7.5KW shower with 6mm cable

[La Poste]

Greetings.
Just had the upstairs shower die, water is leaking all over the place and it is highly dangerous.
We have a 6mm cable fused at 32A at the CU with no RCD.
My father is a real difficult old bloke of 85 years and whenever I try to tell him about RCD's and new fuse boards he gets really angry like I am trying to cheat him out of money.
All I can see available are 7.5 KW showers these days, can't seem to find a 7KW one.
I think I am right in assuming a 7.5KW shower should be fused at 40A.
Do you think the 6mm cable will be allright as it is with no need to fit a new cable?
It seems really borderline to me, cable is surface clipped up to the loft then it drops down to behind the upstairs shower. Cable run is about 15 metres.
An RCD in its own enclosure seems the only way to do this as a new fuse board is out of the question.
Any opinions?
Thanks.

 

[telectrix]

6mm is ok for 7.5kw. 33A. you can fuse/MCB 6mm at 40A. RCD in separate enclosure with 40A MCB should be fine.

 

[miner69er]

hiya la poste
a 7.5kw shower will pull 32.6amps, the cable is o.k. at this and the 32amp breaker will also be o.k. i come across a lot of 8.5 and 9kw showers with a 32amp circuit breaker. the manufacturer is rating the kilowatts at worst case senario with the coldest possible water temperature, in practice it is very rare for them to pull the maximum kw.
regarding the RCD, yes it 'should' have one, but because you are replacing the load/appliance the wiring can stay as it is.. if you were to replace or renew any part of the circuit then it would have to be RCD protected and be notifiable to labc.
good luck

 

[Phil]

beaten to it, agree with telectrix

 

[accordfire]

Greetings.
Just had the upstairs shower die, water is leaking all over the place and it is highly dangerous.
We have a 6mm cable fused at 32A at the CU with no RCD.
My father is a real difficult old bloke of 85 years and whenever I try to tell him about RCD's and new fuse boards he gets really angry like I am trying to cheat him out of money.
All I can see available are 7.5 KW showers these days, can't seem to find a 7KW one.
I think I am right in assuming a 7.5KW shower should be fused at 40A.
Do you think the 6mm cable will be allright as it is with no need to fit a new cable?
It seems really borderline to me, cable is surface clipped up to the loft then it drops down to behind the upstairs shower. Cable run is about 15 metres.
An RCD in its own enclosure seems the only way to do this as a new fuse board is out of the question.
Any opinions?
Thanks.

7.5kW will run give or take 32.5A, so you'll need a 40A MCB.

Providing the 6mm CSA passes tests, it will carry the current no problem - its rated about 34A in conduit and 41A surface clipped.

Also, special locations........triple pole isolator, etc., etc., etc.

 

[Deleted member 9648]

Triple pole isolator??

 

[accordfire]

Triple pole isolator??

Correct. bathroom fans, showers, crossed wires, too many words and not enough eyes........

I'll accept double pole on this one

 

[Amp David]

Re: Uninyvin cable/nyvin cable

Whats this clown all about? I think i'll find a link to a company I like and the reply to every post by posting it. Mods get shut please

 

[accordfire]

Re: Uninyvin cable/nyvin cable

Whats this clown all about? I think i'll find a link to a company I like and the reply to every post by posting it. Mods get shut please

Here - you can reply to every post with (only if it's good advertising though)......a link to my site

Seriously, though - I noticed this idiot had replied to just about every post earlier that mentioned cable in any way, and probably some that didn't.

 

[nickblake]

Re: Uninyvin cable/nyvin cable

Whats this clown all about? I think i'll find a link to a company I like and the reply to every post by posting it. Mods get shut please

Agree with you mate oh and it was an indian company that just lost its Basic approval ,, so there cable is no good to us ,doncaster for me

 

[nickblake]

Re: Uninyvin cable/nyvin cable

Opps mis tracked one thing on cable size loadings etc ,just ensure the cable isnt covered with loads of insulation as this reduces the current carrying capacity

 

[SirKit Breaker]

hiya la poste
a 7.5kw shower will pull 32.6amps, the cable is o.k. at this and the 32amp breaker will also be o.k. i come across a lot of 8.5 and 9kw showers with a 32amp circuit breaker. the manufacturer is rating the kilowatts at worst case senario with the coldest possible water temperature, in practice it is very rare for them to pull the maximum kw.
regarding the RCD, yes it 'should' have one, but because you are replacing the load/appliance the wiring can stay as it is.. if you were to replace or renew any part of the circuit then it would have to be RCD protected and be notifiable to labc.
good luck

It must have RCD protection if the manufacturers instructions say so, and all the ones I have seen recently do state "MUST BE PROTECTED BY A 30ma RCD", and installed to the latest wiring regulations. So just changing like for like may throw up some problems if you dont comply with instructions and it needs repair or replacement.

 

[nickblake]

thats a good point sirkit because if the manufacturers state in must be installed with an RCD then it must , also thinking about it this would require a minor works cert , because you dont know wether the supply to the shower is ok could have a lost cpc and you are disconnecting the cpc when you replace it , when you do a minor works on a circuit in a bathroom its notifiable

 

[GT1]

Yep. Agree with others about 32amp MCB. It will be fine. I've done a few lately where the CU are old models and had to jiggle around the board to accommodate stuff. Had no problems so far on 32amp mcb's.
Don't sweat too much about it. By using 32 rather than 40amp your making the instalation safer. !
It's only if/until you get overcurrent nuisance tripping that you have an issue.
The RCD issue however is a real must. If it were me I would install one in the loft and not tell him !!

 

[nickdnew]

Related question:

I have a property that has 6mm mains swa cable coming into the consumer unit via an RCD isolation switch. The home has a 7.2kw electric shower and I wanted to add a 7kw under sink water heater. So as to prevent overheating of the main cable and tripping of the main incoming fuse which is just 40 amps, could I put a 32 Amp 3 Pole Change Over Switch ahead of the two six mm cable wires which would be serving the shower and the water heater. Therefore negating overloading the main wire coming into the home by allowing only one of the appliances to be used at a time. Would this be acceptable for an EICR. The home is a residential static caravan.