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Zdb

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

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.
 
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.
 
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.
 

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