I’m about to set about installing a new bathroom suite in our house, and I was contemplating fitting a new power shower in place of the old one. Ideally, I’d like to shove in a more powerful unit, as the current one’s only about 8.5Kw from what I can find out about it. I know the building regs require anything over the current power rating to be installed using 10mm cable, but as far as I can see, that’s what ours is in on, and it’s routed through it’s own circuit breaker rated to 45A – it was installed by the previous owners (as far as I can tell by the appropriate tradesman), so I’m just going by what’s visible at the supply.

Anyone able to confirm from the following pic that I’m correct?

Its unlikely that the fuse will be 45Amp, that is teh maximum rating o fthe switch. If you take the screw on the outer cover off (The raised cover which has “fuse” written on it) that will show you what size the fuse is rated at. I would imagine that given the age of when these units were installed that unfortunately for you the cable will be 6mm.

Thanks – just checked and it’s 35A.

Is there any obvious way of telling the difference between 6mm and 10mm cable? The stuff that’s there looks like the thick grey cable that’s used for ring mains and the like.

Just a heads up…you are not allowed to do any electrical work in the Bathroom (or Kitchen). Lots of people do, just be aware that its not allowed and questions may be asked about the paperwork when the house is sold.

Whats the width of the wire shown??

10mm is 17mm x 10mm ish
6mm is 13mm x 7mm ish

spooky… not entirely true, you can do like for like replacement like swapping the shower unit, but not install a new one from scratch.

Now, whether rewiring and upping the rating would be considered like for like is probably open for debate!

you may find an electrician who’s prepared just to do the final ‘joining up’ of cabling that you’ve installed and issue a certificate for it.

Looking round our house, it’s easy to see why they tightened up the regs governing electrical work – some of the ‘aftermarket’ work is pretty ropey. The kitchen appliances are all plugged into surface mounted sockets with the ring circuit cabling hanging out of the wall.

When we got a sparky in to sort out the wiring for a new oven just before Christmas, it took him about 25 mins to figure out how the cooker circuit had been wired. He did a very neat job of tidying it all up, so I’d be happy to get him back in to sort out the shower wiring if need be.

If we had better water pressure, I’d be tempted to fit a mains shower running of the combi, but we struggle to maintain 1bar at the best of times, and I don’t want to start faffing about with the expense of installing a pump.

Just a heads up…you are not allowed to do any electrical work in the Bathroom (or Kitchen). Lots of people do, just be aware that its not allowed and questions may be asked about the paperwork when the house is sold

entirely depends where the property is!

Thanks – just checked and it’s 35A.

are you sure?

Ive never encountered a 35A fuse or breaker

10mm^2 is huge stuff. And costs a fortune. I remember when our shower went in, (10.5kw).
8500/230 = 35amp.
10500/230 = 45amp.

Also never trust a tradesman to do a correct job so double check your wiring, fusing and everything else yourself. So far in my house I’ve found 3 drains draining upwards (and leaking) and some mis-wired lighting. All done by local tradesmen.

turin – just been back to check again. The fuse definitely says 35A on it

fair enough Ill put it down to experience, every day is a school day 🙂 Ive never heard if a 35A fuse.

If your on good terms with the electrician that was at your place before, the best thing to do is to get him to come round to either give you a bit of advice, or give you a quote for a new shower. if he is really friendly or looking to keep his client base happy he will tell you, I would, but if not from the price of the quote you will know if the cable need replaced

If you’ve already got a combi, use that.

Regardless of the water pressure, a shower fed from the combi will always be superior to an electric shower. Also a load cheaper to run, buy, fit……..

If I go with the shower running off the combi, is it simply a matter of running a couple of feeds from the existing pipework for the bath into something like this…
Mira concealed valve shower

The bathroom in question is upstairs, with the combi downstairs – we get about 1.0bar pressure into the house – and there’s a feeder tank for the cold water in the loft above the bathroom.