My heat pump blows cold air: is it normal or a fault?
A heat pump moves heat instead of making it, so its air never feels like a furnace. Some cold air is normal. Some is a warning.
Cold air from a heat pump is not always a failure. Three harmless things cause it: a defrost cycle, the fan setting, and the simple fact that heat pump air is gentler than furnace air. Rule those out before you worry.
Then look for the real faults.
Is the air actually cold?
Your skin is a poor thermometer. Hold a kitchen thermometer in the airflow at a supply vent. Heat pump air in heating mode is usually warm to lukewarm, and that can feel cool next to a furnace. If the reading is at or below room temperature, you have a genuine problem.
Defrost mode is normal
In cold, damp weather the outdoor coil frosts over. The heat pump reverses briefly to melt it, and during that time cool air can come from the vents. Steam may rise from the outdoor unit. The cycle usually lasts a few minutes and ends on its own. If the unit stays iced over, that is no longer normal.
Check the thermostat and fan setting
Confirm the thermostat is on heat and the setpoint is above the room temperature. Then look at the fan. With the fan set to "on" instead of auto, it runs between heating cycles and blows unheated air, which feels like a cold draft. Switch it to auto and wait through one full cycle.
A dirty filter or blocked outdoor unit
A clogged filter restricts airflow and can make a heat pump underperform. So can leaves, snow or a fence pressed against the outdoor unit. Replace the filter and clear the area around the unit by hand, without removing any panel.
Auxiliary heat is the backup, not the cure
When it is very cold, many systems switch on electric backup heat, often labeled "aux" or "emergency heat." If you never see it come on in a deep freeze. Or if you see it running constantly, tell a technician. Either can mean the main system is not doing its job.
When the reversing valve is the cause
If the system is stuck in cooling mode while the thermostat calls for heat, a failed reversing valve is one possible cause. You cannot diagnose or repair that yourself. It sits in the sealed refrigerant circuit, which only a certified technician may open.
What not to do
- Do not remove the outdoor unit's panels or touch the electrical parts inside. Some components can hold a dangerous charge even when the unit is off.
- Do not add or test refrigerant. EPA Section 608 certification is required by federal law.
- Do not chip ice off the coil with a tool. You can puncture it.
When to call a licensed HVAC technician
Call one if the vent air stays colder than the room after a full cycle, ice does not clear, or the unit seems stuck in cooling mode. For gas or carbon monoxide alarms in a home with other fuel-burning equipment, leave and call the gas company or 911.
Frequently asked questions
Why does my heat pump blow cold air in winter?
It may be in a short defrost cycle, the fan may be set to on instead of auto, or the air may only feel cool because heat pump air is milder than furnace air. If a thermometer reads colder than the room, it is a fault.
How long does defrost mode last?
Usually a few minutes. If the outdoor unit stays covered in ice and the cycle never seems to end, call a licensed technician.
Can a bad reversing valve cause cold air?
Yes. If the unit is stuck in cooling mode while the thermostat calls for heat, the reversing valve is one possible cause. It is part of the sealed refrigerant circuit and needs a certified technician.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- ENERGY STAR. Air-Source Heat Pumps
- ENERGY STAR. Energy Savings at Home: Heating & Cooling