supply to garden office / log cabin

[housedad]

Hi, I am hoping someone can give me a few pointers.

I am building a log cabin in my garden so my wife can use it as an office. I need to wire it up for power, light and telephone. I was planning to do the majority of the work myself and get a qualified electrician to test it.

I am planning to run the circuit from a spare way on the house consumer unit through 1.25" plastic conduit buried 600mm underground out to the outbuilding (approx 30m) to a 2 way consumer unit in the outbuilding. I was going to use one way for the sockets and the other for the lights

In the outbuilding there will be one main light and one outside 500w halogen light. Plugged into the sockets will be one small bedside light, a computer, printer, shredder, stereo, answering machine, mobile charger etc. I was budgeting on five 2gang sockets for these .

Can anyone advise me on what size of cables I should use and what rated circuit breakers I need to install in the outbuilding consumer unit and on the existing house consumer unit in order to do a safe installation. I do have experience of cabling and telecoms work but know nothing about circuit design.

If anyone can help I'd be very grateful.

Cheers,
Housedad.

 

[BigJon]

18 inches is the recommended depth to bury your cable, 4" ducting should do the job if you cant get your hands on the proper stuff, Might be an idea to put some of the " caution electric cable" tape in the hole before you fill the hole in. The plastic conduit could be used for your phone line. 10mm armoured cable should do the job or 16mm if you want to cover yourself for any future installs. Feed it from a 40amp MCB, take cable in kabin to your Consumer unit, which should be 30ma RCD protected, wire a 4mm radial circuit to your sockets protected by a 20amp MCB or a ring main on a 32amp MCB wire your lights in 1 or 1.5mm and should be prootected by a 6amp MCB, hope this helps a wee bit

 

[danlightbulb]

The rating of the 2 way fuse box should be the same as your house fuses i think. Thats 32A for ring main and 5A for lights?

As with house wiring, use 2.5 Twin & earth cable for the plugs and 1.5 T&E for the lights.

You would run all your plugs and lights off that no problem.

Sorry don't know anything about buried cables.

EDIT- big jon you beat me to it! Why 4mm for the sockets?

 

[BigJon]

Why 4mm for the sockets?

No reason, Just ease of wiring, no need to return a leg to the fuse board, But I imagine being a kabin it wouldn't be too difficult

 

[The Jeep]

If you're using 4mm² T&E, why not stick it on a 30/32A breaker?
If 20A is plenty for the foreseeable future, then just run the radial in 2.5mm²: it's a lot easier to work with

 

[Spark123]

Instead of an RCD protecting the whole CU a normal CU with an RCBO for the socket circuit is better, 6A MCB for lights. This way if the RCBO should trip the lights won't fail. Are there going to be any extraneous conductive parts (water main with metalic pipes etc) in the outbuilding? What size and type of supply do you have? Are you aware of the regulations regarding this type of work in England / Wales; //wiki.diynot.com/electrics:part_p:diy_electrical_work_and_the_law

 

[JohnD]

...an RCBO for the socket circuit is better...

couldn't agree more

 

[housedad]

Great, thanks for the replies so far. The cabin is made of solid wood and will have no plumbing so what should I do about earthing it?

Should I take the earth from the house or will I need to put in an earth spike or something similar and feed it into the cabin?

Just read the link posted by Spark123. So I need to get the council round to inspect it rather than paying a sparky to do that as they are not allowed to certify someone elses work, only to report that they themselves have installed it to the correct standard.

I'm confident that I can do a good job of connecting the different components together as long as I have bought the right components

 

[Spark123]

What type of supply do you have? Is the earth supplied by the electric company? If so then it will be better to use theirs.

 

[JohnD]

There was a very good IEE article called
2005_16_autumn_wiring_matters_electrical_installations_outdoors.pdf
that some kind person posted a while ago...

Can we find it?

(If not housedad put your email address in your profile for half an hour - to outwit spammers - and I will send it to you - I saved a copy)

Edited - here we are

This article from IEE's Wiring Matters covers most of the issues. Hope it helps.

http://www.iee.org/Publish/WireRegs...electrical_installations_outdoors.pdf[/QUOTE]

 

[housedad]

Thats brilliant, thanks a lot