In cold damp weather a heat pump's outdoor coil collects frost, which blocks the heat it is trying to absorb. The defrost cycle briefly reverses the system to warm that coil and melt the frost, then returns to heating. The steam rising off the unit is melted frost evaporating, and it is normal. In the Fraser Valley, where winters sit near freezing with high humidity, defrost runs more often than in drier climates.
What does a normal defrost look like?
A defrost cycle usually lasts a few minutes and ends on its own. The outdoor fan stops, the unit may sound different, steam rises, and indoor air can feel cooler briefly because the system is temporarily running backwards. Backup heat often engages to cover the gap.
When is it a fault?
The signal is frost that never clears or defrost that never stops. If the coil stays iced after a cycle, or the unit defrosts every few minutes continuously, something is wrong with the sensor, the reversing valve, or the refrigerant charge.
- Solid ice encasing the coil rather than light frost
- Defrost running constantly with little heating in between
- Ice building at the base because meltwater cannot drain
- Backup heat running non-stop, showing as a jump in the electricity bill
What helps it run cleanly?
Drainage and clearance. The unit needs to shed meltwater and needs clear air on all sides, which matters here where units often sit close to fences or under decks.
We commission heat pumps for Fraser Valley conditions specifically, including drainage and clearance at the pad, because defrost runs far more here than the default settings assume.
Book a Heat Pump Check
If the coil is icing over rather than defrosting, we will find why.