) METs and hence their own (separate, maybe different potential) equipotential zones. As above, whether one calls that one or two 'installations' is really a semantic question, which I will leave others to contemplate!

Kind Regards, John
 
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Gas wise what's important is the correct sealing/sleeving at the pipe exit from the box through the cavity.
We need another picture @Wilseus

Wow this thread has blown up quite a bit. I spoke to one of the site managers today, and he showed me that the hole that has been made for the earth wire is designed to be punched out, which you can see more clearly from underneath. He also said that it was inspected by an external body (sorry, not sure who.)

IMG_20220215_150536811.jpg

Here are a couple of better pictures of the inside of the box:

InkedIMG_20220215_150515819_HDR_LI.jpg InkedIMG_20220215_150524846_HDR_LI.jpg

Also, I saw a couple of comments that seemed to imply this was a flat. In fact the property is a detached house.
 
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The gas pipework's fine...the collar and sleeve has been fitted to the box to take the pipe through the cavity and the pipe is correctly sealed with a flexible putty...normally FJC.
 
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Here are a couple of better pictures of the inside of the box:
I was interested to see this on the label attached to the meter ..

upload_2022-2-15_15-30-9.png


I wonder under what circumstances it would be deemed that "cross bonding" (I presume that means 'across the meter') would be 'required', and why!

Kind Regards, John
 
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As I said, I think the problem is that the regs have not considered the possibility that one 'installation' (supplied by the same L+N, DNO fuse and usually meter) may serve more than one building.

When it does serve more than one building (far enough apart for the insides not to be 'simultaneously-touchable'!) then, as I said, I see no rational electrical reason why the insides of both buildings have to be within the same equipotential zone. Each building can therefore have its own MET (at the potential of the building's equipotential zone). That's precisely the situation one has if one has a TTd outhouse in which nothing connected to the main house's MET is accessible.
...but there is something in the outhouse connected to the main house MET - the gas pipe.
You seem to keep quoting situations where that is not the case and obviously different.

As above, I don't think it is the fact that two separate building have the same L+N supply (and DNO fuse, and probably meter) that matters. It is the 'earth' that counts and, as above, I see no reason why two separate buildings cannot have their own (separate) METs and hence their own (separate, maybe different potential) equipotential zones. As above, whether one calls that one or two 'installations' is really a semantic question, which I will leave others to contemplate!
Again - we are discussing a situation where the outhouse and the house do not and cannot have their own separate METs.

Take the case of a large house where the rear room contains a gas fire and (for some reason) an extraneous-c-p.
With a PME supply that e-c-p must be connected to the MET with a 10mm² conductor. It cannot be bonded by the gas pipe nor any of the CPCs that might be present.
Even if the gas fire were the only (earthed electrical) thing in the room, the e-c-p still has to be bonded back to the MET.
No one would dream of TTing the rear room.

I have said several times that I do not understand the difference between an outhouse/shed/garage and a room in the same location if the house were that large.
 

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