Help guys with cable rating?

Bertybert · Jul 20, 2021

Hi Guys,
Berty here.
I used to be a tradesman looong ago, not a sparky though.

I am trying to find out the rating of the cable going to my shower.

It is 7 strands - each 1mm in diameter.
I thought it was a solid cable for some reason...lol.
I fitted it 30 years ago, and now need to replace the shower and dont know what rating of shower the cable can take.

Hoping you guys can help.

I have attached a pic, this uisually helps.

Pete999 · Jul 20, 2021

Bertybert said:
Hi Guys,
Berty here.
I used to be a tradesman looong ago, not a sparky though.

I am trying to find out the rating of the cable going to my shower.

It is 7 strands - each 1mm in diameter.
I thought it was a solid cable for some reason...lol.
I fitted it 30 years ago, and now need to replace the shower and dont know what rating of shower the cable can take.

Hoping you guys can help.

I have attached a pic, this uisually helps.

At A COMPLETE GUESS 7/044 7/052 0R 7/O64

Bertybert · Jul 20, 2021

I tried having a look at what is means, and it looks like it can take a good load?

Its an Electric shower obviously, and it should take 10,8Kw easily?

westward10 · Jul 20, 2021

It looks 6.0 if so the cpc will be pretty stiff at 2.5.

Spoon · Jul 20, 2021

Welcome to the forum mate.
Out of curiosity, what size breaker is the cable fitted to in the consumer unit?
Does your consumer unit or shower circuit have RCD protection?

Lucien Nunes · Jul 20, 2021

1mm diameter strands works out close to 6.0mm² which was by far the most common size for a shower then. You can confirm it with the CPC size which should be 1.78mm diameter which is 2.5mm².
6mm² T+E is the only T+E cable size with 2.5mm² CPC.

Once the size is cofirmed, to discover its current rating you will need to check the installation method. Does it run through loft insulation? Conduit? Is it bunched with other cables?

At A COMPLETE GUESS 7/044 7/052 0R 7/O64

But it was installed 30 years ago, i.e. at least 20 years after those imperial sizes were phased out, and the conductors are plain copper which is a good clue to it being metric.

Bertybert · Jul 20, 2021

Mmm too mcuh complications...lol and still no further forward.

I did measure the strand with the micrometer and it was 1.1mm and just rounded it down. The cable run is behind plastererboard and is the only cable, no trunking or insulation.
The breaker size am not sure, and that can be changed easily. I thought the load the shower can take would be governed by the load the cable can take.

telectrix · Jul 20, 2021

as a general rule ,6.0mm cable will cope with a shower of up to 9.5kW , installed as per your post. the MCB should then be 40A. although many 32A MCBs have coped with a 40A load for short periods,

Bertybert · Jul 20, 2021

Brilliant. that is what I was looking for Telectrix many thanks!
I know it is difficult when you cant see the cable in your hand, but it used to be - the sparky looking at the cable, 'yeah dont go anyhigher than 9.5 Kw'...lol.
I think the MCB or the big block says 80A, I wasnt sure what shower I: was gonna fit at the time 30 years ago and the sparky said get that one, which I did and he fitted it.

But all good many thanks to all!!