Auxiliary Heat – This is the secondary heat source that turns on automatically. Emergency Heat – This is when you turn on the secondary heat source.
Emergency heat is equally as efficient as space heaters, but it is safer. Space heaters start many fires (when not used properly). But, if you use your space heater only in a single room, it will use much less electricity than emergency heat because emergency heat would be heating the entire house.
The difference between emergency heat and auxiliary heat is that emergency heat has to be switched on manually and should only be used in temperatures of 30 degrees or below. However, auxiliary heat will kick on automatically to help heat your home more quickly if there is a sudden drop in temperature.
Your auxiliary heat, or secondary heat source, should come on when your heat pump is struggling to heat your home effectively. The thermostat will trigger auxiliary heat when: The outside temperature is below 40 degrees or a set aux heat trigger temperature. The heat pump is in defrost mode.
Unlike auxiliary heat, which automatically supports the main system, emergency heat takes over as the primary heat source until the main system is fixed. This mode consumes more energy and can lead to higher utility bills, which is why it's advisable only to use it in actual emergencies.
The term “aux” is short for auxiliary. Should your heat pump struggle to reach your desired temperature because of the extreme cold outside, the “aux heat” message shows that a secondary heat source (either gas or electric) has been deployed.
Emergency heat and Auxiliary Heat are different types of backup heating and operate differently. Emergency heat must be turned on manually while Nest thermostats can use Auxiliary Heat automatically as needed.
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.
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.
If the outside fan doesn't run at all in heating mode, it could indicate a problem with the heat pump. When this happens, contact a professional. The outside fan should indeed run when your heat pump is in heating mode. It plays an important role in the heat transfer process and overall system efficiency.
Auxiliary heat isn't a bad thing; in fact, it can be extremely necessary to your comfort and well-being, especially in the event of extreme cold weather. However, auxiliary heat uses a good deal of energy, which leads to an increase in your energy bill.
Auxiliary heat strips supplement the heat pump and produce warm air to quickly heat your home. Those heat strips use substantially more energy and will increase your electric bill.
The heat pump itself might have a problem that needs to be addressed as soon as possible. There could be a refrigerant leak, or the reverse valve is malfunctioning. Either issue prevents the unit from blowing warm air in heating mode, requiring immediate attention from an HVAC technician.
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.
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.
The heater might blow cold air rather than warm if the gas line supply has been turned off. This usually happens when something goes wrong with the heater, and it breaks. For example, maybe there was a problem with a gas valve, the gas supply pipe, or something else in your furnace broke down.
More often than not, the aux heat is coming on because the temperature in the home is set too high. You are asking your HVAC system to work too hard to maintain a comfortable temperature. Setting the thermostat for somewhere between 62-68 degrees is all you should need to do to get the problem under control.
The auxiliary heat should only run for as long as it usually takes for your home to meet the temperature set on the thermostat.
Because your heat pump and backup heat source work together, AUX mode consumes more energy. This leads to increased energy bills — your costs may be up to 50% higher when the device is using AUX heat.
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.
So, to sum up everything that we just covered, emergency heat is not supposed to run the way that your regular heat setting does—and it is especially not meant to run all day and night during the long, frosty winter months.
Auxiliary Heat – This is the secondary heat source that turns on automatically. Emergency Heat – This is when you turn on the secondary heat source.
It's normal for auxiliary heat to turn on when your heat pump needs to heat the home quickly. If you're feeling chilly in the morning, for example, the secondary heat system can help to warm you up. This system turns on automatically, so don't be surprised if it comes on during the night.
If your heat pump isn't working properly, you may be tempted to switch it to emergency heat. However, we advise against this unless your heat pump has completely stopped working. You should only switch to emergency heat when your heat pump isn't working at all to avoid unnecessarily high energy bills.
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.