supplementary bonding

[MrCox1963]

Hi all, this is a classic case of everyone is telling me contradicting methods.

so I have replaced my bathroom suite and found there was no bonding. on further investigation no main bond from water supply either. the supply enters the house in plastic but after stop cock all water pipes are copper with soldered joints bar a few compression fittings. The gas has a main bond and I'm lead to believe even with plastic supply as above the water pipes need bonding too.
I've fitted a unbroken main bond to terminal block next to the CU using 10mm2 .. CU & gas were already bonded...so main bond dealt with, ok so far?

my real question is supplementary bonding. I'm told/researched that regs don't require supplementary bonding in the kitchen so just the bathroom to deal with, is this correct regarding current regs?

The hot and cold under the bathroom tee off to the basin with a mixers tap then further along they tee off to the mixers shower and finally cold tee off to toilet and out the room again . so if I bond the basin h&c there's no need to bond the shower as its fed from same un interrupted pipes no more than 1m away. in fault conditions surely the shower and tap must be at same potential? plus the shower pipes aren't accessible.

so I want to bond the basin h&c to the radiator pipe (or does it need to be both radiator pipes? can't be rad as its a towel rail rad)

then to earth of shaver unit (i understand the purpose of connecting to the power circuit or lights but don't get why would need to connect to both as both circuits are already connected via the earth in CU) am I wrong here?

Finally I'm planning to use 4mm2 does the supplementary bond have to be unbroken.

Please correct me if I'm wrong anywhere
thanks sorry about the essay

Rob

 

[ericmark]

Big question is what version of BS7671 is your house wired to? The use of RCD protection changes what is required.

 

[EFLImpudence]

Hi all, this is a classic case of everyone is telling me contradicting methods.

I shall tell you the truth.

so I have replaced my bathroom suite and found there was no bonding.

Ok.

on further investigation no main bond from water supply either. the supply enters the house in plastic but after stop cock all water pipes are copper with soldered joints bar a few compression fittings.

See below.

The gas has a main bond

Good.

and I'm lead to believe even with plastic supply as above the water pipes need bonding too.

No, as long as none of the copper pipes reenters the ground.

I've fitted a unbroken main bond to terminal block next to the CU using 10mm2 ..

If you mean to the water, then it was not necessary although it will do no harm as, presumably, the pipes are connected to earth somewhere by boiler or immersion heater, for example.

CU & gas were already bonded...so main bond dealt with, ok so far?

Yes.

my real question is supplementary bonding. I'm told/researched that regs don't require supplementary bonding in the kitchen

Correct.

so just the bathroom to deal with, is this correct regarding current regs?

If ALL the circuits in the bathroom are protected by RCDs and other conditions are met then supplementary bonding may be omitted.

The hot and cold under the bathroom tee off to the basin with a mixers tap then further along they tee off to the mixers shower and finally cold tee off to toilet and out the room again . so if I bond the basin h&c there's no need to bond the shower as its fed from same un interrupted pipes no more than 1m away. in fault conditions surely the shower and tap must be at same potential?

Very likely, see below.

plus the shower pipes aren't accessible.

Then you can't touch them.

so I want to bond the basin h&c to the radiator pipe (or does it need to be both radiator pipes? can't be rad as its a towel rail rad)

You do not bond the radiator but the pipes.

then to earth of shaver unit (i understand the purpose of connecting to the power circuit or lights but don't get why would need to connect to both as both circuits are already connected via the earth in CU) am I wrong here?

It is to reduce the resistance between them


Supplementary bonding is more complicated.
Assuming that there is no RCD protection then the resistance between simultaneously accessible parts -[extraneous-conductive-parts (pipes) and exposed-conductive-parts (metal electrical fittings)] must be no greater than 50V / (the current causing automatic operation of the protective device within the time stated of the highest rated device of the bathroom).
Assuming your shower is protected by a 40A MCB, this would then be 50/200 which is 0.25Ω.

If the resistance is below this figure then bonding is not required.

Finally I'm planning to use 4mm2 does the supplementary bond have to be unbroken.

It only has to connect the parts; it does not have to go to the CU.
Also, the pipes and CPCs(earth wires) themselves may be used as the bond.
This means that connecting two pipes, for example, may in actual fact connect them all

Also, the bonding of the bathroom does not have to be in the bathroom.
It can be anywhere that the required results can be achieved.


Anything else?

 

[JohnD]

It can be anywhere that the required results can be achieved.

if you are lucky enough to have an airing cupboard next to the bathroom, it is likely that all the pipes will be easily accessible, and your bonding clamps and cables will not be considered very unsightly.

 

[JohnW2]

Supplementary bonding is more complicated. ... Assuming that there is no RCD protection then the resistance between simultaneously accessible parts -[extraneous-conductive-parts (pipes) and exposed-conductive-parts (metal electrical fittings)] must be no greater than 50V / (the current causing automatic operation of the protective device within the time stated of the highest rated device of the bathroom).

Indeed. The one thing that seems not to get mentioned in these discussions is that I would have thought that (unless there are electric towel rails etc.) it is pretty/very rare for a bathroom to have any exposed-conductive parts - and, if it doesn't, then there's nothing one can apply supplementary bonding to! ... or am I missing something?

Kind Regards, John

 

[deadshort]

Now John, i hope you tell the truth !


Regards,

DS

 

[JohnW2]

Now John, i hope your tell the truth !

Well, I was actually asking a question ("...I would have thought .... or am I missing something?"), rather than 'telling' anything

What I perhaps should have said, rather than just imply (I suppose, cryptically on my part this time!) with my essentially rhetorical question, is that what EFLI said about supplementary bonding does not really seem to correspond (at least in full) to what the regs say. The regs do not say anything about exposed-c-ps in relation to supplementary bonding but, rather, require that extraneous CPs be joined to the CPCs of any circuits in the room which supply Class I or Class II equipment. Therefore, if the conditions for omitting supplementary bonding are not satisfied, then there is still a requirement for supplementary bonding, even if there are no exposed-c-ps. Supplementary bonding is therefore clearly not just about limiting the possible PD between extraneous-c-ps and exposed-c-ps.

Kind Regards, John

 

[EFLImpudence]

The regs do not say anything about exposed-c-ps in relation to supplementary bonding

415.2.1

but, rather, require that extraneous CPs be joined to the CPCs of any circuits in the room which supply Class I or Class II equipment. Therefore, if the conditions for omitting supplementary bonding are not satisfied, then there is still a requirement for supplementary bonding, even if there are no exposed-c-ps. Supplementary bonding is therefore clearly not just about limiting the possible PD between extraneous-c-ps and exposed-c-ps.

You are, as usual, overlooking the main rider in 701.415.2 which says "according to Regulation 415.2".
Also overlooked or ignored, I think by most, is the "simultaneously accessible".

I agree that the reference to Class II is confusing but it does say "circuits of..." which, therefore, does not necessarily mean each item.


I think this situation may be similar to the main bonding of the water service.
Nowhere do the regulations state that if the service is NOT extraneous main bonding is not required but this has to be deduced from the wording elsewhere.

 

[JohnW2]

You are, as usual, overlooking the main rider in 701.415.2 which says "according to Regulation 415.2". Also overlooked or ignored, I think by most, is the "simultaneously accessible".

Fair enough, but I think that what 415.2 says about 'simultaneously accessible' is, at the least, ambiguous. What is your interpretation of:

Supplementary equipotential bonding shall include simultaneously accessible exposed-conductive-parts of fixed equipment and extraneous-conductive-parts ....

I have to say that I (and I suspect others), have taken it to mean exposed-c-ps which could be accessed at the same time as ('simultaneously accessible') extraneous-c-ps (or vice versa), but you presumably interpret it differently?.

Kind Regards, John

 

[EFLImpudence]

What is your interpretation of:

Supplementary equipotential bonding shall include simultaneously accessible exposed-conductive-parts of fixed equipment and extraneous-conductive-parts ....

I have to say that I (and I suspect others), have taken it to mean exposed-c-ps which could be accessed at the same time as ('simultaneously accessible') extraneous-c-ps (or vice versa), but you presumably interpret it differently?.

Of course that is what it means.
Why do you say I interpret it differently?

What I meant was people would apply SB to all parts without considering that they may be inaccessible, either simultaneously or wholly.

 

[JohnW2]

What is your interpretation of:

Supplementary equipotential bonding shall include simultaneously accessible exposed-conductive-parts of fixed equipment and extraneous-conductive-parts ....

I have to say that I (and I suspect others), have taken it to mean exposed-c-ps which could be accessed at the same time as ('simultaneously accessible') extraneous-c-ps (or vice versa), but you presumably interpret it differently?.

Of course that is what it means. Why do you say I interpret it differently?

Because, as I wrote last night, if you agree with that interpretation, it means that the concept of SB cannot exist in the absence of exposed-c-ps (which, as I said, is probably the case in the majority of bathrooms).

Many people (and not necessarily only plumbers ) seem to work with a different interpretation such that, even if there are no exposed-c-ps, if the conditions for omission of SB are not satisfied, then they have to supplementary bond any extraneous-c-ps which are 'simultaneously accessible/touchable'.

Kind Regards, John

 

[EFLImpudence]

Well, you/we are in danger of upsetting TTC again, however:

Because, as I wrote last night, if you agree with that interpretation, it means that the concept of SB cannot exist in the absence of exposed-c-ps

That's a ridiculous interpretation.

You are reading 415.2.1:
Supplementary equipotential bonding shall include simultaneously accessible exposed-conductive-parts of fixed equipment and extraneous-conductive-parts ....

as:
Supplementary equipotential bonding shall include (simultaneously accessible exposed-conductive-parts of fixed equipment) and extraneous-conductive-parts ....
to mean that if there are no exposed-c-ps then the extraneous-c-ps do not require bonding.

instead of:
Supplementary equipotential bonding shall include simultaneously accessible (exposed-conductive-parts of fixed equipment) and (extraneous-conductive-parts) ....
when it is obvious what it means.

 

[JohnW2]

Because, as I wrote last night, if you agree with that interpretation, it means that the concept of SB cannot exist in the absence of exposed-c-ps

That's a ridiculous interpretation.

As I said, it strikes me as ambiguous - I am not expressing a personal view. It's certainly an interpretation which has some 'interesting consequences', but (unless I wasn't clear enough in what I wrote) it's the interpretation with which you seem to have just agreed ("Of course that is what it means").

You are reading 415.2.1: .... as: ... ... instead of: ... when it is obvious what it means.

I'm not sure that our respective attempts to use the notation of logic leaves either of us with a certain idea of what the other is saying! Reverting to good old words, the interpretation I was suggesting (as a possibility) is that there is (if conditions for omission are not satisfied) a requirement to bond together (and to CPCs) any exposed-c-p(s) and any extraneous-c-p(s) that can be touched simultaneously with it/them.

If I understand you correctly, you are suggesting an interpretation which means that (if conditions for omission are not satisfied) supplementary bonding is required between two or more extraneous-c-ps which are 'simultaneously accessible/touchable', even if there are no exposed-c-ps. I can understand (almost per 'plumber thinking') the logic in connecting any such extraneous-c-ps together, so as to minimise any PDs that can exist between those simultaneously-touchable parts. However, SB requires that they also be connected to the CPCs of circuits in the room. As I see it, if there are no exposed-c-ps, that requirement makes no sense - at best it's unnecessary and, at worst (if other things are wrong) it could actually introduce a hazard. ... or am I misunderstanding you, or missing something?

Kind Regards, John

 

[EFLImpudence]

So, you are saying that if there are NO exposed-c-ps in the bathroom then bonding between pipes is not required.

415.2 says SB shall "include all...and..." and not "connect all...to...".

I can see what you are getting at (but am unsure about introducing a hazard as only extraneous parts would be bonded) but if that is what is meant then I think I would have to go back to school and an awful lot of cable has been wasted.

Why then would showers ever need bonding? Do they have exposed-cps?

 

[JohnW2]

So, you are saying that if there are NO exposed-c-ps in the bathroom then bonding between pipes is not required.

I am saying that the reg appears to be ambiguous and that is one of the possible interpretation. As I said, I am not saying thatis my opinion.

415.2 says SB shall "include all...and..." and not "connect all...to...".

Indeed. IMO, another 'ambiguity'- or, at least lack of clarity. Exactly what does "SB shall include ...." mean?

I can see what you are getting at (but am unsure about introducing a hazard as only extraneous parts would be bonded) but if that is what is meant then I think I would have to go back to school and an awful lot of cable has been wasted.

You tell me - as I've been saying, I don't think the regs are at all clear! As for 'introducing a hazard', if there were no exposed-c-ps and all extraneous-c-ps were bonded, then ('unnecessarily') connecting them to CPCs would not introduce any hazard. However, if any extraneous-c-ps were missed (or if new ones were introduced subsequently), the fact that the other extraneous-c-ps had been connected to CPCs could theoretically represent a (tiny) hazard. However, that 'tiny risk' was not my main point - that being that, if there are no exposed-c-ps, connecting to CPCs would seem to be 'unnecessary'/pointless.

Why then would showers ever need bonding? Do they have exposed-cps?

I don't think they do, under any interpretation of the regs - they are not an extraneous-c-p, and if they have no exposed-c-ps, exactly what would/could you bond? However, as previously said, if any SB (of anything) is required in the room, then it would have to connect to (amongst other things) the CPC of the shower circuit.

Kind Regards, John