SHED ELECTRICALS

[Middy]

Hello, Can you knwlegeable peoples take a look at this. ANY comments would be obliged:

8’ x 8’ SHED - ELECTRICALS - NOVEMBER 2007

PLAN - Shed 15 metres from house plus 6 Metres to House CU from house entry point etc.

HOUSE SIDE

SWA cable - 4mm 3 Core - 25 metres used.
Inside termination Gland to be used Size BW20

Wire to House Consumer unit using a 30A MCB to RCD Side

SHED SIDE

SWA Cable buried at 600mm - Outside termination Gland to be used (Size BW20) at CU inside Shed

Garage consumer unit - 63a RCD?? - 2 MCB
1 X 6 amp (Lighting circuit), 1 x 16 amp or 32 amp??? (Socket Circuit)


Lighting Circuit

Radial Lighting Circuit 1.5mm T&E.
From CU to Strip Light on Ceiling then down to Small strip light above workbench, under a proposed shelf - Length of wire Approx 4 - 5 Metres.
(Small strip light to be cord pull for on /off)

Socket Circuit

Radial or Ring Main?? 2.5 T&E - for use with electric Drills etc, nothing too Draining.
2 Double Sockets at workbench
1 Double Socket Below CU possibly to supply outside lights?
(Low voltage on plug in transformer??)

Questions

1. Should my Garage CU MCB for sockets be 16 or 32A?
2. Should Sockets be on Radial Circuit or Ring Main? (returned to CU)
3. Garage consumer unit 63 or 40 Amp?
4. As regards Double socket for Possible outside lights…IF I put a couple(2) of Mini Lamposts 4’ High (Mains Electric) say one at 12 metres and one a further 10 Metres on a Radial Wiring set up would I be better with a third MCB in CU? Or just spur off Socket circuit to Fused Switch? I will probably go for Low volt with a transformer though.
5. When terminating the Shed end of SWA to my Gland do I just screw the Ring onto the body of the CU?
6. If I wire to my mini lampposts I would probably attach wire to Boundary Fence, is this okay to do, I may bury in conduit pipe beside fence, there will be no hazard from digging etc. can someone suggest best way or wire required??

PLEASE NOTE THAT I STAY IN SCOTLAND - NOT PART P REGISTERED
AND THIS IS A THEORETICAL INSTILLATION - I AM GATHERING UP THE PARTS AND WILL EMPLOY A QUALIFIED ELECTRICIAN WHEN I AM HAPPY WITH MY PLAN. ALTHOUGH I WILL BE WIRING SOCKETS, LIGHTS MYSELF, THEORETICALLY.

sorry if i am asking basic things or repeat of previous posts any advice will be greatly appreciated[/img]

 

[comms]

Inside termination Gland to be used Size BW20

You want to use 20sBWN glands.

Wire to House Consumer unit using a 30A MCB to RCD Side

Doesn't have to be on the rcd side, but the choise is yours.

SWA Cable buried at 600mm - Outside termination Gland to be used (Size BW20)

In that case you'll need 20s CWN gland.

Garage consumer unit - 63a RCD??

No need if you have come off the rcd side of house cu, just use normal 100A main switch.

1 x 16 amp or 32 amp??? (Socket Circuit)

In a shed I'd just use 16amp mcb on a radial for sockets.

Radial Lighting Circuit 1.5mm T&E.
From CU to Strip Light on Ceiling then down to Small strip light above workbench, under a proposed shelf - Length of wire Approx 4 - 5 Metres.
(Small strip light to be cord pull for on /off)

Sounds ok ...dont forget the switch though.

Radial or Ring Main?? 2.5 T&E - for use with electric Drills etc, nothing too Draining.
2 Double Sockets at workbench
1 Double Socket Below CU possibly to supply outside lights?
(Low voltage on plug in transformer??)

As said I'd use a radial for sockets.
As for outside lights why not use the lighting circuit ? (unless you want elv lighting)

1&2. Should my Garage CU MCB for sockets be 16 or 32A?

Up to you, 16amp radial will be quicker to install.

3. Garage consumer unit 63 or 40 Amp?

40amp seen as your using 4mm swa.

4. As regards Double socket for Possible outside lights…IF I put a couple(2) of Mini Lamposts 4’ High (Mains Electric) say one at 12 metres and one a further 10 Metres on a Radial Wiring set up would I be better with a third MCB in CU? Or just spur off Socket circuit to Fused Switch? I will probably go for Low volt with a transformer though.

Why not just use the 6amp shed lighting circuit, plenty of scope seen as you are only planning on 2 flories.

5. When terminating the Shed end of SWA to my Gland do I just screw the Ring onto the body of the CU?

You can but on an insulated cu it can be difficult.
Use one of these instead of the nut supplied with the gland.
http://www.tlc-direct.co.uk/Products/PRPEN20.html
(personally I tend to terminate into an adaptable box first then take tails onto cu)

6. If I wire to my mini lampposts I would probably attach wire to Boundary Fence, is this okay to do, I may bury in conduit pipe beside fence, there will be no hazard from digging etc. can someone suggest best way or wire required??

Best not fix to the fence (others will dissagree I'm sure).
Bury 1.5mm swa at a depth of 450mm min & cover with warning tape (100mm below surface).
From cu to switch (L/N/E) L to common of switch, N ito chock block, E into chock block. from switch (SL/n/e) SL in L1 term of switch, n into the N chock block, e into the E chock block. At lamp post 1 connect conductors to terminals then loop out to lamp post 2.

What is the earthing arrangement of the house supply ?

 

[Middy]

thanks Comms very helpful..

1. if i do come off the non RCD Side can i use 40A RCD ON MY GARAGE CU? what is preferred?
2.did have a diagram that didnt paste to post showing Light switch. Is it best to be fused ?
3.does elv lighting= low voltage with transformer? would you go with mains to 2 lamposts or low votage with a few more lights. are low voltage lights bright enough if you are have a night time bbq? for example. Dont want the place floodlighted out but i want to see what i am doing.
4. Adaptable box..metal? the SWA terminates to this box next to the cu. strip wires far enough to stretch to cu ie. TAILS remembering the earth sleeve?
5. House is a new build - 6 months old...need to check earth arrangements
would imagine that is not a problem

 

[comms]

1. if i do come off the non RCD Side can i use 40A RCD ON MY GARAGE CU? what is preferred?

Yes you can use a 40amp 30mA rcd as the main switch at the garage end.
If you come off the house rcd side, you will need to trot back to the house to reset the rcd if it trips + you loose all circuits in the house that are protected by the rcd (not to handy if you are away for a few weeks).

2.did have a diagram that didnt paste to post showing Light switch. Is it best to be fused ?

Not sure what you are after here, you will be comming off the 6amp mcb for lighting?
But if you are on about comming off the socket circuit to power the lights then yes you will need to install a fused spur fused down to 3 or 5 amp.

4. Adaptable box..metal? the SWA terminates to this box next to the cu. strip wires far enough to stretch to cu ie. TAILS remembering the earth sleeve?

Depends on if I'm exporting pme then I use a metal box, if I'm TT'ing the outbuilding (normally do this if distance is greater than 9mtrs ) I use a plastic box

 

[Middy]

Not sure what you are after here, you will be comming off the 6amp mcb for lighting?

Switch between cu and ceiling striplight. mcb will be permanently on so switch required to put on or off lights. was wondering if this has to be fused or not. probably not as if problem mcb will trip??

 

[Steve]

No, it doesn't need to be fused. Think about how your lights are wired in the house.

If you're going to be using any power tools in the shed, go for a High frequency fluorescent light. Standard fittings buzz a lot especially when cold, and flicker at 50Hz, which can cause a strobing effect on rotating power tools. This makes the tool appear stationery, when in fact it is spinning in phase with the light's flickering.

 

[Middy]

Sorry, another question...
what MAKE of cu is best as not everyone Likes screwfix ones etc

40A RCD with 6A MCB and 16 MCB

 

[Steve]

Hager, Wylex are two brands that are easy to use and widely available.

www.tlc-direct.co.uk << you wont go wrong buying from here.