What Does Aux Heat Mean On Carrier Thermostat?

The Carrier thermostat is quite convenient in setting your desired room temperature. But what if it displays "Aux Heat" on its screen? What does it mean and what should you do? Worry no more! We've researched this conundrum to bring you the answer!

Auxiliary heat on a Carrier thermostat means that the heat pump cannot cover up the cold temperature and the unit needs a backup. This automatically activates to reduce the cold temperature with an additional heat source.

Auxiliary heat is usually displayed due to any of the following reasons:

  1. The temperature outside is too cold.
  2. The thermostat wants a higher temperature.
  3. The defrost mode is on.

In this article, we'll help you know what it means when aux heat is displayed on your Carrier thermostat. We'll tackle why this happens, and provide you with some ways to prevent it. You wouldn't want to miss the opportunity to learn with us. So let's continue reading!

a round, modern, programmable digital thermostat, on a clean white wall in cooling mode, What Does Aux Heat Mean On Carrier Thermostat?

What Does Aux Heat Mean On A Carrier Thermostat?

Aux is a short term for auxiliary, meaning supplementary support. When your heat pump shows "AUX" or "AUX Heat" in some thermostats, this indicates that the backup heating system on the heat pump is activated. Such a backup is automatic when it detects that the heat pump is not effective enough in circulating heat.

You need to understand what's happening in a room when aux heat appears on the thermostat. That's why we listed some reasons it's activated. See these reasons below.

A thermostate adjusted by a hand of a woman in a yellow wall

1. It's Too Cold Outside

See the weather conditions outside. If it's winter and it's too cold, then the notification will show that the aux heat is running. Rain can also cause a drop in temperature, especially if it comes from the sea.

Thermostats in general are designed to detect the change in temperature when the room has reached beyond the desired temperature. For instance, you set the temperature to 72 degrees Fahrenheit. The thermostat will react and give you signals if it falls to 71 or rises to 73 degrees Fahrenheit.

2. The Thermostat Wants a Higher Temperature

There can be a situation where the weather is normal. But the thermostat may demand a higher temperature during the operation of a heat pump. When the heat pump struggles to increase the temperature, the heat pump will then activate the aux heat and display the status on the thermostat.

In fact, residential heat pumps, like Carrier heat pumps, do not produce heat themselves. The heat pump simply absorbs the hot temperature from the ground or outside air, then releases the heat inside the room.

The aux heat system, on the other hand, is actually heating up the temperature. There are two types of aux heat that may operate. You may refer below to the differences between these types.

Electric Heating

Heat pumps have electric coils that are usually found inside the air handler. Once activated, the electricity will run through the electric coils and conduct heat. The heat will then evaporate until the fan releases the hot air into the room.

One consequence of an electric heater is the higher bill you may have since the coils consume energy from the household electric source.

Gas Heating

On the other hand, the heat pump may activate the gas furnace if the electric heating system is still not enough to counter the cold temperatures. The fuel will make ignite, increasing the heating capacity of the heat pump. As a result, the temperature will rise quicker.

3. Defrost Mode Is On

Another reason the aux heat activates is when the temperature drops below 32 degrees Fahrenheit. This temperature is enough to start freezing the coils, which will cause serious damage to internal components. So, the heat pump will warm up the coils to melt the ice particles formed inside.

A sign of heat pump defrosting is the noise due to the reversing valve. The heat pump will continue melting the frost until it reaches at least 57 degrees Fahrenheit.

Can You Cancel the Aux Heat?

Man is Adjusting a temperature in modern living room

Unfortunately, heat pumps are programmed to activate the aux heat, and you cannot undo this feature. The only way to prevent the aux heat from activating is to maintain the hot room temperature. You may consider doing these techniques below. Remember that you can do all of them to maximize heat efficiency.

Insulate the area

Insulating the area will help heat up the room faster. You may trap the heat by weatherstripping and sealing the windows that serve as the exit of hot air.  

See this weatherstripping roll on Amazon.

Give Way to Natural Heat

Using glass exteriors, like windows, doors, and walls, can improve the temperature by allowing natural heat to warm up the area. Sunlight is the best natural heat source for both saving energy and making the room temperature healthier.

You can use a thermal curtain for your glass walls to absorb more heat during the day.

See this thermal curtain on Amazon.

However, using glass exteriors may be expensive. You can consider opening the doors and windows every morning to welcome the sunlight into your home. This helps the room conserve the heat that may last for a few hours. This technique that involves sunlight's warmth is applicable only before turning on the heat pump.

Close the Doors and Windows

On the other hand, you may keep the doors and windows closed after you fill the room with the sunlight's warmth. This is to prevent the heat from escaping once you turn the heat pump on.

Adjusting white thermostat

How to Set a Carrier Thermostat

Learning how to set the thermostat saves you a lot of money in exchange for keeping yourself comfortable at home. This is a great way to monitor the temperature with the flexibility of your schedule.

For better understanding, take a look at this image of a Carrier thermostat:

You can proceed to these steps below to get an idea of how to set the thermostat in general.

1. Set the Schedule

Setting the schedule means programming the thermostat at a particular time with a corresponding temperature.

Simply press the TIME/TEMP button. Then press the DAY button to choose the current day of the week from Monday to Sunday. Press the PROGRAM button to enter the chosen day.

Next is to set the time for when you'll wake up in the morning. Press the up and down buttons to choose a time. Once finished, press the TIME/TEMP button again.

2. Set the Temperature

After setting the schedule, you can now set the temperature for when you'll wake up in the morning.

Press the heating and cooling settings simplified as the H/C button. Read the "heat" or "cool" displayed on the screen, then set the desired temperatures accordingly.

Press the TIME/TEMP button to finalize your temperature choice. Then press PROGRAM to enter the options.

3. Make Appropriate Schedules

You will notice that the screen will blink at different times and days. This is an indication if you also want to set the thermostat on another schedule.

Simply go back to the first and second steps to set schedules for the evening, leaving home, or whenever you want to feel such specific temperatures.

Once you're done setting the schedules with corresponding temperatures, simply press the HOLD/END button.

To change the schedule or the temperature for any reason, you can press the H/C button to modify the heating and cooling temperatures. Press the HOLD/END button once. The screen should then display "hold," indicating that the set temperatures are temporary. Press the HOLD/END button again to go back to the original schedule and temperature.

Keep in mind that setting the thermostat may vary by type and manufacturer. Always refer to the user's manual for more specific instructions.

See this Carrier's Ecobee Thermostat on Amazon.

How Long Do Thermostats Last?

Digital thermostat heating and cooling automation system

Ideally, thermostats can last for up to 10 years. You can prolong its lifespan by changing the batteries when necessary. Also, you can keep it away from children's reach. You can consider mounting the thermostat at least 4-5 feet above the ground.

You can use a thermostat cover to prevent children from playing the buttons.

See this thermostat cover on Amazon.


a round, modern, programmable digital thermostat, on a clean white wall in cooling mode

Throughout this article, we discussed why the aux heat displays on a Carrier thermostat and what it implies.

We mentioned that you cannot undo the aux heat from appearing, but we provided ways to prevent it, such as adding insulation.

Finally, we discussed how to set up a Carrier thermostat and how long thermostats typically last. Keep in mind that it's best to keep the room temperature comfortable.

It's another informative article, isn't it? Then you'll also love to read these:

What Temperature To Set Thermostat When Away On Summer Vacation

Do I Need Insulation Between Floors? [Pros And Cons]

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