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Ice Is Nice, But Not on Your Heat Pump or Air Conditioner


I bet I could be a writer for MythBusters, handling all their stories about the misunderstandings people have about air conditioning and heating in homes. Unfortunately, they’re no longer making new episodes of the program, so you’ll have to enjoy me myth-busting all on my own. (I’m sure the appeal of having a dog on the show explain air conditioning would’ve boosted their ratings!)

Here’s a myth I’d like to bust: Ice on your heat pump or AC is normal during hot weather.

Now, I understand why people might think it’s just fine to see ice forming over an air conditioner or a heat pump when these systems are blowing out cool air. It sort of makes sense: ice is cool, you’re getting cool air… it all seems natural.

But it’s not! It is never normal to see ice during the summer anywhere on the inside or the outside of a heat pump or central air conditioner. These appliances don’t use ice to cool the air: they use refrigerant within a sealed system to move heat from inside your house to the outside. If ice is forming, it means something has gone wrong with the process.

  • You might have your thermostat too low (below 70°F), causing the indoor coil to ice up.
  • There could be a refrigerant leak occurring somewhere. Yes, it sounds strange that less refrigerant will cause ice to appear, but what happens is that the refrigerant coil won’t be able to absorb enough heat to warm up the remaining refrigerant, and the cold refrigerant will trigger ice formation.
  • Dirty coils could also cause ice to form, since the layer of grime prevents sufficient heat absorption along the coil.

Not only does ice point toward a problem in the AC, it creates its own problems. It will make it harder for the air conditioner or heat pump to cool down the inside of your house, and ice can deform the coils. It also has the potential to make your ductwork “sweat,” which leads to fungal growth and water damage in your ceiling and walls. Ice can stop your system from working at all.

If you see frost or ice anywhere on your air conditioner or heat pump, turn off the system immediately and (865) 302-3221!