Kitchen Ring Problem

[OxiaUK]

While changing some socket fronts in our kitchen I've realized that there are some mixed cable sizes!

2.5mm goes from the board to the first few sockets then it looks like 1.5mm from one to a few more then 2.5mm back to the board!

There is absolutely no way for me to change the cable at the moment as it's a full rip out to sort it and were not planning on decoration any time soon.

What's the best and safest solution?

I was thinking of de-rating the MCB to 16a?

 

[ericmark]

Are you sure ring final, not spur off ring final?

 

[sparkwright]

Unless by some miracle the 1.5mm2 cable is pyro, you'll need to change things.

As mentioned, is the 1.5mm2 DIRECTLY on the ring, or is it spurred in some way?

If the 1.5mm2 forms part of the ring directly, you MAY be able to use a 20amp device - but more investigation required first.

 

[OxiaUK]

It's 100% a ring final and there are no spurs off any socket. Wouldn't it need to be a 16a breaker in order to provide protection of the length of 1.5mm that is in the ring?

 

[sparkwright]

It's 100% a ring final and there are no spurs off any socket. Wouldn't it need to be a 16a breaker in order to provide protection of the length of 1.5mm that is in the ring?

Well, a ring wired fully in 2.5mm2 can be protected at 32amp,
but a radial in 2.5mm2 is usually only protected by 20amp,
so
one could argue a ring wired in 1.5mm2 could be protected by 20amp as it's a ring; it's fed by two cables, electricity flowing two ways.

Let's see what others think before you do anything.

 

[winston1]

Looks like it has been there a long time with no problems even if it does not comply with the (non statuary) regs. If it is near the centre of the ring it is unlikely to carry more than 20 amps anyway. Your choice, but I know what mine would be until redecoration.

 

[Steve]

Well, a ring wired fully in 2.5mm2 can be protected at 32amp,
but a radial in 2.5mm2 is usually only protected by 20amp,
so
one could argue a ring wired in 1.5mm2 could be protected by 20amp as it's a ring; it's fed by two cables, electricity flowing two ways.

Let's see what others think before you do anything.

All legs of a ring have to be capable of carrying 20A (this is a specific reg). This is why if you wire a ring reference method 101 (bungalows) you must use 4mm² cable or derate it to 20A.

 

[winston1]

All legs of a ring have to be capable of carrying 20A (this is a specific reg).

1.5mm cable is rated at 20a I believe.

 

[EFLImpudence]

It is - but 1.5mm² is not allowed by the regulation because it (the regulation) still caters for a 30A BS3036 fuse protecting the circuit.

With a 32A MCB it would be fine.

 

[OxiaUK]

so would it be best to temporarily chance the MCB to a B20 or B16? until I can get it rectified

 

[winston1]

so would it be best to temporarily chance the MCB to a B20 or B16? until I can get it rectified

That would require you to work on a live CU. Potentially more dangerous than leaving everything as it is.

 

[EFLImpudence]

Well, a ring wired fully in 2.5mm2 can be protected at 32amp,

Only because the regulation still includes the likelihood that it might have a 30A BS3036 fuse.

but a radial in 2.5mm2 is usually only protected by 20amp,

But it could be 25A.

so
one could argue a ring wired in 1.5mm2 could be protected by 20amp as it's a ring;

That's not an argument. If it were protected by a 20A MCB, it could just be a radial circuit.

it's fed by two cables, electricity flowing two ways.

Therefore it has a capacity of 40A.

 

[chivers67]

so would it be best to temporarily chance the MCB to a B20 or B16? until I can get it rectified

If you change it to a 16 A expect it to trip if the washing machine is on spin and someone puts a toaster & kettle on.

 

[EFLImpudence]

How long has it been like it is?

Is there any sign of overheating on the cables?

 

[OxiaUK]

How long has it been like it is?

Is there any sign of overheating on the cables?

few years at least, no obvious damage that I can see