Discuss 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fuses in the UK Electrical Forum area at ElectriciansForums.net
Seems to me that the first set of touching cables would always be warmer (all other things being equal), so I can't understand why it shouldn't be derated slightly relative to the spaced out cables.
What's your point?? What sort of heat increases are you actually talking about here, temperature increases that will affect current ratings, that's just nonsense!!
Are we now saying that the temperature increase of a cable doesnt affect the current rating of the cable??? This is just getting a farce....
Just look at the regs EG table 4E4A. lets take 35mm 4 core cable. How this is installed affects the current rating doesnt it.. The max being 162A (in free air...) the min being 115A (direct in ground or in ducting in the ground...) This is due to the heat dissipation of the cable or temperature.
That is why in parallel cables, if touching (and a couple of other factors) you have to de-rate the cable... Single source supply or multiple supplies, they both need de-rating..
You're talking about installation method, NOT grouping!
Chr!s - wrong sort of maths! Try ignoring the tables and use some trigonometry. The tables aren't designed for this scenario, in fact for certain types of installation methods they are woefully inadequate.
This ive got too see, so we have the "Real Heat" and the "Imaginary Heat"
I'm loosing the will to live, now. FORGET THE SODDING TABLES!! (to a point).
Basic principles -
1) the ability of a cable to radiate heat is proportional to its surface area
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Reply to 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fuses in the UK Electrical Forum area at ElectriciansForums.net
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