7/.036 Cable

[uksparks]

Hi,

Just a question, I know what I would do but wondering what others do.

7/.036 is the old imperial version of 4mm supposedly, do you put it on a 20A MCB or a 32A MCB ??

We are referring to a radial, not a ring.

Personally I put it on a 20A MCB, as looking at the old regs book, not that I have one, but one I found, it can only take 27A if I am correct.

I did a consumer unit change today, had an 8.5kW shower connect on a 7/.036 with 30A Fuse, never been a problem, but I have just disconnected it and put a warning on it etc, we had the conversation of rewiring it which could be done in about 2 hours with minimal effort and the customer didn't want it.

The customer has called me and said he has reconnected it, can't help some people, I did connect it and see how much it was pulling and it was 35.9A.

 

[davesparks]

Firstly, are you sure of the size? Could it be 7/044?

 

[Andy78]

How come this issue did not come up before you changed the board ?
What has the customer reconnected the cable to ?

 

[R G]

As Andy says , this should have been checked before specifying or changing the board , questions like this can't be asked after the work has been done ...

 

[HappyHippyDad]

Should you be looking at current rating 7? One twin core cable with/without earth. That would give you 31A.

 

[uksparks]

I'll be honest it was partially an oversight on my part thinking it was 6mm when briefly looked, it was one of those jobs where I tested it first then changed all on the sand day which I don't usually do. But the customer wanted me to get on with it.

I have not been caught out like this before so am a big annoyed with myself to be honest, but anyway it's where we are, I had got the time today to change the cable as it could easily have been changed to the isolator where it had current 6mm to the shower.

 

[uksparks]

How come this issue did not come up before you changed the board ?
What has the customer reconnected the cable to ?

A 32A type B MCB in the new board.

 

[uksparks]

Firstly, are you sure of the size? Could it be 7/044?

I can only assume so as got my micrometer out and it measured approx 0.036, nowhere near 0.044, plus it has a 1.5mm single CPC which was another tell take that it was the 0.036

 

[uksparks]

Should you be looking at current rating 7? One twin core cable with/without earth. That would give you 31A.

So it does, you are quite right, my eyesight is failing me clearly! Still though, it's still less than 32A and less than 35.9A that the shower was pulling.

 

[davesparks]

To be honest you are a little bit buggered.
You've made a mistake and now the only way you can fix it is install a suitably sized cable on a 40A mcb.
Now if you're good with the bull**** you might get away with the customer paying for it, or maybe paying for materials only. Failing that you're going to have to take it on the chin and accept the cost.
Hopefully you allowed enough contingency in your price that it won't be an overall loss on this ine

 

[Andy78]

A 32A type B MCB in the new board.

Is it a dedicated MCB for the shower or has he tagged it in with something else ?

 

[uksparks]

To be honest you are a little bit buggered.
You've made a mistake and now the only way you can fix it is install a suitably sized cable on a 40A mcb.
Now if you're good with the bull**** you might get away with the customer paying for it, or maybe paying for materials only. Failing that you're going to have to take it on the chin and accept the cost.
Hopefully you allowed enough contingency in your price that it won't be an overall loss on this ine

I agree totally, it was my fault for not spotting it, i don't suppose I'm the first one. It was an easy mistake to make looking at the cable. I'm happy to change the cable for a new one for free other than parts which won't come to much.

Its to an easy run so it's not a major problem.

its had an 8.5kW shower running on it for nearly 10 years with a 30A fuse.

ill give the bloke a call and arrange to swap it.

 

[uksparks]

Is it a dedicated MCB for the shower or has he tagged it in with something else ?

He has put it on its own dedicated circuit.

 

[uksparks]

I've just called him and he will change it, I'll do it free plus parts.

 

[7029 dave]

Okay, so you changed the cu, oversight on your behalf with the under rated shower cable circuit, advised customer of the fact, you disconnect, he has re energized the circuit that has been insitu for 10 years, no thermal damage on cable?, IMO don't replace for free, else stick it on 20amp mcb when it goes pop down to the client to make the move.