In order to understand what causes homeowners to complain about indoor temperatures, and then determine how to troubleshoot the issues, we need to think about a few important ways ductless heat pumps differ from the central heating systems—furnaces, boilers, and ducted heat pumps—that most customers have. I’m writing as a practitioner in Upstate NY, climate zones 5 and 6, where the vast majority of temperature control issues we have with ductless systems are in heating mode. While we do have a significant demand for summer cooling and dehumidification, most of the complaints I’ve handled relate to heating. Some of the reasons for that will become apparent below.
Some of the most common complaints about ductless heat pumps involve temperature control. A few examples include:
“I set the remote control to 72°F but the thermometer on my coffee table never gets above 67°F.”
“The head in my bedroom overheats the room. Even when I turn it off, I can still feel heat coming out of it.”
“Sometimes my heat pump starts blowing cool air, even when I have it set to heat.”
“I feel like this thing has a mind of its own.”
Central heating systems are generally controlled by thermostats located on interior walls, 3-1/2 to 5 ft. off the ground, and away from direct sunlight and heat sources such as appliances and forced-air registers. Temperature at the thermostat serves as a pretty good proxy for the temperatures experienced by occupants. Most ductless heat pumps, on the other hand, sense temperature with a thermistor located on the ductless head itself. (While the default wireless remote control can be used to adjust set points and other settings, it does not provide temperature feedback). For the most common style of head, the “high wall” unit, this places the…