Help putting power to a shed!!

[eskimo39]

Hi this will be my first job for myself since qualifying and just would like a little assurance if possible.

A friend has a garden shed 40 meters from his house and would like sockets and lighting putting in. I am thinking 6mm2 SWA 3 core going from his original house CU (protected by rcd and 40a mcb) to a Wylex 2way Garage Consumer with RCD in the shed. Inside the shed 3 x metal clad double sockets on a 2.5mm ring with 20a MCB and a couple of lights on 1.5mm protected by 6a mcb.

I have done a few calculations and estimate load to be approx 8kw (3 sockets at 13a with voltage at 230v giving 8280w) Also on the length of cable I estimate voltdrop to be 9 volts.

Would this be o.k???

In the garage there will be a fridge on one socket, a freezer on another and one spare for lawnmover/hedgetrimmer etc.

Any suggestions/alterations would be greatly appreciated.

 

[Mac]

Hi this will be my first job for myself since qualifying and just would like a little assurance if possible.

A friend has a garden shed 40 meters from his house and would like sockets and lighting putting in. I am thinking 6mm2 SWA 3 core going from his original house CU (protected by rcd and 40a mcb) to a Wylex 2way Garage Consumer with RCD in the shed. Inside the shed 3 x metal clad double sockets on a 2.5mm ring with 20a MCB and a couple of lights on 1.5mm protected by 6a mcb.

I have done a few calculations and estimate load to be approx 8kw (3 sockets at 13a with voltage at 230v giving 8280w) Also on the length of cable I estimate voltdrop to be 9 volts.

Would this be o.k???

In the garage there will be a fridge on one socket, a freezer on another and one spare for lawnmover/hedgetrimmer etc.

Any suggestions/alterations would be greatly appreciated.

Sounds fine mate,but if you are protecting the circuit with an RCD at the main CU and the shed,then both RCD's will trip.Can you not put the shed circuit on the non RCD side of the board,if the board is suitable.

 

[eskimo39]

That would be possible but I was worried the cable wouldn't be protected between the house and shed.

Also is there any way to work out how much power a ring is going to use. I am putting in 3 double sockets and worked it out that at any one time each socket will only be using 13a, however in all possibility each socket could have 2 x 13a appliances in. Then there is the possibility of people putting multimpl adaptors in these sockets............on and on What is the best way to estimate?

Thanks for your reply

 

[AMST09]

Can you not protect the cable in the house by a 100ma RCBO...don't know if they exist but my 2 cents worth
Or thinking about it a seperate RCD enclosure if you cant get an RCBO

 

[Robo]

hey mate, im in the process of doing a similar thing. put the armoured cable on a 40a mcb on the unprotected side of cu, armour doesnt need to be rcd protected. Then fit your garage cu. Y not fit a 32 a breaker and do a ring main. Then u will easily be able to cope with all those items plugged in.Robo

 

[AMST09]

Also is the armoured to be buried or...

 

[eskimo39]

The cable will be burried at the regulation depth and I have just been given a roll of 'Warning Buried Cable' tape from a friend who works for a major instalation company.

I will have a look at sourcing an rcbo as the original consumer unit is a bit dated. If not, I will fit a 40a MCB to the non-rcd side.

Finally I have decided to go for 3 core to run a seperate earth to the shed as well as using the armouring.

Thanks for all your help, it's a relief to know I am not too far off the mark. Never realised how nerve-racking my first "real" job would be.

 

[solo2771]

That would be possible but I was worried the cable wouldn't be protected between the house and shed.

Also is there any way to work out how much power a ring is going to use. I am putting in 3 double sockets and worked it out that at any one time each socket will only be using 13a, however in all possibility each socket could have 2 x 13a appliances in. Then there is the possibility of people putting multimpl adaptors in these sockets............on and on What is the best way to estimate?

Thanks for your reply

If you have a 32A ring in the shed and it trips from overcurrent then the whole system back to the house would have to be up rated . If it was a real concern couldn't you go for 50 amp mcb and 2 or 3 ring circuits lol.

 

[Modernelectric]

Dont use the armour and a core for earth or you will have parallel paths.

 

[solo2771]

I believe the done thing is to use the armourings too but only to be earthed via 1 end. Is this correct?
Though can't see problem with the parallel path after all so is bonding.

 

[eskimo39]

Dont use the armour and a core for earth or you will have parallel paths.

Hi what would this do? I thought the more earthing the better?

Thanks for the response

 

[Modernelectric]

it would mess with your test results. why not just use a 2 core and use the armour as the earth?

 

[eskimo39]

it would mess with your test results. why not just use a 2 core and use the armour as the earth?

....um....ah....eeee, because I already bought 3 core

Perhaps I will keep 1 core spare in case we ever upgrade.

 

[solo2771]

with ref the 17th edition does it say don't use both? i see no real problem with using both as long as periodics are carried out?

 

[AMST09]

The armour...3 core....live neutral and earth
Then bond the armour down to earth at one end