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Heat Pump Running Nonstop in Cold Weather
Your heat pump has been running almost nonstop since the cold snap hit, the house feels okay but never quite warm, and you are wondering if something is broken or if this is just what heat pumps do. Short answer: long run times in cold weather are often normal. Long run times with a house that keeps losing ground are not. Here is how to tell the difference.
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STM Heating & Air service team · field-reviewed before publishing
What Nonstop Running Actually Means
A heat pump is built to run long and steady. It pulls heat from outdoor air, and when that air drops into the thirties and twenties, there is less heat to pull, so the unit runs longer to deliver the same warmth. On a cold morning across the foothills and ridges, a healthy heat pump may run for hours at a stretch and that is fine. The question is whether it is holding your setpoint. If the thermostat says 70 and the house sits at 70, you have a system working hard, not a failing one. If the house is drifting down to 65 and staying there, something needs attention.
Cause Family One: Settings, Filters and Airflow
Start with the cheap stuff, because it is the most common. A clogged filter starves the indoor coil and forces long runs with weak air at the vents. Closed or blocked supply registers do the same thing in a smaller way. A thermostat left on Emergency Heat or set to a temperature the system cannot reach on the coldest days will run continuously by design. Big setback recoveries also look like a malfunction: if you drop the thermostat overnight and jump it back up in the morning, the heat pump will run for a long time catching up, sometimes an hour or more.
Cause Family Two: The Outdoor Unit and Defrost
Heat pumps ice up in cold, damp weather and run a defrost cycle to shed it. That is normal, and you may see steam rolling off the outdoor unit. What is not normal is a solid block of ice on the coil that never clears, or a unit buried in leaves, pine straw and red clay splash. Airflow through the outdoor coil matters as much as airflow indoors. A failed defrost board, a bad sensor or a stuck reversing valve will leave the unit iced and running without producing much heat. That is a service call, not a homeowner fix.
Cause Family Three: Refrigerant, Compressor and Backup Heat
If airflow is clear and defrost is working, the next layer is the sealed system. Low refrigerant charge from a leak means the heat pump moves less heat per minute, so it runs forever and still falls behind. A worn compressor does the same. On dual-fuel and propane setups common up the ridges, the backup stage may not be staging in at all, leaving the heat pump alone against weather it was never sized to handle by itself. Electric strip heat that has lost a sequencer or blown a limit shows up the same way. All of this needs gauges and meters.
What Is Safe for You to Check, and What We Do Differently
Safe for you: swap the filter, check thermostat batteries and confirm it is set to Heat rather than Emergency Heat, look for a tripped breaker, make sure supply and return vents are open, and clear leaves and debris a couple of feet back from the outdoor unit. Stop there. Refrigerant, gas connections and high voltage are not homeowner territory. When we arrive we measure temperature split across the indoor coil, read superheat and subcooling, check amp draw on the compressor and blower, verify defrost operation and confirm the backup stage is actually firing when the outdoor temperature calls for it. If you ever smell gas, leave the house, call 911 or your gas utility, then call us.
Heat Pump Running Nonstop in Cold Weather — fast answers
Should my heat pump ever shut off in winter?
On mild days it should cycle on and off. In the twenties and below, long continuous runs are normal and expected. The test is whether the house holds the temperature you set, not how often the unit stops.
Is Emergency Heat a good idea during a cold snap?
Only when the heat pump itself has failed. Emergency Heat locks out the compressor and runs expensive backup heat alone. If you switched it on and forgot, that alone can explain nonstop running and high bills.
Why is my outdoor unit covered in ice?
Light frost that clears during defrost cycles is normal. A thick ice block that never melts points to a defrost fault, airflow blockage or low refrigerant. Turn the system off and call us for heating repair before the coil is damaged.
How it works
- Step 1
Tell us the symptom
Call or fill in the quote form and describe what you hear, smell or feel. Warm air, short cycling, a breaker that keeps tripping. That gives us a head start on the likely cause.
- Step 2
We diagnose on site
A technician checks the thermostat, airflow, electrical connections, refrigerant performance and the outdoor unit. We work the crawlspace and the attic too, because ductwork and drainage cause more trouble than people expect.
- Step 3
You decide, then we fix it
We explain what failed, what it takes to repair it, and what we would watch next season. No work starts until you say go. Most repairs finish the same visit when parts are on the truck.
- A real person answers
- Open 7 days
- Written quote before work starts
Why homeowners call us
- Mixed heating is normal to usHeat pumps, propane furnaces and dual-fuel setups all behave differently in cold weather. We know how a heat pump should sound in the thirties and when the backup heat is doing too much of the work.
- We go under the houseRed clay crawlspaces hide crushed ducts, sweating lines and standing water. Comfort problems often start down there, not at the unit, so we look before we start replacing parts you may not need.
- Plain explanationsYou get told what broke and why, in words that make sense. If a repair is a short-term patch on an aging system, we say that out loud so you can plan instead of guessing.
- One crew, six statesWe serve homeowners across Alabama, Georgia, Kentucky, North Carolina, South Carolina and Tennessee. Same approach in every one: show up, diagnose properly, repair what needs repairing, leave the space clean.
- All major brands, gas & electricOne independent crew for Carrier, Trane, Lennox, Goodman, Rheem and more.
- Straight answersNot worth fixing? We say that out loud, and often it saves you the visit fee.
About this guide
Safe checks done and it still misbehaves? That's a real fault
Tell us what you tried and what it did. The booking itself takes a minute.
- A real person answers
- Open 7 days
- Written quotes
- All major brands
- Gas & electric
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