Heat Pump Freezing Up in Greater Vancouver

A heat pump in Greater Vancouver that develops ice beyond the normal frost layer is experiencing a defrost problem that reduces heating efficiency and can damage the outdoor unit if not addressed.

What This Means

Heat pumps naturally collect frost on the outdoor coil in heating mode as moisture from the air freezes on the cold coil surface. A properly functioning defrost cycle melts this frost periodically. When defrost fails or airflow is restricted, ice accumulates and can completely encase the unit.

Common Causes

• Defrost board failure — system does not initiate defrost cycles
• Defrost sensor failure — system does not detect when defrost is needed
• Outdoor fan motor failure — poor airflow causes rapid frost accumulation
• Refrigerant low — low refrigerant causes the coil to run too cold, accelerating frost
• Filter restricted severely — affects the refrigerant circuit balance and coil temperature
• Outdoor unit sited in a location with poor drainage — meltwater refreezes under the unit

What Homeowners Can Check Safely

• Turn the system to fan-only mode or off and allow ice to melt naturally — do not use heat guns, torches, or sharp objects on the coil
• Check and replace the indoor filter
• Ensure the outdoor unit is elevated above normal snow/ice accumulation level
• Check that the area beneath the outdoor unit drains properly and does not pool

When to Call a Licensed Technician

Heat pumps contain refrigerant under pressure, electrical components at line voltage, and control systems that require specialized diagnostic tools. Do not open refrigerant circuits, bypass safety switches, or attempt to recharge refrigerant without proper certification.

• Defrost board testing and replacement
• Defrost sensor testing and replacement
• Outdoor fan motor testing and replacement
• Refrigerant pressure testing
• Outdoor coil inspection for physical damage after ice encasement

Frequently Asked Questions

Is some frost on my heat pump normal?

Yes. A thin, uniform layer of frost on the outdoor coil during heating mode is completely normal, particularly in mild, humid weather like Greater Vancouver winter. The defrost cycle (which runs the outdoor coil warm for a few minutes every 30 to 90 minutes) melts this frost. You may see steam from the outdoor unit during defrost — this is also normal.

What happens if I run my heat pump with the outdoor unit completely iced over?

Running the system with solid ice encasing the outdoor coil forces the compressor to work against extremely high pressures, which can damage the compressor over time. If your outdoor unit is fully iced, shut the system off and allow it to thaw naturally before restarting. Then call a technician to diagnose why the defrost cycle failed.

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