HVAC Fan Speed Too High – What To Do?

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For your HVAC unit to operate optimally, it needs to run as per the speed stated in the manual. However, sometimes the fan speed can be too high, creating an uncomfortable environment. Will your unit still function at full capacity? Can the speed be lowered? We did thorough research to give you answers.

An AC that runs at high speed, may not adequately dehumidify your home during summer. The solution is to lower the speed to the required level, by following the steps below:

  • Disconnect the power.
    • Switch off the power from the AC unit.
    • Switch off from the main panel.
  • Identify the blower fan and the speed wires.
    • Remove the air handler.
    • Locate the speed wires.
  • Change the speed.
    • Move the high-speed wire to low.
  • Test the new speed.
    • Put the air handler back.
    • Switch the power back on and test it.

Continue reading to learn how to lower the fan speed. We'll also elaborate on the reasons for the high speed. Find out too, how a high fan speed can interfere with the optimal operating capacity of your appliance unit. Also, understand the benefits of lowering to the right speed level.  

Air conditioner repairman in uniform using a volt meterAir conditioner repairman in uniform using a volt meter -

How  T0 Lower The Fan Speed Of Your HVAC Unit

Top view of an air conditioner unit outdoors in hot summer season. No people.

According to HVAC professionals, the speed of an AC fan should be 400 CFM  airflow per ton, though it can vary depending on the weather.  A dry climate will require a 400 CFM per ton. A humid climate, on the other hand, needs a fan speed of 350 per ton. And so, if the fan speed happens to be higher than 350 CFM when the weather is humid, it will need to be adjusted lower to the correct level. 

So, let's find out here how you can lower the speed of your HVAC:

Disconnect The Power

As with all electrical appliances, switch off the power before any repairs. It is also best to call an HVAC professional if you do not have the skills or if you're not up to the task.

Switch off the power from the main panel and electrical outlet. It will protect you against potential electric shocks. 

Locate The Blower And The Speed Wires

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Look for where the blower is and identify the speed wires. Go through the manual and learn the colors of the speed wires. Please note there are two brown wires connected to the capacitor. They are not related to the fan speed. 

Speed wires can be blue, yellow, green, and black. For example, in some AC units, black is for high speed, yellow is medium-high, blue for medium, and red for low. 

Change The Speed

By carefully following the instructions in the manual, move the high-speed wire to a lower speed. If you find that the blue wire is high-speed, then position it to low, and if the black wire is high-speed, lower it. 

Test The New Speed

Switch the power back 'on' at the main panel and the electrical outlet. There should be a change in the speed. As the seasons change, you can change the fan speed as well. 

Watch this video that explains how to lower the fan speed of an AC unit:

Benefits Of Lowering The Fan Speed

Testing with an anemometer of an axial fan of the condensing unit

If you want a much cooler environment, increasing the speed of your HVAC unit is the answer. But, as seen earlier in this post, the humidity levels will remain high, unless the fan speed is lowered.

With that in mind, are there other benefits of lowering the fan speed? Let’s find out below:

Less Noise

A high-speed fan rotates more air but is accompanied by more noise. This happens because there is more friction between the bearings as the fan rotates faster. 

The opposite is true when the fan is slower. There’s less friction and thus less noise

Excellent For Use At Night

The HVAC works efficiently more at night than during the day when the cooling capacity is low and the humidity levels are high. 

Is It Worth Upgrading Your Unit To Variable Speed?

Air Conditioning Technician and A part of preparing to install new air conditioner.

For your HVAC to cool your home, office, or any other space more efficiently, you can upgrade it to variable speed. This means replacing the conventional motor in your unit with a variable speed motor. 

You will no longer need to lower the speed manually, instead the variable speed motor blower will change the speed automatically

It consistently cools your environment because it monitors data from your cooling system and increases or lowers the airflow. Subsequently, it balances the humidity and temperature to the required levels. 

In addition, there are other benefits of variable speed in your HVAC system. Let’s explore them to help you decide on whether to upgrade your unit to variable-speed or not:

Improved Air Quality

Since air flows continuously through the filter of an AC with variable speed, pollutants are reduced. More dust, dirt, pollen, and other debris are prevented from passing through the filter, making the air cleaner.

Improved air quality prevents respiratory issues such as asthma. It also reduces many other health problems such as fatigue, allergies, and sore throats, brought about by low-quality air.

Extra Comfort

As mentioned earlier in this post, your home will be more comfortable because a variable-speed HVAC system automatically adjusts the airflow to maintain the right temperature and humidity levels. 

Thus, the temperatures will not fluctuate, and there will be no moments when it is too cold.

Reduction Of Energy Bills

Since there is improved energy efficiency, the operating costs likewise decrease. The conventional blower uses at least 500 watts of electricity, while a variable-speed AC unit uses less than 100 watts. 

Longer Lifespan For HVAC System

An AC system with variable speed motor works at a moderately low rate. Or in other words, it does not overwork because it does not have to turn on and off numerous times. Wear and tear are reduced, making it last longer.

Noise reduction

A variable-speed AC unit works more quietly. It slowly increases the speed, as opposed to the conventional AC motors that suddenly roar when air is blasted through the ducts. 

How Much Does It Cost To Lower The Speed Of An HVAC Unit?

Air conditioner repairman in uniform using a volt meterAir conditioner repairman in uniform using a volt meter.Take a look at my LIGHTBOXS with other related images.

If you need to repair your one-speed motor blower, it will cost you approximately $450 and $600 for a variable-speed motor. 

Depending on how long the technician takes to complete the job, usually between 1 ½ to 2 ½ hours, you can figure out how much you will spend on labor since the technician professionals charge between $75 and $125 per hour.

Does your motor blower need replacement? The costs vary depending on the brand. For example, a Rheem motor blower would cost between $250 and $900, while a York blower costs from $150 to $1,800. 

If you want to repair the blower yourself to save on costs, there may be a few questions you may need to ask yourself, before making a decision:

  • Are you adequately skilled to repair or install an HVAC unit?
  • Are you sure it is the motor that has a problem?
  • What is the root cause of the problem?

If you cannot answer in the affirmative to the above questions, you are better off calling an HVAC professional. Also, remember that the HVAC machines are complex and require a thorough inspection to find out the problem and provide a viable solution. 

In Closing

When the humidity levels are too high, the solution is to lower the speed of your HVAC unit. When the fan rotates at high speeds, the unit only provides a cooling effect. But when the speed is lowered, the AC can reduce the moisture levels and equally cool the area.

A variable-speed motor blower provides a more efficient cooling effect. This is made possible as it works by cooling continuously because the fan speeds are automatically adjusted. The costs of repair and installation of the different motor blowers, including the variable-speed blower, largely depend on how long it takes and the brand of the blower. 

Have a look at our previous posts and learn how to adjust the fan speed on your furnace and what to do when the fan of your Rheem air conditioner is not working:

 How To Adjust Fan Speed On Furnace

Rheem Air Conditioner Fan Not Working

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