With reference to 433.1.204 and cable as installed has min capacity of 20A if protected by a 30A or 32A. If the protective device is reduced to 20A how is the new minimum as installed capacity calculated or arrived at ? I've been looking in the Electrical Installation Design Guide, but the answer is avoiding my eyes.
Yes Zoomup, I saw your post on the old forum about this and wondered if it would have much effect, apparently not in Mike's example, if my sums are correct. The increase in resistance with the constraint of keeping max temp at 70 Deg C doesn't have enough leeway for self-regulation it seems. Good point though.
I would like somebody to offer empirical evidence of any thermal cable damage to a 2.5mm2 P.V.C. cable on a ring final circuit where a socket is positioned close to a consumer unit and heavily loaded. Anyone?
A one degree rise in temperature of copper = a 0.393 per cent rise in electrical resistance.
A 2m length of 2.5mm2 copper conductor carrying approx. 27 Amps will create approx. 10 Watts of heat.
Yes Zoomup, I saw your post on the old forum about this and wondered if it would have much effect, apparently not in Mike's example, if my sums are correct. The increase in resistance with the constraint of keeping max temp at 70 Deg C doesn't have enough leeway for self-regulation it seems. Good point though.
I would like somebody to offer empirical evidence of any thermal cable damage to a 2.5mm2 P.V.C. cable on a ring final circuit where a socket is positioned close to a consumer unit and heavily loaded. Anyone?
A one degree rise in temperature of copper = a 0.393 per cent rise in electrical resistance.
A 2m length of 2.5mm2 copper conductor carrying approx. 27 Amps will create approx. 10 Watts of heat.
