Shower Question

TheFew

TheFew

TheFew

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25 Nov 2017
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352
Hi,

I was looking to sanity check my shower install just to ensure it's not too dangerous...

My house has two small back to back ensuites but no normal size family bathroom, so I am knocking them through to make one.

I am going to keep the electric shower from one room in the same place. Currently it is a 8.5kw shower fed by 6mm cable dating from 2004. The cable comes out from the ground floor consumer unit under the floor boards of a bedroom and to a isolator switch just above the floor in that bedroom. The cable between the CU and this switch is around 4 to 5m. There is then a further 1 to 2m of cable that go up from the isolator switch to the shower on the other side of a stud wall.

To update the bathroom I have removed the isolator switch from the bedroom and have replaced it with a 50 amp pull cord in the bathroom itself. To achieve this I have connected the old 6mm wire that fed the isolator switch into a 50 amp junction box (hidden in the stud wall) and then I have run new wire up in to the loft across to the pull switch on the far side of the bedroom then all the way back across to the shower. This new length of wire is around 10 to 12m in length and is 10mm wire. In the loft it is above the insulation. In the stud walls it is hidden in the insulation.

So the question is... Will using a short run of 6mm wire to feed a long run of 10mm and a 8.5kw likely to be a problem?

I don't really want to have to take up the floor to update the sorry run of 6mm wire...

Thoughts and abuse welcomed.

Ta
 
I would imagine it's against regulation as effectively you have a weak point of the 6mm cable, and no one in future would easily be able to identify that.

I also recall reading that any bathroom electrical work is certifiable / needs certified by an electrician?

(I'm not a sparky..)
 
You should be OK with 6mm. 8.5Kw is 37A, 6mm cable is rated to 47A clipped so you've a bit of headroom.

I'd have continued the run in 6mm though. Problem is if someone rocks up with a 10.5Kw shower in future and sees 10mm in the existing shower they will probably assume its 10mm all the way.

What size is the breaker in the consumer unit? If it's 40A it will mitigate the above to some degree.
 
probably wont cause any problems for a short length but I think* regs would say thicker cable and accessible junction box or crimped connections

*(not an electrician but just put an electric shower in the attic)
 
Thanks for the comments so far.

I probably have enough slack in the 10mm cable to move the junction box from inside the stud wall to under the bedroom floor boards. This would make it more accessible in the future I guess. Not sure if this is worthwhile doing however?

I was thinking of labeling the 10mm cable where it comes out to the shower to say 6mm to CU, just in case in 20 years time someone else moves in.

Looking at the fuse box, the fuse says "B40" so I am guessing it is 40 amps!

ta
 
Yep that will be 40A, they'll see the 6mm cable from the CU when they replace the breaker if they want to install anything bigger.

There's no need for a junction box to be accessible from a regulations POV.

I'd crack on.
 
What type of pull cord are you using? It needs to be a 40a/50a rated switch and preferably double isolating. I have recently just done the same but uprated the cable to 10mm as I was installing a 10.8kw shower.
 
Tbh i would buy a decent brand pullcord, ideally double terminal screw cos that seems to be the weak link and end up burning out or jamming - make sure terminals are tight and maybe check again after using it for a week to see if they have loosened off

Also leave plenty of slack above pullcord for when it burns out in future and needs stripping back 6" each time to get back to clean copper etc
 
HardwareGeek said:
Tbh i would buy a decent brand pullcord, ideally double terminal screw cos that seems to be the weak link and end up burning out or jamming - make sure terminals are tight and maybe check again after using it for a week to see if they have loosened off

Also leave plenty of slack above pullcord for when it burns out in future and needs stripping back 6" each time to get back to clean copper etc
Click to expand...

Thanks for the info. I run the cable around the outside of the loft so there is plenty of slack :-)
 
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