Redundant copper pipe as conduit?

[Jurassicspark]

I presume the OP was talking about connecting the pipe to a CPC - which,in turn, would be 'connected back to the MET'.

If that's the case then that wouldn't bring up an issue. Years ago, someone did similar but got the CPC from the cable and earthed it to the pipe. Not knowing where the pipe lead to he never knew if the pipe really formed part of the protective earth. One day he drilled through the pipe (not knowing it was there) the live touched the earth but never tripped anything because of the pipe not really being connected back to the MET. Later he reported he was getting tingles from the bathroom walls. At the end of the day, there is no need of running the cables through the pipe. If there is then would all other cables need ripping out?

 

[JohnW2]

What does concern me a little more perhaps is could it be construed as misleading. ome might think that it is reasonable for some people to realise that a conduit might contain live wires yet not expect a copper pipe to contain live wires, ....

Fair enough - but, as the OP has responded, one would hope that no sensible person would cut into a pipe 'of unknown purpose' (which might well contain water, OR GAS, under pressure) without first having located at least one end and determining what it was connected to (and whether a cable entered it!).

Having said that, the very reason I suggested that earthing the copper pipe might be 'desirable' was 'just in case' someone managed to penetrate the cable-containing pipe in a manner that rendered it potentially live (or the cable 'melted' within the pipe, again potentially rendering the pipe 'live'.

Kind Regards, John

 

[JohnW2]

If that's the case then that wouldn't bring up an issue.

What else could the OP have meant by 'earthing the pipe'?

When any of us talk about 'earthing' something, we are surely refering to connecting it to a CPC within the installation (hence ultimately the mET), aren't we?

 

[EFLImpudence]

Years ago, someone did similar but got the CPC from the cable and earthed it to the pipe.

Do you not mean he earthed the pipe to the CPC?

Not knowing where the pipe lead to he never knew if the pipe really formed part of the protective earth.

So what difference did connecting a CPC to it make?

One day he drilled through the pipe (not knowing it was there) the live touched the earth but never tripped anything because of the pipe not really being connected back to the MET.

Then where did the CPC go?

@Jurassicspark I think your posts in this thread have been misleading. They must have been very difficult for the OP to follow because I could not.

Have you been confusing earthing and bonding or have I missed something?

 

[EFLImpudence]

I think this thread is similar to the metal bath with cables running underneath it.

In this situation the bath does not require earthing or bonding (it would be earthing if bonding not required) as it is not an exposed-conductive-part and not earthed by any other means.
However, some people would prefer it earthed in case a live conductor escapes from its cable and jumps up and touches the bath and some would not in case a person touches a live wire whilst also touching the bath.
It depends which you think is more likely.

Earthing is not a good thing in its own right.
It is a necessary evil because some metal parts of appliances might become live in fault conditions.
It would be better if no metal parts were earthed.

 

[JohnW2]

@Jurassicspark I think your posts in this thread have been misleading. They must have been very difficult for the OP to follow because I could not.

For what it's worth, I couldn't follow, either.

As I've said, my view is that, whilst creating 'unnecessarily earthed' bits of touchable metal is generally undesirable (since it very slightly increases very small risks of electric shock), it seems to me that this under-floor pipe will probably not be normally touchable, in which case some might feel that the pendulum (in relation to extremely small risks) might swing in the direction of earthing it.

 

[EFLImpudence]

As I've said, my view is that, whilst creating 'unnecessarily earthed' bits of touchable metal is generally undesirable (since it very slightly increases very small risks of electric shock), it seems to me that this under-floor pipe will probably not be normally touchable, in which case some might feel that the pendulum (in relation to extremely small risks) might swing in the direction of earthing it.

I agree.

The only situation if not earthed is if the pipe became live because of a fault on the cable within it then it would remain live until someone did go under the floor and touched it.

 

[ATTQ]

Am i right thinking you're all talking as though RCDs aren't a part of the equation, is that because by policy you dont assume they will work? That makes sense as I can imagine all sorts of shoddy practice would become normal if its like "whatever, the RCD will save you"

 

[ATTQ]

One day he drilled through the pipe (not knowing it was there) the live touched the earth but never tripped anything because of the pipe not really being connected back to the MET. Later he reported he was getting tingles from the bathroom walls.

Was this with an RCD?

At the end of the day, there is no need of running the cables through the pipe. If there is then would all other cables need ripping out?

There is a bit of a need. If i could get the pipes out i could use the space where they are but i cant get them out so i'm thinking put the cable in the pipe and actually using them as a guide might help get the cable there

 

[Jurassicspark]

The only situation if not earthed is if the pipe became live because of a fault on the cable within it then it would remain live until someone did go under the floor and touched it.

I was trying to explain this situation but it may not have come up clearly. Years ago someone did have this issue but the worst thing was the L touched the metal pipe but it wasn't actually earthed back to the main earthing terminal. However it was his mistake as he assumed the pipe formed part of the protective earth but it didn't and instead of bringing an earth wire to the MET he just linked the CPC to the cable.

 

[Jurassicspark]

Was this with an RCD?

No RCD and someone insisted in fitting one.

There is a bit of a need. If i could get the pipes out i could use the space where they are but i cant get them out

Why can't you get them out? Are they notched into the joist or are they drilled through them?

 

[EFLImpudence]

Am i right thinking you're all talking as though RCDs aren't a part of the equation,

Yes.

is that because by policy you dont assume they will work?

They are not magic. They do not reduce shock values of faults, merely the duration of that shock.

That makes sense as I can imagine all sorts of shoddy practice would become normal if its like "whatever, the RCD will save you"

Well - RCDs are supposed to be only regarded as "additional" protection unless unavoidable - TT.
That is the usual protective measures should still be in place.

However, of course, the powers that be then contradict themselves by, for example, allowing the omission of bonding in bathrooms because, as you say, the resistance value has increased to 1666Ω.

 

[ATTQ]

Why can't you get them out? Are they notched into the joist or are they drilled through them?

There is a double bend near one end of both pipes, blocked by a brick wall from coming through. must have been installed with the floor up. Its bends though rather than elbows so i'm confident the cable will make it through.

 

[JohnW2]

Am i right thinking you're all talking as though RCDs aren't a part of the equation, ...

Other than in TT installations, RCDs are not normally 'part of the equation' in terms of the requirement for the Zs of a cireuit to be low enough for automatic disconnection to occur within the specified times in the event of an L-E fault 'of negligible impedance'. In TN installatiuons the primary proection is by over-current devices (e.g. MCBs, or part oof an RCBO), RCDs only being there as 'additional protection'.

 

[JohnW2]

I was trying to explain this situation but it may not have come up clearly. Years ago someone did have this issue but the worst thing was the L touched the metal pipe but it wasn't actually earthed back to the main earthing terminal. However it was his mistake as he assumed the pipe formed part of the protective earth but it didn't and instead of bringing an earth wire to the MET he just linked the CPC to the cable.

I'm still a bit confused. Are you saying that one or both ends of the CPC in the cable (within the pipe) were connected to the pipe, but that neither end of that CPC was connected to anything else? At least one end surely should have been connected, directly ot indirectly, to the MET, shouldn't it?