Heat Pump in Freezing Temperatures

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Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

When temperatures drop below freezing, your heat pump may struggle to extract heat. Ensure the outdoor unit is clear of ice and debris. If the unit is defrosting, it’s normal and should resume heating once complete.

Confirm the symptom

Outdoor temperature is below freezing (32°F or 0°C)
Heat pump is running but not heating effectively
Outdoor unit is covered in ice or frost

Tools and prep

Gloves and ice scraper
Thermometer to check outdoor temperature
Screwdriver for unit access panel
Safety goggles
Turn off power to the heat pump before inspecting or cleaning

Step-by-step troubleshooting

Check Outdoor Unit for Ice Buildup
Do: Inspect the outdoor unit for ice or frost accumulation.
Observe: Ice covering the coils or fan blades.
Means: The unit is in defrost mode or unable to shed ice naturally.
Next: If ice is present, proceed to step 2. If no ice, check thermostat settings.
Allow Defrost Cycle to Complete
Do: Wait 15–30 minutes for the defrost cycle to finish.
Observe: Unit switches from blowing cold air to warm air.
Means: Defrost cycle is working as intended.
Next: If the unit does not resume heating, proceed to step 3.
Clear Ice Manually (If Necessary)
Do: Use gloves and an ice scraper to gently remove ice from the unit.
Observe: Ice is removed without damaging coils or fan blades.
Means: Improved airflow and heat exchange.
Next: Restart the heat pump and monitor performance.
Check Thermostat Settings
Do: Verify the thermostat is set to 'Heat' and the temperature is higher than the indoor setting.
Observe: Thermostat is set correctly.
Means: Incorrect settings may prevent proper operation.
Next: If settings are correct, proceed to step 5.
Inspect Airflow Around the Unit
Do: Ensure the outdoor unit has at least 2 feet of clear space around it.
Observe: No obstructions like snow, plants, or debris.
Means: Blocked airflow reduces efficiency and can cause ice buildup.
Next: Clear any obstructions and restart the unit.
Check for Error Codes
Do: Look for blinking or lit error codes on the unit’s control panel.
Observe: Specific error code displayed (refer to owner’s manual).
Means: The unit may have an internal issue requiring service.
Next: If an error code is present, contact a professional technician.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Ice buildup on outdoor coils Freezing temperatures prevent natural defrosting, reducing heat transfer efficiency.	Common	Easy	None (manual ice removal may be needed)
Defrost cycle malfunction The unit’s defrost timer or sensor may be faulty, preventing proper ice removal.	Sometimes	Medium	Defrost control board
Low refrigerant levels Insufficient refrigerant reduces heat absorption, leading to excessive frost.	Sometimes	Hard	Refrigerant recharge (by professional)
Thermostat issues Incorrect settings or a faulty thermostat may prevent the unit from operating correctly.	Sometimes	Easy	Thermostat replacement or recalibration
Blocked airflow around the unit Snow, debris, or landscaping can restrict airflow, causing ice buildup.	Common	Easy	None (clearing debris)
Dirty air filters Clogged filters reduce airflow, affecting the unit’s ability to heat efficiently.	Sometimes	Easy	Air filters

Parts matching

If manual ice removal isn’t enough, consider these parts for long-term solutions:

Defrost control board for automatic defrost issues
High-efficiency air filters to improve airflow
Outdoor unit cover (weather-resistant, not airtight) to protect from snow

Always match part specifications to your heat pump model. Consult a professional for refrigerant-related issues.

When to call a professional

The unit does not resume heating after a full defrost cycle
Error codes persist after troubleshooting
Ice buildup returns immediately after removal
You hear unusual noises like grinding or squealing
The unit runs constantly but doesn’t heat the home

FAQ

Can I use a heat pump in temperatures below freezing?

Yes, but efficiency drops significantly. Most heat pumps work well down to 25–30°F, with supplemental heating needed in colder climates.

How long does a defrost cycle take?

Typically 15–30 minutes, depending on ice buildup and unit model.

Is it normal for the outdoor unit to blow cold air?

Yes, during normal operation and defrost cycles. It should return to warm air once defrosting is complete.

Should I cover the outdoor unit in winter?

Avoid airtight covers. Use a breathable, weather-resistant cover if snow accumulation is a frequent issue.

Why is my heat pump making a clicking noise in cold weather?

Clicking may indicate the defrost cycle starting or electrical components cycling. Persistent clicking may signal an issue with the defrost system.