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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Sub-main wiring https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1087940552 Message started by Dave on Jun 22^nd, 2004, 10:42pm

Title: Sub-main wiring
Post by Dave on Jun 22^nd, 2004, 10:42pm

I am just completing the rewiring of an old house and have to arrange to get the meter moved from an internal position to an external box. The distance from the meter box to the fuse board will be approx 7m (cable run). I am told that this means I will have to install a sub-main, consisting of a pair of 100A tails from the fuse board to an isolating switch and from there to the meter. My question is about the siting of the isolating switch: I am not allowed to put this into the new meter box, so intend to put it into another housing inside the house. This will be approx 1.5M distant from the meter box. Is this OK, or are there regulations about how far away the isolating switch can be from the meter?

Title: Re: Sub-main wiring
Post by plugwash on Jun 22^nd, 2004, 11:43pm

that should be ok

a lot of sparks apparenly just put them in the meter box

might be an idea to ask your rec if they are ok with this

also iirc you should have your own overcurrent protection as well as isolation

and finally while you may be allowed to use tails i personally dislike the idea of runnign unprotected conductors of that capacity for any significant distance

contactum do a 2 way metalclad CU with a 100A isolator http://www.tlc-direct.co.uk/Products/CMM2N.html and a 100A 2 module wide mcb (http://www.tlc-direct.co.uk/Products/CMDK401.html)

you will want to remove the busbar and neutral bar link and wire the mcb direct to the rcd with single or tail but its a practical cheap and resetable option

Title: Re: Sub-main wiring
Post by Dave on Jun 22^nd, 2004, 11:50pm

Thanks for that. I agree that the idea of using tails over that distance isn't entirely satisfactory.

Can you clarify the rcd comment? I checked the Contactum Metalclad board and it appears to be supplied with a 100A isolator switch, but are you suggesting the addition of an rcd also?

Title: Re: Sub-main wiring
Post by big_all on Jun 23^rd, 2004, 12:03am

helllooo dave
welcome to the house off fun[madness] ;D ;D ;D

Title: Re: Sub-main wiring
Post by plugwash on Jun 23^rd, 2004, 12:11am

i said mcb not rcd

that thing despite being 2 modules wide is just a mcb
its just they need to make them that size at 100A ;)

ignore the long cable and clamp thing in the kit they are for putting it in an extention box on a contactum 3 phase board

Title: Re: Sub-main wiring
Post by supersparky on Jun 23^rd, 2004, 7:31am

http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Hager_Metalclad_Range/index.html

simply cos hager are pathetic units

http://www.tlc-direct.co.uk/Products/HGNC163.html

no need for double pole.

the problem with that setup is you would be limetedto 63 amps- this wouldent trip the mcb at a slight overload for a long time though.

personly id just fit
http://www.tlc-direct.co.uk/Products/WY110M.html
with
http://www.tlc-direct.co.uk/Products/MM100SO.html
or http://www.tlc-direct.co.uk/Products/MM80SO.html
because ive always done that, and its the normal way to do it, ive stuck them in the rec boxs out side before now on occasion....they are quite bulky though-
as for the run, well thats what http://www.tlc-direct.co.uk/Products/SW16slash3.html is for
although 25mm is what id probrably use - depends on house size and main fuse raiting

ss

Title: Re: Sub-main wiring
Post by Dave on Jun 23^rd, 2004, 9:08am

Thanks for all the help guys. I'm a lot wiser now. However, it all turned out to be a bit of a red herring. I phoned ABB, the company that are moving the meter installation, and asked them if it would be OK to put my isolator switch/fuse inside the new outside meter box. They then told me that this is something they install themselves as standard! All I need to do is run the 100A sub-main cable to the box.

Title: Re: Sub-main wiring
Post by Lectrician on Jun 23^rd, 2004, 4:46pm

Ask your REC what the maximum tails distance is, our REC doesnt give a limit anymore for 25mm tails. 3m for 16mm tails.

Other than that, do what was said. Some RECS will install a douple pole 100map switch in the box, it is their property.

You can pay for another meterbox to go adjacent to theirs (by it from them), for your kit.

Title: Re: Sub-main wiring
Post by L.Spark on Jun 23^rd, 2004, 10:47pm

where you located Dave?

Title: Re: Sub-main wiring
Post by Lectrician on Jun 24^th, 2004, 8:01am

missed your last post somehow dave!! I think i was offline looking at a 'saved' page somehow !?!?!?!

Title: Re: Sub-main wiring
Post by Dave on Jun 24^th, 2004, 8:44am

The property is located in Rutland. The service provider is Powergen.

My local wholesaler tells me that because Rutland is in the Eastern Electricity area, their sub-contractors automatically install isolating switch/fuses when moving a meter. Other areas do not, apparently.

It seems there is a lack of standardisation on this issue.

Title: Re: Sub-main wiring
Post by L.Spark on Jun 24^th, 2004, 3:52pm

ok dave, i thought it must be subcontracted out to ABB, and that area sounds just about right ;)