Main Bonding

[EFLImpudence]

Yes. Why not just the usual BS951 clamps?

 

[JohnW2]

I guess I therefore have to change my question to .... "What are your other two?"

On reflection, after a night's sleep, I imagine that the 'third' bond Sunray was thinking about was the outgoing pipe from garage to house.

If that outgoing pipe were going to anywhere other than the house, then it would certainly qualify as an extraneous-c-p that needed to be main bonded. However, if the other end of that presumably not very long) pipe is bonded where it enters the house, I don't see that, in electrical terms, it would really also need to be bonded at the garage end.

However, if one wanted an arrangement which satisfied everyone's views, and all possible interpretations of the regs (even 'silly' ones), then I suppose that one would, as Sunray said, need three bonds - on entry and exit to the garage and on entry to the house.

 

[EFLImpudence]

If that outgoing pipe were going to anywhere other than the house, then it would certainly qualify as an extraneous-c-p that needed to be main bonded. However, if the other end of that presumably not very long) pipe is bonded where it enters the house, I don't see that, in electrical terms, it would really also need to be bonded at the garage end.

However, if one wanted an arrangement which satisfied everyone's views, and all possible interpretations of the regs (even 'silly' ones), then I suppose that one would, as Sunray said, need three bonds - on entry and exit to the garage and on entry to the house.

While I agree with what you write, according to the regulation - not the physics - the supply pipe does not require bonding have to be bonded where it enters the garage.


You asked:

If the earth from the house is being exported to the garage, do house and garage count as the same equipotential zone?

Could the answer be "No" and the house and garage be treated separately?

I.e. just one bond from supply pipe and/or meter outlet to garage CU earth terminal and one from pipe entering house to house MET.

After all one cannot touch anything in one building from the other.

 

[JohnW2]

While I agree with what you write, according to the regulation - not the physics - the supply pipe does not require bonding have to be bonded where it enters the garage.

If the supply pipe between where it enters the garage and the meter is touchable, then electrical common sense (and 'self preservation'/'safety') say that it should be bonded (in case the meter is 'plastic'), don't they - despite the fact that the regs say that one should bond downstream of the meter (which might be plastic) ?

Could the answer be "No" and the house and garage be treated separately?

As I wrote, if one takes that approach, then one would presumably end up with Sunray's "3 bonds" - since, in addition to the bond where the pipe enters the house, there would also have to be bonds on both the incoming (or regs' silly place) and outgoing pipes in the garage?

I.e. just one bond from supply pipe and/or meter outlet to garage CU earth terminal and one from pipe entering house to house MET.

As above, one would surely then (if buildings were being 'treated separately') have to also bond the outgoing pipe from the garage, since that would then be just a standard extraneous-c-p? That would be particularly important if one bonded the incoming supply pipe in the electrically-sensible place (where it enters the garage, before the meter) and the meter was plastic.

After all one cannot touch anything in one building from the other.

Indeed not. However, in that 'particularly important' scenario I've just mentioned, if nothing downstream of the meter were bonded, virtually all of the pipework within the garage would be at the ('extraneous') potential introduced by the outgoing pipe - and hence a definite hazard, since one could touch that pipe at the same time as touching things in the garage which were at 'MET potential'.

On the other hand,if house and garage were NOT 'treated separately', and account was taken of the fact that the garage->house pipe was bonded at the house end (to the same MET that also served the garage) then, at least electrically speaking, there would not be much point/need to also bond the same pipe at the other end?

 

[EFLImpudence]

Ok. I suppose it depends how safe is thought necessary.

So what would be done if it was all one building?

That is - incoming supply pipe and house gas pipe in one room then house gas pipe buried to another room.
Would anyone have three main bonds for that or one main bond and supplementary bonds?

 

[JohnW2]

Ok. I suppose it depends how safe is thought necessary.

It does - and it's not helped by the fact that some of the regs (at least, one interpretation of them) would appear to be contrary to 'safety' (potentially leaving touchable bits of pipe upstream of a meter unbonded).

I think I've made it fairly clear what I regard as 'electrically sensible' (and what I regard as 'electrically unnecessary', so less 'sensible').

So what would be done if it was all one building? .... That is - incoming supply pipe and house gas pipe in one room then house gas pipe buried to another room.

I think that most interpretation of the regs would say that both ends of that bit of buried pipe 'between rooms' would need to be bonded, since both would qualify as extraneous-c-ps. However, as I've said, I do not see any electrical need (or sense) to bond both ends of a short piece of pipe to the same MET. However, returning to the house+garage situation, if, as you suggested, the two buildings were treated as 'separate', then there would be two different METs, so that might well move the goalposts.

Would anyone have three main bonds for that or one main bond and supplementary bonds?

Well, I suppose if Mr Jobsworth had read the regs, he might! Supplementary bonds would not normally have adequate CSA to be compliant as main bonds.

 

[EFLImpudence]

Supplementary bonds would not normally have adequate CSA to be compliant as main bonds.

True but my suggestion was assuming three main bonds were not necessary.



Anyway, if three are required then this would comply:

Possibly dependent on the locations of the parts - and discounting the SWA present in this thread.

 

[JohnW2]

True but my suggestion was assuming three main bonds were not necessary.

OK - but that is obviously the question under debate.

Anyway, if three are required then this would comply: <diagram> Possibly dependent on the locations of the parts - and discounting the SWA present in this thread.

Agreed. That's precisely what I was thinking of (IF one had 3 bonds).

Although the regs seem to require the 'silly' bond (the middle one in your diagram), I don't think there is anything in the regs which says that one "mustn't" have the sensible one (left one in your diagram) - so, as you say, presumably would comply.

 

[Spikes Mavic]

I couldn't have a plastic gas supply pipe in my garage due to the risk of it melting in a fire, but you appear to have a plastic gas meter. I have no idea what would prevent a plastic gas meter from melting in the event of a fire in the garage.

It is a metal gas meter !

 

[Spikes Mavic]

True but my suggestion was assuming three main bonds were not necessary.



Anyway, if three are required then this would comply:

View attachment 381844

Possibly dependent on the locations of the parts - and discounting the SWA present in this thread.

Plus the garage cu !

 

[JohnW2]

It is a metal gas meter!

Fair enough, but I don't think that, in itself, inevitably means that there is electrical continuity through the meter and its fittings from 'input' to 'output'. If it does have such continuity then, from the electrical point-of-view, it doesn't matter which side of it you bond.

 

[Spikes Mavic]

Thanks Guys n Gals for your inputs on this.

This is what I am going (doing) to do:
10mm from MET to a earth block in the garage. then from the earth block: .1.to CU, .2nd to Gas riser, .3rd to Meter outlet to house, plus the gas pipe at the boiler all ready has 10mm to it .

 

[EFLImpudence]

10mm from MET to a earth block in the garage. then from the earth block: .1.to CU, .2nd to Gas riser, .3rd to Meter outlet to house, plus the gas pipe at the boiler all ready has 10mm to it .

Ok. Too much won't hurt.

For future information and knowledge the bonding on the boiler pipe is not and never has been necessary or required but is a favourite with plumbers.

 

[Spikes Mavic]

Yes. Why not just the usual BS951 clamps?

Would like something more robust for the steel pipework !

 

[Spikes Mavic]

Ok. Too much won't hurt.

For future information and knowledge the bonding on the boiler pipe is not and never has been necessary or required but is a favourite with plumbers.

I thought that the gas pipework has to be bonded has it enters the house , has well has the meter in the garage !