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Aux Heat: What Does It Mean and How Do I Stop It From Coming On?


The Short Answer Is: Auxiliary heat on a thermostat refers to a secondary heating system, often electric resistance heat strips, that kicks in when the primary heat pump alone is insufficient to meet the desired temperature. While auxiliary heat is not inherently bad, its use can increase energy consumption and utility costs. To minimize its activation, homeowners can ensure the heat pump is well-maintained, the thermostat settings are appropriate, and the home is adequately insulated, preventing the need for auxiliary heat to engage frequently.

As we all know, thermostats are a crucial component of any heating and cooling system in our homes. It allows us to maintain a comfortable living temperature and also helps us save energy by managing our heating and cooling systems' efficiency. However, some thermostat features and functions may be a bit confusing, especially if you're new to them. One feature that may have left you puzzled is the 'Aux Heat' function, which is quite common on many thermostats.

This blog aims to provide you with a clear-cut understanding of what the auxiliary heat function means on your home thermostat.

What Does Aux Heat Mean?

First off, let's define the term 'Aux Heat'. The term 'Aux' is an abbreviation for auxiliary, which means additional or supplementary. Auxiliary heat, therefore, is a secondary emergency heat source that the thermostat uses when the primary source, such as the heat pump, is not enough to warm up your house to your desired temperature.

"When temperatures dip really low is when homeowners tend to see 'Aux Heat' on their thermostats, and for good reason," says Roger Elkins, Director of HVAC Services at Williams Comfort Air. "The auxiliary heat function is designed to provide additional heating capacity from a secondary heat source when your primary heating system is not enough to meet your home's heating demand."

Essentially, your heat pump can't reach the set temperature on your thermostat and the system is trying additional heat sources (most commonly gas or electric) within it to reach that temperature setting. Let's explain those now.

Auxiliary Heat Options

There are a few types of heating systems that can be installed with heat pumps to provide auxiliary heat.

Electric Resistance Auxiliary Heat

One popular heating system is the electric resistance heating system. Electric resistance heating systems are often used in conjunction with heat pumps because they provide supplemental heat when the ambient temperature drops below the heat pump's operating range. These systems use electricity to generate heat through the use of an auxiliary heat strip inside the heat pump, which is then distributed to the home's ventilation system.

Gas Furnace Emergency Heat

Another type of heating system that can be installed with heat pumps is the gas furnace. Gas furnaces are used as an auxiliary heating system because they are able to supply emergency heat quickly and efficiently when extremely cold outdoor temperatures drop below the programmed set point on the heat pump. Gas furnaces use natural gas to generate heat, which is then sent to the home's ventilation system.

How Does the Aux Heat Emergency Heat Setting Work?

When the temperature inside your home falls below your desired temperature, the thermostat sends a signal to the heating system to turn on and start producing heat. In most homes, the primary heating source is usually a heat pump that uses the outside air to heat your home. However, heat pumps are not always very efficient at producing heat when the outside temperature drops below freezing point, which is where Aux Heat comes in handy.

Whenever your heat pump struggles to produce enough heat to meet your heating demand, the thermostat energizes auxiliary heat, which switches on a secondary heating source, such as electric resistance coils or a gas furnace. These secondary heating sources can provide additional heat to supplement the heat produced by the heat pump to meet your heating demand.

Auxiliary Heat During Defrost Mode

During cold, winter months, the heat pump is susceptible to ice buildup on its outdoor unit. To prevent damage caused by excessive ice buildup, the heat pump goes into defrost mode. During this time, heat production is halted, and the heat pump begins to thaw the ice.

Although the defrost mode is vital to the heat pump's proper functioning, it may lead to a momentary drop in indoor temperature. To mitigate this, a supplementary heating system, also known as an auxiliary heating system, comes into play. This emergency heat setting kicks in whenever the heat pump goes into defrost mode to ensure that the indoor temperature does not dip lower than desired.

Given the importance of maintaining desirable indoor temperatures, particularly during cold seasons, the auxiliary heating system is an indispensable component of a heat pump. Therefore, homeowners must ensure that both heating systems work correctly, providing optimal warmth in different seasons.

Benefits of Using the Aux Heat Function

The Aux Heat function has several benefits that make it a valuable feature in your thermostat. One of the most significant benefits is that it provides added comfort to your home, particularly during extremely cold weather when your heat pump may struggle to produce enough heat to warm up your home. The additional heat provided by the Aux Heat function ensures that the temperature maintained in your home is consistent with your desired room temperature.

Another advantage of using an Aux Heat function is that it is an energy-efficient way of keeping your home warm. Auxiliary heat sources such as a gas furnace or electric resistance coils use less energy compared to compared to the primary heat pump under certain conditions. Using these sources only when necessary can help reduce your winter energy bills and make your heating system more efficient.

How to Use the Aux Heat Function Correctly

It is crucial that the auxiliary heating system automatically switches on and off based on the temperature outside. This not only ensures that you are comfortable at all times but also helps to conserve energy. When the auxiliary heating is left on for extended periods, it can cause energy waste and lead to higher energy bills.

Many homeowners may be tempted to manually set their thermostats to auxiliary heat, thinking they are helping the heating system operate more efficiently. However, this approach is counterproductive as it can cause energy waste and ultimately drive up energy costs.

An automatic switching system works by detecting the difference between the indoor and outdoor temperature and automatically adjusts the auxiliary heating accordingly. This ensures that the heating system delivers the right amount of heat to the home, at the right time, without any unnecessary waste. By operating in this manner, homeowners don't have to worry about manually adjusting the thermostat and can trust the system to make the best decisions on their behalf.

It's also important to note that using the Aux Heat indicator function continuously can put a strain on your heating system, leading to wear and tear and, in some cases, system breakdowns. To avoid heat pump repair calls, consider setting your thermostat to the 'emergency' or 'auto' mode instead of the 'Aux Heat' mode. This will ensure that the heating system only uses the Aux Heat function when necessary, reducing the chances of overworking the system and increasing its lifespan.

With the proper setup, homeowners can rely on an efficient heating system to operate optimally and maintain a comfortable environment.

Add a Secondary Heating Source for Maximum Comfort and Efficiency

The Aux Heat function on your home thermostat is a vital feature that provides additional emergency heat to supplement your primary heating system during extreme weather conditions. It ensures that your home remains comfortable and warm, even when your heat pump struggles to maintain your desired room temperature.

However, it's important to use this function correctly to avoid straining your heating system and increasing your energy bills. For help with your home's heat pump or Aux Heat system, contact Williams Comfort Air today. Our team can install a secondary heat source to provide the auxiliary heat your home needs when your heat pump isn't able to operate efficiently and solve any Aux Heat issues to ensure maximum energy efficiency.

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