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The Scoop on Variable Speed Motors

May 1, 2013 | Blog

The rising demand for energy-efficient models, increased home comfort and better indoor air quality has pushed the heating and air conditioning industry to incorporate variable speed motors into many of its product lines. But what are these motors anyway? A variable-speed motor is simply a component of an air conditioning and heater system that allows the unit to run at any speed at or between it’s maximum and minimum speeds.

Introducing the product to the average consumer took a little longer than expected. In fact, this product has been around for a long time but didn’t get its start in residential homes until the 1990s. The reason: price. Variable speed motors enable an air conditioner to do a lot more than ever before but, but when they were first introduced, they were costly. Nowadays, the price for a variable-speed motor is not earth-shattering, and the units are standard in residential and commercial settings.

Why Variable Speed Motors are Standard

For many years, the single-speed blower motor was the standard in the industry. When your thermostat told your air conditioner it was too hot or too cold in the home, your system would turn on abruptly, and air came out at one consistent speed until the thermostat was satisfied. Then the whole system would shut down just as quickly as it started.

Then the multi-speed blower motor came along. This is not to be confused with the modern-day variable-speed motor. A multi-speed motor, in many cases, had three speeds. Depending on the load, the motor could run on speed 1, 2, or 3. This was a huge step up from the single-speed and required a circuit board that was much “smarter” and could tell the blower motor what speed to use at what time.

Finally, the variable-speed motor entered the playing field. The new motor could achieve the desired temperature faster and more efficiently than ever before. Instead of limiting itself to one or even three speeds, the motor could run anywhere from 0 RPM to the max RPM of the particular model.

Why Should You Use Variable Speed Motors?

There are three main reasons why you should use an air conditioning unit with a variable-speed motor.

  1. Energy Efficiency: The variable speed motor can ramp up or ramp down to the necessary speed based on the load required for the home. This means extra electricity isn’t being spent during times where the temperature is milder. Secondly, since the circuitry in the system has been upgraded, it knows that after the compressor stops running, the air conditioning coil (evaporator coil) is still cold. So in order to take advantage of that, the circuit board will tell the blower motor to keep running for a little while to blow a little more air across that coil and get every last bit of cold air into the home, making the system much more efficient. The same is true on the heating side.
  2. Comfort: When a system with a variable speed motor starts, it starts very slowly. In most cases, the homeowner cannot even hear it startup. It also does not immediately start blowing really warm or cold air. The temperature slowly increases or decreases, so by the time the system reaches full force, the homeowner may not even realize it’s on because they have gotten used to it. This is opposed to the older systems that sounded like a freight train every time it started up.
  3. In addition, with conventional motors, most people do not use the “Fan On’ setting because it makes the fan run continuously and its fairly loud while using a lot of energy. With a variable speed motor, when the user sets the thermostat to the “Fan on” position, the circuit board will tell the motor to run at a very low speed continuously. This allows the system to constantly circulate air for a lower cost. That prevents warm and cool spots in the home because the air is constantly moving, creating a consistent temperature throughout the house.
  4. Indoor Air Quality: When an air conditioner is on, it cycles air through an air filter, which then releases clean air. In the HVAC industry, we call this “washing the air.” Since a variable-speed motor can run constantly and efficiently, it can continuously wash the air. A frequently changed and high-quality air filter paired with a variable speed motor will make your indoor air quality improve every minute. Of course, the best way to improve indoor air quality is to have an air purifier installed in your home.

To learn more about variable speed blower motors or to learn about how to get one installed in your home, call Lee’s Air to set up a free consultation.

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