About 2 weeks ago I posted a thread here relating how the ECM motor on our new ClimateMaster 27 unit had failed after 6 weeks use.

I was dumbfounded to find out that it take 2 weeks to get a new motor, as each motor has to be programmed for your specific unit by ClimateMaster. Luckily, the a/c tech was able to rig a different, non ECM motor into the unit to keep it running in the interim.

Our A/C company called my wife yesterday, and said they finally have the motor, but wanted to know if we'd mind waiting a few days as they are swamped. She said OK, which is also fine with me, but I have noticed a couple things that I have questions about, thought I'd run them by here first.

Obviously, the spare motor has only one speed setting. My question is the nature of the two stage operation. Is it just higher blower motor settings, or does the compressor actually run at two stages?

There is a monitor panel with the unit that says "Cool 1" and "Cool 2"
I had noticed before the ECM went out, that if you set the thermostat down a few degrees, it would go to "cool 2" for the system to to try to catch up. Right now, the system never goes to cool 2, always stays in cool 1, and seems to be running longer. Of course, it is hotter now, also. Is this a result of putting in a foreign motor? The unit reverts down to the lowest stage and stays there?

Just curious, I can go over all this with the installers later, they've always done a good job.

Two stage operation involves a mechanism that partially unloads the compressor. The compressor keeps turning at the same speed but some of the refrigerant gas bypasses being compressed. The result is that the system operates at about 2/3 capacity in low stage. Blower speed is reduced accordingly via the geo unit's control board interacting with the ECM blower.

Nearly all variable speed air handlers use the same GE / Regency / Beloit series of ECM blowers. From what I've been able to determine online each manufacturer of HVAC equipment custom-configures the ECM blower according to their own CFM and ESP desires. I believe the ECM blowers come in just three sizes - 1/3, 1/2 and 1 HP - HVAC manufacturers choose the power and configure the CFMs per the tonnage and airflow needs of their various air handlers. There may also be custom configurations as to ramp up when the unit starts a cycle

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Curt Kinder

www.hoviscustombuilders.com

Without data, you have but an opinion.
No thing done well is as simple as it seems

I won't repeat what others have said satisfactorily. I am a commercial hvac tech amd have the same unit under the Carrier brand name. I'm in my second year without any ecm problems so far. I am intrigued that your technician rigged up a workable psc motor to get you going. That's fine for a temporary 'get you going kind of thing'.

One of the things about that though is that even if the motor is in the same horsepower range, it will run at one speed for both partial and full loading. Most techs would choose a higher speed "to be safe" and have enough air flow. My guess is that medium or medium high speed would work for you.

It actually may work fairly well on either stage or perhaps not so well. Your psc (permanent split capacitor) motor on one speed almost certainly cannot be optimal, because optimal settings are set up by design, in this case for two different capacities; by engineers, and under actual test conditions when they first decide to release a model heat pump.

One last thought: probably 80% of failures are likely to be the electronics module which can be replaced separately, more cheaply. There is a test box which which geo servicing companies ought to have. The motor which has ball bearings, and is fairly rugged, should hold up fairly well over at least five years; possibly as long as 15