Garage circuit question

Quite unnecessary. If it's wired with 2.5sqmm cable and is protected by a 20 amp MCB it's exactly as it should be.

I think radial circuits like this are much more sensible than ring circuits, easier to test etc.

Doesn't sound like there's any need for that, what is it a 16A or 20A radial, using 2.5mm^2 cable?

If that is all you require it is not worth going for a ring. I have a ring circuit for my garage only because I have multiple sockets in a large garage/workshop with attached office. I have a freezer and tumble dryer in the garage and need to charge my plug-in hybrid with A “ Granny” lead plus the need to plug in various power tools in a number of locations. The office section has several sockets mainly for office stuff, laptop, printer and WiFi access point as well a fan heater when required.

Back to the fuse box on a separate circuit, or as a branch (at origin) from an existing one?

Integral garage, or detached?

Suggesting it was just a part of a normal "house" socket circuit previously?

I can see no benefit in doing so - and possibly some reasons that would recommend against.

Rings are very good at providing socket coverage over a wide area. Well suited to diverse and varied loads, that are spread out (in terms of position on the circuit). They are less well suited to high current fixed loads at single points - especially if the point is near one of the ends of the socket.

Typically with things like a garage circuit, it is common to wire in a radial (which you might class as a "sub main" if running externally to an outbuilding). The MCB at the origin being adequate to protect the circuit from both fault and overload current. If you need lots of sockets at the far end, then another CU fed from the submain would be the way to go since you could then run a ring circuit on that if required.

So long as the exterior socket has RCD protection somewhere, I can't see any reason to change.

Separate circuit.

Integral.

No, it wasn't. It was provided just for a double 13a outlet originally but probably shared a fuse with one of the house circuits. I don't remember, it was over 20 years ago.

Thanks.

Thanks

That's not right then, it would need to be 4mm^2 cable for a 30A radial, if it's 2.5mm^2 you ought to drop it to a 20A MCB/RCBO.

If it has a 30 amp MCB then it should be wired with 4sqmm cable, I doubt if it is. Change the MCB to a 16A or 20A one.

ok

The fuse is what delimits a circuit - if you have 5 fuses, then that is five circuits typically.

So even if you take a separate single cable right back to the CU, and then hook it up to the fuse currently supplying the downstairs socket ring, then that new cable[1] becomes part of the downstairs socket circuit.

The devil is in the detail...

Say the original circuit was a 30A fused ring circuit feeding sockets elsewhere in the house. The addition of a spur in 2.5mm^2 cable to feed a garage socket would be fine. (Even if the connection point of the spur was at the fuse in the CU rather than at an accessory / JB on the circuit).

However, when that original garage socket was augmented with an additional one for the roller shutter, that technically became a spur feeding a spur. (probably not an actual risk in the grand scheme of things - however to be properly compliant the split to feed both sockets could have been done with a fused connection unit to turn the pair of sockets into a fused spur, or the single socket could have been replaced with a double since one double socket is permitted on an unfused spur)

I can't remember now, but I think we've been told the garage has now become its own circuit?