electrical power to steel garden shed

irish bloke

Hi All,

As the title suggests I am looking to bring electrical power to my steel garden shed.

I currently have 3 core 4mm sq SWA cable layed and ready for termination. Cable run is approx 50M.

My current household consumer unit has a 63A main fuse with 2 outputs from it.

Output 1: 63A RCD feeding 4 x 20A MCB's (sockets)
Output 2: 2 x 32A MCB's (shower and cooker), 3 x 10A MCB's (lights) and a 5A MCB (alarm)

What I am thinking of doing at the consumer end is taking a third feed out of the 63A main fuse for the shed power and running it through a second RCD here.
I will also earth the earth core here and the armour cable at this end only.

Was thinking an isolator switch with 2 MCB and the shed earthed at the other end.

I thinking with 4mm sq cable over 50M I should be good for about 20A.

2 question I have:

1. Do you think Im going about this the correct way and is it over/under kill.

2. What RCD and MCB amp ratings do you think I should be thinking about.

Thanks in advance..

leeomurchu

irish bloke wrote: »

Hi All,

As the title suggests I am looking to bring electrical power to my steel garden shed.

I currently have 3 core 4mm sq SWA cable layed and ready for termination. Cable run is approx 50M.

My current household consumer unit has a 63A main fuse with 2 outputs from it.

Output 1: 63A RCD feeding 4 x 20A MCB's (sockets)
Output 2: 2 x 32A MCB's (shower and cooker), 3 x 10A MCB's (lights) and a 5A MCB (alarm)

What I am thinking of doing at the consumer end is taking a third feed out of the 63A main fuse for the shed power and running it through a second RCD here.
I will also earth the earth core here and the armour cable at this end only.

Was thinking an isolator switch with 2 MCB and the shed earthed at the other end.

I thinking with 4mm sq cable over 50M I should be good for about 20A.

2 question I have:

1. Do you think Im going about this the correct way and is it over/under kill.

2. What RCD and MCB amp ratings do you think I should be thinking about.

Thanks in advance..

No need for your supply to be fed through an rcd at he main board if you want to isolate it at the main board it'll depend on what you're supplying in the shed.

Do you need 20A? what are you putting in the shed?

Earth the sheath at both ends. 4sq with a 50M run would only really be suitable for a couple of 13A skts and a flouro, It'd be a small cable for supplying a workshop.

freddyuk

Cable is small for that distance but if you just want to run something high power like a power tool you could install a solar system with an inverter which may be cheaper than relaying all the cable. Depends what loads you are planning.

maxfresh

I think a 3x 10mm sq cable would have been better as its quite a long run

M cebee

3*4 is small for 50m
i would fit a c25/c32 at house
and isolating switch,lighting mcb and B16amp rcbo at shed,if the fault loop impedance is ok for it.

you'll need an electrician anyhow

irish bloke

M cebee wrote: »

3*4 is small for 50m
i would fit a c25/c32 at house
and isolating switch,lighting mcb and B16amp rcbo at shed,if the fault loop impedance is ok for it.

you'll need an electrician anyhow

Thanks guys, I know 4 sq is small but it's by design and plenty big for what I will need.

I will fit the slower blow c type MCB at the house and RCBO for sockets at shed.

Will be doing it myself but will check for earth fault loop impedance.
Thanks for tip

M cebee

irish bloke wrote: »

Thanks guys, I know 4 sq is small but it's by design and plenty big for what I will need.

I will fit the slower blow c type MCB at the house and RCBO for sockets at shed.

Will be doing it myself but will check for earth fault loop impedance.
Thanks for tip

well-gland the swa both ends anyhow-that will keep the reading down

Bruthal

M cebee wrote: »

well-gland the swa both ends anyhow-that will keep the reading down

Yes once the glands have the earth tags properly fitted and earthed both ends.

M cebee

robbie7730 wrote: »

Yes once the glands have the earth tags properly fitted and earthed both ends.

yes
- its not good for 20amp anyhow with voltage drop