New Shower cable thickness advice and max shower watts

[clubb699]

Hi all,


My Question is i have twin and earth cable to a very old shower unit the shower is rated at 7 KW, with a chat to the local B&Q helper he mentioned the cable could be 4mm as the fuse is 30 AMPS. looking at there cables on the shelf it does look like 6MM but to be safe im going to say its 4MM whats the max Watt of shower i could put on to this 4MM cable, the cable is 5 meteres max from the CU.

Thanks in advance.

 

[GaryMo]

You say fuse, is it actually a fuse containing fuse wire or is it a circuit breaker? Many people on here call every protective device a fuse!
Does the cable run through trunking or any thermal insulation? Or is it plaster within walls?

 

[flameport]

If it is 4mm (very unlikely), then it should be ok for the fuse rating (30A), provided it is not covered with insulation. Even if it is 6mm, the limiting factor is still the 30A fuse.

7kW is your maximum, without replacing the fuse. It is also unlikely that the fusebox will accept fuses greater than 30A.

 

[GaryMo]

If it is 4mm (very unlikely), then it should be ok for the fuse rating (30A)

Not if it is a BS3036 rewirable fuse it won't. Apply a correction factor (Cc) to the 30A fuse and you'll require a cable capable of carrying 41.4A which is out of reach for 4mm2 t&e.

 

[clubb699]

Hi lads

Thanks for quick repies i should of added i will be having the CU replaced once i can get a local elecy to actually get back in touch with me( not having any luck ATM) so with the CU being replaced and its 4mm or 6mm whats the limits then of the shower Watts

So Heres some pics of the wire

Measured across its showing 4.5mm across the black cable.

Yes at the moment the CU is the old style fuse wire fuses, and it goes across ceiling under the stairs up through the ceiling for a max of 1 meter through a plastered wall and then across under the bath and then up under tiled wall to the shower.

CU

Cheers in advance

 

[rssteve]

you need to measure the copper mm2 not the insulation. I think thats 4mm if you compare it to the cables in the shower and these are usually only 2.5/4mm. I've seen quite a few old showers fed with 4mm.

 

[clubb699]

Hi

Ok so if its 4MM the max is 7 watts then for the shower Not seen 7 in B&Q 8.5 was lowest.

 

[shotgun]

Hi all,


My Question is i have twin and earth cable to a very old shower unit the shower is rated at 7 KW, with a chat to the local B&Q helper he mentioned the cable could be 4mm as the fuse is 30 AMPS. looking at there cables on the shelf it does look like 6MM but to be safe im going to say its 4MM whats the max Watt of shower i could put on to this 4MM cable, the cable is 5 meteres max from the CU.

Thanks in advance.

If it is only 5m away and your having the CU replaced why not upgrade the cable to a 10mm and put in a 10.8Kw shower for nearly twice the power of a 7kw unit

 

[clubb699]

Hi,

House is decorated and finished cable routing is something i dont really want to go down its not far but it looks awkward it goes up 3/4 under stairs across landing then into corner of bathroom, i was sure its more above the CU but it seems looking again its slightly back a meter and goes under the landing before entering the bathroom.

Will 4MM take 7.5 Amps still cant find 7KW shower but seems 7.5Amps


Cheers though

 

[ban-all-sheds]

Hi

Ok so if its 4MM the max is 7 watts then for the shower

No - once the CU is upgraded to one with MCBs you should be OK for a 7500W shower.

Not seen 7 in B&Q 8.5 was lowest.

People don't want low power showers - they just don't work well enough.

Hi,

House is decorated and finished

You knew you had a very old shower.

You know that cables are buried in walls.

Do you not think you should have sorted out the shower replacement before finishing the decorating?

Will 4MM take 7.5 Amps

It will take up to 37 amps, depending on how it's installed..

 

[clubb699]

You knew you had a very old shower.

You know that cables are buried in walls.

Do you not think you should have sorted out the shower replacement before finishing the decorating?

Hi Ban all sheds new it wouldent be long before i got an erupt answer somewere down the line

Only been in house 3 months all the main decorating was all done for us i blame them for not pre planning the future of the shower

 

[holmslaw]

..

 

[holmslaw]

..

 

[GaryMo]

It will take up to 37 amps, depending on how it's installed..

Thats interesting, how does the way the shower is installed affect the current?

He was talking about the cable which is pretty obvious.

 

[ban-all-sheds]

It will take up to 37 amps, depending on how it's installed..

Thats interesting, how does the way the shower is installed affect the current?

FGS holmslaw - don't be such a child:

Will 4MM take 7.5 Amps

It will take up to 37 amps, depending on how it's installed..