Outdoor Switch Wiring

[tomlyall]

Just wondering if anyone can think of any potential problems with this...

The feed will be 2.5mm single core in plastic conduit to the switches on the left, on the outside of the house wall. This is fed from a 16A MCB on the RCD side of the CU.

The switches are IP55 and 16A rated.

All the cables from the switches on the left to those on the right will be underground in also be in suitable conduit (its not going to be just the normal plastic stuff).

The switches on the right will be mounted on the outside of a shed, at the end of the garden.

Omitted from the diagram, is of course earth. For which I plan to use 2.5mm single core from the CU connected to all the switches. The earth for all the lights will be linked to the earth in the switches.

Also is it okay that the links from the L1s to L2s are all red. I'll label them so I know I connect them right.

 

[plugwash]

i wouldn't use conduit for the underground runs myself would require great care in joining and generally be a pita

i would also make provision for a socket at the far end

a 3 core and a 4 core armoured cable (or a 7 core but such cable is hard to get) is i think your best bet wired like this (i haven't bothered to show the individual switches)

note: from now on i am using new core colors in my new diagrams as theese are what are likely to be availible now

 

[tomlyall]

Thanks for the reply, I shall concider the SWA. Although I would rather not use it [SWA], and by conduit I ment something more along the MDPE pipe (not the water stuff) route, not PVC or metal conduit.

Btw the socket is a good idea but not needed, this is as well as the power circuits I already have installed, using SWA etc

 

[plugwash]

using conduit with singles underground is asking for trouble unless you know exactly what you are doing (and you really need to use steel conduit and weld it)

swa is a much easier option

 

[tomlyall]

Okay thanks for the advice.

Would it not be okay to use 'conduit' even if it was one long length of MDPE tubing?

The only reason I'm reluctant to use SWA is because the run is around 30m, and the only lengths I've been able to find are 25m or 50m, which either means joins, or a fair bit of waste.

Also I've already got conduit cable already,

But if theres no alternative I shall get some SWA...

 

[plugwash]

mpde is definatly out of the question you would dig through that in seconds and there is notihgng to earth your spade an insure disconenctino of supply if you do

electricalshop.net sell swa by the meter btw

 

[tomlyall]

Okay. Thanks for the advice I think I shall buy some from them.

Just another quick question...

I've got 2.5mm SWA running to the shed in question for power.
I've also got the outdoor lighting to power.
Finally I also intend to have a 16A outlet outside (on the kitchen wall).

I only have two spare spaces on the RCD protected side of my CU, what would be the best combination to use?

 

[ban-all-sheds]

Okay. Thanks for the advice I think I shall buy some from them.

Just another quick question...

I've got 2.5mm SWA running to the shed in question for power.

That's a bit thin for a 30m run. Factor in the distance inside the house as well, and you'll not be able to draw much current at all on that circuit.

I've also got the outdoor lighting to power.
Finally I also intend to have a 16A outlet outside (on the kitchen wall).

Like this?

Well - not like that exactly, you'll need an IPx4 or 5 one, but that type of socket? What for?

I only have two spare spaces on the RCD protected side of my CU, what would be the best combination to use?

Use one for the 16A socket on the wall.
Forget your existing 2.5mm SWA, lay in some 6mm, or even 10mm (you don't want to have to dig that trench for a 3rd time) to the shed, and put a CU out there to provide the power, outside lighting etc.

 

[tomlyall]

Yep that type of socket... and yes, an IP44 one. Reason being that all the equipment I intend to use outdoors is fitted with these, and I personally like these connectors.

I see what your saying about the SWA, I shall use the 2.5 that's in at the moment for the lighting then. Btw the trench has'nt been filled in yet, I'm saving that until I know everything works.

Out of interest, by little current, how much do you mean? The 30m is from the CU right to inside the shed, so theres little to no extra length to include.

Thanks for all your advice so far, its good to have someone else point out the errors in your workings.

 

[securespark]

30m of 2.5 SWA will supply 16A with a volt drop of 8.64V over that length.

This is taking into account no other factors.

This 8.64 value is quite high - max is 9.6V. Ideal is to get the VD figure as low as is practically possible.