Outside wiring

Postby gl9dg » Tue Jul 10, 2007 7:28 am

Hi all

I am shortly going to install some 4mm 3 core SWA from an existing MCB (new split load board will be installed in the house) to a garage with a 30mA RCD and 2 x MCB (16 / 6 Amp) for sockets and lights. SWA buried to 24", marker tape e.t.c. The cable run is approx. 25 metres.

1. The new split load CU: is it best to get a metal one or are the plastic ones equally as good? The garage unit has a 40A RCD, would I have to make sure I used a 40A CPD at the main consumer unit?

2. The kitchen is fed by a radial cct on a 20A MCB for dishwasher, washer, dryer, sockets. However, part of the ring main also goes through the kitchen and the fridge/freezer runs off the ring. The socket ring would be fitted to the RCD side of the new CU, but this means the fridge/freezer being on it. Is this the normal thing or do people generally try and fit it onto the non-RCD side of the CU with the lighting ccts??? [u]What other ccts go on the non-RCD side? [/u]
Are split load boards with adjustable RCD/non-RCD sides better??? Am I using too many question marks
I cannot extend the radial and have this on the Non RCD side to serve the fridge freezer as it is is impossible (or very hard) as I have a slate floor. The only way would to be to channel up the wall one side of the kitchen, under floor boards and channel down the other side to the fridge position. Lot of work indeed. So what are the implications Standards wise of having it on the RCD side if any?

3. OUTSIDE lighting. I am going to install some outside lighting. Am i best using mains lighting or opting for extra low voltage? I know with mains I would have to run all cabling within conduit and bury it or use SWA. With LV you can run the cabling on the surface (I intend to run the cabling within a planter running around my garden). If I opt for ELV I would then have to run SWA to a weatherproof socket outlet capable of housing the ELV transformers. I would rather not have to go out into the garden to switch the lights on.

Hope all this makes sense, all answers very much appreciated! I know this work will be notifiable.
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Joined: Thu Jun 21, 2007 5:37 pm


Simply Build It

Postby sparx » Tue Jul 10, 2007 4:16 pm

Hi, lots of ???'s so ;
1)no particular reason for either, for TT system with RCD main sw. must use plastic, not metal, if feeding several SWA cables dirrect from con. unit better to use metal, u pays ur money....
1b) your supply MCB has to be rated to protect the cable & any devices in line, your 40A RCD means that is the largest size MCB u can fit although cable could, depending on type be rated up to 53A. all good so far.
2)It is nice to have freezer on non RCD side, (but unless trips out whilst on holiday) most freezers are ok up to 18 hrs or so without power.
2B) at the moment only lights , cooker points (without skt fitted), smoke detectors immersion heaters,normally non-RCD side ; however 17th edition regs out Jan, in force from next July call for ALL bathroom equipment including the light and fans to be RCD protected.
2c) Most kitchens only have one power circuit, and as 'likely to feed equipment used out doors ' must have RCD so no worries.
3) If you don't want to have to bother with switching cable for lights why not use as I do a weather proof box from 'Sheds' terminate SWA cable at box into double standard 13A skt, then use 'plug-through' wireless zappers to control from indoors set of 3 adaptors plus 3 channel control cost me less than £25.00 (maplins) also available in 'Sheds' from time to time, regards (Knackered) SPARX
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Joined: Wed Mar 21, 2007 8:33 pm
Location: The fifth continent.

Postby gl9dg » Tue Jul 10, 2007 5:13 pm

Thanks sparx, very much appreciated.

Just to clarify, if the garage CU has a 30mA 40A RCD, then I must use a min. rated 40A MCB in the RCD side of the new CU to supply it or a lower rated (32A) as the sub main load will not be that high?

Thought as much re: the fridge/freezer. Its a good job I'm too busy for a holiday.

I am a sparky by trade, however it is many moons since I actually worked as one. Over the past couple of months I have done the 2381 and am in the process of completing the 2391. Hope to have the certificate come December.
Meanwhile I am absorbing as much info as possible (when I get a spare minute) in the hope I can supplement my current work with domestic/light commercial work next year (I want to be prepared). I am also aiming to obtain NICEIC registration early next year too. Do you think they would they accept the work I am doing at my home for inspection (sorry I have yet to look into the exact requirements)

Re: OUTSIDE lighting. Very good idea, I will look into that, thanks again. I presume you use ELV lighting?

How long have you been a sparky if you don't mind me asking?
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Joined: Thu Jun 21, 2007 5:37 pm

Postby sparx » Tue Jul 10, 2007 6:57 pm

Hi agn.
just to clarify, max MCB at bd will be 40A otherwise not protecting RCD in garage, as not appreciated by most folks the RCD gives NO over current protection , it's rating is only max it can carry/break on fault trips.
Good luck with getting back in harness! as you asked (& will regret it);
I did apprenticeship with smallish contractor from 1963-68, housebashin', and local authority / farm work.
left 'sticks (kent) for London bedsit till 1971, general sparkin' , then moved back to Kent with new wife, worked in paper mills as leckie + pneumatic instrument mechanic, then went 'all lectronic' C&G 222 digital electronic mechs. worked in chemical works as lec/pneu/electronic mech,
then into full electronics MOD nav/weapons control for RAF. NIMROD, Jaguar, Harrier, Hawk etc. then needing money for growing family went to work @ Nuclear power stations as leckie/ Instrument Foreman, 14 years, took early retirement & started own leckie business, 14 years later now M.D. (flash title, still on tools most days) was working for MOD ranges mainly as ECA contractor but with Part P lots of local firms (plumbers/kitchen fitters ) did the right thing & stopped bodgeing it themselves & now I do mainly domestic work,
If you get the testing part really 'under your belt' the rest is easy, bldg regs (not part P, pt L,M etc) are the things to study.
I am member of NAPIT for Part P as I think they are by far the best, still ECA as larger co's want it, NICEIC, cr*p in my book. they make up regs to suit, let any one in just want members/money. Elecsa OK.
Bet you wished u didn't ask!!!!best wishes for future, I got a form today asking where i wanted my first winter fuel payment made in September!
Time marches on & I don't feel a day over 90, Hi HI
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Joined: Wed Mar 21, 2007 8:33 pm
Location: The fifth continent.

Postby gl9dg » Tue Jul 10, 2007 7:51 pm

Lol :P

Thanks again for taking the time and the advice on the various bodies. Hope to not have to bother you with too many 'stupid' questions over the coming months.

Best regards
Posts: 5
Joined: Thu Jun 21, 2007 5:37 pm

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