Rebate-eligible heat pumps can reach over 400% efficiency in mild temperatures and can maintain well over 200% efficiency even into negative temperatures. This is why turning off a heat pump in frigid temperatures and opting to use a fossil fuel boiler or furnace instead is a mistake.
Below 40° f or 5° C the heat pump will frost up and need to turn off to allow the exterior unit to melt. The thing is though, about 10 years ago or longer, heat pumps started to have four-way valves that would switch between cooling and heating.
In general, heat pumps can run continuously in winter without wasting energy. They can maintain a consistent indoor temperature efficiently.
Short answer: No. Switching your thermostat to emergency heat or “em heat” just because it's cold outside will just raise your energy bills like crazy. Don't use emergency heat mode unless your heat pump stops heating your home altogether. If that happens, contact a professional heat pump repairman for help.
As long as your house is properly air-sealed and insulated, an air-source heat pump can perform well beyond temperatures of -13 degrees Fahrenheit!
Auixiliary Heat will turn on automatically when heat can no longer efficiently transfer heat from the outside air to heat pump. This is when the outside is around 35-40 degrees and the indoor temperature is around three degrees cooler than the thermostat setting.
For this reason, heat pumps start to lose efficiency at around 40 degrees F and become less efficient than furnaces at around 25 degrees F. Heat pumps continue to be effective at cooling the indoors, even at high temperatures. In the South, it rarely gets below 25 degrees.
– Will Emergency Heat Defrost Heat Pump? Emergency heat mode bypasses the heat pump, using auxiliary heat sources instead. It does not actively defrost the heat pump but can provide heating if the pump is not functioning correctly due to excessive frost.
Spotting the Signs: Indications that a heat pump is in emergency heat mode include increased utility bills, constant running of the backup system, reduced airflow, and no change in room temperature.
If freezing has already occurred, shut off the unit (keeping it on could damage the unit) and pour water over the unit to melt the ice (do NOT attempt breaking up ice with heavy tools!). In addition, check to make sure no damage has been done to the copper coolant lines, this might be a job for a professional plumber!
It states that the control for the lockout temperature shall have a maximum setting of 40 degrees F, and set for 32 degrees or less at final inspection.
Most cold-climate heat pumps can run at total capacity until the outdoor temperature gets to about 5 F or below. It will still heat your home at those lower temperatures, but not necessarily keep it as warm as you may typically like. That's where backup heat sources come in.
It shouldn't harm it to turn it off but it won't be running very efficiently at those outside temperatures. You have two choices: 1. run it and it will undoubtedly use the auxiliary heat; 2. turn it to emergency heat and run the backup heat strips only.
Increase your home's temperature by a couple degrees above your normal setting now, before the worst hits, and then leave your thermostat alone. Do not turn it back down at night. In this extreme cold, your heating system will struggle to return to where you originally had it set.
In the defrost cycle, the heat pump is automatically operated in reverse, for a moment, in the cooling cycle. This action temporarily warms up the outdoor coil and melts the frost from the coil.
This heating method works incredibly efficiently until the outdoor temperature reaches about 35 degrees. At this point, the heat pump has difficulty extracting enough heat from outside to keep up with the thermostat setting. This is when many people assume it's time for switching their heat pump to emergency heat.
Run the Heat Pump's Fan
Running the fan can help you thaw the heating system within an hour. If the temperature outside is too low, you could even set the fan on exhaust setting. While this step might not solve the freezing problem entirely, it absolutely works as a temporary solution.
Frost and ice shreds may also collect around the heat pump. However, if extreme amounts of ice and snow buildup over the unit, it's strongly recommended to switch it off or to 'emergency heat' to remove the snow. The easiest way to get the snow off the heat pump is by pouring warm water over time.
Contrary to popular belief, heat pumps don't ever stop working when it's cold. These systems are built to withstand frigid weather, operating at 100% efficiency even down to -13 degrees Fahrenheit.
Most standard heat pumps will function at 100% efficiency until the outside temperature reaches about 40° F. However, when the temperature dips below this, most heat pumps are not able to maintain efficiency. They become much less effective at temperatures between 20° F to 30° F.
Don't run your heat pump constantly
A lot of people believe that keeping a heat pump running 24/7 is an efficient, cost-effective way to heat their home. But in fact, that idea is actually a myth.
This can cause concern, as auxiliary heat typically is not supposed to run all the time. While it's normal for auxiliary heat to kick in during exceedingly cold temperatures, running it too long may indicate an issue with the heat pump.
Heat pumps do not operate as efficiently when temperatures drop to between 25 and 40 degrees Fahrenheit for most systems. A heat pump works best when the temperature is above 40. Once outdoor temperatures drop to 40 degrees, heat pumps start losing efficiency, and they consume more energy to do their jobs.
The short answer is when you have a heat pump not working, various issues can be responsible. These include a power switch or circuit breaker issue, using the wrong temperature or emergency heat thermostat settings, clogged filters, and faulty components within the indoor and outdoor units.