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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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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.
Dave was very pleasant to deal with and Twintech responded quickly when our furnace needed to be replaced ASAP. Installation was done on time and the crew were neat and tidy. We now have a great furnace that suits the needs of our family.
When your furnace kicks in over the holidays and you're not sure where to turn.. I'm so thankful that this company returned my phone call. I appreciated their transparency and clarity which allowed me to make an informed decision. With various quotes thrown at you, it can be difficult to make the right decision and trust the solutions offered by different companies. TwinTech spoke the truth and delivered on their word. Neat, timely and clean service; the peace of mind I needed during a very cold holiday season. I highly recommend them!
Pulling a old unit out and installing a modern heating system! Required drilling holes in the wall for the newer pipes. We went from 70% (I am willing to bet it was far less due to lack of maintenance and just old) to 96% newer . It now feels warmer and more pressure and we use to run extra heaters and feel as though they are not necessary!
I received three quotes before deciding to choose Twintech. Dave's prices was much more reasonable than the competitors. I most appreciated their honest recommendations. Others tried to oversell their products and services. Thank you Dave!
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My 19 year old furnace stopped working when the cold weather hit in November, and I was left without heat. I interviewed several companies and found TWINTECH HEATING and COOLING to be very knowledgeable, quick to respond to my inquiries and very competitively priced.
Dave provided all of the information and pricing ahead of time and set up the appointment for the installation. Greg and Mitch arrived on time to do the installation and worked quickly and efficiently to complete the job.
After the completion of the installation, Dave followed up to ensure that everything was working well and that I didn't have any concerns.
Overall, this was a low-stress and flawless experience from start to finish. I would highly recommend TWINTECH HEATING and COOLING to anyone that requires a new furnace.
Our 20 year old furnace broke down during the first cold weekend this past November and our usual HVAC company never returned our phone call. Their loss, missing out on a sale since we didn't want to spend much fixing an old furnace and our 40 year old air conditioner was also long overdue for replacement. We proceeded in obtaining three different quotes for furnace and air conditioner replacement, and proceeded with the one we received from Twintech.
Dave was friendly, knowledgable and accommodating to our schedule and provided with us with a price that fell in the middle of the three quotes that we had. We felt that the Amana furnace and air conditioner he quoted us on were the best products and value offered to us and felt most comfortable with the professionalism and reputation of Twintech.
Greg, Grant and Mitch were at our house for installation the day after we decided to proceed. The guys were friendly and informative, the job was completed efficiently and workmanship appears excellent. Our house is certainly much more comfortable with the new two-stage variable speed Amana furnace compared to the old clunker! And, we're looking forward to enjoying the new air conditioner once summer rolls around again. Thanks Twintech!
We are very happy to recommend this company to everyone. Our furnace broke down on Sunday morning. We phoned them and before noon Grant the owner showed up. He worked on the furnace for about a hour not wanting to give up to fix the problem. The furnace was 17 years old. I was the one talking about replacing it. End result was the next day it was all done. On the Sunday Bob came over with heaters to warm up the house. We decided to replace the water heater at the same time. Thanks Grant for the excellent work. Thumbs up.
Right on time. Explained how to work the HRV in a different way so the house would not be so dry. Changed my whole house water filter for me as well. Friendly, helpful, caring service!
Very pleased with the professional service that TwinTech Heating and Cooling provided in replacing my furnace. I got several quotes from different service providers. Their price was excellent and they explained the features very well. We are very glad we went with TwinTech and highly recommend their services.
We were new homeowners in need of a second opinion. TwinTech Heating & Cooling were Amazing and professional. Very knowledgeable and great service all around. Recommend to anyone looking for honest and reliable services. Treated with respect and care. Thank you Greg, Mitch and Bob!
TwinTech is an excellent and honest company! I called them for a second opinion after being told by another company that I needed to replace my furnace. Turns out this was not the case at all! I did not need a new furnace. TwinTech did not push to make an unnecessary sale and saved me from a huge expense. Bob and Mitch were extremely professional and above all honest! I definitely recommend TwinTech!
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