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ECM / Variable Speed Motors On Furnaces & Air Handlers

 
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Old 08-04-2013, 04:39 PM   #1
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ECM / Variable Speed Motors On Furnaces & Air Handlers


Yesterday, I had my first repair on a v.s. motor (Trane). I know there is a lot of confusion about how they operate within the industry. So, I was hoping to simplify what they are about. B.T., feel free to chime in, as I am confident you are more famliar than I am.

Basicly, the motor is not a DC motor. It's a three phase motor, that is controlled by a module (bell housing). Within The module itself there is a dc power component that is responsible for controlling the fan speed.

Not sure if the motor is bad? Separate the module from the motor, and omega (continuity test) the three leads. I don't know exactly what the readings should be, but they all should have the same resistance readings across them. Get an o.l. reading, across any of the leads, then you know the fan is bad. If there is no bearring play, wheel spins freely, and equal resistance, then the motor is fine.

Again, my intention is learn the other heater dogs what is up with v.s.. Maybe, I am way off base,as I have gone to several seminars. Just trying to help out
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Old 08-04-2013, 04:57 PM   #2
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


When you say the motor is a VS.....are there several windings in the motor / lead winding pairs that control the speed and is controlled by a relay ,or is the speed varied by a frequency change by something such as a VFD ...

Reason i am asking is There were several Oliver lathes that were variable speed made back in the day (3ph). You changed the 4 speed motor (mechanically-lever handle) . Basically it just engaged different windings on the motor as you moved the lever to what ever speed it was you were after. 12 leads came out and hooked up to the mechanical switch box.


If is being changed electronically (by frequency) then more than likely it would have to be the controller/module. Most 3ph motors are variable speed as long as it has an "f" class insulation (inverter duty )
I'm no hvac guy as you know but do dabble in 3ph motors and VFD's .....

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Old 08-04-2013, 07:27 PM   #3
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


Consider it a 3 phase DC motor.

Ohm check the 3 motor leads to each other as you would a standard 3 phase motor. Should have 20 ohms between each lead. Might have a 10% plus or minus on the 20 ohms.

Then read from each lead to frame ground. Should have 100,000 ohms or more on each lead to ground.

These are the 3 motor lead wires, the ones that connect right from the motor to the module.
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Old 08-04-2013, 08:47 PM   #4
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


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Consider it a 3 phase DC motor.

Ohm check the 3 motor leads to each other as you would a standard 3 phase motor. Should have 20 ohms between each lead. Might have a 10% plus or minus on the 20 ohms.

Then read from each lead to frame ground. Should have 100,000 ohms or more on each lead to ground.

These are the 3 motor lead wires, the ones that connect right from the motor to the module.
I had picked up a motor in case. Went to read the box, and it indicated 120/240 in regards to voltage. That's all a/c isn't it? I am under the impression, the dc module varies the speed via changing the frequencies.
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Old 08-04-2013, 08:48 PM   #5
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


If anyone wants to learn about troubleshooting ECM's, the Genteq Dealer Toolbox site is a great resource. You can either order a copy of their free DVD on ECM's or just watch the videos in the training section on their website. They cover all the needed info for testing windings and modules. You can also download and print copy of their ECM service guide in the link below to keep in the truck. If you happen to be an RSES member, their SAM has several chapters on ECM's you can look over on their website.
www.thedealertoolbox.com

http://www.thedealertoolbox.com/thed...rviceGuide.pdf
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Old 08-04-2013, 09:02 PM   #6
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


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Originally Posted by flashheatingand View Post
I had picked up a motor in case. Went to read the box, and it indicated 120/240 in regards to voltage. That's all a/c isn't it? I am under the impression, the dc module varies the speed via changing the frequencies.
The module is supplied with A/C current, and converts it to D/C current.
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Old 08-16-2013, 12:03 PM   #7
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


I have some great literature somewhere and will try to find it for you. I don't see the ECM in large commercial too much , but I took a great Trane class on it. If you send me a address , I will try and get you my packet. In commercial I deal with more VFDs . All about teamwork!
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Old 08-16-2013, 09:34 PM   #8
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


VFDs are more commercial applications aren't they? I did take a class once that focused on VFD's, and found it interesting. But, I decided to focus my gig on the residential field. For the most part, aren't those motors A/C? I thought the residential ones were a/c as well, but, B.T. set me straight (again ).

The job I went to was as a second opinion, and the guy wasn't impressed with the first guy. I admitted to him, the only difference, is that I had a heads up with what I was going against. Truth is, there is a lot of techs out there that aren't that familiar with v.s. motors.
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Old 08-16-2013, 11:47 PM   #9
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


I have only seen them in light commercial applications. My residential buddies see them all the time. Here in california we have title 24 laws which now require them in all up to 5 ton units. I believe this to be the case, I could be wrong. I was told that by our install dept, gentleman has been doing this a long time and tends to be on top of the new regulations. Carrier uses small ABB drives in some of their smaller units above 5 tons.
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Old 08-17-2013, 04:33 AM   #10
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


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Originally Posted by Jeremy Bednarsh View Post
I have only seen them in light commercial applications. My residential buddies see them all the time. Here in california we have title 24 laws which now require them in all up to 5 ton units. I believe this to be the case, I could be wrong. I was told that by our install dept, gentleman has been doing this a long time and tends to be on top of the new regulations. Carrier uses small ABB drives in some of their smaller units above 5 tons.
Probably doesn't require them to be VS ECM blowers. ECM/X13 blowers are as efficient as VS ECM blowers.
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Old 08-17-2013, 07:29 AM   #11
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


I would surmize that the motors being used are 3ph a/c drives. Not that their couldn't be d/c applications but they would have to have the converter I believe.


VFD's are used for for fans ,pumps , blower applications amongst a lot of other applications outside comercial HVAC situations. Once you becaome familiar with how they function through the Peramiters in the drive it becomes easier to manipulate and configure what ever application it is running.

JMPO ,

Example:
http://youtu.be/Rl29kqVZAOc


B,
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Old 08-17-2013, 09:04 AM   #12
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


Quote:
Originally Posted by PrestigeR&D View Post
I would surmize that the motors being used are 3ph a/c drives. Not that their couldn't be d/c applications but they would have to have the converter I believe.


VFD's are used for for fans ,pumps , blower applications amongst a lot of other applications outside comercial HVAC situations. Once you becaome familiar with how they function through the Peramiters in the drive it becomes easier to manipulate and configure what ever application it is running.

JMPO ,

Example:
http://youtu.be/Rl29kqVZAOc


B,
No, they are DC motors. If the motor goes out. You have to get the motor and module.

A motor on a VFD can be changed out without changing out the VFD control.
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Old 08-17-2013, 10:54 AM   #13
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


You can have a motor failure or a module failure independent of each other. I found this manual online, hopefully this will be helpful.

http://www.prokupmedia.com/seminarfi...m_textbook.pdf
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Old 09-04-2013, 10:08 PM   #14
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


My ECM motor died on my 6 year old Rudd Modulating furnace this spring. It was the control module that was bad. I noticed a burned component on the pcb that turned out to be a thermistor. Long story short, a $3.00 part and 10 minutes with a solder iron and all was back to normal. A new module would have been $140.00. Damn you GE for planned obsolescence.
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Old 09-05-2013, 08:55 AM   #15
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


Props to you for being able to locate the faulty component, finding a replacement thermistor, and fixing the problem yourself. I remember at a e.c.m. course, the guy was mentioning how those thermistors go out due to high static pressures.

It's not a GE. thing. He mentioned that only 8% of high efficiency systems were installed correctly, biggest culprit is the static pressure thing.
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Old 09-11-2013, 06:23 PM   #16
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


It probably does have something to do with static pressure but the thermistors have a limited life span. I'd bet there are hundreds if not thousands of ECM motors in the junk pile because of a $3 part.
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Old 09-11-2013, 06:51 PM   #17
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


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It probably does have something to do with static pressure but the thermistors have a limited life span. I'd bet there are hundreds if not thousands of ECM motors in the junk pile because of a $3 part.
The higher the static, the hotter the thermistor gets. And the quicker it burns up/out.
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Old 09-29-2013, 06:33 PM   #18
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


A little tidbit, but if you disconnect the module and jumper the windings, the shaft gets more difficult to turn. Although Ohming the windings should indicate an issue via the variance in readings, difficulty turning the shaft usually indicates they're shorted together.
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Old 09-29-2013, 11:23 PM   #19
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Re: ECM / Variable Speed Motors On Furnaces & Air Handlers


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Originally Posted by R.J. View Post
A little tidbit, but if you disconnect the module and jumper the windings, the shaft gets more difficult to turn. Although Ohming the windings should indicate an issue via the variance in readings, difficulty turning the shaft usually indicates they're shorted together.
i remember doing an experiment like that in high school physics. we had small hand powered generators and basically turned them into motors by hooking them up (electrically) to each other and trying to turn them in opposite directions and found that you encounter much physical resistance when the windings were hooked together or basically shorted.

see i did remember something useful from high school.

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