Pardon me for hijacking the thread, but I have a similar question regarding variable speed, vs mult-speed as well. I am looking at getting a 2-stage Rheem furnace (see my previous post asking about dual-fuel and such) I see on their web page, that they have 2-stage furnaces with variable speed ECM motors, and with PSC motors. Now I am of the thought that a PSC motor is the regular old-school AC induction motor that has been used in appliances and such for the past 70 years or so. They have multiple windings for different speeds. Now, the big question is that on a PSC equipped furnace, does the furnace run the blower on a lower speed winding when it is on a lower heating stage, or does it blow at the designated speed at install all the time? Also, I have heard that the ECM-equipped furnaces are a bit more unreliable because the circuit boards have semiconductors on them regulating the high power requirements of the blower to regulate the speed, versus a PSC motor equipped furnace would merely have relays to switch on and off the different windings, and only be carrying low voltages through the circuit boards.
Am I correct on these assumptions? If not, please correct me.