No idea> maybe just for start up noise? but our local trane dealer and Johnstone Supply has a universal ECM (have not tried) that supposedly cost less and will fit majority of units

 

It uses less electric, which helps boost the SEER of the unit.

 

Better energy efficiency, and able to do soft starts and stops which is much easier on electrical and mechanical components by reducing inrush current and mechanical stress. Ecms are a miracle motor technology found on many supermarket condenser and evaporator fans. These brushless dc motors are the future!

Not to forget mentioning, these motors are the best type for variable speed. 3 phase ac motor being the other option.

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At full rated load, a efficienct PSC motor uses similar watts to ECM motor. The big benefit is in changing speed to what you want including very slow. Also at less rpm, the ECM motors, watts used decline proportionally. While PSC motors use near full watts at reduced speed.
Regards TB

 

Energy savings.
The motor itself uses less energy, and they will maintain airflow through the condenser coil better.
The GE ones AS/Trane have been using since the 90's are very reliable.

 

the weird part is the name plate said it draws 2.8 amps which seems like alot for a ECM motor I know they are more efficent but I have seen some pretty low hp psc motors in the newer equipment

 

Its probably pulling .7 -.9 A. On Tranes w/ ECM motors you can usually check the amp draw on the brown wire to the fan. The wiring bundle has 2 plugs and eventually goes to a board and I don't think the wiring diagram shows which wire is which but there is only like 6 wires so the process of elimination went pretty quickly.

 

RLA is 2.8 amps. Actual running will be a lot less. Kind of like an x13 on a 2 ton air handler is rated at 4.1 amps, but actually draws about 0.3.

Ditto on the SEER rating. It's all about marketing.

 

I've often wondered about that myself. If you change the ECM to a regular PSC would you then look to match the rated amps on the ECM? They usually seem a little high even for a PSC motor.

 

I'm a commercial guy, with no experience on ECM motors, but can they be used to vary the motor speed up and down beyond simple soft starts? If so, could they be used as part of a head pressure control for low ambient conditions? To maintain sufficient condenser pressure on a cold day. Seems that would also help a tech to troubleshoot and check the charge on a mild to cold day.

 

It's that way on mini split fans. Haven't seen oem do that for conventional split yet.

 

Most of them that I've seen in use on splits are wired for constant speed. Now that we're getting into really high end units with variable capacity I imagine more CFMs will be variable speed to follow the load.

 

ECM condenser motors could ramp up as the coil gets dirty in order to maintain airflow. ECM system could be used as part of a demand defrost system for heat pumps. When used with a full communicating system the homeowner could be alerted on the thermostat when the coil gets dirty. Other uses could be for low ambient operation as previously mentioned.

Not sure how I feel about sticking a motor with a bunch of internal electronic components in the weather...

 

It's a good idea if it is reliable.

 

FWIW...
My 5 year old Affinity unit had very noticeable harmonics on start up. Enough that people in the guest BR (next to the unit) complained. When I got the opportunity I changed the C.U. motor to an ECM type. Made a Hugh difference, you can only hear a hummm now.

 

ECM condenser fan motors are nothing more than a means to get a tinch more efficiency out of an already watt hungry beast. Usually most of the condensing units I see that utilize an ECM motor are married in conjunction with an equally expensive high efficient furnace/air-handler, to offer two stage comfort cooling. And the ECM is nothing more than a pre-programmed expensive two speed motor.
I know that the ramping characteristics will maintain cfm across the condenser coils, thus it will maintain the programmed cfm as the condenser coil gets restricted over time due to lack of maintenance....that is one thing that is a positive about these motors, but that is about it.
Another thing to think about is any local utility company rebates that were being offered at the time...these can drive the up-sell of anything with an ECM/CT motor, in certain areas during certain eras. Our utility company was giving about $250 per ECM, there was a lot of people dooped to drop big bucks on very expensive equipment to take advantage of factory and utility company rebates, to find that they purchased something on credit card under the assumption they would have it payed off in two years with the payback in efficiencies. Now a month after the warranty expires, they are still paying off something they couldn't afford in the first place.....then about poop themselves when you drop the ball on the price to replace one of these bad boy ECM motors.

In all accounts, over my years, I have found the outdoor ECM fan motor quite surprisingly resilient for being an outdoor motor, wonder why some of the weatherproofing methods used on these motors could not have been adopted on the indoor ECM/TC motors, that seem to fry-up with a single droplet of water.

 

Higher resistance rotor on a PSC motor? Not sure how that changes because motor is multispeed.

 

The explanation is a bit complex, but basically, a low resistance rotor gives a "sharp" peak in the torque/speed plot (when driven at a constant frequency) while a high resistance rotor has a much broader peak. If you tried to slow down an induction motor with a low resistance rotor by reducing the flux (what multi speed PSC motors do), you'll find that the speed only goes down a small amount before the motor suddenly stalls.

The way PSC motors can be made multi speed is really a kludge. Maybe someone can do a dyno test of a multi speed vs a single speed PSC motor to see how significant the difference is in practice.

A trick to improving multi speed PSC efficiency when driving from a VFD (or other adjustable voltage supply) is to wire the motor for low speed, then increase the V/Hz ratio such that at the rated frequency, the voltage measured from the high tap to common is the rated voltage of the motor. That makes use of the entire stator winding.

 

Possibly to help with head pressure control

 

Lots of good info in here. I assume these ECM motors are showing up in some less desirable locations simply because the manufactures purchase them in bulk, for reduced cost. Then due to having budgets lower the purchase or use numbers on some other motors to find a home for some of their new ECMs.

 

I know the cheap chinese electronics mostly don't hold up forever.

 

That name is Broad Ocean!
And is sooo true....