electic shower

[jonno]

Not really, none in the wall and 6" in loft but cable only meets this when it comes out of wall cavity, it then travels across joists to pull switch and back again - so, voltage drop is not a problem, I know you gave me the formula for working it out so pardon my ignorance but does that mean I could step up to 10.5kW without changing my 45A pull switch and MCB or am I still pushing it a bit ?

 

[securespark]

10,500kW works out at 45.65 Amps at 230V.

 

[AdamW]

10,500kW works out at 45.65 Amps at 230V.

Seeing as mains voltage is now 230V +/- 10% then 10.5kW could draw between 41.5A and 50.7A. This is not including any tolerances for the shower. Now, I don't know what these are but if they are available they should at least be read (why doesn't EVERY piece of electrical equipment have a legend including all of this vital information?).

Perhaps a little off topic but I thought I should give in to my pedantic tendencies

 

[ban-all-sheds]

10,500kW works out at 45.65 Amps at 230V.

Seeing as mains voltage is now 230V +/- 10% then 10.5kW could draw between 41.5A and 50.7A.

Well, if we want to be pedantic.

1) It depends on what voltage the manufacturer assumed when quoting "10.5kW". If it was 240, then at your "230V ±10%" limits the current drawn would be between 37.7A and 46.1A

2) In 1988 an agreement was reached that voltage levels across Europe should be unified at 230V single phase and 400V three-phase with effect from January 1st, 1995. Those countries with a nominal voltage of 240V (like the UK) were obliged to move to 230V +10% -6%, and those on 220V moved to 230V +6% -10%.

It was proposed that on January 1st, 2003 the tolerance levels would be widened to ±10%, and then that was pushed back to 2005, and then in July 2001 the CENELEC Technical Board decided to continue with the existing tolerances until 2008.

3) In any event, the European-wide harmonisation is not being done by having common supply voltages, but by requiring manufacturers to make products which operate over a much wider range. Our supply used to be a nominal 240V. It is still the same, as no generating company wants to reduce it to a nominal 230V, as that would cut their revenue by over 8%. If the specifications for the shower don't make it clear, the most reasonable assumption would be that it is rated at 10.5kW at 230V, and therefore most of the time it will be drawing 47.6A from a 240V supply.

So, jonno - I would suggest that you use a 50A breaker and a 50A isolation switch, and that you should read the information here to determine what correction factors, if any, should be applied to your 10mm cable, which might be OK for 64A, or might be a lot less.

 

[jonno]

Thanks folks
didn't expect so much detail but all very interesting, I don't think I'll bother upgrading to 10.5kW, not that desperate that I want to change the breaker and isolation switch