Best Heat Pump Fan Settings: Auto or On

Your thermostat settings are critical to maintaining a comfortable environment inside your house. Thermostats have a fan setting of “Auto” or “On.” This setting controls the blower fan inside the heat pump.

AUTO’s best efficiency setting because the blower fan only runs when the heat pump is in use. The blower fan will run continuously in the ON setting even when the heat pump system does not consume more energy, causing higher electric bills.

The AUTO setting is the best thermostat setting. This setting uses less energy and is less stressful on the blower fan. The heat pump blower fan only turns on when signaled by the thermostat for the heat pump to turn on.

What Does the AUTO Thermostat Setting Mean?

The AUTO and ON settings control the operation of the heat pump’s blower fan. The blower fan draws air into the return duct, across the evaporator coil, and then distributes air from the heat pump through the ductwork and into your home.

So what does AUTO mean? AUTO is short for AUTOMATIC, meaning the heat pump turns on and off automatically by the thermostat temperature setting, which is the most energy-efficient option as the fan only runs when the heat pump is in use.

Depending on your personal preference, the heat pump blower fan can either be used in the AUTO or ON setting. Many people don’t understand both settings.

For instance, turning the fan on can circulate air throughout the house, especially if no one will be home.

In the long run, however, switching the fan in auto mode is recommended. Once the conditioned air is already well-circulated inside the room, the auto mode will turn on and off the fan at regular intervals to keep the room temperature at optimal levels. 

While the need to turn the heat pump fan on or switched it in auto depends on the needs of the people inside the room, the two options have corresponding advantages and disadvantages, which you also need to consider and may affect your decision.

What’s the Difference between “ON” and “AUTO” Settings?

The thermostat controls not only the indoor temperature but the operation of the heat pump. However, the way you set the thermostat can drastically affect the way the heat pump operates.

So what’s the difference? The difference between the ON and AUTO settings is the control of the blower fan inside the air handler. When in the ON setting, the blower motor will run continuously. In the AUTO setting, the blower fan only runs when the heat pump is in use.

The ON Setting Explained

If you turn the fan “on” in your heat pump, this means that the fan will continuously run until you turn it off. If you switch the fan in auto mode, the fan in the heat pump will run and stop at regular intervals. 

The ON setting keeps the fan continually blowing and maintains steady air circulation inside a room. This ensures indoor air quality is clean and fresh. Airflow helps keep the room well ventilated. The fan also helps dissipate and spread hot or cold air. Thus, it helps in effectively redistributing cool or warm air around the house. 

However, keeping the fan running will result in higher electric consumption and higher electric bills. A fan that is running nonstop also increases its chance of accumulating more dirt.

Thus, the need to clean the fan and replace filters more frequently may be necessary. Finally, keeping the fan running can overstrain it, increase wear and tear or raise the possibility of overheating or breaking down the fan.

The AUTO setting explained

The AUTO setting, on the other hand, will automatically turn on the fan for a certain period and turn it off routinely. AUTO mode helps keep the temperature at optimal levels, which is particularly efficient in mild weather.

Setting the fan in auto mode helps optimize electric consumption and improve monthly energy bills. The auto mode brings the device to its ideal or optimum settings in which it can deliver its function effectively without overworking its mechanism.

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However, this optimal setting is based on very controlled and general factors set by the factory. These factors do generally not apply to different houses and weather conditions, which are very diverse. 

The auto setting may not effectively achieve your preferred or needed room temperature and comfort. It may not be able to distribute the cooling or heating throughout your house evenly.

There are cold and hot spots in the house because the air doesn’t circulate well.

Finally, you may not attain optimal indoor air quality if, for instance, you have numerous guests or visitors in the house, which calls for more air circulation and ventilation.

Should You Run the Fan Continuously?

The settings on the thermostat can be somewhat confusing. When setting your thermostat, logic would say ON is used the turn on the heat pump. “On” only turns the blower fan on, which causes it to run continuously.

Should you run the heat pump fan continuously? I don’t recommend you run the fan of your heat pump continuously. Running the fan all the time can overheat the fan motor causing it to wear out faster.

In my opinion, you shouldn’t run the fan of your heat pump continuously. There are several reasons why, but it primarily prevents your fan motor from overheating and premature failure and prevents your fan from consuming electricity unnecessarily.

The function of the fan in heat pumps is to facilitate airflow and circulation. It blows air to distribute warm or cold air in the room. 

You can switch the fan “on” at the onset for a few minutes after turning on the heat pump to accelerate the distribution of cold or warm air in the room. Once you have achieved sufficient air circulation or enough warm or cold temperature in the room, you can switch the fan in auto-mode and let it run optimally.   

Does Running the Fan in ON Cool Your House?

Many people try to cool their homes with the heat pump fan ON. Contrary to popular belief, running the fan in “on” will not make or keep your room cool.

Running the heat pump in the ON setting doesn’t cool your house. The ON setting turns the blower fan on and circulates the hot or cool air already inside your home.

Running the fan continuously is merely circulating the air inside the house constantly without the heat pump heating or cooling the air. However, they don’t cause a temperature change, mainly when used in a closed room. 

While the blower fan won’t change the temperature or make a room cooler, it can help balance out how the air feels throughout the house. Keeping room doors open also helps because the air will naturally circulate better.

Is Running the Heat Pump Fan Continuously Bad for Your Heat Pump?

So, why is running the fan continuously bad for your heat pump?

Allowing your heat pump fan is run continuously is bad for the heat pump because it:

  • uses more power causing higher energy bills
  • causes premature failure of heat pump components 
  • can contribute to air loss around the ductwork
  • can remove necessary indoor humidity

Let’s look at each of these.

High Energy Bills. First off, turning the fan on nonstop will not help in further cooling or warming a room. Thus, it will only result in higher electric consumption without improving the coldness or warmness of a room.

Fans do not have a direct impact on temperature. It does not change the air temperature. It contributes to cooling or warming a room by diffusing or distributing cool or warm air.

Leaving your fan on when you have already distributed, or circulated air inside the room only increases energy consumption, which ultimately translates to higher electric bills.

Frequent Break Downs. Leaving the fans always “on” can inadvertently overwork its mechanism. This can increase wear and tear, speed up deterioration or depreciation of the fan, and increase the chances of breaking down.  When this happens, this will result in expensive repairs to your heat pump.

Air duct Leaks. Switching your fan “on” continuously can increase the losses of conditioned air. Fans are used to spread out warm or cold air inside a room.

However, keeping the fan on can also blow away warm or cold-conditioned air to leak out of the room. Instead of keeping the warm or cold-conditioned air inside the room, continuous blowing can push them out or let them escape in gaps and openings. 

Drying. The continuous blast of air from the fan can make air dry and cause people to feel dry. It not only evaporates sweat or moisture from the skin but also in your mouth, throat, and nasal passages, which can cause people to feel uncomfortable. Breathing in dry, heated air can cause coughing, disrupting sleep, or leading to other health issues.

What is the Best Thermostat Setting for Your Heat Pump?

There is no single best thermostat setting for your heat pump. The ideal temperature setting would depend on:

  • the season
  • time of the day
  • humidity levels
  • frequency of your stay in or out of the house.

The best heat pump setting depends on your comfort level. The best efficiency setting is to set the Fan to AUTO and set the desired temperature to 68 degrees in the winter on Heat mode or to 78 degrees in Cooling mode.

The key is to set the thermostat and leave it alone. Consistently changing your thermostat causes the system to run out of balance. If the above temperatures are too hot or cold, find the desired temperature that works for you and leave it alone.

The bottom line is that you need to find your comfort level and let the heat pump do its job to maintain the temperature.

Most importantly, you set your heat pump thermostat at the temperature where you are most comfortable so that the heat pump achieves its primary purpose. 

You can set the thermostat to the highest possible setting you feel comfortable in during summer and the lowest comfortable setting during winter.

If you are momentarily leaving the house, you can set the temperature a few degrees higher than during summer or a few degrees lower than your ideal temperature during winter.  

It is not advisable to switch off your heat pump no matter what time of year it is—turning the heat pump off risks freezing pipes during the winter. Worse is that the heat pump helps control humidity in the home, too, and high humidity can cause mold growth in the house if left unattended.

Conclusion

Turning the heat pump fan on or in auto depends on the people’s needs in the room. You may turn the fan on initially to quickly spread or distribute warm or cold conditioned air in the room.

In the long run, however, you should switch the fan in auto mode because keeping the fan on will no longer add to changing the room’s temperature but will only consume unnecessary energy that will add up to your bill.

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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