Is that smoke coming from my heat pump? Why is it making that loud noise?
We hear that question often from our customers with heat pumps, especially in conditions when it’s icy and cold with temperatures below freezing. If you see what looks like smoke coming from your heat pump when it’s cold outside, don’t worry, this is normal operation. It’s not smoke, but steam rising as the heat pump enters its defrost cycle. This is normal operation. The outdoor coils on a heat pump tend to frost or ice-up in the winter – especially when there are moist conditions. The ice will cause the unit to lose efficiency because it obstructs air flow across the coils. Periodically, the unit cycles into the defrost mode (dependent on the settings in your unit) to keep the coils clear and the unit running efficiently.
When the defrost cycle begins, the outdoor fan motor will stop running. Sometimes this part of the operation sounds like a loud “whoosh”. Some customers even report this as a loud booming sound. Again, if you notice these sounds periodically, there’s no cause for worry. The unit may cycle into defrost more often during extreme weather conditions that include snow, ice and sleet.
Also during ice storms, your outdoor unit’s fan blade can ice over and become restricted. It’s best when this happens to turn the unit off and let it thaw naturally. Trying to break the ice off can damage the fan blade and cause it to be out of balance.
Of course, if you actually see smoke and smell a burning smell, this is a problem and you need to call for service. And, if you find that your unit is a “block of ice”, this could indicate a problem. It could be caused by a faulty defrost circuit board that isn’t signaling properly or for a number of reasons. But, you won’t be without heat. Turn your thermostat to the “supplemental” or “emergency” heat setting and you will continue to have heat until you can get a qualified service technician out to look at your unit.