Shed electrics

[botg6969]

I'm planning on doing the following and would like some advice on whether what I'm proposing is acceptable.

I've just put up a shed in my garden and need to get an electric supply to it.

It needs lighting (3ft fluorescent strip inside and a PIR security light outside) and half a dozen sockets which will be for a chest freezer, extractor fan (with thermostat) and possibly to power a water pump of some description (I've also recently installed some rainwater harvesting stuff and the tanks are sited close to the shed). One of the double sockets will be an IP56 rated external socket for occasional use of gardening equipment such as lawnmower and strimmer.

In the shed I will install a small 2-way consumer unit (63A master switch, non RCD) with a 20A MCB for a 2.5mm T&E radial circuit for the sockets and a 6A MCB for a 1.0mm T&E radial circuit for the interior light, the exterior security light and extractor fan.

The radial circuit for the sockets will have a fused & switched spur in it ready for supplying to the water pump in the future if required.

The radial circuit for the lighting will have 2 fused & switched spurs in it to supply the outside security light and the extractor fan via a room-type thermostat.

The shed is sited close to my garage, less than a metre away from the back wall. The garage has it's own CU fed from a split off the incoming electricity supply before it goes into the house.

On the exterior wall of the garage next to the shed is an IP56 double socket which is on a 20A RCBO 2.5mm T&E radial circuit off the CU in the garage, along with 5 other double sockets inside the garage itself.

So my question is, can I replace the IP56 double socket with an IP56 metal junction box and then run 2.5mm 3 core SWA to another IP56 metal junction box on the shed, connecting internally to the shed CU using 2.5mm T&E? I will terminate the SWA correctly at both ends and will be using the third core for earth.

This would put the shed electrics on the same 20A RCBO circuit as the 5 sockets in the garage. The sockets in the garage on this circuit are only used for light power tools, a radio and battery chargers (I have separate circuits in the garage for heavier duty tools). I'm sure that the circuit will cope with the additional loads of the chest freezer, water pump, etc in the shed.

Is what I'm proposing acceptable and does it comply with regulations?

I'm aware that with this arrangement any fault in the shed side may trip the RCBO in the garage and I accept that.

I'm also aware that this work is notifiable to my local BCO.


Thanks for your help, I hope my question is posed adequately instead of the usual "how do I electrify my shed"


Martyn

 

[ban-all-sheds]

Water harvesting & pumps implies a real possibility of extraneous-conductive-parts. Do you have a PME supply?

And what route do you propose for the SWA?

 

[botg6969]

Thanks for the quick reply bas.

I probably made it sound a bit grander than it actually is, think 2 big plastic water butts (400l each) and lots of guttering / pipwork off all available water gathering surfaces. It's all plastic, no metal work (aside from screws).

I'm considering a water pump at a later date to provide some water pressure out of the water butts to allow use of pressure washers should gravity not provide adequate pressure..

>>> Do you have a PME supply?

No, it's TN-S.

>>> And what route do you propose for the SWA?

Since the garage is so close to the shed I was proposing to replace the IP56 double socket on the outside of the garage (about a metre up from the ground) with a suitable SWA junction box. Then come down the wall, go underground about a foot deep (under paving slabs) for a metre or so, then up the shed outside wall about a metre to another junction box. So about 3 metres or so in total distance for the SWA. Then 2.5mm T&E internally up to the CU in the shed.


Thanks agan,

Martyn

 

[breezer]

as an aside i would suggest that you do not use a pump to supply a pressure washer.
Raise the water butts off the grond in the first place (several concrete blocks) if you are able.

If your pressure washer is like mine (Karcher) it only uses water when its running (obviously) so that would mean your pump would be pumping no where, which will not do it any good.

 

[botg6969]

Raise the water butts off the grond in the first place (several concrete blocks) if you are able.

Yup, I did that, got them about 450mm off the ground.

If your pressure washer is like mine (Karcher) it only uses water when its running (obviously) so that would mean your pump would be pumping no where, which will not do it any good.

Another good point, it's not 100% certain I'll need a pump, I need to wait until there's some water in the butts to test with

But, I had considered the pump pumping nowhere and would be fitting a fluid flow switch to detect if water was flowing or not so as to fire up the pump only when needed.


Cheers,

Martyn