planned conservatory wiring

[wemyss]

Having a conservatory built early in the new year and will be wiring it up myself. As a plumber can understand and carry out basic wiring but would appreciate advice on what I plan.
Where the conservatory will be located is next to a patio window. I have a SWA 2.5 cable from my garage coming up to a security light.
I plan to shorten this down and use this supply for 3 S/O 2 wall lights and a ceiling fan.
My thoughts on how to do this is to fit a 2 way consumer unit one for the S/O and the other for the rest.
I will wire in twin and earth although I do prefer singles to avoid joints but the wall will be plastered. Have read previous posts regarding using steel capping for the cable so am up to speed on that one.
Also read advice on depth of steel boxes and will be using 25mm for all of them and check first with the plasterer.
I'm unsure on how I will proceed with fitting the consumer unit and leaving the SWA coming out of the wall ready to connect after the plasterer will have finished and also with the T&E cables above the unit.
Do you just leave them clipped and sticking out and the same for the SWA.
Doing it like this would leave them showing afterwards and look a bit unsightly so I'm sure you guys must have a better way.
Incidentally I will be supplying directly from a 2 way consumer unit already installed in the garage supplying a ring main in there and the garage lighting.
Any advice or suggestions please.
wemyss

 

[brown-nought]

I’m a bit confused by your description – probably me - but can we run through it again.

You are building a conservatory onto the back of your house with access via an existing Patio door. Power runs from your garage (attached to the house) in SWA to a security light? (How is the SWA terminated incidentally?)

You want to install a fan, 2 wall lights and 3 socket outlets?

You have a 2 way Cu in the garage. Does it supply the existing light and if so from which circuit? I take it the Garage Cu runs back to your houses main Cu? The various fuse ratings would be helpful too.

If you could clarify this it would help.

If the conservatory is to be water proofed and used as a habitable room rather than an out building why can it not be supplied from the existing house circuits? The sockets will need to be on a 30ma RCD.

Also if you are doing the work under a building notice the electrics will fall under Part P next year.

 

[Damocles]

Only 6 weeks to go and we can stop warning people about the impending part P!

 

[ban-all-sheds]

No, I think in 6 weeks time every piece of advice will have to be prefaced with a warning about Part P...

 

[wemyss]

Thanks for your reply BN.

You are building a conservatory onto the back of your house with access via an existing Patio door. Power runs from your garage (attached to the house) in SWA to a security light? (How is the SWA terminated incidentally)

No the garage is not conected to the house and is about 5 metres away.
It is supplied from the consumer unit by a pyro cable from the house CU which feeds into a 2 way consumer unit. One supplies a S/O ring and the other for the lights in the garage
The supply to the patio is by a SWA which I laid in when block paving was done. It terminates in a weatherproof fitting to a security light but plan to cut back about 2 metres to where the new CU will be.
At present it is supplied from the lighting circuit on the CU but would be switched to power.
The reason I am planning to use this is that it would be more difficult physically to get a connection from inside the house particularly the lighting one and as the SWA is there it seems to make sense to use this.
However please feel free to correct me if I'm wrong.
The S/O in the conservatory would of course be a radial and not a ring main.
The fuse ratings in the garage CU are at present 30 and 15 although I have the supply to the security light through a DP 5amp fused switch below the CU.
Also if you are doing the work under a building notice the electrics will fall under Part P next year.
Sorry but I'm not sure what you mean by this.
regards
wemyss

__________________________
wemyss, click this post's

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[wemyss]

Sorry if my message seems a little garbled in quoting your own comments but being my first post on this site I don't know how you paste into a little white box which I notice many of you have done.
wemyss

 

[Damocles]

going from the house to the freestanding garage back to the house does not sound brilliant. What is the size of cable/breaker feeding power into the garage.

Next year although I think you can build a conservatory without building control being interested, they will expect to inspect your new electrics.(and be paid at least £100 for the privilege)

 

[comms]

If you did extend the ringmain of the house into the conservatory, you could fit an fcu with 5 amp fuse & supply power for a lighting circuit in the conservatory.

 

[wemyss]

The fuse in the house CU to the garage is a 20ampMCB
What is a FCU?.
The nearest S/O to the patio is a spur off the ring main and I understand that you shouldn't take another spur of an existing spur?.
wemyss

 

[comms]

FCU = fused connection unit
Your right you cant run off of a spur.
So ignore all I've said

 

[wemyss]

Thanks moderator will remember that.
wemyss

 

[ban-all-sheds]

Sorry if my message seems a little garbled in quoting your own comments but being my first post on this site I don't know how you paste into a little white box which I notice many of you have done.
wemyss

Click on the

button instead of

Alternatively, if you've copied/pasted text in by hand, you can highlight what you want to appear as a quote and click the Quote button that you see with the other formatting stuff:

Once you get the hang of how it works, you'll find it's no trouble to take somebody's post

Sorry if my message seems a little garbled in quoting your own comments

and split it up so that

but being my first post on this site I don't know how you paste

you can intersperse comments/answers

into a little white box which I notice many of you have done.
wemyss

etc.

Don't forget to use the preview facility to make sure that you've got all your [ quote ] [ /quote ] pairs matching up.....

 

[Damocles]

Um, ok. It is not a brilliant plan to have a 20A breaker feeding a combination of a 30A fuse and a 15A fuse. 15A is a bit big for lighting, so I would hope your lights all go through the 5A switch, so the 15A isn't really doing anything. 30A is definitely too big when it is being fed by a 20A. The 20A will likely trip first. From a 20A supply, this should be a 15A and a 5A.

You can not spur from an unfused spur, but you can from a fused spur. So if you insert a FCU (plate with a 13A plug fuse in it) into the cable feeding the spur, then you can spur off extra sockets as well. If you add a further FCU to this spur chain, then you can use a 5 or even 3A fuse to run a few lights.

This depends a bit on how much power you might need in this conservatory. There is a bit more scope for taking power from the 20A garage circuit, but if you want to allow some power used there as well, then there is really not a lot in it from that point of view.

 

[wemyss]

Damocles, thanks for that. From your response and others I detect a lack of enthusiasm for my grand scheme so tomorrow will look at getting a supply from within the house.
I simply thought that with the SWA being closer it would be easier and imagined that I would have to get both a lighting circuit and power from within the house. Reading other posts not related to this one the mentions of voltage drop came into my mind as combined with the pyro it would be a fair distance.
However if you are saying that its OK to use a power cable from the house to supply both power and lighting this makes it more practical.
There would be no big use on the power circuit envisaged so will try and go down this route.
Where the ring spur comes into the conservatory from the house would I then couple two FCUs close together. One for lighting and the other for power.
Any advice appreciated as I like to have it all fixed in my mind before I begin and what I need to purchase.

 

[ban-all-sheds]

Where the ring spur comes into the conservatory from the house would I then couple two FCUs close together. One for lighting and the other for power.

Can't you extend the ring into the conservatory, rather than put in a spur?