Twin & Earth CCC

[Zdb]

I've got a RFC that I need to split into two 20A radials.

I've looked in the BBB but it doesn't state the current carrying capacity of twin and earth in surface mounted trunking (reference method B).

I've had a little look online and I think that it might be 23A (before taking other derating factors into account).

Can anyone verify this?

 

[Ian1981]

For these situations I use the table for multi core cables ,thermoplastic sheathed cables Non armoured operating at max 70 degree

 

[Andy78]

23A would seem suitable to me as this figure is ref method B for 2.5mm PVC/PVC cable from table 4D2A. As the other values from this table are congruent with table 4D5 then I would say you're good to use this table.

 

[pirate]

I just love the use of "congruent" Andy78!
here was me thinking that term had fallen into desuetude!

 

[Zdb]

23A would seem suitable to me as this figure is ref method B for 2.5mm PVC/PVC cable from table 4D2A. As the other values from this table are congruent with table 4D5 then I would say you're good to use this table.

Nice one, thanks

 

[telectrix]

I've looked in the BBB but it doesn't state the current carrying capacity of twin and earth in surface mounted trunking (reference method B).


that's because the IET assume that cables run in conduit are singles.

 

[Andy78]

I've looked in the BBB but it doesn't state the current carrying capacity of twin and earth in surface mounted trunking (reference method B).


that's because the IET assume that cables run in conduit are singles.

It does give method B for multicore pvc pvc in trunking which is the closest.
Methods 8 and 9 from appx 3. Or appx 4 maybe, I forget.

 

[Zdb]

I've looked in the BBB but it doesn't state the current carrying capacity of twin and earth in surface mounted trunking (reference method B).


that's because the IET assume that cables run in conduit are singles.

I'm sure I'm not the only one who has put twin and earth in trunking or even conduit before.

They need to update the book

 

[Risteard]

I'm sure I'm not the only one who has put twin and earth in trunking or even conduit before.

They need to update the book

It's never been included because containment is for non-sheathed singles. Insulated and sheathed cable is designed to have its own mechanical protection (the sheath) where risk of impact is low.

 

[static zap]

There are times I feel like we are dealing with :-
a) A legal team
b) A politician.

 

[Ian1981]

It's never been included because containment is for non-sheathed singles. Insulated and sheathed cable is designed to have its own mechanical protection (the sheath) where risk of impact is low.

It is however extremely common to install pvc sheathed cables inside mini trunking or where they come into a CU and the cables are trunked above 50x50 mm pvc etc.

 

[Risteard]

It is however extremely common to install pvc sheathed cables inside mini trunking or where they come into a CU and the cables are trunked above 50x50 mm pvc etc.

I'm not disputing any of that - just trying to explain why there never have been (and likely never will be) reference methods for this type of thing.

 

[Ian1981]

I'm not disputing any of that - just trying to explain why there never have been (and likely never will be) reference methods for this type of thing.

I’m just saying that maybe it should be included in the relevant table for flat pvc pvc twin and earth cables as it’s a common situation. Or maybe just refer to the other table.