31 Jul

Variable Speed Blowers

Until faced with purchasing a HVAC system, most people think of air conditioning or furnaces simply as providing cool or warm air. Not until we have brochures in hand and a salesperson in front of us do we realize just how sophisticated, complex and varied the options on a HVAC system can be. Blower, or motor, speed is one options that will need to be considered. As a new HVAC system is a long term investment, expected to last about 15 years, being informed helps to make wise decisions.

Here is a basic primer on how blower speeds differ and what to think about when faced with a repair or HVAC investment.

The term “speed” actually refers to the blower motor inside the furnace or air handler. In modern units, most are variable speed, which are an electronically commutated motor, or (ECM). ECMs are low-maintenance, energy efficient, and have lower operating costs. The initial cost of a furnace with an ECM will be higher than a traditional single speed furnace, but the typical payback on a variable speed furnace is just 4 to 5 years.

Unlike conventional fan motors, a variable speed blower motor runs at different speeds to precisely control the flow of heated or cooled air throughout your home. Better airflow control means a better balance of temperature and humidity.

Since we are talking about motor speeds, let’s use an analogy that most of us can related to easily – regulating a car’s speed.


On or Off

For many years, the single speed blower motor was the standard in the industry. Think of a car as being either on or off, running at one speed only. When your thermostat tells your system it is too hot or too cold in the home, your system will turn on abruptly, the blower motor turns on, and air comes out at one consistent speed until the thermostat is satisfied. The whole system shuts down just as quickly as it started.


Static Settings

The multi-speed blower has been the “standard” blower type for a few decades. You have more control over the speed of the car but are limited to predetermined speeds. These motors tend to have 3 settings, which you can select based on average airflow needs – low, medium or high. You have greater control of the blower speed, but not much precision in adjusting comfort levels.


Cruise Control

Finally, the variable speed motor comes along. This modern type of motor works more like a car’s gas pedal that has cruise control. The variable speed blower motor is completely adjustable and can run at any level between 0 RPM and the maximum possible speed for the motor. You are able to select exactly the temperature you desire, and the motor will adjust to run precisely and automatically at a steady speed. Until you change your mind.

Even when your AC or furnace isn’t running, the variable speed blower stays on most of the time, but at a low, energy efficient setting. Operating in this way, it can constantly clean your air if you have an air cleaner or constantly humidify your air if you have a humidifier.


Benefits of Variable Speed Blower

The technology for these variable speed blower motors actually has been around for some time and is tried and tested in commercial and industrial applications. Only since the 1990s has variable speed blowers been used in the residential applications. This means the technology in units being installed in homes today are designed to be long lasting, offering homeowners several benefits. Variable speed blowers:

  • Perform better so consume roughly two-thirds less electricity, saving you on electric bills
  • Operate quietly by ramping up motor speed slowly and only running at higher levels during the most extreme weather days
  • Offer better humidity control by removing more moisture from the air
  • Offer better air quality control by slowly circulating air, allowing air filters to capture more contaminants
  • Work well for homes with zones, which allows you to customize your comfort in different areas of your home
  • Have greater reliability as they can adjust to situations that are not ideal, making them more flexible and robust.

The advanced technology found in today’s variable speed blowers constantly monitors the data coming from your heating and cooling system, automatically making necessary adjustments to meet your comfort needs. They can adjust the amount of circulated air, compensate for factors like dirty filters or blocked vents by increasing the fan speed, and simply make your home more comfortable.

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