T&E in conduit, grouping, derating questions

[JohnW2]

That's 3 tubes ?

If you (now) say so - but as you can see from BAS's response (and I had interpreted your post similarly), that was far from clear from what you originally wrote.

Kind Regards, John

 

[lxboy]

Sorry,

I didn't for a second think anybody with be stupid enough to think they would all go down one 25mm tube !!!!!

silly me,

Lxboy

 

[SimonH2]

Roughly Area inside conduit is 490mm². (not sure of internal measurements)
45% of 490mm² = 220mm² which is maximum allowed.

I'd suggest that the normal rules for conduit fill don't really apply here. T&E in white oval is a bit of a special case IMO.
I'd also suggest that the normal rules for conduit fill don't really apply when using T&E in round conduit. Unless you are really careful, then the odd shape of the T&E makes the space it takes in the conduit somewhat more than a simple consideration of it's actual size suggests. Ie, if there are any twists (almost guaranteed without a lot of care), then the effective size is more like a round cable with a diameter equal to the larger dimension of the oval cable. So your fill factor would have to be lower when using T&E (or any other flat/oval cable).

 

[JohnW2]

I'd suggest that the normal rules for conduit fill don't really apply here. T&E in white oval is a bit of a special case IMO. I'd also suggest that the normal rules for conduit fill don't really apply when using T&E in round conduit. Unless you are really careful, then the odd shape of the T&E makes the space it takes in the conduit somewhat more than a simple consideration of it's actual size suggests.

Indeed so. As I wrote in the footnote of my table of approximate overall CSAs of T&E:

However, guidelines in relation to CSA's is obvioulsy only part of the story when deciding what cables will even fit in what conduit (particularly if oval)!

Kind Regards, John