This past week, some of us may have turned on our heat for the first time this season. While a few homes in the area have furnaces, most Central Floridians have heat pumps. Heat pumps are basically air conditioners that can run in reverse; while your typical A/C unit absorbs indoor heat and takes it outside, heat pumps have a heating mode that absorbs heat from the outdoors and brings it inside. The heat is transferred to the refrigerant, so heat pumps can extract heat from outside in climates way colder than ours if the system is designed correctly.
However, heat pumps do things that can be concerning to homeowners who don’t fully know how they work. We get a lot of calls about “smoking” heat pumps and frozen outdoor coils when those are actually normal for heat pumps.
Frozen Outdoor Coils
Most people call an HVAC contractor immediately when their indoor coil freezes up, so it only makes sense that they’d do the same when the outdoor coil is the problem. However, a thin sheet of frost on the outdoor coil is normal.
Heat pumps absorb air from the outdoors and bring it indoors when they run in heating mode. Since the outdoor temperature is low, condensation on the outdoor coil can freeze a lot more easily than it normally would on an indoor coil. Heat pump manufacturers know this, so their heat pumps go through a defrost cycle where hot gas runs through the coil and melts the ice off. When this happens, the heat pump essentially runs in cooling mode, but it will have backup heat (usually electric) to keep you from getting too cold during the defrost cycle.
A thin sheet of ice on the outdoor coil is normal and no cause for concern. It will melt during the defrost cycle, and there’s no need to call a professional. If the coil is a block of ice and there’s no chance for air to move in and out of it, then you’ll want to give an HVAC contractor a call.
Smoking Outdoor Unit
If you were to hear strange noises and see something that looks like smoke coming from your outdoor coil, you’d probably call Kalos or another HVAC contractor. However, those noises and “smoke” coming out of the unit could actually be normal.
The defrost cycle reverses the flow of refrigerant, so the compressor pumps hot, high-pressure refrigerant through the frosty outdoor coil while the fan stays off. As a result, you might hear a hissing or grinding noise as the refrigerant changes pressure, and you may not hear the outdoor fan. That is all a normal part of the defrost cycle.
Since that hot gas is melting the ice off, you may also see steam coming off the coil, which can look like smoke and be alarming. However, that steam is completely normal, and it just means the defrost cycle is doing its job.
When to Call Kalos
Since those weird things are actually part of normal heat pump operation, when should homeowners call an HVAC contractor?
The only time you’ll really need to call an HVAC contractor is if there’s no heat at all in heating mode. Airflow and fan speeds change temporarily during the defrost cycle, and the heat may not be as strong during that time, but again, that’s all temporary and built into the heat pump.
A heat pump that doesn’t heat at all has a bigger problem, and we’ll gladly send someone out to check it. If you’re in the Central Florida area and want to call someone out, you can reach out to us 24/7 by calling or texting (352)-243-7099.
