Garden Building Electrics

[Levy]

Looking for some sound advice.
I have a studio 50m from the house (70m from house CU) Is it permissible to clip SWA around from the front of the house to the back? I plan to dig the trench from the back of the house to the studio over the summer for the SWA, and have a sparky fit the CU in the studio and any additional work required for a permanent supply.
500w psu on the pc (probably pulling no more than 250w)
Two laptops
Two Monitors
42" TV
3 x 5m indoor led strip lighting (600w psu)
Kettle
1 1500w oil filled radiator
Small fridge (for the beer)
Two game consoles (xbox ps4)
Two outdoor 5m led strip lighting
1 outdoor socket (for lawnmower, power tools, etc.)
Assuming everything on at once (unlikely) estimated pull 35A. What size SWA allowing for possible expansion of outdoor lighting, water features? (LED Lighting, Pumps.)
(working out costs at the moment)
Before I go out and buy anything. As a temporary supply would this be acceptable:
13A 3pin plug (off of 13A fused spur socket in kitchen) - Fly lead - Industrial Plug IP44 240V 16A female - Industrial Plug IP44 240V 16A male - 50m 2.5mm arctic cable (enclosed in 20mm conduit fixed to concrete posts 3m apart) - Industrial Plug IP44 240V 16A female - Industrial Plug IP44 240V 16A male - Fly lead - Extension socket to run a PC (500w) 2 x Monitors, 1 x Laptop, Oil filled radiator. (led lighting is currently running off batteries)
Any advice greatly appreciated.
Levy

 

[Simon35]

You probably have 2.5kW hanging off what is a 50m extension lead, 2.5mm flex will be fine for both volt drop and current.

Temporarily, electrically it's OK, assuming the kitchen socket is RCD protected.

Permanently, it's a lash up, as I'm sure you know.

As for costs, the cost of the SWA is neither here nor there. The price difference between 50m of 2.5 SWA and 50m of 10.0 SWA is about 50 quid.

If you are getting an electrician to fit a CU, then they should design the entire thing. They might be happy to let you dig a trench for them, but that's about it.

 

[Levy]

Thanks Simon
Yes I realise it's not the best solution for a temporary supply and as long as I am not contravening any regs and it is safe to do so, it seems like the only solution until June/July. I have an audio book to record and the neighbours are not the quietest, hence the need to get down to the studio. I believe the spur is protected by RCD at the CU for the kitchen ring and I have always used the dedicated RCD socket for outside equipment, lawnmower etc. Would it be ott to plug in a RCD to the spur socket and then plug into that? (Belt and Braces) And you're probably right with regards the SWA. I'm sure the electrician will advise on cable size.
Levy

 

[flameport]

13A 3pin plug (off of 13A fused spur socket in kitchen) - Fly lead - Industrial Plug IP44 240V 16A female - Industrial Plug IP44 240V 16A male - 50m 2.5mm arctic cable (enclosed in 20mm conduit fixed to concrete posts 3m apart) - Industrial Plug IP44 240V 16A female - Industrial Plug IP44 240V 16A male - Fly lead - Extension socket

All of that would work, but most of it's unnecessary. None of the 16A plugs and sockets are needed, and plastic conduit supported at 3m intervals will be a sagging mess within minutes.
There are 13A plugs that 2.5mm flex can be fitted into, likewise trailing sockets.
Or you could just go and buy a ready made 50m extension lead, which will probably be cheaper than the component parts.

 

[bernardgreen]

 

[Levy]

Thanks Flameport
Okay. That would work for me. The only reason I thought of putting the cable into conduit was to stop the foxes (and grandchildren from chewing through it.) they bit my new network cable in half (Nov) and dragged it out into the middle of the lawn. I already bought a 50m 2.5mm Arctic blue. Would it prudent and safer to run it through conduit just laying on the ground behind the flowerbeds and polytunnel? I just don't like the thought of all that electrickery being so accessable to the wildlife and kids. Could you also point me in the direction of a 13A plug for the 2.5 cable, are they different from normal ones? (deeper)
Levy

 

[winston1]

You only need one RCD, the one in the house CU. A RCD socket for outside is not required nor is an RCD plug on the cable. In the event of a fault all will trip.

 

[Levy]

Thanks Bernard
Does that mean that the cable for the permanent installation should be 4mm or for the temporary extension?
Levy

 

[Levy]

Thanks Winston
This is like a Sherlock Holmes episode, a process of elimination. Whatever remains must be the truth.
I've now been whittled down from a convoluted series of plugs, sockets & rcd's to a straight forward extension lead with a trailing socket. Great stuff.
Really glad I came on here.
Levy

 

[bernardgreen]

should be 4mm or for the temporary extension?

For both. You might be OK with the 2.5 mm² for the temporary connection but voltage drop might affect some of the items in the garden building.

As regard to RCD protection

You only need one RCD, the one in the house CU

If the garden building is supplied via the RCD in the consumer unit then, depending on how the CU is configured, a fault in the garden building could result in loss of power and lighting in the house.

An electrician should fit an RCD next to the house consumer unit to protect the garden building and the cable feeding it. This RCD would be fed from a new MCB in the consumer unit that is supplied from the non RCD supply. Alternatively the garden building could be supplied from an RCBO fitted in the consumer unit RCBO = MCB and RCD in a single unit.

 

[JohnW2]

An electrician should fit an RCD next to the house consumer unit to protect the garden building and the cable feeding it. This RCD would be fed from a new MCB in the consumer unit that is supplied from the non RCD supply. Alternatively the garden building could be supplied from an RCBO fitted in the consumer unit RCBO = MCB and RCD in a single unit.

I think that the more common advice would be to have an RCD in the outbuilding (ideally fed from a switch fuse, rather than the CU - although a non-RCD protected MCB in the CU would be an option), but not at the house end - with the cable between the two being SWA and/or 'not buried'.

Kind Regards, John

 

[ban-all-sheds]

1 1500w oil filled radiator

Forget that, and install an air-source heat pump (aka aircon) - cheaper to run, and it will also mean you can use the building in the summer.