Drain line heater
Also known as: drain heater, drain heating cable
Short definitionA heating cable that keeps the defrost drain pipe warm in a sub-zero room. It is fitted so the water does not freeze and block the line before it gets outside.
In a freezer room, when defrost ends the water in the drip tray enters the pipe and starts to freeze before it even reaches the wall. A few days later the line is blocked, the tray overflows and ice grows under the unit. To prevent this, a flexible, watertight, silicone-sheathed cable is pushed inside the pipe. It draws around 40–50 W per metre. The cable starts at the tray outlet and runs to the outer face of the wall.
It is a small line in the quote, but if it is forgotten the complaint arrives the day water drips on the product. The cable alone is not enough: the run inside the room is kept short, laid with a 5–10% fall, and the trap goes on the warm side outside. Where the cable overlaps itself in the pipe, that spot overheats and can melt the plastic. Most installations leave the heater on permanently. Before winter, measure its current to confirm it works.