Hi, I have 10 circuits (14 multicore cables) coming out of the consumer unit into about 500mm of 50x50mm plastic trunking. This is reference method B which beneath says group rating factor in table 4C1 needs to be applied. This gives a factor of 0.41!!! Is this right? The rest of the install is either C (clipped direct), B (oval conduit in plaster or in a void), 100 (plasterboard ceiling), 102 (stud wall), or E (free air though joists).
The cables are all back entry by spacing the consumer unit off the wall 20mm with metal bushes. Trunking looks neat and helps with the consumer unit IP rating and mechanical protection requirements but might be better taking the trunking away and spreading the cables out a bit through free air (more than 0.3 diameter of cable) so no rating factor?
I haven't done the calculations yet but I'm thinking the 0.41 group rating factor will make the CCC of some / most of my cables too small / less than In (protective device rating).
Any help appreciated, thanks.
