7 core NYYJ cable to extend ring final circuit?

[Williamshoeste]

Hi,

Extending a ring final circuit off a socket in the kitchen through the wall into the shed on the other side. I already have 7 core NYYJ 2.5mm cable and I was wondering if I could use that to go through the wall to a J/B then connect to singles in conduit which would add about 4 meters in total to the ring (2 meters there and back)

Do people use multi core cable to extend rings? Or is it always 2 x 3 core? Do they use multi core to go through walls? I liked the added protection of the cable.

If you have any suggestions that would be great help.

 

[Timbo]

Why not run the conduit through the wall from the socket to the shed and use singles?

 

[radiohead]

No reason why you cant use the 7 core, but as above, it would be a better job to use conduit and singles all the way into the kitchen socket.
As an aside have you actually verified the socket you are coming from is on a ring? Just because there are two cables don't assume, particularly if a kitchen fitter has altered/installed anything in the past.

 

[westward10]

You need to check the ccc of a 7-core cable as it may well fall below what is required for a ring final circuit.

 

[Ian1981]

2 core 2.5 mm Nyyj on eland cables web site is 27 amps in air.
7 core is 16 amps in air however the 7 core ccc rating is for 7 loaded cores, if your only using 2 cores (not counting the cpc core as it’s not carrying current) id imagine you can use the higher rated ccc.
I’d rather not have all the extra cores there to be honest , I wouldn’t use it.

 

[Lucien Nunes]

Although, as part of a ring, four cores could be equally loaded by a concentration of load just to one side of the multicore-fed section. I am suspicious, without any data to back it up, that on paper it would not have sufficient CCC.

 

[SJD]

Given that the length of cable in question is about only 4m in total, I'd suggest the OP ignores the fact of happening to have some 7-core NYYJ, and just buys suitable cable for the job.

 

[Ian1981]

I’ve mistakenly read it as spurring off the ring using 7 core, not extending it

 

[westward10]

The cores must be rated at 20A if being used on a ring final circuit normally sized at 2.5 unless it is MI where 1.5 can be used however, plenty of ring finals have been installed over the years using 4-core MI which is not actually rated for 20A. Like SY, correction factors are applied to NYY J cables when the quantity of cores exceeds five.