SILICONE RUBBER SPACE HEATERS

Electric motors frequently have space heaters installed to prevent moisture condensation in the motor during times the motor is not running.

Many motor manufacturers use metallic or ceramic cartridge heaters for this purpose. Because such heaters are small they must operate at a high surface watt density and consequently high temperature. The high temperature causes rapid heater failure, often within the first year.

To combat this high failure rate, many smart users specify that space heaters are to be operated at one-half their rated voltage. This lowers the surface watt density to one-fourth the value with rated voltage, and increases the heater life more than proportionally.

U. S. Electrical Motors has another, better, solution to heater failure rate - the use of silicone rubber space heaters. The heaters are manufactured by sandwiching a resistance wire network between two pieces of high-temperature silicone rubber and bonding the silicone rubber pieces together. The silicone rubber heaters are designed for low surface watt density by providing a large surface area (a heater measuring 45" X 2.5" is rated at 169 watts, or 1.5 watts per square inch). In operation, the heaters are cool enough to touch with the bare hand without being burned. The life of these heaters typically exceeds the life of the motor.

Silicone rubber heaters enjoy another advantage over metallic or ceramic heaters. Because they are applied directly to the winding end turns, it is usually possible to achieve the required condensation prevention with a lower power consumption.

These silicone robber heaters are used, when specified, on all U. S. Electrical Motors motors. It is not necessary for the user to specify operation at one-half rated voltage to get the long heater life that is desired.

* Space heaters must be operated at +/- 10% rated voltage to be effective.