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what can I expect when elec board arrive on site

Postby deepbluearcher » Sun Feb 24, 2008 1:37 am

Hi all I am an electrical fitter by trade so competent around electrical engineering but a bit green when dealing with domestics. I am currently updating my quals to the 17th but in the mean time here is my problem:

I have just bought a barn and have a 3phase supply coming in but no meters. It is a tt supply and therre is an earth spike with a 6mm2 earth.

I need to connect some temp supplies for lighting, power and also a feed to my caravan. I am planning on installing a 63A RCD consumer unit using standard mains tails then running 6mm2 SWA to the caravan and then to a 40A garage rcd unit in my workshop. I was planning on using the armour as the earth which is Ok according to the regs, and was going to upgrade the earth cable to the eartth spike with 16mm2 which would make it all complient with the 17th as far as I can see. Can anyone advise me if this seems OK.

Also what are the electric board going to want to see before connecting this installation as I am not an niceic approved installer or hold part p etc.

Any advice much appreciated.
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Postby ericmark » Sun Feb 24, 2008 2:12 pm

Electric board will normally supply either to an isolating switch or to some form of consumer unit.
63A is under sized really normally 100A supply and since three phase I would a MG three phase board as they have handy neutral bar down the middle to fit RCBO's to no silly neutral tails. Main incomer I would use a 100A 100ma type S RCB. As to earths depends on size of SWA but equivalent to 25mm² is min I think you will find so I would think you will need a copper earth cable.
The earth connection may also be a problem and may need to be up graded to 16mm² before you connect supply.
The size of RCD may need to change according to the ELI but if possible using 100ma will mean more readily available.

Postby sparx » Sun Feb 24, 2008 7:12 pm

In my experience your supplier will only give a temp. 'builders supply' if you have as Ericmark says a 100A/30mA rcd to a single phase consumer unit, it only need have a single circuit to a socket local to board but they will want a completion cert. filled in as far as possible without power ie insulation readings, r1+r2, and confinmation of bonding to any other services ie Gas, Water, Oil. They will then be able to use local circuit outlet to test Zs when powered up. Locally here they want the test cert. to be issued by a member of ECA/NICEIC may take others depending on who turns up to give connection, all a bit vague,
good luck, SPARX
BTW as you don't have part-p someone else will have to run sub-main to van outlet point, galling I know but that's building regs!
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Postby ericmark » Sun Feb 24, 2008 8:54 pm

According to the IET web site caravans do not come under Part P as they are not a building. For Part P here in North Wales they want a C&G 2391 and will often accept a C&G 2381 and are not interested in any organization unless something like the IET as to 3 phase supplies they are not keen if considered as domestic but as I read what you say your not domestic but a building with a caravan parked in it. But he may be right in some area's they want to see the paper work as to the tests they seem to want it in Liverpool but in North Wales they seem to consider its no longer their concern and will connect to incoming board even if it only has a single socket connected to it. But if your not considered as domestic you will come under Electricity at Work Act which has more teeth and HSE are a lot more likely to take you to court for non compliance than building controls. The IET doc was "PART P COMES INTO FORCE By Geoff Cronshaw" should you want to check it yourself. And I would not use a 30ma RCD as the main incomer it would cause problems later I would use a 100ma type S and then a second 30ma supplying the caravan as it is hard to get the supply removed to change main incomer remember under Electricity at Work Act no live working they are very hot on that.

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