Heat pump outdoor unit steaming in Greater Vancouver

Seeing steam or vapour rising off your heat pump's outdoor unit can look alarming, especially on a cold morning in the Lower Mainland. In the vast majority of cases this is not smoke and not a fault. It is water vapour released during the normal defrost cycle, and it is one of the more common heat pump questions we hear from Greater Vancouver homeowners.

Why your outdoor unit gives off steam

In heating mode, the outdoor coil gets very cold and pulls heat from the air. In our humid coastal climate, frost builds up on that coil. To clear it, the heat pump runs a defrost cycle that briefly warms the outdoor coil and melts the frost. The melt water flashes into vapour against the cold air, and that vapour is the steam you see rising from the top of the unit.

This is most noticeable on damp, near-freezing mornings, exactly the conditions Metro Vancouver delivers all winter. The steam usually appears for a few minutes, then stops once defrost finishes and the unit returns to normal heating.

• Steam during defrost is water vapour, not smoke
• Most visible on cold, humid mornings common here
• Typically lasts only a few minutes per cycle

When steam is worth a closer look

True smoke smells like burning and is often dark or oily, while defrost vapour is white, odourless, and short-lived. If you ever smell burning plastic or notice a chemical odour, switch the system off at the thermostat and have a licensed technician inspect it. Do not open panels or touch internal parts yourself.

It is also worth a safe visual check that the unit drains freely. If meltwater pools and refreezes under the unit cycle after cycle, or if the steam is paired with constant ice that never clears, that points to a defrost or drainage problem a technician should diagnose.

• Burning smell or dark smoke means shut it off and call a pro
• Odourless white vapour that clears quickly is normal
• Persistent ice with the steam warrants professional service

Frequently Asked Questions

Is steam from my outdoor heat pump dangerous?

Not on its own. It is water vapour produced when the defrost cycle melts frost off the outdoor coil. In humid Greater Vancouver winters it is a routine sight and clears within a few minutes.

How do I tell steam from real smoke?

Defrost vapour is white, odourless, and disappears quickly. Smoke tends to be dark or oily with a burning smell. If you smell anything burning, turn the system off and book a licensed technician.

Why does it only happen on cold mornings?

Cold, damp air causes the most frost on the outdoor coil, so the system runs more defrost cycles. The contrast between warm meltwater and cold air also makes the vapour far more visible.

Should I clear ice off the unit myself?

You can gently clear loose snow or leaves from around and on top of the unit. Never chip or pour hot water at ice on the coil. If ice keeps returning after each cycle, have a technician check the defrost system.

HeatLand Heating & Cooling is a licensed and insured, TSBC-certified HVAC company serving homeowners across Greater Vancouver. Our technicians diagnose the real fault, explain your options in plain language, and complete the work safely and to code.

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