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PSC vs. ECM Motors: Know Their Differences
The heating, ventilation and air conditioning (HVAC) industry uses a variety of motor technologies in its equipment. Historically, the two predominant motor types have been permanent split capacitor (PSC) single speed motors and electronically commutated motors (ECM) with variable-speed capability. HVAC professionals understand the key differences between these motor types. This article aims to share those differences to you today.
PSC Motors
For many years, PSC single-speed motor technology has been the standard in the HVAC industry. It represents the highest installed base.
PSC motors are considered single-speed (speed refers to rate of rotational motion) because they have no internal controls that can be programmed automatically to vary the rotation of the motor over an operating range. In order to make PSC motors more flexible for various applications, speed taps are included to allow the mechanical contractor to manipulate the motor’s speed to ensure that the correct amount of airflow is delivered. There is, of course, a limit to the amount of static pressure the motor can handle, so it is important to keep in mind the optimal performance and safety. As static pressure increases, a PSC motor’s performance tends to drop off because it cannot adjust torque or speed.
Because of its design, there are some disadvantages intrinsic in PSC motors. They are less efficient than other motors because they consume more watts. They are not ideal for continuous fan operation because since they run close to full speed, they use more energy than what the function requires. This also makes them less attractive for other continuous filtration applications. They are also the least quiet among the motor technologies. They do not offer customized airflow patterns that are often critical when it comes to managing humidity.
ECM Motors
ECM variable speed motor technology is highly variable and is ideal for various advanced applications.
ECM technology is based on a direct current (DC) design that is more efficient and it runs cooler than AC PSC motors. They are, in fact, approximately 80% efficient compared to the 60% efficiency rating of PSC designs. ECM motors are programmable. In the case of a failure, the control or the motor can be replaced without having to replace the entire unit. They are also designed to run over a wide range of speeds, making them ideal for delivering airflow in a multitude of system designs. They also draw the least amount of watts, making them the most efficient motor technology. They are also the quietest among the motor technologies since they have the ability to ramp up and down slowly, making them ideal for certain applications with noise concerns.
When it comes to disadvantages, ECM variable-speed motors come at a premium cost.
To see the difference in performance between the two types of motors, check out this chart:
*Chart data courtesy of: Biemayer, P., Lutz, J., & Lekov, A. (2004). Measurement of airflow in residential furnaces*
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My special thanks to Twintech teams! They had replaced my furnace and A/C, and installed a new humidifier for me 2 weeks ago. Dave, the sales manager, not only provided me with an honest quote on the best HVAC products with best quality and warranties, he also arranged portable heaters for me and sent supporting docs to energy company for energy audit. Above and beyond service!
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Great work guys! This company sure knows their products and they stand behind their services. My home comfort level has improved! I am glad that I can support an ethical and honest local family business.
Professional, flexible on price and delivered on time...well done. All you can ask for when getting a new furnace.
The work was done quickly and professionally. Workers were really polite and easy to work with.
Product works great!
Furnace broke down on a Wednesday, shopped around for prices and Friday Twintechs name came up from a referral from my wife's work. Called Dave 11 am, he came over around 1 pm. Gave me a very good price, I accepted. The guys were there two hours later to take the old furnace out and install the new one. All finished by 6:30pm. Finally heat.
They were very pleasant and helpful. As a result we are doing our A/C later this year with this company.
After some extensive research, we settled on Twintech for our new furnace. The service - from Dave's initial visit - through to the installation was absolutely fantastic.
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I've forgotten the names of the installers but they were superb as well. They showed up on-time, did all the work with no mess or intrusion, removed the old furnace and installed the new one in one day; all with no impacts to our day-to-day life.
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Appreciated a quick response to my request. Dave and Greg were very professional and made the experience seamless.
Very professional through the entire process. Installation and removel was done on a sloppy winter day, they put down runners on the floors and stairs and when they left, there wasn;t any sign of someone being in our house. Furnace works great as promised.
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Amazing experience with TwinTech Heating & Cooling! Their team was professional, knowledgeable, and efficient from start to finish. They installed my new furnace quickly and left everything spotless. The technicians took the time to explain everything and made sure I was comfortable with the system before they left. Great customer service and fair pricing. I highly recommend them for anyone needing HVAC services!
Great experience all around. Bob was sharp and easy to talk to, and Greg handled the installation perfectly. Would hire them again in a heartbeat.
The vent shown at the beginning is the only vent in my bedroom, it NEVER has or has had in the 3 or so years of being here had air blowing out of it, rather it almost feels like it's pulling air out of the room. I've shown the duct work it
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