shower cable question

[jackmort]

hi everyone,
basically have ensuite shower already set up and running in main bedroom, my problem is this have just done main bathroom and put in a shower unit over bath with isolator box in ceiling etc now i'm thinking run the cable as ensuite all the way thru floorboards etc to main box downstairs however just realised we have layed a laminate floor in bedrooms so pulling up the floor is a no go.my question is this can i run my new shower cable to the existying ensuite shower cable isolator box and draw the power off from there, im thinking is there some kind of double isolator box you could buy or am i talking total pap, any advice...?

 

[ban-all-sheds]

What type of showers are these? Pumped or instant? Please tell us that you've not now got 2 instant electric showers on one installation...

And are you aware that this work is notifiable?

 

[Chri5]

The cable for the existing shower will have been designed for the load on that shower.

So how would it be able to run 2 x showers ? In theory you could have a 2 way device that switches shower A off when you want shower B powered subject to the new shower having the same load requirements as the old one.

There have been many posts on this site about contactors and relays used to auto switch a single shower cable from shower A to shower B and (as far as I know) the general consensus is that the 'right' way, is a dedicated cable for each, with seperate MCB and RCD or RCBO protection at the main board.

It might be better (if you have a HW storage tank) to consider a power shower pump rather than an electric heated shower unit.
Reason being that even if you get a new cable to the shower, 2 showers both drawing approx 40A could overload the house and pop the main head fuse.

Daft it maybe, but the typical head fuse is between 60A-100A and as such it's not that hard to imagine the dishwasher being on, the kettle and 2 showers, An overload situation.

 

[jackmort]

thanks for reply,shower is instant and no i've not got the two running off one etc,and no i wasn't aware of the notifying thing either. so if i do all the donkey work ie running the cable to the box and then getting a leccy in to do the dangerous stuff do i need to get someone in to pass it or does he sign it off or summit cheers

 

[Chri5]

thanks for reply,shower is instant and no i've not got the two running off one etc,and no i wasn't aware of the notifying thing either. so if i do all the donkey work ie running the cable to the box and then getting a leccy in to do the dangerous stuff do i need to get someone in to pass it or does he sign it off or summit cheers

You didn't really read the replies, did you

Having 2 x instant (electrically heated) showers is a PITA. It will (potentially) pop your main head fuse leaving you without power for the whole house. Added to this, the vast majority of main CU / fuse boards are unable to accomodate multiple large amp load fuses.

A house electrics design relies on a thing called 'diversity'. A situation where although the house may have a maximum 100A load, you may have 200A+ of fuses, but since they will never all be on at the same time the total load won't exceed the 100A capacity.

Electric showers have no diversity. So 2 x 10.5kw units will use (2 x 10.5 - 21kw / 230v = 91A). 91 amps used, will mean that the head fuse will pop when minor other items of electrical equipment is used at the same time.

So, you and the wife have seperate showers, at the same time and have say the tumble drier on and the kettle boiling for a cuppa. Result, darkness and a bill for £100+ for your electric supplier to come out and change the main head fuse.

Best bet? Get an electrician round to review and see what he says or (as I mentioned in my earlier reply) get a hw pumped shower for one of the showers, is you have stored HW and CW (tanks).

 

[ban-all-sheds]

thanks for reply,shower is instant and no i've not got the two running off one etc,

You've got two in the same installation, i.e. on the same single supply to the house, which is what I meant. Not good - quite possibly unsupportable.

and no i wasn't aware of the notifying thing either. so if i do all the donkey work ie running the cable to the box and then getting a leccy in to do the dangerous stuff do i need to get someone in to pass it or does he sign it off or summit cheers

It doesn't work like that - read this: //www.diynot.com/wiki/electrics:part-p.

 

[ban-all-sheds]

get a hw pumped shower for one of the showers, is you have stored HW and CW (tanks).

A good powerful combi should also be able to cope (not pumped, obviously).