Twin & Earth CPC sizes?

[trevmai]

In T & E, is the CPC always one size lower than the live conductors? and if so what size is the CPC on a 1.0mm bit of T & E?

 

[RF Lighting]

1.0mm² and 1.5mm² T&E both have a 1.0mm² CPC

 

[trevmai]

Thanks, but what about other cable sizes 2.5 4 6.......

 

[securespark]

2.5 has 1.5, although older 2.5 will have 1.0...

6 has 2.5.

10 has 4.0.

 

[plugwash]

I could be wrong but i belive it used to be 6/4 and 10/6 was the norm and that the cheaper 6/2.5 and 10/4 are a fairly modern introduction.

 

[Cremeegg]

No one ever seems to mention 4mm T&E - but unless I'm mistaken its CPC is 1.5mm

 

[trevmai]

Thanks for the help, but i thought the CPC should not be less than the size of the live conductors!

 

[Cremeegg]

If thats the case an awful lot of cable makers have got it wrong!!

 

[RF Lighting]

Thanks for the help, but i thought the CPC should not be less than the size of the live conductors!

This is only an example and not a real life scenario:

A length of 2.5mm² with a 1.5mm²

This cable will happily carry 27A all day, every day. This will not cause the cable to overheat and become damaged.

The CPC may be carring a very small current in normal use (only a few mA). In the event of a fault the CPC will carry a large amount of current which would cause the cable to melt if sustained, but circuits are designed to automatically disconnect the power within 5 seconds of the fault occouring (although in reality it will be much quicker) then the CPC will only carry the current for a short duration which will not be long enough to damage the cable.