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.

Is it best to use the “Auto” or “On” setting? The best efficiency setting is AUTO because the blower fan only runs when the heat pump is in use. In the ON setting, the blower fan will run continuously even when the heat pump system is not in use. This consumes more energy causing higher electric bills.

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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 is used to draw air into the return duct, across the evaporator coil, and then distribute 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. This is the most energy-efficient option as the fan only runs when the heat pump is in use.

The heat pump blower fan can either be used in the AUTO or ON setting depending on your personal preference. There are reasons for both settings that often misunderstood.

For instance, turning the fan on is necessary if you want to quickly dispense the cold or warm conditioned air throughout the room especially if you have relatives who have allergies or are very sensitive to temperature. This will allow the fan to constantly blow air and ensure consistent air circulation in the room.

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 the optimal levels. 

While the need to turn the heat pump fan on or switched 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 the thermostat is set 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, this means that the fan in the heat pump will run and stop at regular intervals. 

The ON setting that keeps the fan continually blowing and maintains steady air circulation inside a room. This ensues 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. 

Keeping the fan always running however will result in higher electric consumption of the heat pumps and therefore 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 always 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 if the work is done. AUTO mode helps to keep the temperature at optimal levels which is particularly efficient if the weather is mild or extremely hot or cold temperatures are not experienced.

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.

However, this optimal setting is based on very controlled and general factors set by the factory. These factors do not normally 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 evenly distribute the cooling or heating throughout your house.

There are cold and hot spots in the house because the air is not sufficiently circulated.

Finally, the indoor air quality may not also be attained if, for instance, you have numerous guests or visitors in the house at the moment, which calls for greater 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 the heat pump on. But’s that’s not the case. On only turns the blower fan on which causes it to run continuously.

Should you run the heat pump fan continuously? It is not recommended that you run the fan of your heat pump continuously. Running the fan continuously 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 mostly it prevents your fan motor from overheating, 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 when sufficient warm or cold temperature is achieved 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 that is already inside your house.

Running the fan continuously is merely circulating the air inside the house continuously without the heat pump heating or cooling the air. However, they really don’t cause a change in temperature, especially 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 the consumption of energy 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 it breaking down.  When this happens, this would result in expensive repairs of 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, if you keep the fan on, it 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 of the room. 

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 skin but also in your mouth, throat and nasal passages. This is turn can cause people to feel uncomfortable. Breathing dry heated air can cause coughing, which can disrupt sleep or lead 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, and the 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 a desired temperature that works for you and leave it alone.

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

What is most important is that you set your heat pump thermostat at the temperature where you are most comfortable so that the heat pump achieves its primary purpose. This is exactly why the thermostat was designed to be adjustable in the first place. 

In general, you can set the thermostat to the highest possible setting you feel comfortable 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 your ideal temperature 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 completely 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 need of the people 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 in changing the temperature of the room 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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