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bathroom electrics (shower, lighting, ventilation)

Postby whitewash » Sat Mar 08, 2008 11:22 pm


im about to embark on a full refit of my bathroom where i will be undertaking the majority of work myself.

ill be renewing the ceiling (water damage caused by leaking roof) so ill have access to the small loftspace above it for ventilation and lighting install

first the shower

im going to fit an electric shower which will need to be plumbed and wired, im going to fit the highest powered one i can find (10.8 so i know ill have to fit the correct wire size for the aplication, no wiring is currently present so this will have to be installed along with a new type consumer unit (currently old fusewire type so ill get this replaced at the same time as i get an electrian in to make connections to the shower. does this require a pull chord next to the shower, to turn the circuit on?)

i wish to fit 2/4 low voltage downlighters lights one above the sink and toilet, am i correct in thinking that these can be controlled by a pull cord switch within the bathroom itself? (switch is currently some distance away outside the door to the bathroom)

i wish to fit a ventilation fan( to exit via the loftspace to an external wall) with an inbuild light above the bath/shower) however im unsure how this will be controlled, i dont want the vent fan or light to work when the bathroom lights are on, only when the shower is in use, how can i control this without another pull chord switch, can it be operated via the pull chord for the shower? this is my main confusion, how to control this vent fan/light to come on with the shower but not with the main lights in the room.

thanks in advance :)

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Simply Build It

Postby ericmark » Sun Mar 09, 2008 11:56 am

1) Shower it will require isolator but not necessary next to it could be just outside the door if in the bathroom then it will need to be outside the zones.
2) Lights Yes you can use pull cords again normally outside the zones.
3) Fan you can get water vapour controlled fans, not sure on building regulations any automatic unit will need an isolator somewhere. And to fit 10mm² cable into a fan near impossible so if feeding off shower supply it would need some fuse unit so you can reduce cable size this would normally be switched fuse unit to allow isolation as well. Whole idea is to remove water vapour and odour and I am unsure to if you are allowed to have it not run when bathroom is occupied so do check on building regs. Also you will normally have live at the lights all the time anyway so don’t really see why you want to run off shower supply?
Also you will need to comply with Part P which means its installation must be controlled by an electrician for him to be able to sign for design and installation so you will be able to check this all with him. Also timing on the 1st of July we must use the new regulations in most houses this means everything goes through an earth leakage device and there will need to be at least 2. Consumer units have been redesigned with three neutral bars if you have mains powered smoke alarms then three RCDs will be fitted this means whole house will have to be good enough it could mean cooker change etc. As to biggest shower this will depend on supply some old houses only have 60 amp supply I would check with your electrician first before buying. The zones in bathrooms have changed with 17th Edition normally ceiling is just outside the zone but check first before fitting switches and lights.
All we say hear is of course only a guide the person signing the paperwork is the one to ask including cable selection and routes now three common cables PVC and XLPE twin and earth plus the new Flexishield the latter specially designed for burying in walls. All have different operating temperatures and current carrying capacity.
I would recommend you following links on projects to Part P and reading the document it gives sample forms and will answer a lot of your questions about what you can do.

Postby whitewash » Sun Mar 09, 2008 6:54 pm

thanks vry much ericmark, lots of things to consider for me as well as some stuff to read.

thanks again.
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