sdh2903
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| posted on 4/3/13 at 07:37 PM |
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OT garage electrics
Hi All
I'm finally getting fixed electrics in my shed/garage, I have a tame electrician to terminate everything but I'm to do all the donkey work
and route all the cabling. I however completely forgot to ask his advice on cable before he went on holiday. I will have a run of about 6m Max of
Armoured cable feeding the RCD consumer unit in the garage. From there will be a lighting circuit powering 4 4ft fluorescent lights and a circuit for
4 double plug sockets.
Usage wise the biggest loads will be a 3hp compressor and a mig welder (but not at same time).
Can any of the sparkies in the house suggest some cable sizings for me? I had pencilled in 2.5mm armoured, 2.5mm twin and earth for the sockets and
1.5mm for the lighting? Or am I being a bit light on the armoured feed?
Cheers in advance
Steve
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daniel mason
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| posted on 4/3/13 at 07:49 PM |
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id run a 10mm 3 core armoured then you have a 10mm earth out there. or are you TT'ing it outside?
actually think current regs state that your not supposed to use PME earth on a garage/outbuilding if not ajoined to the house
[Edited on 4/3/13 by daniel mason]
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motorcycle_mayhem
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| posted on 4/3/13 at 07:54 PM |
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I'm not a qualified Part P guy, but my garage installation was carried out by a Company that was. I have all the paperwork, including the vital
earth loop impedance test data and planning certification.
Looking at my installation, I would say that 2.5mm out to the shed is woefully inadequate with a 16A compressor requirement on the end of it!
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daniel mason
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| posted on 4/3/13 at 07:58 PM |
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a 2.5mm swa will comfortably carry over 20 amps. this however is not the issue.
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franky
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| posted on 4/3/13 at 08:00 PM |
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Just to clear up, you've put 2.5mm cable to the garage? is it 3 core?
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sdh2903
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| posted on 4/3/13 at 08:02 PM |
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quote:
Originally posted by daniel mason
id run a 10mm 3 core armoured then you have a 10mm earth out there. or are you TT'ing it outside?
actually think current regs state that your not supposed to use PME earth on a garage/outbuilding if not ajoined to the house
[Edited on 4/3/13 by daniel mason]
The plan is to sink a local earth rod.
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JoelP
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| posted on 4/3/13 at 08:02 PM |
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2.5mm is likely adequate but you'd be annoyed if it turned out not to be. 10mm on the other hand is the excessive! Id suggest 6mm with a 32A mcb
at source. I wouldnt worry about exporting pme, its a bit of a technicality. So long as you have a good connection to earth, the rcd will sort the
rest.
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sdh2903
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| posted on 4/3/13 at 08:03 PM |
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quote:
Originally posted by franky
Just to clear up, you've put 2.5mm cable to the garage? is it 3 core?
I haven't done anything yet I'm just compiling a shopping list, bit hard when you're an electrical noob!
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daniel mason
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| posted on 4/3/13 at 08:23 PM |
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6mm swa to garage on a 32amp mcb, earth spike at garage end with a 10mm earth. is the way forward!
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Westy1994
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| posted on 4/3/13 at 10:00 PM |
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Agreed 6mm SWA and your internal wiring to the specs you already mention would be ideal without being over the top.
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franky
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| posted on 4/3/13 at 10:24 PM |
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quote:
Originally posted by sdh2903
quote:
Originally posted by franky
Just to clear up, you've put 2.5mm cable to the garage? is it 3 core?
I haven't done anything yet I'm just compiling a shopping list, bit hard when you're an electrical noob!
Cool, 6mm or anything over 4mm. You'll work it out, house electrics are very very simple and easy to do, not like wiring your car up!
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whitestu
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| posted on 5/3/13 at 08:01 AM |
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3 core 6mm SWA should be fine but you need to check the load and distance and work out volt drop and current requirements to be sure. The electrician
should work all this out for you.
I would also use the main earth fom the house assuming the house isn't on a TT supply. You will have a much lower earth loop impedance and no
rod to install or maintain. There is absolutely nothing wrong with using the supply company's earth in an outbuilding.
Stu
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motorcycle_mayhem
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| posted on 5/3/13 at 08:47 AM |
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For peace of mind, yep, my certified installation out to the garage has the earth hooked into the house PME. The impedance here was in specification,
given the application (more rigorous for Type B MCB for the compressor and TIG).
Get digging!
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sdh2903
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| posted on 6/3/13 at 08:17 PM |
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Cheers guys
I've managed to locate some "end of line" 6mm armoured cable at the missus' work (a well known orange diy store ) just need
to find some similarly end of line twin and earth now and I'm set
Steve
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