External Power Socket

[Chitter]

Good morning all,

I've recently had a new extension built at the back of the house and the whole house just been decorated.

The house was also rewired and at the time I asked the electrician to install an external power socket. However he forgot and I didn't really notice myself till recently. I now also want a shed at the back of the garden and will need power and lighting in there too.

I asked the electrician to come over again and to fit one for me and he has given me the following options (most expensive option listed first and cheapest last):

1. He will run 2 cables from the consumer unit to a 'cut off switch' and then from here the cables will pass into the crawl space below the floor boards, below the WC, into the kitchen, run up and along the wall, above the kitchen units. Once it reaches the extension, he will drill through the side wall and bring the cables out to the side of the extension and then bring them around to the back of the extension to the external socket and take the other cable directly to the shed. (Please see attached diagram and note I've only drawn 1 cable from the CU to the garden to make it neater but the electrician has assured me he'll run 2 cables).

2. There are plug points in the extension ring final circuit and he can run a cable from one of them to the shed and another cable from a different extension socket to the external power socket. Neither of these however will have a 'cut off ' switch as there's no space for it and so the electric to the external power socket and shed will always remain on.

3. He can run a cable from a socket in the extension to the external power socket and then from here to the shed at the back of the garden. There will still be no 'cut off switch'.

The electrician has asked me to let him know how much I'd like to spend on the job and he'll then arrange the wiring accordingly.

I'm not an electrician and would like a second opinion on which is the best solution as it's easy to go with the cheapest option but I don't want to make the wrong choice. If one of the other solutions is better by design and safety then I'd rather take that then save money now and get into trouble later.

Many thanks.

 

[ban-all-sheds]

Options 2 & 3 are to be avoided like the plague. If you get water in any of the external bits (a realistic possibility) it will probably trip the RCD, leaving you with no power on those circuits in the house until you disconnect the outside stuff from the socket(s) in the extension. The least disruptive failure mode would be if those sockets are on an RCBO, in which case you would only () lose them.

2 or 3 would be fine if you have isolation switches in the house.

Option #1 is the best one, as it would give you the potential for a larger supply in the future, e.g. if you decide to kit the shed out with a particle accelerator. Or a kiln, or a hot-tub.

Given how disruptive putting that cable in will be (and how time consuming, and therefore how expensive in terms of labour), you only want to be having it done once. The extra cost of a larger cable would be fairly minor compared to the total cost.

You only need one cable, BTW, not two - Lord knows why he wants to do that.

IMO the ideal answer would be a 10mm² cable, taken from a switchfuse, not from the house CU, to a CU in the shed. With the route shown that might mean the right cable or installation method in the indoor section where it is buried in a wall to be used to remove the need for an RCD at source. As it will end up going outside anyway, why not go outside from the understairs cupboard and run along the wall all the way? A single run of 10mm² armoured cable would do nicely. (Don't tell me - it's a terrace or halls-adjoining semi....)

 

[Chitter]

Yep, it's a terraced property and so he cannot take the cable straight out from where the CU is.

The reason for the 2 cables was so that 1 would go to the shed and the second would go to the external socket - putting them both on their own circuit so that they are totally independent of each other.

You say 2 or 3 could be a possibility if there is an isolation switch...... The issue here is that the electrician suggested this but said he'd have to start cutting into the walls etc - something which I want to avoid as much as possible as its a brand new kitchen, all just painted etc. I really don't want all the mess and repairing walls etc......

Thanks for your advice though, just now wondering if I could have him connect the socket via an isolator somehow????

 

[Chitter]

Sorry to post again - I've been racking my brain to find a more convenient solution. I have a dishwasher socket under the counter at present. It is spurred off of the extension ring final circuit with an isolation switch between the 2.

Would it be ok to swap the isolation switch for a 13amp FCU and then connect the external power socket to the dishwasher spur and then extend the cable from the external power socket to the shed?

There are very minimal power requirements in the shed such as a light and maybe a phone charger etc. The external power socket will be used to power the lawnmower and garden power tools though.

Just to add the shed is approx. 15m from where the 'radial' part of the circuit would start from - would it still need a 10mm cable?

 

[ban-all-sheds]

Yep, it's a terraced property and so he cannot take the cable straight out from where the CU is.

Ah.

The reason for the 2 cables was so that 1 would go to the shed and the second would go to the external socket - putting them both on their own circuit so that they are totally independent of each other.

Seems rather unnecessary.

You say 2 or 3 could be a possibility if there is an isolation switch......

2 Isolation switches - 1 per circuit.

The issue here is that the electrician suggested this but said he'd have to start cutting into the walls etc - something which I want to avoid as much as possible as its a brand new kitchen, all just painted etc. I really don't want all the mess and repairing walls etc......

Thanks for your advice though, just now wondering if I could have him connect the socket via an isolator somehow????

It has to go:

[Internal]------[Internal]------[ External]
[ Socket ]------[Isolator]------[Accessory]

Surely they would be adjacent to the donor sockets in the extension?

 

[Chitter]

Hi again, the current sockets etc all sit inside the wall. If he were to put in another isolator, he'll have to cut a piece of the wall out and that's something I'd like to avoid if at all possible.

But I posted the above suggestion - would something like that work at all?

 

[securespark]

e.g. if you decide to kit the shed out with a particle accelerator.

Or a flux capacitor requiring 1.21 gigawatts?

If the power fails, no problem...just get 8,066,666,670 hamsters and harness the power from their spinning wheels, it'll be the same.

 

[Chitter]

e.g. if you decide to kit the shed out with a particle accelerator.

Or a flux capacitor requiring 1.21 gigawatts?

If the power fails, no problem...just get 8,066,666,670 hamsters and harness the power from their spinning wheels, it'll be the same.

I assure you I won't be needing that much power...... Would the above idea work at all though? converting the dishwasher spur into a radial via an FCU with a 13amp fuse fitted and then continuing it up to the shed?

 

[ban-all-sheds]

Yup.

 

[Chitter]

Thanks for the help all

 

[deadshort]

Hi, i would go with option one, with the following changes -

Run a one supply for the shed from the CU and install a external socket on the side of the shed.

DS

 

[winston1]

Option 3 is a spur on a spur which is not allowed on a ring final.

 

[bhm1712]

Option 3 would be ok if the socket was changed to a FCU

 

[ban-all-sheds]

Option 3 is a spur on a spur which is not allowed on a ring final.

Where does it say that?

 

[AndyPRK]

Is there no room next to the socket for a single width fcu ?

It's what I did on a freshly decorated room.
Fit an FCU next to an existing socket and then run a cable out the back of that to go outside.

Just about got away with it decoration wise. Maybe a bit of filler but at least its a good longterm solution.