Hi i have been asked to install a new shower supply cable for a 8.5kw shower. The cable run is approx 15 metres long with about 3 metres through a cupboard with a boiler in it and 8 metres through a loft. The cable will be clipped directly to joists by itself and avoids all insulation or going through walls. taking into account all factors will a 10mm cable be sufficient? Also the consumer unit is an old(ish) one with an rcd covering just the sockets. Will a 40 amp mcb on the rcd side of the c.u be ok?
New shower supply
- Thread starter daveynez
- Start date
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Please don't take offence but you've been asked to carry out this work and you don't seem to be competant to correctly size up the required cable.
Also, do you intend to pre-notify building control before commencing your work (Part P of the Building Regulations)?
Also, do you intend to pre-notify building control before commencing your work (Part P of the Building Regulations)?
Is it acceptable because of the temperature in the boiler cupboard or loft affecting what size cable i could use?
See Paragraphs 5.x of Appendix 4 in the Wiring Regulations, pp256-257.
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J
Johnmelad502
6mm would surfice as a minimum.
And a complete waste of effort given that the material difference between 6mm and 10mm is only about a £1 a metre.
Doing the job in larger cable allows the comfort of knowing that when they discover an 8.5kw shower is under powered, they can up size and have no cabling issue.
If the CU only has 1 x RCD rail and it just has 2 x circuits / ring 32a then adding in a shower mcb will be fine (diversity).
You could always have a mini CU with the shower circuit on that with a separate supply link. You should also get the bathroom lighting moved on to RCD- although supplementary bonding of circuits to pipes is adequate for 16th ed.
Has your gas and water pipe bonding been done ? 10mm earths between main incoming cock / meter and the main earth terminal ?
J
Johnmelad502
In agreement with the above, ......and if you are not famiiar with the Regs then contact a spark who is !
thanks for the advice everyone. 
J
Johnmelad502
Just a question,
If he is replacing like cable for like, same route etc, is it notifiable?
No, assuming the circuits protective measures are unaffected (no shiney new larger MCB/RCBO).
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10mm cable will be fine mate.
I took it as a question that may have or may not have related to the original post and answered it as such.
In any case when replacing a cable you install a new cable.
In any case when replacing a cable you install a new cable.
So is he replacing a cable which isn't connected to an MCB?
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