Unless you can show where someone has made some blower CFM measurements in a real house, then you have no real evidense to support that paradoxical statement.
And in any case, an ECM motor has no way to know how much CFM is being moved by the fan its running, especially as a drop-in replacement for a PSC motor.
And I bet that modern furnaces that come with ECM motors also don't know how much CFM they're actually pushing. They probably only know indirectly by monitoring return-air and output-air temperature difference. Do any of them have an integrated wind-speed sensor?
Then put a number on it.
The home-owner is "often" too stupid ... in some instances. ?
That's a mixed message. You want to say that some arbitrarily large fraction of home-owners would (or are) choosing a fan-speed that too high (you'd have to show me how they have any real control over that, btw) then you back away by saying "in some instances".
You are showing a strange bias against homeowners that is affecting your ability to think rationally about this.
Yes, let's compare these other situations, where micro-power DC motors have been used:
So you think that these tiny, micro-power DC motors make for a good analogy when we're talking about the furnace fan motor market eh?
Tell me how many consumer furnaces were available in 1985 with ECM motors.
And you haven't told me anything to support your claim that ECM motors last longer.
Saying that the first ECM motor was made a hundred years ago, or that GE supposedly actually sold a furnace with an ECM motor in 1969 (which maybe they withdrew from the market a few years later ?) is not an answer to why ECM motors last longer (your claim).
Don't change the subject. We're talking about longevity, not efficiency.
Yes, they run hotter. They are also constantly cooled by the airflow generated by the fan.
Tell me which motor is more likely to survive constant use in a high-resistance duct system? Or survive a fan bearing that gets gummed-up over time? Or a filter that's not properly cared for? Or a power spike or brown-out on the AC grid?
That depends on how many PSC motors are multi-speed vs single speed.
And you can get high-efficienty PSC motors in the range of 62%, as claimed here:
And I suggest you also read this:
Any furnace that has a shaded-pole variable-speed fan motor does have horrible efficiency, and perhaps some people here are confusing shaded-pole motors with PSC motors in these discussions about motor efficiency.
It's clear that when we're talking about 1/4 and 1/3 hp single-speed PSC motors, efficiencies up to 60 - 65% are obviously the norm, and bring us much closer to ECM motor efficiency than most people think possible.
It's clear that some furnace makers are using puny or wimpy ECM motors in their furnaces. But none of the HVAC regulars reading this will chime in and agree.
ECM motors have sophisticated electronics that PSC motors don't have. When-ever you include additional components into any system or device, you have more points of failure. You stubbornly refuse to believe that the electronics in an ECM motor represents an addition point-of-failure that PSC motors simply don't have.