Wiring a Garden Shed

[LaughingJon]

Hi, I'm installing power down to my garden shed and have done/intend the following...
Installed a basic RCD with both a 6A lighting and 16A power circuit, and provided a simple ring main circuit and a couple of lights connected respectively.
Layed a 2.5mm SWA cable down the garden and plan to route through the garage wall some 30m away.

My main question is based around the connection to the main fuse board. There are two disused Independent Switched circuits I could potentially use, one was for some old off-peak heating system. The question is how do I safely isolate this switch as it's connected directly to the tails?

My fuse board is quite old and having just 8 circuits is full to capacity.

I then have a number of questions on how to terminate the SWA through the garage wall.
I planned to terminate externally through a waterproof junction box with a gland pack and feed the internal cable through the wall to another junction box and then route on to this nasty switch.

Many Thanks
Jon

 

[Iggifer]

There's so much wrong with this post i don't really know where to start besides 'you need to get an electrician'. I'm not trying to be difficult, but I think it's in your best interests.

 

[EFLImpudence]

Yes, outside power is not a DIY job.

 

[Taylortwocities]

Jon, welcome.

I, too, have so many queries and comments and much that you have done may be not as necessary.

Lets take a bit of constructive time.

30metres is a long way for 2.5mm² SWA. Although, you are limited to 16A for the sockets and an amp or two for the lights, so you may get away with the volt drop..... (volt drop is what happens when you put a load on a long bit if skinny wire. If you are not careful you put 230V in one end and get a lot less out at the other).

Installed a basic RCD with both a 6A lighting and 16A power circuit, and provided a simple ring main circuit

Basic RCD? this is an RCD

Did you mean a consumer unit, with an RCD and two MCBs in it?
If so, why on earth do you need a ring FINAL for the sockets, you can only get 16A out, a radial circuit would have been adequate. How many sockets do you have?
What are you planning to run on these sockets?

Layed a 2.5mm SWA cable down the garden

How did you 'lay' this? in a trench, or just draped through the flower bed?

There are two disused Independent Switched circuits I could potentially use, one was for some old off-peak heating system.

I do not understand this, if it is an old off-peak supply, you'll only get power to the shed after midnight. That may not be what you want.
What is an independent switched circuit. Picture might help.

route on to this nasty switch

NAsty switch, what do you mean? More pictures, please.

 

[deadshort]

Please take the advice given. Get an electrician

DS

 

[LaughingJon]

Okay, Taylor...

You're quite right, please excuse my lack of knowledge on the terminology front and elsewhere too.

I did indeed mean a small consumer unit, with 2 MCBs in it (6A and 16A), I have 3 double sockets wired in a ring not radial circuit which will be used to power a PC, a few low peripherals (printer/ network switch etc) and a couple of lamps. I'm not going to run any heavy equipment down there.

The cable will be either dropped in a trench and buried or fixed to the concrete fence with cleats and buried in concrete on the final run up to the house.

There are two independent circuits each isolated by an old 45A switch fed directly from the tails effectively by-passing the main fuse board.
It looks like these used to be used for an old immersion heater and Off Peak heating (they are labeled as such).

 

[Taylortwocities]

here are two independent circuits each isolated by an old 45A switch fed directly from the tails effectively by-passing the main fuse board.
It looks like these used to be used for an old immersion heater and Off Peak heating (they are labeled as such).

Need pictures of this. And the associated wiring.
This is all notifiable work, so you are going to need a registered electrician in any case. You are going to need one who is prepared to lie when he certifies that the work was designed, installed and tested by him.

 

[LaughingJon]

Thanks TTC, I'll take some pictures tonight and post them.

Incidentally the garage already has a dedicated similar switched circuit to the boiler, but I was reluctant to just take a feed off that.

I hoped to do most of the work myself and ask an electrician to make the final connection at the house end thus saving a few bob. Fairly predictable I know (I'll await the venom of all)

LJ

 

[LaughingJon]

Here are some photos of my fine example of modernity....

You can see the two independent circuits with 45A switches side by side, fed directly from newer tails provided through the Henley Block below.

The other switch below is for the Boiler Circuit, that seems to be fed from some wires coming out the bottom of the main fuse board, maybe they're just taken straight of the live feed in, who knows?

 

[Iggifer]

The supply to the boiler is less of a concern than the feed to your main consumer unit, thats rough as!

That can be no more than a 10mm² supply, if you're lucky, could even be 6mm², hard to tell. Floating earth block is always nice to see

 

[LaughingJon]

So are you saying that the cable to the main board is too small?

That aside I really wanted to have the two other switches removed anyway but thought I could re-use one to supply the shed, if you think that's a poor idea, what other options are there?

Could I get a new fused supply put in, one which I could safely isolate and connect the SWA later on?

Or even use the Boiler circuit, although I though this might be a bit daft as any short would knock out the boiler.

 

[Adam_151]

I can't see an earth to the MEM switchfuse (the one with the orange label) which feeds the socket below (which seems to be for a freezer according to the label) and the boiler

 

[Adam_151]

@op generally what you have is a bit of a mess, ideally it could do with sorting out, but if you just needed the shed supply on now with a view to sorting out the rest later. The way to do it would be to fit a small 1 or 2 way unit or switch fuse off the henleys. SWA would be glanded straight into unit, not messing around with an external box. So when you lay the cable in drill at a downwards angle and leave long enough. Don't even attempt to connect it yourself, to make the henleys dead requires touching the service fuse which can be hazardous.

 

[LaughingJon]

Yes, it does feed the boiler and there's a couple of sockets on the back of it which feed a freezer too.

I can't see an earth either, although I've never looked until now, that is a worry.

Okay, Adam thanks for that, it is a bit of a mess, I'm not about to touch anything which I cant isolate (safely), I think I will call an electrician.

 

[Adam_151]

No worries. If you were to elaborate on where abouts in the midlands you were, there might be someone on these boards local to you. Otherwise, best think to do is ask family/friends for recomendations