Shower - can I replace an 8.5kw with a 9kw, and keep 6mm wiring?

Risteard

albert_s wrote: »

OK, wiring regs BS7671 state that manufacturers instructions must be followed,
I'll bet you a pound to a penny the instructions for the shower say that a 30mA RCD is required.

They also state that every circuit in a bathroom must be protected by an RCD with a rated residual operating current not exceeding 30mA.

If the shower is being replaced it is hard to argue that BS 7671 should be ignored. (And as you correctly state the manufacturer will certainly state a requirement for a 30mA RCD, and compliance with BS 7671:2008 (2015).)

Risteard

macman wrote: »

If the cabling were uprated to 10mm, it would still not be a 'new' circuit.

Connecting new wiring to a protective device would absolutely meet the definition of a new circuit.

Micky_d

Hi, as an electrical and testing qualified electrician, I can say that if the run of the cable from the board to the shower is 10m or more then good practice would be to upgrade to a 10mm cable. By running this new cable and ensuring you are wiring it into an RCD protected board, you are complying with BS7671, future proofing your cable in case you want to fit a more powerful shower and protecting your home from cable degridation and a possible fire risk. If your shower is 15 years old then your cable will probably be at least this age and more, so it would be recommended to replace this with a 10mm cable at this stage.

This new cable will definately constitute a new circuit and will require a minor works certificate by a qualified domestic tester. Please do not skimp and get a bodge it and scarper merchant in as this could be putting yourself , family and your home at risk. Hope this helps.

Risteard

The cross-sectional area of cable required depends on a number of factors.

Also, a Minor Electrical Installation Works Certificate may not be issued where a new circuit has been installed. An Electrical Installation Certificate must be used.

albert_s

Micky_d wrote: »

Hi, as an electrical and testing qualified electrician, I can say that if the run of the cable from the board to the shower is 10m or more then good practice would be to upgrade to a 10mm cable. By running this new cable and ensuring you are wiring it into an RCD protected board, you are complying with BS7671, future proofing your cable in case you want to fit a more powerful shower and protecting your home from cable degridation and a possible fire risk. If your shower is 15 years old then your cable will probably be at least this age and more, so it would be recommended to replace this with a 10mm cable at this stage.

This new cable will definately constitute a new circuit and will require a minor works certificate by a qualified domestic tester. Please do not skimp and get a bodge it and scarper merchant in as this could be putting yourself , family and your home at risk. Hope this helps.

there is NO such thing.!
if you mean an installer 'qualified' to partP, then I'd suggest the OP runs a mile from them, (they are most certainly not an electrician), and gets a proper fully qualified time served electrician to do the work.
Who will, as Risteard states, test it properly and provide an EIC (electrical installation certificate) for the work.

buyitall

Thanks so much for the replies.

The shower is directly above the utiility room, which is where the consumer board is, with a 40A MCB. So I don't think that the wire is more than 10 metres long.

However, I agree that it is best to upgrade the wiring as part of the refurb.

This will involve employing someone else - our bathroom fitter has said that he can replace the shower itself on a like for like basis, but we will need to get a specialist electrician if we need to upgrade the wiring to 10mm. We haven't budgeted for this - any idea of the cost of the rewiring (we are based in the Midlands)?

Also, the main reason I was reluctant to upgrade in the first place, is that previously we have been told that our consumer unit is quite full of wires (it's only a few years old, but has had extra wires added as part of an extension), so I didn't want to open a can of worms if adding more powerful shower wiring led to tipping it over the edge and needing other electrical work done. Hope that makes sense!

cyclonebri1

buyitall wrote: »

Also, the main reason I was reluctant to upgrade in the first place, is that previously we have been told that our consumer unit is quite full of wires (it's only a few years old, but has had extra wires added as part of an extension), so I didn't want to open a can of worms if adding more powerful shower wiring led to tipping it over the edge and needing other electrical work done. Hope that makes sense!

It would be very sensible to future proof it buy changing it at this time then??

Ok, not exactly your 1st priority but I give it serious consideration especially if at full capacity and with other possible work pending??:beer: