September 12, 2022
Is It Possible to Change the Fan Speed on an Air Conditioner?
Adjusting an air conditioner’s fan speed is no easy feat. Although 400 cubic feet per minute (CFM) is the standard fan setting, each AC make and model may require slight variations. There are also factors that are unique to your St. Louis, MO home that also play a role in determining the ideal rate of air flow. Thus, although it’s possible to make these changes, this is never a job you should attempt to do on your own. Read on to find out why.
Fast, Forceful Air Doesn’t Mean More Efficient Cooling
Often, when homeowners want to adjust their AC fans, it’s because they want to speed them up. Many consumers believe that faster and more forceful airflow will make their homes feel much cooler. In reality, this is rarely the case. In fact, in most instances, speeding the AC fan up can actually make your living environment feel both hotter and more humid.
To understand why this occurs, it’s important to understand the standard cooling process. Rather than “creating” cold air, air conditioners extract warm air from the building’s interior and then cool it down. As warm indoor air passes over an air conditioner’s evaporator coil, refrigerant within this coil absorbs its heat. Although this process is relatively fast, it’s still slow enough for the necessary heat transfer to occur.
When AC fan speeds are raised, warm indoor air moves rapidly over the evaporator coil. As a result, there’s little opportunity for the AC refrigerant to absorb its heat. Even though there’s more air flowing out of the HVAC air vents, it’s either lukewarm or merely cool rather than cold. An air conditioner with the correct fan speed setting should distribute crisp, cold air all of the time.
High AC Fan Speeds and Insufficient Humidity Extraction
In certain environments, speeding a fan up can also result in humidity issues. Your fan speed may be too high if your home feels cool but also feels clammy. During a normal cooling cycle, air conditioners simultaneously cool down the indoor air and remove excess humidity. When cooling cycles are too fast, there isn’t much opportunity for an air conditioner to extract moisture.
With excess indoor humidity, the consequences of setting a fan speed too high can be both serious and widespread, especially if the fan isn’t adjusted within a reasonable amount of time. Constantly having excess moisture in the air during the hottest season of the year can result in mold and mildew growth. Unchecked mold leads to indoor air quality issues, respiratory health issues, and building damage.
Factors That Determine Your Ideal AC Fan Speed
While most air conditioner fans are set to blow air at 400 CFM, this standard setting is representative of a “typical” living environment. It may not account for the overall efficiency of your home or the amount of people that you have living with you. In addition to the rate and force of air delivery, fan speeds affect air temperature, humidity control, and efficiency.
Homes that are highly efficient are usually airtight. They have lots of insulation with high R values, quality weatherstripping, and efficient, multi-pane windows. In this type of environment, an air conditioner’s cooling cycle is invariably shortened given that the demand for cooling is consistently lower than it is in a “typical” and significantly less efficient home. This is known as having a “tight envelope.” In a tight envelope, shorter cooling cycles and less outside airflow both contribute to increases in humidity. This remains true even for homes that have kept their AC fans at the standard setting of 400 CFM. With a tight envelope, a lower setting like 350 CFM is often required.
Other factors that might help an HVAC technician determine your ideal fan setting are:
- The height of your ceilings
- They layout of your home
- The age of your HVAC ductwork
- The air conditioner model you own
Ultimately, these adjustments should always be precise. If they aren’t, your indoor comfort levels can decline and your air conditioner may be subject to unnecessary stress.
When Should Air Conditioner Fan Speeds Be Changed?
Your HVAC technician will check and adjust your AC fan speed when installing any integrated HVAC accessories that you opt to include. For instance, if you decide to have a media filter or an air scrubber put in, your AC fan speed should be adjusted to account for the resulting changes in air pressure that these accessories create. Having HVAC dampers installed is another good reason for having fan settings adjusted.
Whenever major building alterations are made, fan settings should be altered to reflect their effects. This is especially true when homeowners have energy audits performed and take measures to improve their home’s efficiency. Moreover, as your cooling equipment grows older and its efficiency starts to decline, changes in fan speed may be able to offset some of its decreases in overall performance.
Making Model-Specific Adjustments
The correct AC fan speed for any home isn’t just specific to the indoor environment. It’s also specific to the AC model that’s in place. Even if you’ve successfully adjusted the fan speed on an air conditioner before, this doesn’t mean that you’ll be able to correctly adjust the fan on your current AC. To get this task just right, it’s important to have a clear understanding of the needs and nuances of individual air conditioner models. In short, this is a job best left to a trained professional.
Keeping Your AC Warranty Intact
There are several things that homeowners can do to maintain and troubleshoot their air conditioners on their own. For instance, when your air conditioner shuts off unexpectedly, you can try resetting the circuit breaker. At times, simply putting a new AC filter in can resolve cooling system issues. However, whenever maintenance or repairs require you to touch moving parts within the interior of your AC, you should have a licensed HVAC technician take care of the issue instead. This is the only way to ensure that you don’t accidentally void your product warranty or inadvertently cause more problems than you resolve.
Making Sure That No Underlying Problems Exist
Knowing that excessively high fan speeds can make your home warmer and more humid, you may think that resolving these issues is always as simple as lowering the air conditioner’s fan setting. However, with modern home cooling systems, each problem that develops has a lengthy list of possible causes. There might be other reasons why your home feels oppressive and muggy, or why you’ve got warm air coming out of your AC vents. Only licensed HVAC technicians can accurately diagnose air conditioner problems, determine their causes, and resolve them without the risk of voiding product warranties.
Since 1978, Scott-Lee Heating Company has been providing reliable heating and cooling services to homeowners in St. Louis, MO and the surrounding area. We also offer metalwork, geothermal heating solutions, and ductless mini-splits. If you need help adjusting the fan speed in your air conditioner, our seasoned technicians can provide it. Get in touch with us today to get started.