All the failures I have encountered, the excessive heat has clearly come from the connection as the insulation has melted at that end only, and the connection is corroded.
To give you an idea of self heating, the 17th edition has tables of rated currect for various cable sizes and various means of mounting. The rating is based on cables getting to 70C in ambient temperature of 30C
e.g. 25mm sq. cable (6mm dia copper)
Free air (horizontal) - 146A
Free air (vertical) - 130A (heat rises and further heats the cable above)
In conduit in thermally insulating wall - 80A (description below)
Quote:
The wall consists of an outer weatherproof skin, thermal insulation and an inner skin of wood having a thermal conductance of at least 10W/m2.K The conduit is is fixed so that it is close to the inner skin. Heat from the cables is assumed to escape through the inner skin only.
It would be interesting to put a temperature sensor near the wire and measure the surrounding air - it may be cooler than the wire would be in a nice cosy jacket with all the lights and fans on.
I still think a better solution would be a heat shield and maybe duct some cold air over it - a use for the cam belt snorkel ?
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