Shower Cable Sizing

[Bahco]

Am I correct that you can use 6 mm cable for showers up to 8.5 kw as long as the cable does not exceed 15 metres.
I have been asked to fit 10.5 kw showers on 6mm and have refused as they need to have 10mm cable.
Be grateful for clarification

 

[triumphman]

You are right to refuse.
A 10.5 kw shower will draw around 45A which is too much for 6mm ( even without applying any derating factors).

Dont forget that the appropriately rated mcb and isolator switch will also be required if a 10.5kw is fitted