Note 1 of table 4C1 in Apdx 4, says that the factors are applicable to uniform groups of cables, equally loaded. However, I see some publications that apply these factors to ccts, in trunking, for example, with no reference to cables being equally loaded (as though it's a belt-and-braces approach and apply the factors regardless).
So what is your interpretation of equally loaded? It could apply to cables in conduit or trunking supplying heaters or conveyor belt motors, for example, all on for long durations. But what of cables supplying e.g. ring f. ccts, an EVC and other ccts, such as in domestic settings? Can they basically be ignored from such grouping factors or apply them regardless just to be in the safe side?
Where I think that this concept fails is in ring circuits. By definition only one circuit, but imagine a circuit high up in conduit: down and up, over a door, down and up again, etc; or domestic under the floorboards, down and up (or up and down) under the capping, down and up again, etc. If the main load is half way round, that's the whole lot in two adjacent cables. Should that not be treated as two circuits?
I agree - the rating applies to each bundle of as many loaded conductors as normally represents that kind of circuit (i.e. 2 for a single phase circuit, 3 for a 3-phase one) - indeed some of the wording in the regs is catching up e.g. the heading for 4C1 says 'group of circuits or group of multicore cables'.
Where I think that this concept fails is in ring circuits. By definition only one circuit, but imagine a circuit high up in conduit: down and up, over a door, down and up again, etc; or domestic under the floorboards, down and up (or up and down) under the capping, down and up again, etc. If the main load is half way round, that's the whole lot in two adjacent cables. Should that not be treated as two circuits?
I agree - the rating applies to each bundle of as many loaded conductors as normally represents that kind of circuit (i.e. 2 for a single phase circuit, 3 for a 3-phase one) - indeed some of the wording in the regs is catching up e.g. the heading for 4C1 says 'group of circuits or group of multicore cables'.
