Heaters for refrigeration equipment – cords, PTC and tubular

How to choose

The heater is chosen for the power per metre, the voltage and the bending radius

A constant wattage heating cord gives off the same heat along its whole length, regardless of what is happening around it. It is predictable and cheap, but if part of it is coiled up or covered by insulation, it will overheat at that point – because there is no way for it to reduce its power.

A self-regulating cable behaves differently: its resistance rises with temperature, so warmer sections heat less and colder ones more. It can be cut to length and will not overheat where it overlaps. It costs more, but in uneven conditions it solves a problem a constant wattage heater cannot.

The third parameter, easy to forget, is the minimum bending radius. A heater routed tighter than the manufacturer allows cracks in the core – sometimes not at once, but after a few hundred cycles. On door frames with sharp corners this is the most common cause of failure.

PTC and rod heaters work at a point, not along a line: in an evaporation tray, in a drain, in a specific socket. A PTC has the property of limiting its own power as the temperature rises, so it does not run dry as aggressively as a resistance heater.