Kitchen refit and CPC problem

[NewOrder]

In the next few weeks once the post Christmas rush is over I hope to rip out the kitchen and put a new one in. The problem is the existing CPC cable from the consumer unit to the kitchen sink pipe (main water pipe coming into the house) is built round the existing unit which is about 50 years old and I need to rip it out.

I plan to install the new cable round the back of the void and then clamp into onto the cold water pipe. At the moment the cable is simply wrapped around it with no mechanical fixing.

Also I noticed there is a plastic compression joint supplying the water to the bathroom should I bridge this with an earth wire and two clamps in order to restore the continuity?

As for the new cable I put in, can I simply make a connection to the old one as longs as the join is accessible? E.g in a covered chocbox under the cupboard under the stairs?

 

[flyingsparks]

Main bonding conductors must be continuos, so no screwed connections. You could crimp and extra length on if needed. What size is the earth wire at the moment. It should be 10mm, if it isn't id replace the whole length.
Yes bridge the plastic fitting. The loose connection there at present could do with sorting out in the mean time, even if you are planning to start the kitchen fairly soon.

 

[NewOrder]

I am not sure where the existing cable starts from, so I may not be able to replace the entire length So what you're saying is there is no way I can simply extend the existing cable? If so I will probably just have to run it inside the cabinet if I can't replace it.

Not sure what size the existing one is, I doubt it is 10mm. My parents are probably selling so they won't get a sparky in (even though I have suggested it many times) so if I can't extend it, and if I can't replace it then all I can really do is just hope there is enough slack in the existing one

 

[NewOrder]

I have just traced the cable back, it is a 6mm cable from a metal bar underneath the consumer unit where another 6mm cable branches of it. One goes to the gas tank the other to the pipes in the kitchen. There is a 10mm (I assume) cable also branching of it to the main supply from the ground. There is another 6mm cable from this bar which goes to the consumer unit.

It is the cable to the kitchen that will get disturbed, it is built into the cupboard and I cannot see how I can remove that without damaging the cable.

I would have thought I can't legally even replace the cable anyway?

Just checked the route again and I think I may able to remove the old cupboard without damaging it as it runs at the back not the front, the cable at the front is just for the alarm.

 

[EFLImpudence]

I have just traced the cable back, it is a 6mm cable from a metal bar underneath the consumer unit where another 6mm cable branches of it. One goes to the gas tank the other to the pipes in the kitchen. There is a 10mm (I assume) cable also branching of it to the main supply from the ground. There is another 6mm cable from this bar which goes to the consumer unit pretty useless thing it looks like!

It would appear from what you say that to replace it with 6mm² would be satisfactory.

I would have thought I can't legally even replace the cable anyway?

No reason to think that.
It is a Main Bonding Conductor, not a CPC.

Is it possible to get a spark in just to replace this cable and nothing else?

Of course.

There is no RCD in the house which is why I am a bit concerned about this.

Not really relevant.

 

[NewOrder]

Thanks edited my post above as now I have seen the cable is at the back I am not quite so concerned. I will post a picture of the main bar if I need to replace the cable, if not I will leave it in its place and just get a clamp to properly attach it to the pipe and bridge the plastic compression joint.

 

[Taylortwocities]

The bar is called the Main Earthing Terminal. This is the place that all of the main earth and bonding conductors come together. New consumer units have space for all of these to connect inside the consumer unit itself.

You will probably need to replace the bonding conductor to the water as it sounds like it is undersized. It depends on your electricity supply type.

While you are at it, you should also renew the bonding to gas, oil, or other services.

 

[ricicle]

Main bonding conductors must be continuos,.

Which reg. no. please ?

 

[NewOrder]

Thanks just done a bit of reading on all this, and because it is not the main earth I can upgrade the cable without having to notify building control but if it was the main earth (e.g it acted as only earth rod) it would be.

I would also be interested if I can just join a new wire onto the existing one as it would make the job much easier. It seems people are a bit confused.

 

[JohnW2]

Thanks just done a bit of reading on all this, and because it is not the main earth I can upgrade the cable without having to notify building control but if it was the main earth (e.g it acted as only earth rod) it would be.

I'm not sure where you read that. Even if it were an 'earthing conductor' (going to earth rod or DNO-supplied earth terminal), it would not be notifiable work.

I would also be interested if I can just join a new wire onto the existing one as it would make the job much easier. It seems people are a bit confused.

I think that it's more a matter of 'myths' than confusion. Many (including some 'guidelines') consider it 'good practice' for bonding conductors to be continuous, but you won't find a regulation which requires that. The reality is that there will always be at least a few screwed connections between the bonded pipe (or whatever) and the earth (rod or DNO-supplied). Any screwed connection should be accessible for maintenance, inspection and testing - for earth/bonding conductors, just as for live conductors. Even those who advocate continuous bonding conductors would probably be hard-pressed to argue against properly constructed crimped joints.

Kind Regards, John

 

[NewOrder]

Thanks John,

My concern was that access might be very difficult due to a glued down fitted carpet which would need to be lifted in order to reroute the earth cable. I am hoping that I can simple keep the old cable but it might not be possible. If I did join the cable I would make sure it is crimped and that it is in accessible place, probably behind a cupboard but with a small cut out in the void.

I still may end up just replacing the entire thing, I will see what access is like once I have gutted the kitchen.

At least I know that if I do damage the existing cable it won't be a disaster.

Also the part of the pipe were the earth wire hangs on (there is no clamp) it is all painted, would be worth while removing a lot of that paint as I am assuming the paint must cause higher resistance?

 

[JohnW2]

Thanks John, My concern was that access might be very difficult due to a glued down fitted carpet which would need to be lifted in order to reroute the earth cable. I am hoping that I can simple keep the old cable but it might not be possible. I still may end up just replacing the entire thing, ...

As has been said, depending on the supply (earth) type, 6mm² cable may not be adequate, so you might have to replace it with 10mm² anyway, if you want it to be reg-compliant.

If I did join the cable I would make sure it is crimped and that it is in accessible place, probably behind a cupboard but with a small cut out in the void.

Others may disagree but (even though I am, in general, no lover of crimping), and provided that the CSA of the cable was adequate, I personally would probably have no problems with crimped joints formed properly by someone who was experienced in crimping. As I said, you won't find a regulation which prohibits joints.

Also the part of the pipe were the earth wire hangs on (there is no clamp) it is all painted, would be worth while removing a lot of that paint as I am assuming the paint must cause higher resistance?

There obviously has to be a good electrical connection, utilising a proper BS-marked clamp onto clean bare metal. 'Wrapped around the pipe' and/or intervening paint are clearly both unacceptable.

Kind Regards, John

 

[EFLImpudence]

Thanks just done a bit of reading on all this, and because it is not the main earth I can upgrade the cable without having to notify building control but if it was the main earth (e.g it acted as only earth rod) it would be.

I'm not sure where you read that. Even if it were an 'earthing conductor' (going to earth rod or DNO-supplied earth terminal), it would not be notifiable work.

It was until April.

Thanks John, My concern was that access might be very difficult due to a glued down fitted carpet which would need to be lifted in order to reroute the earth cable. I am hoping that I can simple keep the old cable but it might not be possible. I still may end up just replacing the entire thing, ...

As has been said, depending on the supply (earth) type, 6mm² cable may not be adequate, so you might have to replace it with 10mm² anyway, if you want it to be reg-compliant.

Equally, or perhaps more, it may be and you might not.


Is it TN-S?

 

[JohnW2]

I'm not sure where you read that. Even if it were an 'earthing conductor' (going to earth rod or DNO-supplied earth terminal), it would not be notifiable work.

It was until April.

Yes, probably (unless it constituted 'replacement of a damaged cable) - but most things (other than in the brief list of non-notifiable works) were then notifiable. I assumed that joydivision's interest is in the situation now, not what it was 9 months ago.

As has been said, depending on the supply (earth) type, 6mm² cable may not be adequate, so you might have to replace it with 10mm² anyway, if you want it to be reg-compliant.

Equally, or perhaps more, it may be and you might not.

True - there is nothing in my 'may' or 'might' which precludes that possibility. Indeed, had I not accepted that, I probably would not have bothered to add my comments about crimping, which obvioulsy would not have been relevant if the whole cable had to be replaced.

Is it TN-S?

You're asking me? My crystal ball is no better than yours. All we've been told is that the earthing conductor comes from "the main supply from the ground" - so probably (although not definitely) not TT, but beyond that it probably comes down to a contest between crystal balls.

Kind Regards, John

 

[NewOrder]

It is a TN-S supply.

I am not sure if this makes much different as I assume a fault can cause can cause a large amount of current to flow through the earth cable regardless of what the appliance consumes, but we have no electric cooker or shower.