Effects of mineral wool insulation on electric cables in buildings

Since the seventies, energy conservation in all its forms has grown. This mindset has lead to the addition of thermal insulation in existing buildings, without concern for the existing electric cables. The addition over-insulates the cables, inhibiting heat dissipation, and possibly creating a hazardous situation.Our laboratory performed, between 1981 and 1990, a series of technical tests to determine the effect of this additional thermal insulation on the electric cables.This paper is the result of a research program giving the risks of fires caused by cables submitted to over-insulation, as a function of the type of thermal insulation and the current.Nomenclature L cable life expectancy (years) - A constant which depends on the specific chemical reaction - B constant which depends on the specific chemical reaction - T temperature (°C or °K) - T_I initial conductor temperature (°C) - T_F final conductor temperature (°C) - t time (seconds) - I current (amperes) - W heat dissipation (Watt-seconds) - R resistance (ohms)