Electric heating wire

Electric heating wire is used in two places on a refrigeration system, and they are quite different jobs.

The first is defrost: a wire element fitted to the evaporator, the drain tray or the drain line to melt frost during the defrost cycle and to keep the condensate path open. Without drain line heating, water refreezes in the drain and the tray overflows into the room - a failure that shows up as ice on the floor rather than as an electrical fault.

The second is the crankcase heater: a wire element wrapped around or inserted into the compressor crankcase to keep the oil warm while the compressor is stopped. Oil that is cold absorbs refrigerant, and when the compressor starts the pressure drop boils that refrigerant out of the oil, foaming the crankcase and starving the bearings. A crankcase heater is cheap insurance on any system that can sit idle in a cold ambient.

Two insulation materials are offered: silica gel in white, and a high temperature plastic in black. The silica gel version is the more flexible of the two and is used where the wire has to follow a curved drain line or be wrapped around a component; the black plastic version is used where the wire runs close to hot pipework or where mechanical abrasion is a risk.

Because the catalogue does not publish ratings for this item, the electrical specification - voltage, wattage per metre and total length - has to be confirmed against the application. Sizing a defrost heater is not a matter of using the longest wire available: too much power scorches the coil fins, too little leaves frost at the far end of the evaporator.