Log Cabin Power

[meno]

Been browsing this very useful resource for a few days now, but its now time to post a Q.

Im in the process of building a log cabin in the garden and would like someone to clarify a few electric plans.

First of all, yes Building Control are being informed.

My plans are:

20a in Main CU -> 4m 4mm T&E -> IP65 Box -> 11m 4mm 3 core SWA buried 6inches under patio and 18inches under lawn -> Small CU 16amp/6amp in cabin -> 2.5mm T&E ring with x4 double sockets and 1.5mm T&E to x2 Wall Lights and x1 Energy Saver External Lantern

Powering:
x2 PC'c
x3 LCD Monitors
x1 Laser Printer
x1 Mini Fridge

How does this sound?

Is there any other way i can run SWA without digging up my lovely lawn? bottom of fence posts (timber)?

Also is it ok to run a pipe underground and run SWA through it with CAT6 Network Cable?

Many Thanks

 

[ericmark]

Most sounds OK. Often people do feed outbuilding using fence line I see nothing wrong with that but not to run a pipe underground and run SWA through it with CAT6 Network Cable? They need to be min 100 mm apart regulation 528.2 most likely you would get away with it but you asked if allowed and it is not.
Eric

 

[electronicsuk]

In terms of total load, volt drop, etc the basic plan looks sound after a cursory glance. First few things that come to mind:

Earthing arrangements - depending on how your incoming supply to the house is earthed, the construction of the cabin and the services that will be entering it, you may find that you need a local earth electrode. Unable to clarify without further information.

Burial depth - I'd prefer to see that SWA buried a bit deeper under the paving slabs. Clipping to a fence is generally considered a no-no on account of it not being a permanent structure, although one might argue that it is no less permanent than a wooden cabin!

Ring - If you're going to protect with a 16A breaker, you probably don't need to wire in a ring. One would assume the cables will be surface clipped or at worst enclosed inside a plasterboard partition, so you'd probably be able to use a radial in 2.5mmsq. That is, unless your calculations for derating say otherwise.

 

[Pensdown]

Is there any other way i can run SWA without digging up my lovely lawn? bottom of fence posts (timber)?

As long as your fence is in good order you can clip the cable to it. I would run it along the bottom as you've suggested but make sure it's in view. If it's hidden the gardener may hit it by mistake.

Because of the increased risk of damage to the cable if the fence blows away, IMO, under these circumstances it's better to install the RCCD in the house rather than in the cabin.

What sort of heating will you be using in the winter?

 

[meno]

Earthing arrangements - depending on how your incoming supply to the house is earthed, the construction of the cabin and the services that will be entering it, you may find that you need a local earth electrode. Unable to clarify without further information.

Big fat cable wrapped in some sort of black tape coming from the ground understairs with live Neutral and a bare copper wire between the 2, does that help?

Burial depth - I'd prefer to see that SWA buried a bit deeper under the paving slabs. Clipping to a fence is generally considered a no-no on account of it not being a permanent structure, although one might argue that it is no less permanent than a wooden cabin!

I can go deeper just didnt want to disturb too many slabs, i cant clip cable to a fence post that is concreted in, but can to a cabin that just sits there. i see what you mean

Ring - If you're going to protect with a 16A breaker, you probably don't need to wire in a ring. One would assume the cables will be surface clipped or at worst enclosed inside a plasterboard partition, so you'd probably be able to use a radial in 2.5mmsq. That is, unless your calculations for derating say otherwise.

Just need 2 sockets on opposite walls so by the time ive cabled them im nearly all the way round

Most sounds OK. Often people do feed outbuilding using fence line I see nothing wrong with that but not to run a pipe underground and run SWA through it with CAT6 Network Cable? They need to be min 100 mm apart regulation 528.2 most likely you would get away with it but you asked if allowed and it is not.

Thanks

 

[meno]

As long as your fence is in good order you can clip the cable to it. I would run it along the bottom as you've suggested but make sure it's in view. If it's hidden the gardener may hit it by mistake.

Because of the increased risk of damage to the cable if the fence blows away, IMO, under these circumstances it's better to install the RCCD in the house rather than in the cabin.

What sort of heating will you be using in the winter?

Would it be better to put it in the RCCD side of the Main CU

Heating, probaby a small electric or portable calor gas heater if required

What way can i run the SWA and still get the OK from Building Control, must it be buried? what is classed as permanent?

 

[Lectrician]

6mm from house CU to outside, fed from a 32amp MCB. Then 4 or 6mm SWA to shed.

20amp RADIAL circuit in shed for sockets.

The cat6 should ideally be a duct grade type, or even SWA.

ELV cables do not need segregating from SWA.

 

[Pensdown]

Would it be better to put it in the RCCD side of the Main CU?

Yes

Heating, probaby a small electric or portable calor gas heater if required

If electric heating (which is better in confined spaces than calor) as Lectrian has suggested, up rate to 32amp & 6mm.

What way can i run the SWA and still get the OK from Building Control, must it be buried? what is classed as permanent?

You can run the cable along the fence line but because most fence panels are deigned to blow out, don't fix to the actual panels. You can run a 100x50 timber between the posts around 300mm above ground level and clip the cable to that or you could install a 150mm basket tray.

 

[meno]

Thanks for all your help, will go for 6mm buried to be on the safe side

 

[Pensdown]

Good decision.

 

[meno]

starting this project now, is it ok to put an ip66 junction box on the side of the cabin gland the swa into it and take the tails thru the back of the box straight thru the wall into back of CU, basicly drill a hole thru the back of junction box - wall - CU with silicone between?

Oh and i have got 6mm SWA as you recommended, and 6mm T&E to main CU, do i still go 20amp breaker in main CU

Thanks

 

[Taylortwocities]

You could go to a 32A breaker for the 6mm SWA.

I'd suggest putting in a 32A RCBO on the non-RCD side. That way, it wont trip all your house sockets (freezer, etc) if there's a fault....

Or 32A breaker in CU and RCD in the cabin

 

[meno]

ok thanks, thinking about it ill stick to 20a as the cabin CU is 16a/6a

Is it ok to joint 6mm 3core SWA to 6mm T&E in a IP66 Junction Box, the earth size would be different using the 3rd core of SWA and the earth of the T&E, is this ok?

Many Thanks

 

[Spark123]

I don't think there are any issues with joining the SWA to twin and earth in the IP66 box as long as it is done correctly, i.e. is the armour earthed correctly? The twin and earth should not run outside unprotected.
How does the twin and earth connect to the Main CU, does it pass down any walls where it is concealled?

 

[meno]

will be from main cu to the floor then along the bottom of wall all in trunking.

also whats best IYHO

swa thru the cabin wall then gland in small cu

swa thru the cabin wall then gland in ip66 box next to small cu, long tail into small cu

swa gland in ip66 box on outside cabin wall, long tail thru back of box thru wall into small cu

swa gland in ip66 box on outside cabin wall joined to t&e, t&e thru cabin wall to small cu

other, please specify

many thanks