Is my existing feed suitable for this:

[JohnW2]

yep, ... if you treat 2 x 2.5 as 5.0mm conductors and a 3.0 earthwire then you will not be far wrong, although a little bit of interpolation on the current carrying capacity, volt drop and expected Zs might be required because they are non standard sizes to look up in tables. The nearer the lengths match the better your "guess" would be.

True. Although 2 x 2.5 mm² T+E cables in parallel would obviously have a higher CCC, and a lower R2 for a given length, than would 4mm² T+E, I was not suggesting that one should consider it as any 'better' than 4 mm² T+E. As you say, if one did want to use it as 'more than 4 mm² (see *** below)', one would have the problem of its CCC not being available from the usual tabulations.

[ *** interpolation between CCCs given for standard sizes of T+E suggest that the CCC of 2 x 2.5mm² cables would, if it were included in the tabulations) probably have a CCC (with Method C) of a bit over 40 A (maybe appreciably higher, because of different heat loss behaviour when there are two cables) - so a 40 A OPD may well be acceptable, but one would presumably have to find some 'official confirmation (or strong evidence of one's own) to confirm that ...

Kind Regards, John

 

[JohnW2]

There are certain regulations for "conductors in parallel". You can't just count two separate wires that you have connected as such.

There are such regulations but, although I haven';t looked at them for a long time, I don't think they have much impact if one has two identical cables following identical routes.

 

[EFLImpudence]

I don't think they have much impact if one has two identical cables following identical routes.

...maybe not - but if they are not doing that, then they will.

 

[JohnW2]

...maybe not - but if they are not doing that, then they will.

Yes, maybe - but in the situation we're discussing, if one did use parallel cables they would presumably be identical, of identical length and following identical paths.

 

[EFLImpudence]

Yes, maybe - but in the situation we're discussing, if one did use parallel cables they would presumably be identical, of identical length and following identical paths.

Or not.

 

[JohnW2]

Or not.

Again,maybe, but in the present context, "not" would just be daft

 

[Mottie]

I have two 20A double pole switches (one for each oven) right next to each other with a short piece of cable connecting the two of them together to make a ring circuit. Both have a 2.5mm cable following the same path back to the consumer unit going to a 32A breaker.

 

[JohnW2]

I have two 20A double pole switches (one for each oven) right next to each other with a short piece of cable connecting the two of them together to make a ring circuit. Both have a 2.5mm cable following the same path back to the consumer unit going to a 32A breaker.

As I've said that is virtually a 5 mm² radial - and would be even closer to that if you 'doubled up' the short 2.5 mm² cable between the switches

 

[EFLImpudence]

...but it is not necessary.

 

[JohnW2]

...but it is not necessary.

I don't think that anyone has suggested otherwise.

I'll let you have the last word on this one if that pleases you