T&E current carrying capacity

[rustus]

Extending an existing ring main which is on 2.5mm2 T&E, my only reasonably easy route for the extra cable is within an insulated 250mm thick (!) stud wall.

Referring to table 4D5A, I see that the existing 2.5mm2 T&E is rated at 27A if clipped direct. The same table lists 4mm2 routed in an insulated wall at the same figure - 27A.

All other things being equal, am I OK to use 4mm2 T&E for this part of the circuit, or am I missing something vital?

Cheers.

 

[plugwash]

no problem to use larger cable for parts of a cuircuit to account for thermal insulation.

 

[rustus]

I suppose what I really meant to ask was whether 4mm2 is large enough for a cable totally enclosed in a thermally-insulated wall?

 

[Spark123]

2.5mm² is rated 21A (for method 15) which still complies with regulation 433-02-04.

 

[rustus]

Thanks for that Spark. I've just found that out from another source as well. Typically I have now bought a reel of 4mm2 and started the job this afternoon. Never mind...

The only potential problem now is handling the connections - two, or even three 4mm2 conductors in one terminal will be tight, but I hope manageable.

Thanks again.

 

[Adam_151]

The only potential problem now is handling the connections - two, or even three 4mm2 conductors in one terminal will be tight, but I hope manageable.

Thanks again.

BS1363 requires the outlets to hold 3x2.5mm² conductors, or 2x4mm² conductors, so two shouldn't be a problem, and not quite sure why you want 3?

 

[securespark]

Spurs, probably. But best to put every outlet on the ring, then no need for spurs....

 

[Adam_151]

Spurs, probably. But best to put every outlet on the ring, then no need for spurs....

Yeah, my line of though was that if he is 're-jigging' the ring, why is it going to end up with spurs on it...

 

[rustus]

Spurs, as guessed, but I only envisage one - to an external Masterseal socket with single rear cable entry (optional back plate).

 

[plugwash]

MK claim their sockets can take 3x4mm though i'd imagine a deep backbox would be in order.

 

[rustus]

I'm going for MK Logic Plus sockets and 47mm boxes, so don't anticipate too much trouble.