Derek ColeGM, Simmons One Hour Heating & Air · AI HVAC Answers

Freezing Heat Pump During Heat | HVAC Tips

11 Jan 2021 · 2 min

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1:40

In this concise HVAC tip, Derek Cole explains why a heat pump can freeze even during warm weather. He identifies two primary culprits: a refrigerant leak or insufficient refrigerant, and restricted airflow caused by overly dense high‑MERV filters that choke the return grill. He describes the visual symptom—frost or ice forming on the refrigerant line—as a sign that the unit cannot “breathe.” Cole advises homeowners to first inspect the air filter, ensuring it can be removed with a gentle tug and does not present excessive resistance. He notes the inherent trade‑off between filtration efficiency and airflow, suggesting that while advanced air‑cleaning systems can balance both, standard high‑efficiency filters cannot. If the filter is not the issue, the next step is to suspect a refrigerant problem and seek professional service.

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Uh, if it's a heat pump, refrigerant still can flow back and forth. So you could have a refrigerant leak causing the unit to freeze, or you could have an airflow problem. What I've seen in that regard are people who are buying filters that are high rated in MERV rating, which means they're very allergy efficient filters. But the problem is they're also stopping up the airflow as it comes into the return grill. So when the unit starves for air, it then freezes up. You see that if you go outside to your unit, you'll see the frost and the ice buildup around the refrigerant line. That's because it can't breathe. It's trying to run a marathon through breathing out of a straw. It's not working out very well, so therefore it's freezing up. So usually those are the two big problems. Refrigerant and a lack of refrigerant, or it's leaking, and airflow. So I would check— first of all, check your air filter. I mean, it should be a gentle tug to get it out. It shouldn't be a, you know, bear against the wall to get it out of the return grill. It shouldn't be that hard because there's always a trade-off between buying a high-quality filter and then having airflow. So With air cleaning, you can do both, but with regular filtration, you cannot. There has to be a give and take. You can't have the best filter and get the best airflow from an air filter. You can when you start air cleaning, but not with a filter. So check that one. That will be easier. If it's not that, then you have a refrigerant problem.