Good evening all, I'm sure i'll get shot down in flames for even asking this but what mcb/ cable size do you all use if installing a 9.5kW shower?
230V = 41A
240V = 39A
It's for a family member and i'm trying to keep the cost down for them and as we all know, cable isnt the bargain it once was

What voltage does the manufacturer's data say the 9.5kW relates to? The last time I looked it was often 240V (presumably as this yielded bigger numbers which marketing departments seem to like) with a smaller 230V figure in the small print, but just to be safe, I wouldn't assume that.

(Technically, a shower is a fixed load, so you can get away with sizing the cable to the shower draw, rather than then MCB size - Zs and v.d. permitting of course.)

- Andy.

If it's not an excessively long run and the cable isn't running through insulation 6.00mm cable will be fine (and a 40 amp mcb)

Dave.

Thanks chaps, the run is about 16m in swa to isolator and then T&E to shower so no v.d. or ccc issues on 6mm with 40a mcb. I was just thinking about In>Ib if voltage is on the lower end of the scale.

If the voltage is low, then the current draw will be lower too. Showers are just simple heating elements - the fixed thing is the element's resistance. You can only read the rated kW figure at the corresponding rated voltage - at a lower voltage the actual kW draw will be lower (and the water won't get so warm).
- Andy.

a MCB will draw run indefinately on 1.13x In, so at 41A, a 40A MCB is only 1.025 x In.

As the above fella mentioned, its a fixed loads, and as such doesnt require overload protection, just short circuit.

I would put it on a 40AMCB, and i wouldnt worry at all about it.
cable sized to the load as above.