The Daring Dufas wrote:

From looking at the information, I understand that the 1/2hp ECM
motor is the replacement for 1/3 through 1/2hp PSC motors and the
1hp ECM is the replacement for the 3/4 through 1hp motors.

Would you even use a 1/2 hp ECM motor for a home furnace? You certainly
wouldn't save any money if you were replacing a 1/4 hp single-speed PSC
motor with these 1/2 hp ECM units.

The ECM motors are adaptable according to the literature and
have the programming to learn how to operate

How exactly do they do that?

How does a motor know how much CFM the fan is moving?

Are there pressure or flow sensors mounted in the duct work for that?

How would you use one of those replacement motors when you have an
ordinary single-speed PSC motor in a 25+ year old furnace?

Can you apply 115 vac directly to those motors to the appropriate set of
wires to make them operate - to hell with this learning crap?

I don't get this learning crap anyways. What is an ECM motor supposed
to learn? Don't you just want it to turn at a given RPM? Why all the
fuss about finessing the CFM?

If the controller can make the unit start at low RPM and then speed up,
that's great. Do it. Why worry about CFM? If the house isin't
reaching the thermostat set-point fast enough, then speed up the motor,
or turn up the burners.

To me, the feedback the motor controller should get is the difference
between actual house temperature and the thermostat set-point
temperature. The smaller that difference, the slower the motor needs to
turn and the less BTU's the furnace needs to put out. What the actual
CFM is is neither here nor there. If the occupants want to over-ride
the motor RPM to get ambient circulation, then fine, given them the
option for low and medium speed constant circulation mode based on motor
RPM - not on some sort of "learning" crap.