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?
well, it should be treated as two adjacent cables carrying the same current, and grouped, just the same as you would (I hope) for a hairpin of cables going up and down the wall to call in at a switch for a heater or similar on a radial as well.
Some of us sidestep this with 2 pieces of oval conduit or capping, each with one cable inside. I must admit I would not read it as 'circuit' literally, the same wire looped back on itself is still "grouped" from a heating point of view.
M.
presumably then each leg should also be run separately in floor joists - at the risk of making Swiss cheese out of the joists with all the cables run in separate holes, or upping the cable size based on rating factors. I'm still pondering how to alter the factors for cables that are not equally loaded but which shouldn't be ignored.
well, it should be treated as two adjacent cables carrying the same current, and grouped, just the same as you would (I hope) for a hairpin of cables going up and down the wall to call in at a switch for a heater or similar on a radial as well.
Some of us sidestep this with 2 pieces of oval conduit or capping, each with one cable inside. I must admit I would not read it as 'circuit' literally, the same wire looped back on itself is still "grouped" from a heating point of view.
M.
presumably then each leg should also be run separately in floor joists - at the risk of making Swiss cheese out of the joists with all the cables run in separate holes, or upping the cable size based on rating factors. I'm still pondering how to alter the factors for cables that are not equally loaded but which shouldn't be ignored.
