Bonding in Bathroom

[noxfort]

Hello,

Just wanted too double check everything is as it should be with bonding in Bathroom.

For reference only my sockets have RCD lighting doesnt.

Currently a radiator in my bathroom is going to be replaced by a towel heater (non electrical). The radiator is fed by copper pipe and has a wire attached directly to the radiator.

My mains cold feed comes into thee bathroom then has copper pipe with plastic fittings. Like this:

Mains Copper --- Push Fit Plastic Stop Cock --- Plastic Tee --- 1 Way to tap 1 way to bath.

Hot water is comes from floorboards ans same again goes to plastic fittings with copper pipe.

The hot water pipe is bonded at the hot water cylinder outlet (the same with cold mains).

Hopefully that explains the setup now some questions.

1. a) Does the new Towel radiator need the bonding cable attached to the old radiator need connecting to the towel radiator? b) is connecting it to the flow pipe enough?

2. Should my mains cold water have bonding after the plastic fitting?

3. Should the hot water have bonding after the plastic fitting?

Cheers

 

[EFLImpudence]

1. a) Does the new Towel radiator need the bonding cable attached to the old radiator need connecting to the towel radiator?
b) is connecting it to the flow pipe enough?

a) No
b) Yes

2. Should my mains cold water have bonding after the plastic fitting?
3. Should the hot water have bonding after the plastic fitting?

Can't tell from here or by looking at it.

Measurements need to be taken to determine if bonding is required.

 

[JohnW2]

2. Should my mains cold water have bonding after the plastic fitting? 3. Should the hot water have bonding after the plastic fitting?

Can't tell from here or by looking at it. ... Measurements need to be taken to determine if bonding is required.

Are you thinking of the conductivity of water in the pipes? If not, then bonding of a pipe downstream of a 'plastic interruption' would surely not be required?

Kind Regards, John

 

[EFLImpudence]

Are you thinking of the conductivity of water in the pipes?

Not really, just don't know the situation for certain.

 

[JohnW2]

Are you thinking of the conductivity of water in the pipes?

Not really, just don't know the situation for certain.

Fair enough - but on the basis of what we've been told (which seems fairly clear), I don't see that those pipes could need bonding (unless you were concerned about the conductivity of the water - which is presumably what you would be measuring, if you undertook your 'measurements').

Kind Regards, John

 

[noxfort]

Thanks Guys,

Just noticed the old bonding was on the return pipe not flow. I take it that doesn't change anything?

I take it I need one of these? https://www.tlc-direct.co.uk/Products/EC15.html

I remember overhearing someone in TLC explaining E15 is for humid conditions and E14 is for dry.

 

[EFLImpudence]

Just noticed the old bonding was on the return pipe not flow. I take it that doesn't change anything?

Well, we really cannot tell from here.
One on each connected together may be required.
Bonding (joining together electrically) is to connect - if required - extraneous-conductive-parts to the exposed-conductive-parts.

I take it I need one of these? https://www.tlc-direct.co.uk/Products/EC15.html[/QUOTE]
Yes, but you don't have to have them in the bathroom if there is somewhere else less unsightly.

There really is a lot more to it than just attaching clamps to pipes.

I remember overhearing someone in TLC explaining E15 is for humid conditions and E14 is for dry.

http://www.elecsa.co.uk/Documents/C...al-Downloads/BS951-clamp-colour-guide_PI.aspx

 

[ban-all-sheds]

Fair enough - but on the basis of what we've been told (which seems fairly clear), I don't see that those pipes could need bonding (unless you were concerned about the conductivity of the water - which is presumably what you would be measuring, if you undertook your 'measurements').

Why shouldn't one be concerned about its conductivity? It is conductive, after all.

What impedance between a conductive part, such as a copper pipe, and earth (measured to the MET, I guess) would you like to see before you judged that it was not an extraneous-conductive-part which required bonding?

 

[JohnW2]

Fair enough - but on the basis of what we've been told (which seems fairly clear), I don't see that those pipes could need bonding (unless you were concerned about the conductivity of the water - which is presumably what you would be measuring, if you undertook your 'measurements').

Why shouldn't one be concerned about its conductivity? It is conductive, after all.

One would/should be concerned if the impedance of the water were low enough - but I don't think it would be.

What impedance between a conductive part, such as a copper pipe, and earth (measured to the MET, I guess) would you like to see before you judged that it was not an extraneous-conductive-part which required bonding?

EFLI is seemingly the expert on that 'test' of whether or not something should be considered to be an extraneous-c-p, and his threshold (based on the regs) is, I believe, 23kΩ (i.e. 10mA at 230V) (although I think it's a bit pessimistic to consider that the potential of a simultaneously-touchable exposed-c-p would be likely to be 230V, since that would require at least two faults).

Kind Regards, John

 

[EFLImpudence]

It's not a question of being an expert nor is it based on the regs.

10mA is the accepted limit above which it may cause muscle contraction and be impossible to let go so is used to define extraneousness (if such a word).

Some may wish to use 5mA; the accepted harmless limit.

(although I think it's a bit pessimistic to consider that the potential of a simultaneously-touchable exposed-c-p would be likely to be 230V, since that would require at least two faults).

Do you mean two exposed-c-ps - hence the two faults?

Surely we have to allow for 230V.

 

[JohnW2]

It's not a question of being an expert nor is it based on the regs. 10mA is the accepted limit above which it may cause muscle contraction and be impossible to let go so is used to define extraneousness (if such a word). Some may wish to use 5mA; the accepted harmless limit.

I don't disagree with any of that. As you say, the regs do not prescribe a test of whether or not something is an extraneous-c-p, but they do define a test of the adequacy of supplementary bonding, and I thought you had been known to suggest that this test can also be used to determine whether supplementary bonding is required (i.e. whether a part qualifies as 'extraneous'). However, that test is not related to the physiological effects of electric shocks of a given current but, rather, in relation to the operation of a protective device - i.e. R≤50/Ia. The problem with that one is that "Ia" can be 30mA for an RCD or, say, 160A for a B32 - so that the maximum permissible resistance can be 1667Ω or 0.3125Ω !! (either of which is a lot less than 23k&#937.

(although I think it's a bit pessimistic to consider that the potential of a simultaneously-touchable exposed-c-p would be likely to be 230V, since that would require at least two faults).

Do you mean two exposed-c-ps - hence the two faults? Surely we have to allow for 230V.

Yes, I suppose one has one has to 'allow for 230V' (which I did), since the occurrence of two simultaneous faults is not impossible (although extremely improbable). As for those 'two faults' ... if an exposed conductive part comes in contact with L, then, if the CPC connected to that exposed-c-p is intact, then the voltage of the exposed-c-p should only be a little over half of the supply voltage (i.e. around 115V) ('a little over' because R1<R2 within the installation). Only if the CPC is disconnected or broken (second fault) will the potential of the exposed-c-p rise to the full supply voltage.

Kind Regards, John

 

[bernardgreen]

I suppose one has one has to 'allow for 230V' (which I did), since the occurrence of two simultaneous faults is not impossible (although extremely improbable).

It is improbable only if the first of the two faults is detected and rectified before the second fault occurs.

In reality the first fault may go undetected as it causes no problems. Only when a second fault occurs and together with the first fault causes an accident or injury is there any indication that there is a fault.

 

[ban-all-sheds]

EFLI is seemingly the expert on that 'test' of whether or not something should be considered to be an extraneous-c-p, and his threshold (based on the regs) is, I believe, 23k&#937; (i.e. 10mA at 230V)

That would be about 200mm of 15mm² water.



The OP has copper pipes joined by plastic push-fit connectors which create a gap in the copper piping of a lot less than 200mm.

So yes, you do need to worry about the conductivity of the water.

 

[JohnW2]

[of 23k&#937;] ... That would be about 200mm of 15mm² water. The OP has copper pipes joined by plastic push-fit connectors which create a gap in the copper piping of a lot less than 200mm. ... So yes, you do need to worry about the conductivity of the water.

Interesting, with some interesting implications. In the OP's case, whether the 'copper gap' is more or less than 200mm obviously depends on the material and length of the pipe joining the plastic stopcock to the plastic tee.

Kind Regards, John

 

[EFLImpudence]

It's not a question of being an expert nor is it based on the regs. 10mA is the accepted limit above which it may cause muscle contraction and be impossible to let go so is used to define extraneousness (if such a word). Some may wish to use 5mA; the accepted harmless limit.

I don't disagree with any of that. As you say, the regs do not prescribe a test of whether or not something is an extraneous-c-p, but they do define a test of the adequacy of supplementary bonding, and I thought you had been known to suggest that this test can also be used to determine whether supplementary bonding is required (i.e. whether a part qualifies as 'extraneous').

That is true.
As you have often stated the figure (23 or 46k&#937 is purely arbitrary and the actual values are going to be a few ohms or many (virtually isolated) so there will be no indecision.

However, that test is not related to the physiological effects of electric shocks of a given current but, rather, in relation to the operation of a protective device - i.e. R&#8804;50/Ia.

Is the outcome not the same?

The problem with that one is that "Ia" can be 30mA for an RCD or, say, 160A for a B32 - so that the maximum permissible resistance can be 1667&#937; or 0.3125&#937; !!

Why is that a problem?
That is why supplementary bonding may be omitted when RCDs are fitted.
However, should the resistance be between 1667 and 23,000 (or 46,000) then supplementary bonding would still be required.

(Just as the Zs on a TT system is alowed to be more than the OPD's max Zs - although vice versa, in practice.
Perhaps the regs. for SB should be rewritten to say that if R>50/Ia then you must fit an RCD.)

(either of which is a lot less than 23k&#937.

Well, yes but as above.
It just means that values between 0.3125 (or 1,667) and 23,000 (or 46,000) require SB.