Convert a radial to ring?

[scubamike]

I have a radial (only on set of 2.5mm cable to the Consumer Unit) which runs to my garage (which is attached to my house. This *may* extend out to the garden (from a junction box in the garage).

I would like to provide power & a permanent light fitting in my loft and this is the most accessible cable to which I can connect.

What I want to do:-
*IF* the cable does extend into the Garden, complete the ring (from the junction box to which the garden extension connects) back to the Consumer Unit.
*OR* find the end socket in the garage and extend the cable from that back to the CU.

Then spur from the (what is now a) ring to provide a spur to a socket in the loft.

Currently the radial is fused with a 20A RCD.
Current load on the radial is a freezer, a fridge freezer, 2 fluorescent lights and a double socket (used for gardening equipment with an extension lead plugged in). In the garden there is just an 18w UV light and a 220w pond pump.

It may be that this is overkill and I need not make the connection back to the CU to make a ring, but just extend from the end of the existing radial.


Questions:-
Is this acceptable?
Is this good practice?
Do I need a qualified electrician to make the CU connection?
Is it safe to have both socket & light on the same spur (or should I run two separate spurs).
Is fusing the Garden junction box at 3A a good idea?

Kind regards.

 

[Chri5]

I'd keep off the existing circuit covering the external stuff.

If you are in the loft, what's wrong with picking up a LNE from the light cabling in the loft serving the floor below ?

Keep lights on light circuits, or run a new circuit for loft lights when you can.

NB There's no such thing as a 20 amp rcd, a 20a mcb or 20a rcbo, but NOT a 20a RCD !

 

[ban-all-sheds]

There's no such thing as a 20 amp rcd, a 20a mcb or 20a rcbo, but NOT a 20a RCD !

http://updates.clipsal.com/ClipsalOnline/Files/Brochures/W0000877.pdf

 

[scubamike]

I'd keep off the existing circuit covering the external stuff.

OK, thanks. I'll try to pick up an existing ring for the socket in the loft

If you are in the loft, what's wrong with picking up a LNE from the light cabling in the loft serving the floor below ?

Doh !OK to spur from an existing lighting ring (hadn't even considered it to be honest).

Keep lights on light circuits, or run a new circuit for loft lights when you can.

OK, will keep then seperate.

NB There's no such thing as a 20 amp rcd, a 20a mcb or 20a rcbo, but NOT a 20a RCD !

You are of course correct - it is a 20A mcb

 

[Chri5]

Mike I missed the power (socket) bit for the loft.

Sockets can't really run from light circuits, although low demand ones (under 3 amp) could be taken via the light circuit via a 3 amp fused spur.

If the socket is general use and likely to want more than 3 amp you will need to get a cable down to the ring on the 1st floor and spur off.

Some have a redundant emersion point in the airing cupboard, might you ?

If you have an airing cupboard that tends to make a decent cable route between loft and 1st floor.

Rgds


BaS

 

[scubamike]

Thanks BaS.

Its a bungalow, so all the socket rings should be in the loft, I just have to identify the correct one under the boarding.

There is a socket in the loft already (believe it or not, the power for the combi-boiler runs via a plug in this socket so no socket in the boiler cupboard), so it might be better for me just to extend that and permanently wire in the boiler and underfloor heating from it. I'll fuse and switch them both individually

The power in the loft is for a network cabinet (Gigabit switched network with NAS storage - geeky I know!) so power draw will be low.

In summary, the power draw on the socket I can rewire in the loft will be about 1Kw made up with:-
power for combi-boiler (estimate 100W)
power for underfloor heating (400W)
Total Power in network cabinet (500W)
The power to the network cabinet will be via a small UPS, but the draw on this will not increase the drawn load by any appreciable amount

Casting my mind back to my my A-level physics, I make this just over 4A maximum draw

So I don't think there will be a problem with supplying that from the existing socket in the loft (which is fused at 5A and using 2.5M csa cable).

This would mean that there would be three sockets (or junction boxes) in series on a spur though, which I though was a big no-no. Would the fuse at 5A be sufficient protection to make this acceptable? (The fuse is before any of the junctions so the whole spur is protected).

Thanks for taking the time to respond. It has made me rethink my solution and probably made it a lot easier for me too.

 

[Chri5]

A clean unfused spur froma ring main is limited to 1 x d/socket.

Put a f/spur 13 amp on the spur cable from the ring and you can then have as many sockets as you want- but they will be limited to a total load of 13 amps.

Avoid j/ boxes and since you can do the following, there shouldn't be a need:-


Spur from ring terminated on 13 amp fuse spur

cable fuse spur to socket Boiler

cable boiler to next socket

and on, and on, and on- if you wish

 

[scubamike]

Thanks Chri5,
You have put my mind at rest. I will probably fuse at 5A as I'd rather fuse on the low side if I won't need the additional current.

Didn't think it would be a problem, but nice to have it confirmed.