Just wondering if anyone has replaced their conventional furnace / HVAC fan motor (PSC, single phase, etc) with one of the new ECM motors to realize a reduction in your electricity bill.
Does anyone know what the "over-the-counter" cost is of these motors?
Also, do ECM motors generate electrical or RF noise that is either radiated by the motor or fed back into the household wiring, thereby messing up AM radio reception?
What is an ECM motor? Just a few thoughts. Most conventional induction motors don't get that warm, so how much electricity are they wasting? Also; let's say that it is a 200 watt (quarter horsepower motor?) and you can 'save' one quarter of that consumption. Also the motor runs half the time? So saving =3D 0.05 kilowatts x 24/2 =3D 0.6 kilowatt hours per day. At 10 cents per k.watt.hr that =3D 6 cents per day. Roughly $25 per year? Versus cost of new motor? On other hand that 'wasted' electricity is dissipated within the house as heat so the furnace would have to run a few more minutes, burning a little more oil/gas each time to compensate? Might realise more gains by making furnace itself more efficient?
You'll never recoup the cost. Wait for the unit to wear out and then replace it with something more efficient. If the entire unit is hopelessly inefficient, then retrofitting makes no sense; replace the entire unit.
Does anybody know how to use a web search tool?
Probably not; the motor is likely to be inside a metal housing.
you need the electronics to run it, you cant just replace it my Lennox guy said
snipped-for-privacy@Guy.net (Some Guy) wrote in news: snipped-for-privacy@Guy.net:
Maybe, maybe not.
If you bought a commercial furnace that included one, the complete assembly would have to comply with FCC regulations (or those of your own national regulating body, if you're not in the US) regarding EMI in a household environment, so you shouldn't experience any radio interference.
On the other hand, if you just go buy some random motor that happens to fit in your old furnace, you won't know 'til you fire it up.
Conventional small AC motors (fractional HP motors) are VERY inefficient at converting electricity into motion. I've seen numbers around 50% efficiency.
Many new furnaces today come with ECM motors because furnace fans run longer (higher duty cycle) in modern HVAC systems today vs 20+ years ago.
If the cost of an ECM motor is, say, less than $200 (for the do-it-yourself-er) then it's highly likely that just replacing a conventional AC motor with an ECM motor in an existing furnace would pay itself back in 1 to 2 years - plus you have the existing motor as a backup if or when the ECM motor breaks down.
There are many mid-efficiency (80%) furnaces out there that DON't have ECM motors, and there are many older furnaces that with simple additions and modifications to intake and exhaust ducting (and by turning down the burners and adjusting the burner primary air baffles) can bring them to near 80% efficiency. You can convert a 30-year-old
60% efficient furnance to closed-combustion with some ducting and modification to the cabinet's venting for example.Nobody's posting any over-the-counter or "cash'n'carry" prices for these motors on their websites.
I don't think too many of them are being sold for retro-fit or non-HVAC systems.
In fact, there may even be supply shortages such that all production is going straight to HVAC manufacturers.
My experience with electronically-controlled, variable-speed AC motors (that you find in some treadmills and science-labs fume hoods) is that they are extremely noisy (EM/RF noise) and without a lot of filtering they inject a lot of noise back into the main supply wiring.
If there is a lot of high-current switching going on inside an ECM motor, then I would think they too would be electrically noisy.
I'm pretty sure that's not correct.
From what I can tell, all the electronics are inside the motor. You hook up the main AC supply directly to the motor, just like a conventional AC motor.
This furnace "modification" suggestion sounds very dubious and full of obvious and potentially serious drawbacks to me. Like people screwing around and winding up killing a house full of people with CO or fire. If you have a 60% 30 year old furnace and it's worth increasing it's efficiency, then it's worth getting a new furnace.
It sounds like a tumor transplant to me. I put a regular motor in my Trane air handler when the ECM motor went bad. They wanted over $1000 for the motor. Nobody could convince me I was going to save $125 a year with this (the original lasted 8 years)
PV
Actually, the main benefits from a true variable speed are comfort and noise reduction. Energy saving is just a fringe benefit. What you are wanting to do is certainly possible. You could retrofit a Model T engine to electronic fuel injection with enough time and money. I seriously doubt you are going to find an ECM for any where near $200 though. Fwiw, we have installed a lot of variable speed furnaces and air handlers (mostly Trane, Amana and Carrier) and I have not heard of any problems with electrical noise at all. Good luck with your project if you go thru with it. Larry
I checked comparitive airflow and watts consumed at the Lennox site years ago, I saw a 20% increase in efficency. The motor was 600, not
200$, Noise will be introduced from non shielded wiring and electronics into your tv, I think Trane had an issue with that a few years ago. As a retrofit my lennox dealer said no, at least you wont get any variable speed which is what the whole deal is about, a low speed on AC mode 50% more moisure is removed. I looked into doing it and decided it was not worth it.
But the motor is outside the conditioned-air area, so it won't affect the heating/cooling.
Assuming the motor costs $200, according to your calculations you would break even in only eight years.
However, there is the opportunity cost to consider. $200 in a savings account instead of a new motor, at 6% interest, generates $12 per year, making the savings only $13. At that rate, the break-even point occurs in fifteen years.
Then there's the labor to install the motor, increased taxes, and other variables.
Where can you get a 600$ vsdc motor for 200?
ECM motors require a control signal in addition to line voltage. Also, you cannot just wire the power to the motor, it requires a pre- wired molex plug specifically designed to plug into the motor. Likewise for the control signal. A control board is also required, that is, unless you know how to hot wire the motor control signal.
There is however a new ECM design avialable called the "Evergreen AH". It is specifically designed as a retrofit for PSC motors. I have no idea how much they cost. They are not rated at this time for furnaces, air handlers only. This limitation can also be worked around by someone with the correct skills.
The retrofit isn't really practical from any standpoint, even though it is possible to do.
Not really. You can create a closed-loop for the intake air very simply with the appropriate additions of ductwork that takes outside air directly into the cabinet and sealing the cabinet so that the combustion side can't mix with household air. The secondary flue air intake (directly below where the flue starts) can also be sealed and ducted so that it pulls air from a dedicated outside supply duct and not from household air near the furnace. So in this scenario no outside air can enter the house through the flue, and no combustion products or gasses can enter the interior air of the house.
That is exactly what mid and high efficiency furnaces do, and there's no reason the same mods can't be done with low efficiency furnaces that are 20+ years old.
You're actually making it safer by creating a closed loop. By doing so, there is no way that the blower can suck air back through the flue. Given an un-modified low-efficiency furnace, that's exactly what can happen if the house is sealed too tightly and too many exhaust fans are operating in the house.
The furnaces made today are riddled with problems with short-lived heat exchangers, sensors and electronic controllers.
Have a look at this site for an example of a poorly-designed secondary heat exchanger:
Was that $1000 for the motor only, or did it include labor?
How old was the Trane unit? I'm surprised that the motor wasn't covered by at least a 5 year parts warranty (and more likely 10 year parts warranty) - given that I don't think that ECM motors have been around for more than 5 years.
The retail price for some mid and high-efficiency furnaces (with ECM motors) is usually less then $3500, so I can't see the motor alone costing $1000.
Actually, you're wrong.
There are some ECM motors that are single or maybe dual-speed (not variable speed).
The main benefit DOES come from more efficiency at converting electricity into motion.
No it isn't generally accepted. What you're referring to isn't unsolved problems, what it's called is "planned obsolescence". If it doens't break they can't sell you a new one. The hvac industry is a relative late-comer to that game, thats all.
What's the difference between a furnace-fan motor and an air-handler-fan motor?
Seems you're wrong. It's being marketed directly to HVAC repair shops exactly as a replacement for furnace PSC motors.
"Evergreen AH is the world?s first high-efficiency ECM replacement motor that is designed to replace factory PSC blower motors in residential air handlers. That means you can now offer your customers the comfort and efficiency of ECM in an easy-to-install replacement motor.
Built from the same trusted, field-proven ECM technology that is found in millions of OEM systems nationwide, Evergreen AH uses up to 25% fewer watts in operating mode and up to 74% fewer Watts than a PSC motor in constant fan."
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