Mains to a summer house

markthespark24 · 17 Jul 2012

I need some proffesional advice NOT advice to 'leave it to the profesionals' or just negative stuff thank you.

I am building a summer house at the bottom of my garden and would like to get mains to it from my fuse board in my house, there is a spare fuse way so can accomadate a circuit to the summer house, it is a total of 35metres away from the main house fuse board, and i will be having a couple of oil filler rads and some lighing in the new build am i right to be using 3 core 4mm swa to a small consumer unit in the summer house with say 40amp rcbo then 2 local trips 16A for power and 6A for lights? and do i need a 16 or 32A in the main consumer unit?

RF Lighting · 17 Jul 2012

First of all, we only ever advise people to use professionals for their and their families own safety and no other reason, and only when it is clear they are out of their depth like your self.

Designing distribution circuits, especially to remote biuldings is not a trivial excersize, and involves knowing far more than you think it does.

You've not mentioned what your supply type is, whether there will be any extraneous conductive parts in the summer house, what size the oil filled rads are, how much lighting you intend to run, wether the SWA is going to be clipped direct or buried under ground.

Every single one of those things makes a different to the supply you will require.

You say you intend putting a 4.0mm² supply on a 40A RCBO. That is not acceptable. What is the MAXIMUM current carrying capacity of 4.0mm² SWA? Also, why do you what the RCD protection remote from the point of utilisation?

ban-all-sheds · 17 Jul 2012

markthespark24 said:
I need some proffesional advice NOT advice to 'leave it to the profesionals' or just negative stuff thank you.

Advising you to use an electrician is not negative - it is positive, you really can't DIY this.

ban-all-sheds · 17 Jul 2012

RF Lighting said:
You say you intend putting a 4.0mm² supply on a 40A RCBO.

He didn't say that.

markthespark24 said:
a small consumer unit in the summer house with say 40amp rcbo....do i need a 16 or 32A in the main consumer unit?

But given his questions I'd like to know why he calls himself Mark The Spark...

RF Lighting · 17 Jul 2012

I misread the post, but now I'm even more confused as to where this RCBO is going and what it's purpose is.

ban-all-sheds · 17 Jul 2012

It's going in the outbuilding CU upstream of a 16A and a 6A MCB.

Or so he thinks.

JohnW2 · 17 Jul 2012

RF Lighting said:
I misread the post, but now I'm even more confused as to where this RCBO is going and what it's purpose is.

I assume he meant that the new small CU would have a 40A RCD (not RCBO, as stated) as it's incomer with one 6A and one 16A MCB.

Kind Regards, John.

b1llt · 18 Jul 2012

Nothing like a straight answer I sometimes wonder why people bother even asking electrical questions based on half the answers - ffs its a DIY forum not a debate on H&S or government involvment in our lives.

Mate I don't have the answers but if it was me I'd be looking at the loading of the summer house especially if you're using oil filled electric rads (I have power to a summer house myself) then use a cable calc to work out the size of cable required and check my loadings don't overload the CU in the home. Run the correct size to the summer house CU, earth the summer house via an earth rod from the cu then as per normal rcd - mcb - circuit.

As I'm no sparky I'd be looking to find out how you manage the earth from the house cu running to the summer house cu - my guess is you do not run it as you'll have a tt system in the summer house and whatever you have in the house. The rest is micky mouse imho. The benefit of getting a sparky in this case to me is the testing. Hope that helps and I hope someone offers you some diy advice which will hopefully be better than mine

ban-all-sheds · 18 Jul 2012

b1llt said:
ffs its a DIY forum not a debate on H&S

So you don't think that anybody here should be concerned about the health and safety of people asking for advice, or of others who wil come into contact with work that they do?

You don't think that with nothing to go on except questions which indicate an overall level of ignorance which is incompatible with being able to safely undertake the work proposed that we should advise that it not be tackled?

or government involvment in our lives.

Please show where anything relevant to that has been mentioned here.

earth the summer house via an earth rod from the cu

You're sure that's the best design?

As I'm no sparky I'd be looking to find out how you manage the earth from the house cu running to the summer house cu - my guess is you do not run it as you'll have a tt system in the summer house and whatever you have in the house.

So you're advising people who are ignorant on the basis of guesses?

securespark · 18 Jul 2012

Also depends on type of SWA.

35m is a long way and depending upon design current, voltage drop may be an issue.

Also, what size is the fuse in your cutout?

How big are the tails feeding your consumer unit?

Your consumer unit does have a 100A capability, doesn't it?

You may well be better off with gas heating, and just install a smaller supply for a few sockets for PC's etc and a circuit for lighting.

b1llt · 18 Jul 2012

BAS - Blah blah blah is all I can hear. Please highlight that too. Its a DIY forum help end of. Not going to get into a barny with you as that does not help the thread

Taylortwocities · 18 Jul 2012

b1llt said:
As I'm no sparky

No you are not, and neither is markthespark24, even though his handle tries to indicate that he is

b1llt said:
The benefit of getting a sparky in this case to me is the testing.

Umm, think you missed out a couple of big steps there.
What about design, installation. Or do you think that you can get all this expertise from the Internet?

securespark · 18 Jul 2012

MTS 24 (and for that matter other would be DIY'ers)

You would fare better here if you made more of an effort with research rather than relying on the forum to spoonfeed you everything.

Buy a book or two, they will be a good investment. Work out exactly what you want to do. Work out the cable type, the cable length. Find out the design current of your circuit and the maximum current carrying capacity of your chosen cable under the chosen installation conditions.

If it is a heavy load, work out the implications for your existing installation. Consider the need for RCD protection, PEB's to services, possible upgrades to existing consumer units and even your existing supply.

ban-all-sheds · 18 Jul 2012

*************

EngStudent · 18 Jul 2012

b1llt said:
Nothing like a straight answer I sometimes wonder why people bother even asking electrical questions based on half the answers - ffs its a DIY forum not a debate on H&S or government involvment in our lives.

Because electricity is dangerous.

Mate I don't have the answers but if it was me I'd be looking at the loading of the summer house especially if you're using oil filled electric rads (I have power to a summer house myself) then use a cable calc to work out the size of cable required and check my loadings don't overload the CU in the home. Run the correct size to the summer house CU, earth the summer house via an earth rod from the cu then as per normal rcd - mcb - circuit.

Nice. Except you make no mention of how the OP should do that. Do you know how to calculate the anticipated load?

As I'm no sparky I'd be looking to find out how you manage the earth from the house cu running to the summer house cu - my guess is you do not run it as you'll have a tt system in the summer house and whatever you have in the house. The rest is micky mouse imho. The benefit of getting a sparky in this case to me is the testing. Hope that helps and I hope someone offers you some diy advice which will hopefully be better than mine

Does anybody else read this as 'don't connect the cable to earth at the house'?

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Mains to a summer house

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