Auxiliary heat can be incredibly beneficial in the winter months when temperatures drop substantially. It reaches a point when the heat pump is overwhelmed and can no longer pump enough heat into your home. Auxiliary heat can step up to save the day.
Unfortunately, sometimes aux heat can misbehave. For example, if there’s a thermostat malfunction, the auxiliary heat function may come on too often or fail to come on at all.
Today, we want to find out why aux heat sometimes comes on too often or comes on unnecessarily, how it can impact you, and how to stop it from coming on until you need supplemental heating.
How AUX Heat Works
Auxiliary heat means supplemental heat. It’s designed to supplement the heat pump whenever the heat pump is overwhelmed.
Heat pumps work by extracting heat from outdoor air and pumping it into the house. They don’t burn any fuels or extract heat from electricity. Instead, the electricity merely powers the motor to get the unit running. So all the heat that ends up inside your home comes from the air outside.
As such, heat pumps are extremely energy efficient. Some studies show that a heat pump uses only about 10% of the electricity an electric heater consumes. It’s the main reason consumers are so interested in heat pumps.
Unfortunately, the working mechanism means that heat pumps can only go so far. If temperatures outside dip below a certain point, the heat pump may no longer be able to send much heat indoors. Indeed, sometimes the heat pump shuts off altogether when it gets extremely cold outside.
Additionally, heat pumps need to defrost periodically during winter to protect internal components from freezing. Therefore, the little heat produced during winter is often engaged elsewhere.
Auxiliary heaters are electric heating strips of fins that convert electric current to heat to supplement the heat pump when the heat pump is overwhelmed.
When Should Auxiliary Heat Be ON?
From the explanation above, you can tell that auxiliary heat isn’t meant to be ON all the time. Instead, it’s only supposed to be on when needed. In normal conditions, it should only be ON under the following conditions;
Temperatures outside are lower than 40˚F
The exact value here varies. For instance, although most heat pumps can only withstand temperatures down to 40˚F, others continue to pump sufficient heat down to 35˚F. A few may also continue working until 31˚F.
The bottom line is that auxiliary heat is rarely needed when outdoor temperatures are above 40˚F. If it comes on when it’s 50˚F outside, there’s a problem.
Indoor temperatures are 3˚F lower than ideal levels
The Department of Energy (DOE) recommends setting the thermostat to 68˚F when someone is home and around 65˚F when no one is home. Most people prefer to raise just a little, though. Whichever setting you choose, expect the auxiliary heat function to kick in if temperatures dip below the setting 3˚F or more.
If you’ve set your winter temperature at 68˚F, aux heat will spring to action as soon as temperatures to 65˚F or lower.
There’s not enough power in the heat pump to heat the home
The thermostat constantly monitors to heat pump’s performance. Among other things, it monitors heat output, fan performance, and refrigerant levels. If it determines that something is slowing down the heat pump’s performance, thus compromising the heat output, it may request aux heat to step up and help out.
A great example is when there’s freezing inside the heat pump, perhaps due to low refrigerant levels. You’ll most likely see aux heat running to keep your home warm.
Can You Avoid/Prevent Auxiliary Heat
Before we answer whether you can stop auxiliary heat, perhaps we should begin with whether you can avoid auxiliary heating altogether. Unfortunately, the answer is – NO, you can’t prevent auxiliary heating.
The only way to avoid auxiliary heating is to buy a heat pump without an auxiliary heat function. Otherwise, the auxiliary feature will always kick on when called upon by the thermostat – whether you like it or not.
The reason is that auxiliary heaters are designed as an extension of the heat pump. As long as it’s present on the heat pump, it will always support the heat pump. Otherwise, three things would happen;
- Excessively cold indoor conditions
If it becomes too cold outside or inside the home and there’s no auxiliary heat source to supplement the heat pump, you’d be left in stingingly cold conditions. Extreme cold exposes you to all kinds of health issues, including respiratory illnesses and frostbite. Excessively cold conditions can also lead to water damage in the home.
- Heat pump damage
Auxiliary heat doesn’t just protect you and your home; it also protects the heat pump. For example, when it gets extremely cold outside, the condenser component outside is at a greater risk of freezing. Frozen coils can damage the condenser, necessitating expensive repairs or a replacement. Auxiliary heat allows the heat pump to focus on keeping the condenser warm while the aux heat function warms your home.
- Emergency heat would kick on
Standard heat pumps have at least three types of heat, i.e., the main heat pump, aux heat, and emergency heat. Whereas aux heat supplements the heat pump, emergency heat is designed to replace the pump. It comes on when the heat pump stops working. You don’t want to engage emergency heat unless it’s necessary for two reasons – it’s costly and puts a lot of strain on your heating system.
Can You Stop Auxiliary Heating?
Unfortunately, the answer here is also – NO. Just as you cannot prevent auxiliary, so can’t you stop it once it kicks on.
You might have even noticed that your heat pump doesn’t have an ON/OF switch for auxiliary heat (there’s usually one for emergency heat, though). It’s not a mistake. Very few (if any) heat pumps have a switch for auxiliary heat because you’re not supposed to turn it on or off.
The reasons are pretty much the same as avoiding or preventing aux heat. The auxiliary heating component is designed to protect you, your home, and the heat pump.
It keeps you warm when the heat pump is overwhelmed to protect you from health issues related to extreme cold. It also protects your heat pump from damages due to freezing and the home from potential water damage due to a frozen heat pump. Therefore, it would be too risky to allow you to turn it on and off as you wish.
What to Do if Aux Heat Comes ON Too Often or Unnecessarily
If you determine that your aux heat function comes on too often, even when temperatures outside and inside the house are reasonably warm, there’s likely something wrong. Perhaps it’s low refrigerant levels causing a noticeable temperature drop inside the heat pump, or a malfunctioned indoor or outdoor fan causing low air pressure. Whichever the cause, you can do something about it;
1. Lower the thermostat setting
One of the reasons aux heat may come on too often is a low thermostat setting. Ideally, aux heat should only come if temperatures outside the house are lower than 40˚F and indoor temperatures at least 3˚F lower than 68˚F as recommended by the DOE.
If you set the heat pump 72˚F, for instance, aux heat will come on as soon as temperatures reach 69˚F – which can be most of the winter season. Lowering the thermostat a few degrees can rectify the problem.
2. Add extra insulation to your home
You’ve likely heard about insulation a million times by now. That should tell you something about its importance. Proper insulation prevents the loss of warm air during the winter season, thus keeping your home warmer. This effectively reduces the frequency at which temperatures inside your home will drop below the thermostat setting.
3. Close your doors and windows
Closing the doors and windows is a clever way to increase home insulation. It keeps warm air inside and cold air out. Warmer indoor air means that your heat pump will work less, and indoor temperatures will drop below the thermostat setting less often. The result is usually a reduced need for auxiliary and even emergency heating.
4. Consider space heating
With the knowledge that the heat pump is sometimes overwhelmed, especially in the peak of winter, you should make arrangements to acquire supplemental heat when it gets too cold. A space heat, whether electric or gas-powered, can help. When it gets too cold, turn on your space heater. This way, the thermostat won’t see a need to switch on the auxiliary heater.
5. Ensure regular maintenance
Finally, you can stop the auxiliary heater from coming on unnecessarily by keeping your HVAC system clean and well maintained. Make sure the filters and fans are spotlessly clean. Also, lubricate the fans as necessary. Additionally, check for and repair dents and leaks that may impede airflow or impact pressure inside the heat pump.
Know When to Call the Pros
Though auxiliary heat is invaluable in the cold season, it can also cause you unending headaches, especially when it keeps coming on even when you don’t need it. If you can’t fix the problem yourself, don’t hesitate to call an HVAC pro.