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  1. #1
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    What is an ECM motor?

    I want an energy efficient blower fan motor, and have seen in other threads these referred to as ECM. What does ECM mean? Are all the variable speed blower fan motors ECM, or do I need to specify that?

    Thanks

  2. #2
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    Upsized heat better for night setback?

    I know I am asking a lot of questions, but its because I keep getting great answers. Thanks in advance, everyone.

    I will downsize my cooling from 3 tons to 2.5 or 2 tons, since I made my house more energy efficient. I don't change my temp setting much in the summer.

    But in the winter I regularly set the temps back from 70 to 60 from about 9pm to 6:30 am. The temperature rarely drifts all the way to 60 during that time--if the furnace comes on before 6:30 am, I know it is really cold outside (for Charlotte).

    I assume I should keep my gas furnace a bit oversized so it can get back to normal fairly quickly each morning, and that my current practice of doing the night setback saves money. I would not think there is a big downside to a larger gas furnace like there is to a oversized heatpump.

    Will I be getting everything out of whack if I have a three ton gas furnace with its associated blower paired with a 2 ton heat pump in a dual fuel system?

    Is a three ton gas furnace going to say 36,000 btuh output, or are they measured differently? I am confused because one quote says 3.5 ton furnace at 57,000 btu. I would have thought 3.5 tons was 42,000.

    PS-- Sorry--Meant to make separate thread.
    Last edited by Maikerum; 07-01-2010 at 04:17 PM. Reason: meant to make separate thread

  3. #3
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    Quote Originally Posted by Maikerum View Post
    I want an energy efficient blower fan motor, and have seen in other threads these referred to as ECM. What does ECM mean? Are all the variable speed blower fan motors ECM, or do I need to specify that?

    Thanks
    ECM = Electronically Commutated Motor. It's a DC motor. Here's a pdf with more info
    http://www.nailor.com/pdf/ecm_1.pdf

    VS blower motors are ECM. not all ECM are VS like X-13

  4. #4
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    Quote Originally Posted by Maikerum View Post

    Is a three ton gas furnace going to say 36,000 btuh output, or are they measured differently? I am confused because one quote says 3.5 ton furnace at 57,000 btu. I would have thought 3.5 tons was 42,000.

    PS-- Sorry--Meant to make separate thread.
    Normally a furnace is rated in BTUs and cooling in tons (but you may also see cooling specs in BTUs). The 3.5 ton number you see on the furnace is the blower rating, meaning it can support a 3.5 ton (42000) cooling unit (blower has a max of at least 1400 CFM).

    Blower speeds (CFM) are set separately for heating and cooling.

  5. #5
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    New York State
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    Th eproblem with over sizing a gas furnace is that you waste energy and you might short cycle the unit. What you should do is install a variable speed blower furncae(ECM) with a modulating gas valve. This will give you the best effeciency. Carrier has a hybrid system for this. I believe it is their Infinity sysytem.

    Gas furnaces are rated in btu's for heat. The blower is rated in cfm. The heat pump a refrigeration unit is also rated in tons and btu's. One ton is equal to 12,000 btu's. You have to remember these are seperate items. One is a gas furnace, the other a refrigeration unit.

  6. #6
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    Quote Originally Posted by Maikerum View Post
    I want an energy efficient blower fan motor, and have seen in other threads these referred to as ECM. What does ECM mean? Are all the variable speed blower fan motors ECM, or do I need to specify that?

    Thanks
    You don't need to specify an ECM motor if you buy a variable speed furnace, as all VS furnaces have ECM motors.

    There is one ECM motor, the X-13, that is ECM but has fixed (multiple) speeds so cannot ramp the speed. The Goodman GME8 is one example of a furnace with this motor, but I know there are others. The X-13 motor is very efficient, but not VS.

  7. #7
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    Quote Originally Posted by Air Doctor, Inc View Post
    Th eproblem with over sizing a gas furnace is that you waste energy...
    Hmm. I'm a little simple so I don't quite understand this. Does the gas flame become less efficient as the furnace size increases? Does the flame become hotter and waste more heat up the chimney as the furnace size increases?

    Let me get this straight. So if my house is losing heat on a 40-degree day at a rate of 8,000 Btu's/hr and my furnace is a 60,000 Btu output furnace, isn't it oversized? Does that mean it's less efficient or that it just runs for a shorter time? What about when it's 10-degrees outdoors (assuming a 0-degree design temp)? Isn't the furnace still oversized? But less efficient?

    I don't think so. Oversizing of a furnace (warm air furnace, NOT to be confused with a boiler) has absolutely nothing to do with efficiency. It does have everything to do with comfort. Smaller flames lead to less Btu's/hour delivered into the home, which means the furnace run cycle is very much longer and therefore eliminates the on/off/on/off/on/off short cycles. With a multi-stage furnace it also means that there is a calculated outdoor temperature at which the 1st stage can no longer provide enough heat to keep the home at set-point. That's when the furnace is running without turning off but rather begins to cycle the 2nd stage. Now that's comfort but the number of Btu's needed and delivered doesn't change and the efficiency of the burner doesn't change and the cost of operation doesn't change. Unless I'm missing something. Do tell.
    If YOU want change, YOU have to first change.

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  8. #8
    Join Date
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    Quote Originally Posted by garya505 View Post
    You don't need to specify an ECM motor if you buy a variable speed furnace, as all VS furnaces have ECM motors.

    There is one ECM motor, the X-13, that is ECM but has fixed (multiple) speeds so cannot ramp the speed. The Goodman GME8 is one example of a furnace with this motor, but I know there are others. The X-13 motor is very efficient, but not VS.
    The X-13 is not an "ECM" motor. It is similar but has a different method for maintaining output. It does not control CFM output as well as an ECM and is a lower quality motor.

    EDIT: Yes, oversizing the furnace DOES affect efficiency. The more oversized the furnace is, the more it will cycle on and off. While the steady state combustion efficiency is the same, most of the sever losses occur during startup while trying to heat up the heat exchanger. Smaller furnace will run longer which in turn leads to operating with a fully heated heat exchanger for a higher % of the time.

  9. #9
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    Thanks, everyone for replies. I now know what ECM stands for, and how it works, and that I should get one.

    I also understand that oversizing a furnace is not as bad as oversizing ac, but still far from optimum. However, I feel a little oversized is not going to be a bad thing in this case. Since I am going dual fuel, gas will only come into play when it is either very cold and during morning recovery and so won't short cycle much. The heat pump will then take over to maintain temps most of the time.

    With the heat pump and doing dual fuel, is it still worth it to get a two stage or modulating burner? My initial inclination was to get a two-stage burner.

  10. #10
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    Quote Originally Posted by Maikerum View Post
    Thanks, everyone for replies. I now know what ECM stands for, and how it works, and that I should get one.

    I also understand that oversizing a furnace is not as bad as oversizing ac, but still far from optimum. However, I feel a little oversized is not going to be a bad thing in this case. Since I am going dual fuel, gas will only come into play when it is either very cold and during morning recovery and so won't short cycle much. The heat pump will then take over to maintain temps most of the time.

    With the heat pump and doing dual fuel, is it still worth it to get a two stage or modulating burner? My initial inclination was to get a two-stage burner.
    Yes.

    Actually, allmost all (or all) furnaces with VS will be 2-stage so you won't have much to decide on that.

    In an case, 2-stage will usually be more comfortable and quiet.

    ETA: Also, when you are looking at specs, be careful of advertising terminology. If it says "multispeed" that's probably a PSC motor, with selectable blower motor speeds that are set by your installer. If it says "variable speed" that's going to be ECM. The X-13 motors are a little harder to discern, but if it says it's ECM but not Variable Speed, that's probably a X-13. IMO, the X-13 is just as good as the VS, if you don't care about the ramping capability of the VS motor.
    Last edited by garya505; 07-02-2010 at 12:15 PM. Reason: added last paragraph

  11. #11
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    The X-13 cannot maintain CFMs throughout the static pressure range as well as an ECM motor. That is the biggest negative of the x-13 vs the true ECM motor.

  12. #12
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    Quote Originally Posted by badtlc View Post
    The X-13 cannot maintain CFMs throughout the static pressure range as well as an ECM motor. That is the biggest negative of the x-13 vs the true ECM motor.
    Ah, I forgot about that, the X-13 is a constant-torque motor, right?

    From the charts I've seen though, the X-13 does way better at maintaining CFM than the PSC does.

  13. #13
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    Quote Originally Posted by badtlc View Post
    The X-13 is not an "ECM" motor. It is similar but has a different method for maintaining output. It does not control CFM output as well as an ECM and is a lower quality motor.
    you're mixing up Variable Speed vs. ECM.

    ECM is the motor technology. Variable Speed is the buzzword for Constant CFM control technology.

    X-13 is an ECM motor with a constant torque controller. it's not a lower quality motor. it just has a simplier control algorithm so cheaper.

    Here's a link from Genteq. They call Premium ECM = VS. Standard ECM = X13

    ECM vs. PSC comparison chart
    http://www.thedealertoolbox.com/Resi...s/Default.aspx

    X13 ECM page
    http://www.thedealertoolbox.com/Resi...rs/ECMX13.aspx
    Last edited by drewski11; 07-02-2010 at 02:44 PM. Reason: added link

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