External gas supply bonding

[JohnW2]

It would be interesting to do an adiabatic equation and see what size is required at an 80 degree ambient temperature, but off the top of my head it'll be fine and it's not going to have any real detrimental effects to a bonding conductor.

I don't think an adiabatic calculation would be appropriate/relevant to a bonding conductor, since the conditions under which it might have to operate are far from adiabatic. In the worst-case scenario (of a network neutral fault) very high currents could flow in a main bonding conductor 'continuously' (without being rapidly terminated by operation of any OPD) - certainly for far more than the few seconds beyond which the process ceases to be adiabatic.

However, I'm quite sure that an ambient temperature of 80° C would have no material effect on the ability of the bonding conductor to 'do its job' - and, as I said, even if the insulation were to melt (which is won't as a consequence from the hot pipe alone), I don't think that would be any great deal!

Kind Regards, John

 

[JohnW2]

... What I want to do is replace the 2-way earth block with a 6-way block, making that the MET. I will connect this with 16mm2 to the isolator and with 10mm2 to my gas and water supplies. Am I OK to do that?

That sounds OK to me. 16mm² is probably unnecessarily large - I would say that 10mm² would be OK for that as well.

Am I OK to move the earth from the supply to this new earth block?

Yes, but to be cautious/safe, you should turn off your entire installation (with the isolator) whilst you are moving earths around.

Kind Regards, John

 

[EFLImpudence]

Am I OK to move the earth from the supply to this new earth block?

Maybe just a terminology issue but -

you cannot move the earth from the supply; that's where it is.

You can replace the earthing block with a larger one. That will be the MET.

 

[JohnW2]

Maybe just a terminology issue but - you cannot move the earth from the supply; that's where it is. You can replace the earthing block with a larger one. That will be the MET.

I suppose I could be wrong, but I thought that was precisely what the OP was proposing and asking about - such was certainly the basis of my response. Apart from anything else, there is no reason why he would need to interfere with the supply-side end of the earthing conductor. At worst he might need to extend it (at the MET end), but it sounds as if that would not be required.

Kind Regards, John

 

[MikeAustin]

Maybe just a terminology issue but - you cannot move the earth from the supply; that's where it is. You can replace the earthing block with a larger one. That will be the MET.

I suppose I could be wrong, but I thought that was precisely what the OP was proposing and asking about - such was certainly the basis of my response. Apart from anything else, there is no reason why he would need to interfere with the supply-side end of the earthing conductor. At worst he might need to extend it (at the MET end), but it sounds as if that would not be required.
Kind Regards, John

Thanks both of you. My question concerned disconnecting the supply earth from the old block and connecting to the new block. Because of space restrictions, it would be easier for me to add a new block (the new MET) and connect it to the old block. Is this an option, or must there be just the one block?

 

[EFLImpudence]

You may be right but I am not as good as you at determining what people actually mean when it is not what they actually wrote.

At worst he might need to extend it (at the MET end), but it sounds as if that would not be required.

Why would he need to extend it?

Am I OK to move the earth from the supply to this new earth block?

It depends what you mean by 'move the earth'.

You may not (that means you must not) tamper with the connection to the supply cable.

 

[JohnW2]

You may be right but I am not as good as you at determining what people actually mean when it is not what they actually wrote.

I will obviously sometimes be wrong, but I have decades of experience of working in various fields in which a high proportion of people have a poor (and/or incorrect) understanding of 'correct technical terminology', so one becomes quite experienced at working out (hopefully usually correctly) what they 'actually mean'!

At worst he might need to extend it (at the MET end), but it sounds as if that would not be required.

Why would he need to extend it?

As I said, it sounds as if he wouldn't need to. That would only arise if, for some reason, he chose to locate the earth block/MET 'out of reach' of the existing earthing conductor - but there is no suggestion that the OP would be doing that.

You may not (that means you must not) tamper with the connection to the supply cable.

No argument with that - but, as I said, I do not think that is what the OP was proposing, not the least because I can't see why he would want/need to.

Kind Regards, John

 

[MikeAustin]

Just to repeat my last question, with a pikky. Because of space restrictions, it would be easier for me to add a new block (the new MET) above the cutout and connect it to the old block. Is this an option, or must there be just the one block? I don't think it would be wise to bend the earth from the mains supply round to the other side of the cutout.

Electric Power Supply

• MikeAustin
• 3 Feb 2016
• 1

Main board installed at purchase, September 1985. Meter updated by SWEB April 2002.

 

[EFLImpudence]

That's unfortunate.

Yes, you can put another block somewhere and connect it.

Will the cable not reach to just above the cut-out?

 

[MikeAustin]

That's unfortunate.

Yes, you can put another block somewhere and connect it.

Thanks. The reason I asked is because the 10mm2 earthing cable from MET to gas/water has to be continuous and unbroken. Two blocks on the board would seem to be inconsistent with this requirement.

Will the cable not reach to just above the cut-out?

It would be tight, and I don't feel comfortable about it being close even to the N terminal (there is probably a requirement somewhere). Maybe I could add an extension board to the side just for the new MET so I could dispose of the old block.

 

[Taylortwocities]

I would intercept the green earth wire (power off first!) and put a supplementary MET in the run between the existing 2-way block and the CU.
Do not stress the black earth connection!

the 10mm2 earthing cable from MET to gas/water has to be continuous and unbroken.

There is no regulation that says that is must be.

 

[MikeAustin]

the 10mm2 earthing cable from MET to gas/water has to be continuous and unbroken.

There is no regulation that says that is must be.

Ah, my misunderstanding. It has to be continuous if more than one 'extraneous-conductive-part" is connected to it. This is not the case in my situation.

 

[EFLImpudence]

the 10mm2 earthing cable from MET to gas/water has to be continuous and unbroken.

There is no regulation that says that is must be.

Ah, my misunderstanding. It has to be continuous if more than one 'extraneous-conductive-part" is connected to it.

It may be a good idea but there is no requirement for it to be continuous.

In fact, you may use the water pipe, or any other suitable part except the gas pipe, as a main bond.
Obviously, when this is done it cannot be continuous.

 

[MikeAustin]

the 10mm2 earthing cable from MET to gas/water has to be continuous and unbroken.

There is no regulation that says that is must be.

Ah, my misunderstanding. It has to be continuous if more than one 'extraneous-conductive-part" is connected to it.

It may be a good idea but there is no requirement for it to be continuous.

In fact, you may use the water pipe, or any other suitable part except the gas pipe, as a main bond.
Obviously, when this is done it cannot be continuous.

I am probably not understanding what you say here. Can I strap an earth cable to the water pipes underneath my supply board and that would be my water supply bonding sorted? And could I then strap the water pipe at the boiler to the gas pipe and that is my gas supply bonding sorted? I just spent £40 on a roll of 10mm2 cable!

 

[Taylortwocities]

Earth strap(s) need to be within 600mm of the stop cock/service meter or at the point of entry to the building if the meter is external. And on the consumer's side of the stop cock before any branch pipework.
Its all in teh WIKI at //www.diynot.com/wiki/Electrics:main_equipotential_bonding