Rings, spurs and things

[Guy King]

I've got to the wiring up the conservatory stage.

I can run a new circuit back to a spare way on the fusebox.

This would be either a new ring or a spur - I need only about three double sockets, but it would also allow me to tap off through a local fuse for a lighting circuit.

Or, I can extend the existing ring which passes within inches of where I want it. The existing ring already serves the whole house - but it's a small house!

Or I can run spurs off the existing ring, as I have close access at each end of the conservatory so a spur each end would be easy.

The lighting - five 7W LE spots mounted in wall fittings - not sure yet. Could connect to the existing house lighting circuit, or feed from the socket supply via a local 5A (or 6A or whatever they are now) fuse.

Any thoughts?

[Owain]

The best way, with the advantage that you can use a DP isolator to take out the conservatory in the event of dampness causing nuisance tripping, or if you do not want your neighbours stealing your electricity while you are on holiday.

The second best way.

The third best way.

Depends on how serious it would be if the lights fail on RCD tripping. How worried are you about falling through the conservatory glass?

You might also want a point for an electronic insect killer/repellent.

Owain

[Guy King]

The message from Owain contains these words:

Not even slightly. The windows are up at hip height, and toughened[1] so of little hazard. As for the neighbours stealing the leccy, both sides have keys to the house anyway, so if they wanted to steal anything, the electricity would be the least of the stealables.

Can I get a DP isolator that will fit in a single slot in the fusebox? It'd be a bugger to have to fit an external unit just for that.

[1] Well - sort of toughened. I /ordered/ toughend, paid for toughened, and the glazier swears they are toughened, but with luck the replacements that actually have the kitemark etched into them will arrive Monday. Meanwhile the probably toughened units are in place, partly 'cos I wanted to see whether they'd fit and partly to keep them out of the way. I've never made window frames before - and I'm dead chuffed!

[David Hansen]

On Sun, 25 Jun 2006 18:36:41 +0100 someone who may be Guy King wrote this:-

A 20A radial circuit should have more than enough capacity for a conservatory. Probably the same size cable as your ring main, but you will presumably save a considerable amount of cable by not having the "return leg" of a ring.

Ensure you allow for the likely conditions in the conservatory when sizing the cable and selecting fittings.

Either would allow you to do this?

I wouldn't adopt either of your alternatives for sockets, unless a radial circuit is difficult.

Only one lighting circuit? Check the loadings. If it is not heavily loaded this is the one to connect to. I take it there is not a second spare way?

[Roger Mills]

Agreed - from a technical point of view.

However, from a political point of view - if my understanding is correct - running a new circuit from the CU involves the dreaded Part P certification - whereas extending existing circuits doesn't.

It really encourages you to do it the right way, doesn't it?!

[Guy King]

The message from David Hansen contains these words:

It would only save about ten meters - hardly worth worrying about.

There are three spare slots on the fusebox. I suppose I could be really posh and run a lighting circuit and a power circuit exclusively for the conservatory.

[Guy King]

The message from "Roger Mills" contains these words:

Frankly, I'll do it the right way and bugger the Part P compliance.

[Owain]

You could use an RCBO if it's a consumer unit with MCBs and you have 3 spare slots.

Otherwise for a 20A radial circuit you can use a 20A plateswitch - maybe just inside the house before the cable leaves for the conservatory.

Remember ordinary PVC cable may not be suitable for a conservatory and you might have to apply temperature-related derating because of solar gain.

Owain

[Owain]

Oh, I assumed that this was work done in 2003 and was simply a like-for-like replacement of various existing cables and fittings :-)

Owain

[Guy King]

The message from Owain contains these words:

My thoughts exactly. Except I didn't get planning permission for the conservatory till last year!

[Owain]

But the walls on which you mounted all these sockets pre-existed the conservatory :-)

Owain

[Guy King]

The message from Owain contains these words:

Sadly - not.