Electric shower wiring

[I'm with stupid]

We are replacing our current 8kw electric shower, all that seems readily avalible are 8.5kw versions. I have been looking at the wiring and I have been advised that a 6mm wire will handle the load. I have been trying to measure the wire and not sure whether to take the measurement of the with the insulation still left on it? Or to measure the copper strands?

Any help would be appreciated, thanks.

 

[MANDATE]

I think you'll find it relates to the cross sectional area of the copper strand(s) in sq.mm. but do you need to go to that degree, theres quite a difference between 6mm and 10mm cable. just have a look at it in one of the diy stores.
I believe showers at 9.5 kw and above need 10 mm, but 6mm is ok for 8.5 kw.

 

[davelx]

8.5kW @230V = 37A

Best case CCC of 6mm cable is 47A, so may be OK with 40A MCB depending on length of run and method of installation. If you can tell us the length of the run and how the cable is installed we can advise further.

Also confirm that you have MCBs rather than rewireable fuses, in which case it would be a different story.