PSC Motor vs Constant Torque Motor vs Variable Speed Motor | Comparison Video

This is a comparison video of a PSC Motor vs Constant Torque Motor vs Variable Speed Motor. We will explain what a variable speed motor is, and how it is different from a constant torque motor. We will also discuss the difference between a regular permanent split capacitor motor and an ECM motor. I'd like to discuss the benefits of a constant torque motor and if it can save money for you.

PSC motors are simple, fairly inexpensive, moderately efficient motors with a reputation for being loud and not very dynamic. They also come hitched with the always unpredictable capacitor, which can go out due to overheating.

ECM constant torque and ECM variable-speed motors are pretty complex in design, high-efficiency motors, known for being much quieter on start-up and shutdown. Their ability to control airflow better than PSC motors makes them smart motors because they can ramp up power as needed (the variable speed more so than the constant torque motor.) All of this comes with a higher price tag, though, when it comes to repairs.

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00:00 Intro
2:18 PSC Motors
4:47 ECM Constant Torque Motor
8:42 ECM Variable Speed Motor
12:10 Conclusion

[InsideOfMyOwnMind]

Great explanation of the motor types. You covered exactly all the things I was wondering about.

[ralphriffle]

This Gentleman is giving a lecture at an academic level equal to a professor at the graduate level.

[robinwboyd]

Excellent explanation of these three types of motors. I am an HVAC instructor for a college HVAC course as well as tech support for HVAC technicians. This is the best overall explanation for these motors I have heard.

[danam]

The ECM in our furnace failed over Christmas while we were out of town. The service company would not honor their lifetime warranty sold to the previous owner, but the technicians showed me the small, overvoltage protection device had failed, shutting down the motor. They wanted more than $1000 to replace the entire motor plus controller assembly. I told the technician I would have to think about replacing the motor. I paid him for his service call and then ordered the new part online for delivery the next day. The part arrived, I took out the remains of the failed part, soldered in the new part and it has been working fine and for the last eight years. I spent $35 for the part and shipping. I got a spare just in case the part fails again. I wonder how many people’s financial lives fall apart because they can’t make a $25 repair of something that is essential to modern life.
The part which failed was a surge suppressor in which research indicated a vulnerability to power cycles and surges. The explosive failure of the part coincided with a power outage and subsequent restoration. That were very likely to have caused voltage surges. I have sense installed a whole house, surge, suppression device at my electrical panel.

[baileysair]

Good video, but you got the PSC and ECM amp draws backwards. PSC motors love high static and restricted duct work, they draw less amps and deliver less air because they are one speed only High, Med., or Low. depending on how they are wired. So, when the ducts and or coil are restricted the amp draws will be less on a PSC compared to a ECM. However, the exact opposite happens to the ECM because they are constant torque, and always will ramp up to deliver the programmed cfm, they will pull more amps with restricted ducts while trying to deliver the right amount of CFM. In fact, this is one reason ECM motors don't seem to last as long as a PSC, when they have restricted ducts or coils they are running at much higher rpm's, basically max rpm's and pulling max current, which makes them fail prematurely.

In the past this was a dirty little secret, where the contractor would put in a variable speed motor to overcome duct work problems, sacrificing efficiency for better airflow, instead of fixing the duct problems. Now, because of the FER Fan Efficiency Rules we have to use a ECM motor on almost all systems. So, it is imperative that you take a static pressure of the old system, including a duct leakage test to determine duct work problems and fix the ducts before replacing that old PSC system with an ECM. Otherwise, you will be back out in a few years replacing a motor that costs over a thousand dollars.

Good video

[austindillon]

PSC motors draw fewer amps under high static / restricted conditions

The Split phase refers to the fact that the capacitor creates a phase shift which creates a difference in phase angle between the run and start windings - residential power from the utility, regardless of voltage, is single phase there is no phase difference between the legs; just potential difference

[watermanone]

Nice explanation: However I don't know any tech's that carry both parts of an ECM motor. Most of them change the whole thing and not split the motor and change the affected part. One replacement will wipe out all the savings that ECM motors may have produced.

[vorteck]

Capacitor takes the place of a shaded pole and provides the 90 degree phase shift needed for a PSC motor to turn. It is pretty cool seeing it in an oscilloscope.

[Garth]

Cost of ownership plays an important role for most folks I believe. If a variable speed motor is going to be 4 times the cost of a PSC, it does make one wonder if they want that supposed to be "20%" savings and less noise. It also is important to know that those higher end motors have PCB, circuit boards, with solder joints, printed circuits and electronics on them that will also likely find more break downs vs. PSC. Sometimes it is best to stay with old reliable and focus on other mechanic parts that can be more efficient that don't have a short or limited life cycle. We all know that much of today's parts are made with less quality, robust and longevity in mind so a $750 motor replacement once seems more interesting than a $2, 800 replacement likely three times during an HVAC lifespan.

[skutahuniai]

Good video but your description of the PSC is not correct. The utility does nothing to operate this motor other than supply the operational voltage. The utility does not "split" anything. It is the capacitor that provides a shift in the phases between the two windings, thereby allowing rotational forces.

[jpvalentine]

The difference is price not worth it tho. Psc all day

[JA-vygp]

Great video man thank you for the knowledge, been hvac for 2 years now got a lot to learn

[andrewrolfe]

S-Split, comes from Phase Shift that takes place in a stator winding set perpendicular to the run winding in the stator. It is less inductive than the run and in series with a capacitor. The combination of the ANGLE and capacitors leading current "Shifts" and "splits" the phase and attempts to achieve an optimal 90deg shift.

[leonardkellum]

I'm a retired electronics technician, the short lifespan of our parts is due to "designed obsolescence" from a short sighted type in Detroit, AND capitalism's insane allowance of allowing limited resources to be wasted in lousy products imo. I would like to add more restrictive filtering to my furnace blower motor. Ive ordered a manual D, and considering a bigger psc motor, thanks to your honest cost assessment. Thank you for a good video.

[BryanTorok]

I looked at the prices in your chart. Those prices seemed awfully high to me. The last time I replaced a blower motor a generic 1/3 or 1/2 HP motor was under $50. Well, I just checked Amazon and those motors are $125 to $250. And, Grainger's prices run into the $500 to $600 range.

[bjleau]

New eco motor complete with install is $430… not thousands or am I missing something

[larrymartin]

your knowledge and detailed explanation is greatly appreciated. i learn something from every one of your tutorials.

[MattSpradley-EVTHVAC]

Awesome break down video of each motor. Thank you

[sherriefox]

3-4 weeks ago I read your posts about insulation in vents. I had same problem . Brother in law said i was being neurotic thinking it was from animals. Well it was Rodents--- MICE in particular. Had H/V Guy over to fix ducts, & exterminators over for MICE. Thanks to your post I stuck to my guns knowing something was Wrong. Always go w/gut feeling & thanks to you guys problem solved!!!

[mythril]

The incredibly high quotes I've gotten for repairs or new systems made me so angry... I now own all the special tools (bender, swager, gauges, recovery unit, scales, probes, brazing etc..) Educated the crap out of myself, became certified for the gasses and now perform 100% of my own work. My systems in my homes perform perfect with exact humidity/air/temp control and my repairs cost little to nothing, even ECM or full VFD 3 phase motors, I am also a high and low voltage electronic controls expert, that helps a lot. My variable speed systems are all 3 phase VFD driven with single phase inputs, now were talking my language.