But here's the problem. You claimed that slowing down a blower doesn't necessarily reduce the air flow. If you were taking about the pathological case where the blower can't move air because it's cavitating, they you should have pointed that out. Because if that's the case, there is a problem that needs to be fixed with the system that has nothing to do with an ECM vs conventional motor. To do otherwise is just to spread FUD.
Who said anyone was screwing around with anything? In the current discussion, all I saw was Home Guy asking some very relevant questions about ECM motors, including those installed in modern furnaces at the factory.
So then Home Guy's point remains valid. Apparently the motor can't know how much air is actually flowing. Sounds more and more like it's just a multi- speed motor that will be more efficient in most applications, ie those with typical or better ducting. In the typical install, that equates to using 20% less energy. Now, if we don't intend to run our blower 24/7, instead using it only when actually heating or cooling, how much will that amount to?
The question of course remains if cost is the only issue, with typical use, will you save enough in electricity to recover the cost? I'm looking at quotes where it's $1000 more for a 95%efficiency furnace with a two stage burner and variable speed ECM blower, compared to one without those features. Clearly all that cost isn't due to the blower but it comes with it, without choice. Combine that with the exposure to increased repair cost for the ECM and drive electronics and I'm not sure of the value proposition.
If you have issues other than saving energy that the variable speed drive will help with then it's another story. But for me, I don't see that extra value.
Around here, NJ/NYC area, I'd say the majority are not. My house isn't. And I see plenty of new construction where they have dual zone systems, putting one furnace in an unfinished basement, the other in the attic, which is even worse if you keep air moving 24/7.
Also, not one person that's hawking the wonders of variable speed blowers even mentions the above points. It's obvious I don't have a finished basement and not one contractor said a word about it. All of them are spouting mostly what we call marketing BS. Like the variable speed blower in a 5 ton AC is gonna use the same electricity as a 40W bulb. That the furnace which is still rated at
95% AFUE, just like the single stage, is now going to be way more efficient. Both of those are fiction. There's some truth that the furnace will be slightly more efficient when firing at 70%, but from physics and what I've been able to gather, it's a small percentage, a couple percent at best. And around here, it's gonna be firing at 70% in the Fall and Spring, when I use the smallest amount of energy anyway. So the gas usage difference is very slight.You dismissed all the above on the basis that there are lots of finished basements, so the heat lost by constantly pumping hot air through cold basements, garages, attics etc isn't an issue. I say it is.
Explain to us how it's possible to send air through typical ducts in the outside walls of homes when it's 20 outside and not have them lose heat. Maybe you've re-written the laws of physics. Actually it sounds like you have, since you say the air coming out is room temp or better with the burner off. How is it possible to gain heat?
I can take the two stage complexity and the ECM out by simply choosing to not buy it and still get a 95% AFUE furnace. And as to repair cost, he has a valid issue. Are you going to claim that the replacement cost of the ECM motor or drive electronics is the same as a conventional motor? I've seen plenty of stories here over the years of people paying $800 to replace them. If a plain old motor goes, I can replace it for $100. Does that mean all the technology in today's furnaces isn't justified? No, but IMO you can't lump it all together. It's like buying a new car that has headlights that autmatically adjust and react to the cars pitch up or down at any given moment, to maintain them perfectly pointed evenly ahead. A nifty feature? Yes. But when that system goes out, it sure isn't gonna cost the same to fix as a conventional headlamp system.