Extending a ring.

hi guys

When extending with a spur ,you can fuse it down to 13A and that's ok but if you didn't want to fuse it down can you spur with a 4mm T+E allowing for Zs.

any advice or comment welcomed.

Well if you were going to do that why not just run in 2 legs of 2.5 ?

Why fusing it down?

Well if you were going to do that why not just run in 2 legs of 2.5 ?

Click to expand...

That is definitely an option but with 4mm it only needs to go one way.

I generally use 4mm for spurs that way it allows for another socket when they want one.

Batty

Are you confusing spurs with radials?

You can spur off a lets say 2.5mm ring in anything from 0.50 to 2.5 depending on the rating off the appliance.

So if I had an extractor fan spured of a 2.5mm ring it would not be required for me to continue in 2.5mm up to the extractor, given the fuse rating is 3 amp, so a suitable cable from the spur could be in 0.50mm, or o.75.

I would never spur off a cable of a lower csa with one of a higher csa.

A radial circuit in 4mm would take a 32 amp breaker, whereas a 2.5 radial would reqire a 20 amp breaker.

Is the issue here that the ring has 2 legs and we assume the load is equally spread so we can have the ring in 2.5mm rated 24A per leg on a 32A breaker, but the same radial would be on a 20A breaker as only 1 leg.

If we spur off a ring to another socket would 4mm be more appropriate than 2.5mm?

A spur from any ring, or for that matter a radial would only have to be of a csa required for the purpose of the appliance or load.

A combi boiler spurred from a 2.5 ring would only require to be in 1.5, fuse rating 3amp.

A socket outlet spuured from a 2.5 ring could be for all intent be in 1.5, however I wouild prefer for it to be of the same csa as the supply ring.

What I would not do is connect a 4mm cable to a fused spur supplied from a 2.5 ring.

I just would not find any justification for doing so, as the only fuse that could be fitted in the spur is a 13amp.

Is the issue here that the ring has 2 legs and we assume the load is equally spread so we can have the ring in 2.5mm rated 24A per leg on a 32A breaker, but the same radial would be on a 20A breaker as only 1 leg.If we spur off a ring to another socket would 4mm be more appropriate than 2.5mm?

Click to expand...

how much power can the socket safely draw?

single... 13A

double... 20A

why go for 32A capacity....

or are we talking off taking a "radial" branch off a ring...

e.g. Spur off spur off spur...

You still need to consider the current rating of the accessory where the spur/radial branch actually joins the ring...

e.g. a double socket on ring with a double socket spurred off it, will be carrying all of the spur current across the screw terminal joints in the back of it.

IMHO if your spur/radial branch is gong to be carrying so much power it needs 4mm,

I would think you need to look at proper radial back to CU,

or full extension of the ring circuit to ensure balancing load.

So if you are expecting big power consumption down your new spur branch, the ring as a whole may not be suitably balanced.

But if NOT need high power consumption... then no need for 4mm anyway!

:|

how much power can the socket safely draw?single... 13A

double... 20A

why go for 32A capacity....

or are we talking off taking a "radial" branch off a ring...

e.g. Spur off spur off spur...

You still need to consider the current rating of the accessory where the spur/radial branch actually joins the ring...

e.g. a double socket on ring with a double socket spurred off it, will be carrying all of the spur current across the screw terminal joints in the back of it.

IMHO if your spur/radial branch is gong to be carrying so much power it needs 4mm,

I would think you need to look at proper radial back to CU,

or full extension of the ring circuit to ensure balancing load.

So if you are expecting big power consumption down your new spur branch, the ring as a whole may not be suitably balanced.

But if NOT need high power consumption... then no need for 4mm anyway!

:|

Click to expand...

Agree completely,it was theoretical, the ring is getting extended in the bedroom via a fused rcd spur where the most will be a hair drier for few minutes.thanks for the reply.