6mm Cable sufficient for 10.8kW shower??

[JaseUK]

Just a quick question really - is 6mm cable sufficient for running a 10.8kW shower?

I have replaced a 6kW electric shower with a 10.8kW one. I have replaced the breaker in the consumer unit and upgraded it from a 32A to a 45A. I have checked the isolating switch (pull cord thing) and it is set at 45A. The cable runs from the shower to the pull cord isolator, into the loft (insulated) then down a conduit to the consumer unit (no more than 10M of wiring at MOST) - I have installed it all but a friend advised that 6mm cable won't do... is he right!?

How hot will the cables get!? And: will the MCB trip before anything dangerous happens (if it should happen!)?

Thanks for your help

 

[Scoby_Beasley]

45 amp mcb will handle 10.8 kw (exactly). 6mm cable will take 40amp. Theoretically your cable will start to overheat/melt before the mcb even thinks of tripping out. Change it to 10mm (53 amp) or just hope you are the one under the water when it decides to give up the ghost and goes up in flames!!!
Seriously, change it for safety's sake, whats a tenner in the end? (working on £1 a m)

 

[breezer]

following on from what scoby_beasley said, if there is a major problem yes the cable will get hot then catch fire while the mcb sits there, then when the insurance assesor comes round as if by magic your name appears, the insurance company will then pay out your friend no problem, because they will then take you to court and sue you for all the money & anything else they like to add on to the bill (could be thousands)

I once read in the paper about a bloke who changed his mates cars' brakes, they failed same thing, insurance paid out, took the friend to court sued him, the question was does the person who was being taken to court have a leg to stand on, the answer was NO.

Ask your friend to stop using the shower untill you have changed all the cable, Put your self in their shoes, they KNOW the cable is too small, wont they thank you and still be your friends if you change to a bigger cable, but you and them will not be friends after the court case.

Choice is yours

 

[JaseUK]

Are two lengths of 6mm cable (joined like for like at both ends - consumer unit and shower) the same as one length of 10mm cable? effectively 12mm? or does that simply not work? should I just replace with a 10mm and be done with it? It is going to be a pain in the *rse replacing some of this cable....

Thanks

 

[Scoby_Beasley]

But if you are adding another length of 6mm (not advisable) it will be a bigger pain in the butt as you already have to push against one cable blocking the holes you need to go through (nobody drills a hole bigger than they need to!!).
Use the 6mm to pull ya 10mm (masked / twisted ends, together) cable through your run. Be careful and you'll have a nice piece of 6mm wire you can use again.
You'll also struggle with 2 pcs of 6mm cable, gets very hard to move/bend.

 

[breezer]

10mm cable will better, you could always tie it on and pull the new one in as you pull the old one out, it will need 2 of you one to feed and one to pull

 

[ogoshi]

This reply is a bit late but worth mentioning.
I fitted a Gainsborough 10.8kw shower 10 days ago.It was replacing an 8.5kw.According to the instruction leaflet 6mm cable was perfectly adequate as long as it did not exceed a length of 16meters and was not inside trunking or conduit.It also required a 45 amp mcb.
As im not an electrician i told the customer to get a sparky to check the wiring +mcb before i fitted the shower.Sparky fitted a 45 amp mcb (previous one was 40) and tested the cable.He said cable was ok.(i dont know what he did to test it ).I fitted the shower, no problems have been reported back to me,and if there is any electric problems its the sparky who carries the blame.

 

[Scoby_Beasley]

Years ago 6mm was rated at 45amp, now generally its rated at 40amp, this is because we have to cater for the lowest common denominator, i.e. people who wire in showers using bell wire and then wonder why their house went up in flames (DOH!).
I would say that 6mm could cope quite easily with the draw reqd. but if I had to go and buy the cable I'd pay the bit extra and get 10mm.
I would guess that the company says 6mm is o.k. for up to 16m in "fresh air" as they know this will push the cable current capacity to its limit. Once encased it would (possibly) overheat.
But do you really want bare grey cables up your walls ?