Making my shower safe...

Hi all,

I need some help! I need to replace the run of cable from the consumer unit to the electric shower as it's only 6mm rather than 10mm as is required by an 8.5 kw shower (apparently).

However I have also read that an electric shower should be run from a consumer unit with an RCBO rather than a 30A piece of fuse wire which it currently has.

My consumer unit is very old (well it was fitted in the mid 80's) so I doubt I'll find an RCBO that fits it. What I would like to know is, can I fit a small secondary consumer unit alongside the existing one that will take an RCBO? I have attached a picture to try and explain how I want to do this as I woudl be waffling on all night otherwise!!

I have checked my meter and there is no way I can isolate the house other than pulling the fuse, which I understand is an offense.... so I don't want to replace the consumer unit completely and I don't think I can afford to pay for a sparky to come in and do it for me.



Does this make sense? Is it permittable?

And the big question - If I flick the main switch on the consumer unit is it safe to repalce that run of cable or is it still live in there?!

Thos replacement devices are NOT RCDs, they are mini trip contact breakers. They are just an updated type of fuse and have no added safety device.

You would need a separate mini consumer unit that has an RCD and a fuse, or an RCBO in it to serve the shower.

You would not run this from your existing fuseboard - it is not capable of handling a load bigger than 30amps.

A qualified electrician would be able to connect this up by using what is called a Henley Block to split the thick cable (metertails) that run from the meter to the fuseboard.

6mm cable may be OK for a 8.5KW shower. It depends on the length of the cable run and other factors like the route of the cable, ambient temperature, if route is thru thermal insulation etc..

All of the above is notifiable work. With respect, I do not think that you have a sufficient level of skill to do this work yourself. You should get a registered sparky. These are listed at www.competentperson.co.uk.

If the existing board is only 4way.
You would be better off looking at getting the old consumer unit replaced, with one that accepts Rcbo's and enough spare ways for your shower and future use.
Slightly dearer than the stand alone Rcd unit but worth it in my opinion.

Thanks for the replies, and you're quite right Taylortwocities I certainly don't have the skills to do this myself, in fact I'm bloody terrified of electricity!

I'll use your link and start asking for quotes to replace the consumer unit with something more up to date.

As for the cable, there's definatley something not right with it, we are on our third shower now as the internal wiring in the last two melted!

With some help I replaced the short run of cable between the switch and the shower unit (and the cabling inside the unit itself) with the 10mm stuff and this has stopped the smell of melting wires. However the the isolator switch and the end of the wires from the Consumer Unit to this switch started to melt!

So I have pulled the fuse and we now have no shower

lbaker78 said:

So I have pulled the fuse and we now have no shower

Click to expand...

That's your best move. It sounds like the cables are probably undersized and the connections are loose. Both are recipes for disaster. Check your fire insurance!