Extending a ring

No a spur is like putting a double socket instead of a single one, the ring is what it says on the tin, so to speak. Brian

That's if the circuit in question is a 30 A ring and not a 32 A radial. "Cooker" circuits are normally 32 A radials in 6 mm^2.

You do if it's a 6 mm^2 radial as a single 2.5 mm^2 cable isn't rated for 32 A.

Personally I'd I'd rather use a "general purpose" ring rather than hi-jack a "cooker" radial circuit. It may be "safe and legal" but is unconventional and could well trap the unwary.

I doubt if it's a ring then. What is the rating of the MCB/RCBO in the CU feeding the oven?

It sounds a bit odd altogether, a dedicated circuit for an oven tends to be a 32A (or something like that) with a single 4sqmm or 6sqmm feed to the oven which would be hard wired (i.e. not a plug). The oven connection unit with the switch on the kitchen wall often has a single socket for something other than the oven to be plugged in.

Has your oven been changed? I.e. could it have been hard wired once and changed to one that can be plugged in?

Should be OK, even connected to a dedicated oven circuit, but I'd be happier knowing exactly what the oven [not] ring circuit actually is.

on 29/08/2020, JoeJoe supposed :

Ovens are not usually on a ring, they are more usually on a separate dedicated circuit.

That's built-in ovens. Baby Bellings are usually plugged into a 13A outlet

Correction (my mistake, got mixed up and should have checked before posting):

The oven is indeed (as indicated here) hard wired rather than plugged into a socket. In fact I replaced the oven myself a few years back and forgot all about it...

It does have its own circuit - not sure about the cable rating (can empty the cupboard it is in and check if it matters?), and protected by a 32A breaker in the CU.

All was done properly (I hope...) and signed off when we had an extension built a few years go.

That was what I meant, just used the wrong terminology.

A fair few single fitted ovens are rate 13 A or less and can be plugged in. It's a pain that others (especially the better ones) ate 16 A: tempting but ...

On a Sunday morning?

In bed with girlfriend, I would assume.

Owain

Fitting emergency lights for Geoff in Watford actually.

No fuse needed as the overload protection is provided by the load on the socket.

So in theory no different to a 2.5mm unfused spur off a 32A (2.5mm) ring or 32A (4mm) radial socket circuit.

When we bought this house, the Rayburn was supplemented by a hard-wired Baby Belling. It now has a plug on it (for occasional emergency use), and a proper, dual-fuel cooker has been installed.

Baby Bellings came in two versions, one for a plug and one for hard-wiring. The plug version had an interlock between one of the rings and the oven to restrict the tital lload.

Owain

This one has that interlock. I'm assuming it came as a plug version, and for some reason was wired in. It came in very handy last summer, when the cooker packed in.

Thanks!

Never heard it called that before.

Owain

It does not need to be if all its feeding is a socket. The situation is no different from a 32A circuit feeding a spur. The overcurrent protection is implicit in the restriction on the load imposed by the requirement it feed no more than one single or double socket.

Fewer surprises are good. Although a label on the CU declaring what the MCB feeds would be a satisfactory mitigation.

Extending the ring is not the same as adding a spur.

Either way I don't see why you need an FSU as long as you wire it in 2.5mm

In that case, in general, you are still allowed a single (not a dual-gang) socket and it only costs you 5A in the diversity calculation. You won't fall foul of that if the oven radial is 6mm. Use 2.5mm to the socket, no fused spur unit required

Disclaimer, IANAE, one will be along in a moment to mark my work.