expert advice, hvac

Should HVAC fan be on or auto? Setting + important points

In order to control the blower of the HVAC system, the fan is set on the thermostat. The blower helps distribute cold or warm air throughout the house until it matches the temperature set by the thermostat. There are two settings on your thermostat to control the fan, i.e. There is always this big argument about which one performs more satisfactorily. Yet, both modes have their benefits and drawbacks, and there is no clear response to hold the AC fan on or off. In addition, the latest thermostats let for custom fan sets.

What is meant by the "on" mode in the fan?

The "On" mode indicates that the HVAC fan is running continuously. This setting means that the system's blower is always running, even when the HVAC does not heat or cool.

Advantages of using "On" mode

  • More satisfactory air circulation
  • Raised life span
  • Fresh air without the odor
  • Enhancing air quality
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Advantages of using "On" mode

More satisfactory air circulation

Although your air conditioner warms or cools the air, it cannot distribute the air adequately alone. A fan will circulate the air in your home sufficiently and allows to eliminate hot and cold spots. Also, keeping the AC fan on constantly allows the spreading of the air on the upper floors.

Raised life span

Keeping an AC fan running implies it won't need to turn on and off as often, which decreases fan stress, and increases the life of the HVAC blower.

Fresh air without the odor

The temperature level during spring and autumn generally remains average in buildings with closed windows. In this situation, the air conditioner may turn off, resulting in air blockage. Keeping your HVAC fan running allows maintaining the air fresh and removes any smells.

Enhancing air quality

By keeping an AC fan on, more air can pass through the AC filters, which removes pollutants such as bacteria, pollen, dust, and mold. Yet, these gifts rely on the type of air filters established in the HVAC system and how they are maintained. High MERV rating filters can virtually clear most fine particles from the air.

Disadvantages of using "on" mode

Regular need to change the air filter

By constantly circulating air from a room through HVAC air filters, the filters become clogged quicker. You should clean the air filter more frequently or replace them regularly.

High power bills

In this case, energy consumption will certainly increase. Depending on the size, type, and how long the AC is used, an air conditioner can consume more than 500 watts of energy.

Warm weather in summer

Ducts established close to the attic or near the walls can fill with warm air in the summer. This air spreads in your home when the fan is always running. So, your room heats up, and the AC turns on additionally to reduce the temperature.

Cold weather during winter

By turning on the fan of the air conditioner in the winter season when the heater is off, a cold current comes out of the ducts. Although the air temperature stays constant, you still feel cold.

Inefficient removal of moisture

During cooling, humidity is extracted from the air. Air passes over the evaporator coils, and humidity accumulates in the form of droplets on the coils. As the system stops cooling, the coils heat up, and droplets trickle down. Constant operation of the HVAC fan causes a portion of this water to evaporate back into the air, thus hindering the sufficient reduction of moisture.

What is meant by the "Auto" mode in the fan?

Setting your air conditioning fan to "Auto" indicates that it just operates when the system heats or cools. After your thermostat matches the needed temperature, the system and AC fan will shut down.

Advantages of using "Auto" mode

More power efficiency
Running the fan automatically will use less energy, and you will receive a lower energy bill compared to running the fan continuously.
 
More efficient dehumidification

As the fan shuts off as soon as cooling stops, moisture droplets on the condensing coils can readily drip into the drain pan below the coils. As a result, moisture is effectively disposed of outside the home.

Disadvantages of using "Auto" mode.

Uneven temperature

Since the air does not circulate after the system is turned off, the hot air rises and the cold air stays at the bottom, and the temperature becomes uneven.

Faster wear

Since the fan motor is turned on and off repeatedly, the fan motor wears out sooner.

Important points about setting the HVAC fan on or auto

There is no clear response to how long the air conditioning fan should operate or whether the fan should be on "Auto" or "On". Setting the AC fan to 'On' or 'Auto' is a personal preference as both modes have some benefits and drawbacks. It should be noted that the only thing that matters is the moisture levels of the region where you live. In high humidity level areas, setting your HVAC fan to "on" causes inadequate moisture reduction and mold expansion. In these areas, it is recommended to use the AC fan on "Auto".

Yet, some choices will help you eliminate the drawbacks while you make the most of the benefits.

  1. Smart thermostat:  Smart thermostats help you set custom timers so that the fan only works at the settings you need. You can decide how long the fan works each hour, regardless of heating or cooling processes.
  2. Variable speed technology: Variable speed fan motor technology is another appropriate choice for your air conditioner. A variable speed fan motor runs at various speeds to optimally control the airflow in your house. With this technology, the AC fan operates constantly to circulate air. Besides, as the system can operate at lower capabilities, it is power efficient. So your energy bills won't go up because of your AC fan and the system won't turn on and off frequently. As a result, this system offers adequate humidity control, more extended fan motor life, uniform temperature, and constant filtration.

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