You’re in your home and hear your heat pump running. You can put your hand over the vent and feel air coming out—not hot, but not cold either. It seems like your heat pump is working fine, but you’ve set your thermostat at 72°F and haven’t seen it budge past 65°F—what’s the deal?
We’re missing a clue: the outdoor temperature. Is it colder than usual? Are we dealing with a rare arctic blast that made its way all the way to Florida?
When HVAC contractors and builders design HVAC systems, they use typical conditions. In Florida, the Arctic Blast is expected to bring unusual weather—colder than what the system was probably designed to handle, especially if you have an older or “single-stage” heat pump. Gas furnaces can usually keep up, and modern multi-stage heat pumps can adjust their operating conditions for colder temperatures. However, older heat pumps and those with only one operating speed may not be able to keep up beyond their design conditions.
Heat Pump Selection and Design
Ideally, an HVAC system should be designed to handle 99% of the temperature conditions it’ll experience in a year. Using climate data, HVAC professionals choose a temperature that accounts for all but the most extreme temperature conditions because oversizing is very detrimental to comfort and efficient operation.
When we design cooling systems (like air conditioners and heat pumps), we look at historical climate data and account for a temperature that will only be exceeded 1% of the time. (For example, that temperature might be in the low to mid-90s in Central Florida; a day where we reach 99°F would be an anomaly.) On the heating side, the actual outdoor temperature should stay above the design temperature 99% of the time.
Unfortunately, when we have events like the Arctic Blast, we end up on the wrong side of that 99%. The heat pump simply wasn’t designed to heat the home completely, and it won’t be able to keep up with the increased demand for heating that we see during unusual cold spells. We can get a bit more out of multi-stage heat pumps that have a wider range of operation, and gas furnaces are combustion appliances that are common up north, where it gets much colder than here. But many older and single-stage heat pumps just weren’t designed to handle this type of cold.
In short, it’s perfectly normal—though not ideal—for an older or single-stage heat pump to manage to keep your home only in the mid-60s when it’s as low as the 20s outside in Florida.
When Should I Call an HVAC Technician?
Again, it’s normal for the heat pump to fail to meet the set point if it’s colder than usual outside. There is no need to call out a technician, as there is nothing they can do, and usually, these cold snaps only last a few days.
However, you’ll want to call an HVAC contractor if your thermostat is blank, you don’t hear or feel your heat pump running, or your outdoor coil is completely ice-bound. (NOTE: It’s normal to have a thin sheet of ice on the coil. It’s time to call a technician when it’s completely surrounded by a thick layer of ice.) These conditions indicate that there is something wrong with the system, and we can diagnose and repair those issues.
If you’re in the Central Florida area and want to call someone from Kalos out to diagnose your heat pump, please call or text us anytime at (352)-243-7099, and we can take the next steps. We also do heat pump replacements, whether you have an existing furnace and want a heat pump or simply want a replacement for your old heat pump.
