17th edition - EXTRACT FANS -bathroom/utility/shower/kitchen


Postby Cyrus » Thu Sep 18, 2008 8:55 pm

Hi, doing an extension for myself. Started before 17th edition came in. I understand I could have 16th or 17th edition - is this true? Putting four fans in - bathroom, kitchen, utility, downstairs shower room. Do I need 3 pole switches on each? Where should the switches be mounted? Is it just the wet rooms that need RCD's? Can they come off lighting circuits, or direct from CU? New CU going in and complete rewire, all floors are up so might as well.
Basically looking for some sound advise - wan't the job done right, but money is tight!

Also wondering about ring mains - intend Upstairs/Downstairs/Kitchen, so three rings but don't know which cicuit to put utility on (WM and Dryer)

Many thanks, J
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Postby BLAKEY1963 » Thu Sep 18, 2008 10:25 pm

[quote="Cyrus"]Hi, doing an extension for myself. Started before 17th edition came in. I understand I could have 16th or 17th edition - is this true? Putting four fans in - bathroom, kitchen, utility, downstairs shower room. Do I need 3 pole switches on each? Where should the switches be mounted? Is it just the wet rooms that need RCD's? Can they come off lighting circuits, or direct from CU? New CU going in and complete rewire, all floors are up so might as well.
Basically looking for some sound advise - wan't the job done right, but money is tight!

Also wondering about ring mains - intend Upstairs/Downstairs/Kitchen, so three rings but don't know which cicuit to put utility on (WM and Dryer)

Many thanks, J[/quote]

CYRUS
have u asked an elecrtcian to quote , just 2 Give u an idea of
what would need 2 b done.
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Postby ericmark » Fri Sep 19, 2008 7:43 am

1) Systems designed before the 17th Edition came in can continue to be installed to 16th Edition but since you are asking questions it is not designed as yet so stuck with 17th Edition.
2) 3 Pole switches are required for fans controlled by the lights which need to be bigger than those that run 24/7 so really depends on how the fans are controlled. Humidity controls would not need 3 pole isolators for example.
3) RCD protection is required for everything in a bathroom including the lights. Also all socket outlets under 20 amp. And for any cables buried in a wall at less than 50mm depth and not wired with special cable to BS 5467, BS 6346. BS 6724, BS 7846, BS EN 60702-1 or BS 8436 the latter being the Ali-tube cable specially designed for partition walls. So in general everything needs a RCD.
4) Where fans are controlled by lighting circuits really no option but to power by lighting circuit.
Regulation 314 talks of division of installation and it is now main plain this includes RCD’s as well as MCB’s and has resulted in the duel RCD consumer unit being used. As to how the RCD protection must be divided this would depend on the premises and what battery back-up or shared neutrals on stair ways etc. I suggest the risk assessment method but this is up to system designer. There are 385 pages in the regulations and I have no intention of repeating them all here.
Eric
ericmark

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