HELP - 10.5kw power shower wiring

[RussM]

Hi,

Was hoping somebody could help me out. I have read a number of threads/topics on power showers and the need to use an RCD and MCB with the wiring, however something I saw did confuse me.

I am looking to install a 10.5kw power shower, utilising a 30ma RCD with a 50amp MCB and a 50amp pullcord switch. I was intending to use 10mm twin and earth to connect it up, but it requires approx 25m length to do so.

I noticed on another thread that the length of the cable could be a problem? Could anybody tell be if the length of this cable will present a problem in this set up? and if so what solution would you recommend?

Thanks for your help!

 

[toasty]

you're ok, 10mm is ok provided you don't intend burying it in the wall.

 

[RussM]

thanks toasty,

Only time the wire will need to be out of the way will be the last couple of foot to the shower behind the stud wall.

 

[mapj1]

Just don't fill the stud wall with thermal insulation - the cable needs to run cool. The question of length is more about voltage drop, which for a fixed thing like a shower is usually less of a problem than for socket circuits where the load may be variable. the 4% voltage drop that is often used to calculate the maximum length is only right if the shower makers don't quite a voltage range, many do, and its much often wider than 4%, so the maximum length that is OK may be rather more than the simpler calculation suggests

 

[Damocles]

Voltage drop is not just about whether the equipment will work. It is also about wasted electricity. 4% voltage drop along the cable means 4% of the power you are paying for is being wasted heating the cable.