JoelP
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| posted on 4/10/10 at 05:46 PM |
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electrical query
cant find my reg book right now - i sure i could google it with time but i just thought id check if anyone knows off the top of their head.
16mm tails, 16mm earth, 80A RCCB at the source, feeding the main CU in the house 20 meters away. Is this ok for voltage drop? I feel it should be, but
obviously need to be sure.
Cheers!
[Edited on 4/10/10 by JoelP]
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davestarck
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| posted on 4/10/10 at 06:11 PM |
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Due to it being 20mts away you will need to wire in 25mm swa via a local isolator. Meter tails cannot be used for distances greater than 3 mts from
the supply head.
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mangogrooveworkshop
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| posted on 4/10/10 at 06:48 PM |
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quote:
Originally posted by davestarck
Due to it being 20mts away you will need to wire in 25mm swa via a local isolator. Meter tails cannot be used for distances greater than 3 mts from
the supply head.
Reason for this is the electromagnetic field interference on single conductors......and the induction problems they cause
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JoelP
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| posted on 4/10/10 at 07:05 PM |
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bugger!
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davestarck
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| posted on 4/10/10 at 07:17 PM |
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Needs to be a three core cable as well. BS7671 allows the armouring to be used as a cpc (earth) but EDF do not. They make up their own rules
I also stated an isolator in my previous post but I mean't to say a switch fuse as they do not like you using their supply fuses for the
protection of your sub mains cable. For instance 100A supply head fuse and 80A in the switch fuse.
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JoelP
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| posted on 4/10/10 at 07:27 PM |
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there already is an 80A 100mA rccb at the service head as its a TT system. I thought the 3m rule was if there was no fuse at the supply. Ah well. (i
mean your own fuse, not the suppliers one which is obviously there)
Id priced the 20m of tails at £65, i bet 3 core SWA costs a whole lot more than that.  Is split con cheaper?
I figure that, whatever i do, it will be a lot better than it is now - currently a 6mm cable feeds the entire (gasless) house, including induction hob
and electric shower. Remarkably, the cable doesnt seem damaged and the 45A fuse that 'protects' it in the original rewireable board has
never popped!
[Edited on 4/10/10 by JoelP]
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JoelP
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| posted on 4/10/10 at 07:32 PM |
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Is EDF a supply company or your local DNO? Cos im not sure their rules are relevant up here.
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Liam
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| posted on 4/10/10 at 09:26 PM |
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The RCCB at the source gives no overcurrent protection - 80A is just it's rating. So your cable is only protected by the service head fuse -
what size is that? You probably really need a switch fuse at the source after the RCCB to protect the long tails?
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JoelP
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| posted on 5/10/10 at 06:37 AM |
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are you sure liam, rccb stands for residual current circuit breaker? Surely the circuit breaker parts of that means its overcurrent too?
my bad
[Edited on 5/10/10 by JoelP]
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Liam
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| posted on 5/10/10 at 10:31 AM |
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Yeah the RCCB is just an RCD. Only an RCBO combines RCD with overcurrent protection. I think you would need a switchfuse after the RCCB for such a
long tails extension to the CU location. I'm not really very hot on this though, so I'd suggest asking the sparks at DIYnot.com.
They'll tell you what your options are.
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dan__wright
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| posted on 5/10/10 at 11:00 AM |
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dont know the regs but im having a new 100a single supply to one of my rooms at work, about 30M run from main boards, being cabled in 25mm swa so the
above sounds correct
[Edited on 5/10/10 by dan__wright]
FREE THE ROADSTER ONE…!!
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davestarck
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| posted on 7/10/10 at 06:12 AM |
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Trust me its correct, I do this for a living
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