Video: When Running the AC Should the Fan be on Auto or On: Optimizing Your AC Performance
Figure 1: Air conditioner system set.
When it comes to running your air conditioning system, one of the critical decisions you'll need to make is whether
to set the fan to Auto or On. Both options have their advantages and disadvantages, and choosing
the right setting can significantly impact your comfort and energy efficiency.
In this article, we will explore the characteristics of the On and Auto settings, weigh their pros and cons, and
provide guidance on selecting the most suitable option for your specific needs.
1. What is the On Setting?
When the fan is set to On, it means that the fan will run continuously, regardless of whether the air conditioner is actively cooling the air or not. In this mode, the fan circulates air constantly throughout the space, even when the cooling cycle has completed. The On setting can be manually selected on the thermostat. Let's examine its advantages and disadvantages:
Figure 2: Daikin HVAC thermostat.
1.1 Advantages of the On Setting
1. Enhanced Air Circulation: The continuous operation of the fan ensures a steady flow of air throughout your home.
This helps eliminate hot or stuffy spots and promotes a more consistent temperature distribution.
2. Improved Air Filtration: With the fan running continuously, the air is continuously filtered, capturing airborne
particles such as dust, pollen, and pet dander. This is particularly beneficial for individuals with allergies or
respiratory sensitivities.
3. Fresh Air Exchange (with Integrated Ventilation Systems): The On setting allows for the continuous exchange of
indoor and outdoor air, promoting better indoor air quality. However, note that this feature typically requires an
integrated ventilation system to maintain energy efficiency.
1.2 Disadvantages of the On Setting
1. Higher Energy Consumption: Running the fan continuously consumes more energy compared to the Auto setting,
resulting in potentially higher utility bills.
2. Noise Generation: The continuous operation of the fan can produce more noise, which may be undesirable,
especially during quiet hours or while sleeping.
2. What is the Auto Setting?
When the fan is set to Auto, it means that the fan will only run when the air conditioner is actively cooling the air. In this mode, the fan turns on and off automatically in response to the cooling needs of the space. When the desired temperature is reached, the fan shuts off, eliminating unnecessary energy consumption. The Auto setting is often the default option on most thermostats. Let's examine its advantages and disadvantages:
Figure 3: Remote control setting temperature.
2.1 Advantages of the Auto Setting
1. Energy Efficiency: One of the primary advantages of the Auto setting is its energy-saving potential. The fan runs
only when necessary, reducing energy consumption and lowering utility bills. This is particularly beneficial in
moderate weather conditions when the cooling demand is intermittent.
2. Better Humidity Control: The Auto setting allows the AC unit to dehumidify the air effectively. When the fan
turns off between cooling cycles, the condensation on the evaporator coil can drain away, reducing indoor humidity
levels. This helps maintain a comfortable and healthy environment, as high humidity can lead to mold growth and
other moisture-related issues.
3. Noise Reduction: Since the fan operates intermittently in the Auto mode, it significantly reduces the noise
generated by the AC system. This is particularly advantageous during nighttime when a quiet environment is essential
for uninterrupted sleep.
2.2 Disadvantages of the Auto Setting
1. Decreased Air Circulation: As the fan only runs during the cooling cycle, there may be periods when air
circulation is limited or stagnant, potentially leading to hot spots or inconsistent temperatures.
2. Limited Air Filtration: The intermittent operation of the fan means that air filtration occurs less frequently
compared to the On setting. This may result in a less effective capture of airborne particles.
Figure 4: Mitsubishi air conditioner fan auto mode.
3. Difference Between the Auto and On Settings
The primary distinction between the Auto and On settings lies in the fan's operation during non-cooling periods. The Auto setting allows the fan to turn off, conserving energy and reducing noise, while the On setting maintains continuous air circulation and filtration.
4. Auto or On Setting: Which is Right for You?
Now that we have explored the benefits of both settings, you might be wondering which option is best for you. The
truth is, there is no one-size-fits-all answer. The decision depends on various factors, including climate, personal
preferences, and the specific needs of your household. Here are some guidelines to help you choose:
1. Auto Setting: If energy efficiency is a top priority for you and you live in an area with moderate climate
conditions, the Auto setting is likely the better choice. It provides efficient cooling, reduces energy consumption,
and effectively controls humidity levels.
2. On Setting: If you prioritize consistent air circulation, improved air filtration, or have specific requirements
for fresh air exchange, the On setting may be more suitable. It can be particularly beneficial in areas with high
humidity, poor air quality, or for individuals with allergies or respiratory issues.
3. Hybrid Approach: Some homeowners prefer to use a hybrid approach, utilizing both settings at different times. For
example, during the day, when the house is occupied, they may choose the Auto setting for energy efficiency. At
night, when quieter operation and improved air filtration are desired, they may switch to the On setting.
Figure 5: Central air conditioning thermostat.
5. Under What Circumstances Are These Two Fan Modes Mostly Used?
1. On Setting: The On setting is often recommended in the following scenarios:
- High humidity areas or during humid weather conditions.
- When consistent temperature distribution and air circulation are desired.
- For individuals with allergies or respiratory sensitivities who require improved air filtration.
- When integrated ventilation systems are in place to facilitate fresh air exchange.
2. Auto Setting: The Auto setting is often preferred in the following circumstances:
- Moderate climate conditions where cooling demands are intermittent.
- When energy efficiency is a priority.
- During nighttime or quiet hours to reduce noise levels.
6. FAQs on AC Fan
6.1 Is It OK to Leave AC Fan on All the Time?
Leaving the AC fan on all the time, known as the "fan-only" or "continuous fan" mode, has both advantages and
disadvantages.
Advantages:
1.Improved air circulation: Continuous fan operation can help distribute air more evenly throughout your home,
reducing hot and cold spots.
2.Enhanced air filtration: Running the fan constantly can help filter and purify the air more effectively by
continuously passing it through the air filter.
Disadvantages:
1.Increased energy consumption: Running the fan continuously can lead to higher electricity bills since the fan
motor consumes energy.
2.Potential wear and tear: Continuous operation may put more stress on the fan motor, potentially leading to faster
wear and tear and the need for more frequent maintenance or replacement.
In summary, while leaving the AC fan on all the time can have benefits, it's essential to weigh them against the
increased energy usage and potential maintenance costs. It's generally more common to use the fan in the "AUTO"
mode, where it operates only when the AC or heating system is actively cooling or heating the air.
6.2 What Mode Should My AC be on?
The mode your AC should be on depends on your comfort preferences and the current weather conditions. Here are the
main AC modes:
1.Cooling Mode (Cool): Use this mode when you want to lower the room temperature. Set your desired temperature on
the thermostat.
2.Heating Mode (Heat): This mode is for heating your home during cold weather. It's typically used with heat pumps
or heating systems.
3.Fan-Only Mode (Fan): This circulates air without cooling or heating. It's useful for air circulation and can be
used when you don't need temperature control.
4.Auto Mode (Auto): This mode automatically switches between cooling and heating as needed, maintaining your set
temperature range.
Choose the mode that suits your comfort needs and adjust settings accordingly. Auto mode is efficient for
maintaining a comfortable temperature year-round.
Figure 6: Symbols meaning on the air conditioner panel.
6.3 When to Use Fan Mode in AC?
The "Fan" mode in an AC is used primarily for air circulation without cooling or heating. You may use the "Fan"
mode:
1.Improved Circulation: Use it to enhance air circulation, which can help distribute conditioned air more evenly
throughout a room, reducing hot or cold spots.
2.Air Filtration: The fan can continuously pass air through the air filter, improving indoor air quality by
capturing dust, allergens, and particles.
3.White Noise: Some people use the fan mode for its soothing white noise, which can aid in sleep or create a
background noise buffer.
4.Energy Efficiency: When you only need air circulation and not cooling or heating, using the "Fan" mode can be more
energy-efficient than running the AC in cooling or heating modes.
Remember, the "Fan" mode doesn't actively cool or heat the air but it simply moves it around.
6.4 AC Fan Not Turning on?
If the AC fan isn't turning on, several issues could be the cause.
●Check the thermostat settings to ensure it's in a cooling mode and the temperature is set appropriately.
●Examine the circuit breaker to ensure it hasn't
tripped.
●A malfunctioning capacitor or a faulty motor might be the issue, requiring professional attention.
●Additionally, a broken thermostat, damaged wiring, or issues with the fan relay could be contributing to the problem.
If troubleshooting at the user level doesn't resolve the issue, it's advisable to consult with an HVAC technician to
diagnose and repair any electrical or mechanical problems with the AC unit.
7. Conclusion
Selecting the appropriate fan setting for your AC system plays a crucial role in optimizing your comfort and energy
efficiency. The On setting offers continuous air circulation, improved air filtration, and fresh air exchange but
may consume more energy and generate more noise.
On the other hand, the Auto setting conserves energy, enhances humidity control, and reduces noise but may result in
less consistent air circulation. Consider your climate, personal preferences, and specific needs to determine which
setting is the best fit for your home. Striking the right balance ensures a comfortable environment while minimizing
energy consumption and maximizing efficiency.
