How To Change Blower Speed On Furnace? Essential Guide

Understanding Blower Speed on Furnace

The blower speed on a furnace is key to getting the right air flow and temperature in your living space. You can adjust the blower speed to your liking with many methods.

A common way to control blower speed is with a control board. It alters the motor speed to regulate the airflow into the living room. To find the wiring diagram, you’ll need to look at the user manual or call in a technician. The resistance value allows you to calculate CFM (cubic feet per minute) and temperature rise for efficient heating and cooling.

How To Change Blower Speed On Furnace

By following the service steps, you can adjust the blower speed for ideal HR capacity according to the unit’s size. For instance, 120V PSC blower motors have 3 speeds – low, medium, high – while ECM blower motors are variable-speed units with dip-switches for adjustments. When setting up an ECM blower motor, be sure to note the wiring colors and terminals, and lay them out carefully with insulation and sound deadener.

Knowing the Blower Speed on Furnace is essential for proper AC airflow speed within your HVAC system. High speeds are best in summer while low speeds are better in winter. Using a multimeter helps diagnose wiring color-coding and pin placements from your thermostat.

Basic Components of a Blower Motor System

The blower motor system has several components. These are: blower motor, control board, airflow speed, cold air return, and closet unit. See the table for details.

Blower motorAllows air to be pushed through ducts
Control boardRegulates the speed of the blower motor
Airflow speedSpeed of air movement
Cold air returnPulls air back into the furnace
Close unitHouses the components of the blower motor system

PSC and ECM motors differ in speed. The PSC has a single speed setting, while the ECM has multiple settings that can be altered.

I once serviced a furnace in the summer. The high-speed terminal on the control board was not supplying power to the ECM motor’s high-speed wire. This caused low airflow volumes. After examining resistance values, I realized a wire needed to be replaced.

If you need to adjust your blower speed, here’s what you should do!

Changing Blower Speeds on a Furnace

Adjusting the airflow speed in your furnace requires some thought. In this article, I will guide you through the process.

To change blower motor speed, do these three simple steps:

  1. Locate the control board and remove its cover. Check the wiring diagram to identify where the motor wires connect.
  2. Find out what type of blower motor you have (120V PSC blower or ECM blower). Know how many speeds it can operate on (e.g., high, medium, low).
  3. Adjust the dip switches according to color-coded terminals (red for high speed and yellow for low) next to the wiring diagram. Select desired motor speed and airflow volume for heating or cooling mode.

It’s important to remember that changing blower speeds affects heating/AC airflow and noise level in different rooms. Before making adjustments, calculate the correct CFM rate based on a room’s size and HR capacity required per ton, per local codes.

For instance, Jim Greengo Jun told me about a case when people complained about loud noises from their living room’s cold air return in summer. Increasing airflow would make it worse, so Jim used sound deadener material in the cold-air return grill and insulated ducts from outside with foil-backed insulation. This reduced the vibration and sound level during operation.

If only changing blower speed was as easy as changing your mood! Then we’d all have a constant breeze in our living rooms.

Factors Affecting Blower Speed and Airflow

The blower motor’s speed and airflow are important for an optimal HVAC system. Things that can affect them include the wiring diagram, control board, motor module, the type of blower (PSC or ECM), insulation, damper adjustments, refrigerant charge level, and occupant preferences.

In winter, raise the blower speed to get warm air into living areas. During summer, lower the speed to reduce noise and prevent dryness from cold air return vents.

For variable speed blowers, it’s essential to have proper servicing for optimal HR capacity. Not making adjustments to the HVAC system can lead to uncomfortable temperatures or uneven air distribution. Canceling furnace inspections due to faulty blowers can impact occupants’ health.

For help with model-specific recommendations for optimizing blower speeds, get advice from a professional like Jim Greengo Jun for better energy efficiency and unique demands!

Tips and Best Practices to Change Blower Speed

When it comes to adjusting the blower speed on your furnace, Jim Greengo – an HVAC technician – has some tips. Here’s what you need to know:

Find the Blower MotorIdentify the blower motor and the control board. Identify the wiring diagram for the speed of the blower
Measure ResistanceUse a multimeter to measure the resistance value of each wire. The black wire will have the highest value, while the white wire measures lower. The red or blue wire will have an even lower value.
Adjust Speed SettingsAdjust the settings on the control board. This may involve using dip switches to change settings from “low” to “medium” or “high.”
Check Airflow VolumeMeasure CFM with specialized equipment to ensure your furnace is producing adequate airflow.

ECM blower motors offer variable speeds that automatically adjust airflow. If not insulated well, too little or too much air could flow through the duct system. Use sound deadeners inside supply grille tongs to reduce noise.

Properly install insulation around ducts, including cold air return areas, to maintain consistent temperatures. To achieve a comfortable living environment, you must understand your blower motor and make the right adjustments. Silencing your furnace is the nearest thing we have to hearing nothing at all.

Troubleshooting and Sound Deadening Measures

Consult the wiring diagram of the blower motor. Use a multimeter to test resistance and follow safety measures. Add insulation or sound deadener around the motor module. Keep airflow volume adequate by cleaning/replacing filters, checking airflows through registers and grills.

Be aware of different motor types such as PSC, ECM and variable speed blower motor. They have different power levels that affect HVAC airflow speeds in respective seasons.

For HR capacity units, correctly charge refrigerant as it impacts AC airflow speeds in cooling mode. Refer to service procedures provided by suppliers.

Common Issues and Possible Solutions

As a professional, I have identified common blower speed issues reported on furnaces and their possible solutions. See the table below for details.

IssuePossible Solution
Low Airflow VolumeCheck filter, adjust fan speed, check ductwork, and clean air handler
High Energy ConsumptionCheck motor module, wiring diagram, PM resistance value, CFM rate
Inconsistent Heat/Cold Air ReturnCheck cold air return grille size, damper adjustments, insulation level
Strange Noise from Blower MotorCheck sound deadener placement, motor module sound levels

Remember, each issue may have unique causes depending on the model number and type of system. Furthermore, dip switches or terminal control board settings can affect airflow volume and heating/cooling capacity. Additionally, ECM blower motors provide variable speed options that improve overall energy efficiency and reduce noise levels.

Therefore, understanding the causes behind blower speed issues allows building occupants to make informed decisions. Also, regular maintenance practices like filter replacement and proper insulation between rooms can prevent future problems. So, if you want your blower to keep blowing, make sure to give it the TLC it deserves.

Maintaining Optimal Efficiency and Regular Check-ups

Regularly maintaining and checking the efficiency of your furnace is a must! Here are five tips to help you stay at peak performance:

  • Clean the cold air return grille each month to stop dirt blocking airflow.
  • Switch up the air filter every six weeks, especially in winter.
  • Check all wiring connections are secure and clean. Loose or dirty connections can cause fire risks.
  • Adjust blower motor speed settings on the control board to suit your needs. Get an expert’s help if you lack technical skills.
  • Do annual HVAC preventative maintenance. Like refrigerant charging, heating mode check-up, damper adjustments, belt tension inspection/change if needed, cleaning coils – and insulation on ducts near occupied areas.

Regular maintenance extends the lifespan of your furnace and lowers energy bills. So, it pays off to know your heating capacity per building occupant/HVAC requirements based on local climate zones near/at sea level measurements.

Jim Greengo Jun wrote a blog post on May 25th about adjusting ECM blower motors or PSC variable speed blower motors for different unit models. It can be effective in hot summer periods by circulating cool air inside the house with the right airflow volume (CFM), static pressure measurement across coil sides, and evaporation coil temperature rise. Delta T=10 F is crucial for twinned systems.


Are you wanting to adjust your furnace’s blower speed? Homeowners can easily do this by following the steps in this article. Firstly, understand the wiring diagram of your furnace and identify the model and type of blower motor. It may be necessary to alter dip switches or terminal settings. Use a multimeter to measure resistance values and comprehend CFM ratings for better system performance.

A variable speed blower motor is better than a 120V PSC blower motor. It provides a higher airflow volume with less energy consumption. Sound deadener insulation can also reduce noise from the unit. Refrigerant charging should be done by HVAC professionals.

When heating or cooling, you need to make sure there’s enough tonnage for the building’s occupants needs. Factors like room size and outside weather conditions should be considered. Additionally, dampers and duct design alterations can be used for further adjustments.

In conclusion, understanding your furnace is key if you want to change blower speed successfully. Homeowners can achieve improved AC and heating outcomes by working with professionals (when needed) and following best practices.