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  1. #14
    Join Date
    Mar 2008
    Location
    Central Maryland
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    246
    Quote Originally Posted by hvaclover View Post
    Only thing I see wrong with that is what history has taught us.
    Interesting information, but I understand the Rheem Mod is already a decade old. Seems to me, if some huge recall were to happen to it, there would already be rumblings.

    On the contrary, the only complaints I here are from pro's trying to sell competitor's units.

    -HF

  2. #15
    Join Date
    Mar 2008
    Posts
    28
    My knowledge of what is available in furnaces and air handlers is limited. However, I do know quite a bit about motors, so perhaps I can contribute something in that area.

    PSC (permanent split capacitor motors) are more efficient than shaded pole motors, but I think that shaded pole motors are no longer used anyway. The PSC motors used with blowers often have tapped windings which typically provide 3 or 4 speeds. Generally the motors have 6 poles providing a synchronous speed of 1200 rpm but, because there are not synchronous motors, there is always some slip resulting in a speed somewhat below 1200 rpm. When a lower speed tap is selected to make the blower run more slowly, efficiency is reduced because of the increase in slip. However, because the power required to drive the blower varies with the cube of the speed, running it at a lower speed would reduce the power required even though the motor is less efficient at the lower speed.

    The efficient variable speed blowers control the speed by other means. Some use brushless DC motors. Actually, the motors aren't really DC; there is an inverter built into the motor so that the motor is actually running on AC even though DC is provided to the motor assembly. Generally the motors are permanent magnet synchronous motors. They are very efficient at all speeds and generally the speed is controlled by varying the DC voltage to the motor assembly.

    Another method to control blower speed uses an ECM (electronically commutated motor) controlled via an external 3-phase inverter and the speed is controlled by varying the AC frequency. Another type of motor that uses an external inverter is the VSR (variable switched reluctance) motor. The VSR motor itself is very simple and has no windings on the rotor. It too is controlled via a variable frequency inverter.

    The shaded pole motor is horribly inefficient but cheap to manufacture. The PSC motor is considerably more efficient than the shaded pole motor. The other motors are considerably more efficient than the PSC motor at all speeds and, when the speed is controlled appropriately, will provide more satisfactory performance for the HVAC system. However, the initial cost is greater and it may be that the electronics involved could reduce the reliability. On the other hand, they've been around for a long time and it may be that that has provided sufficient time to work out the bugs and make them reliable.

    Others know more than I do about how these devices are used with HVAC systems.

  3. #16
    Join Date
    Jan 2008
    Posts
    85
    Fairly good analysis of energy saving blower motors. It's five years
    old so the utility rates used in the calculations are a bit low.
    Good read though.

    http://www.aceee.org/pubs/a033full.pdf

  4. #17
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by FRE View Post
    My knowledge of what is available in furnaces and air handlers is limited. However, I do know quite a bit about motors, so perhaps I can contribute something in that area.

    PSC (permanent split capacitor motors) are more efficient than shaded pole motors, but I think that shaded pole motors are no longer used anyway. The PSC motors used with blowers often have tapped windings which typically provide 3 or 4 speeds. Generally the motors have 6 poles providing a synchronous speed of 1200 rpm but, because there are not synchronous motors, there is always some slip resulting in a speed somewhat below 1200 rpm. When a lower speed tap is selected to make the blower run more slowly, efficiency is reduced because of the increase in slip. However, because the power required to drive the blower varies with the cube of the speed, running it at a lower speed would reduce the power required even though the motor is less efficient at the lower speed.

    The efficient variable speed blowers control the speed by other means. Some use brushless DC motors. Actually, the motors aren't really DC; there is an inverter built into the motor so that the motor is actually running on AC even though DC is provided to the motor assembly. Generally the motors are permanent magnet synchronous motors. They are very efficient at all speeds and generally the speed is controlled by varying the DC voltage to the motor assembly.

    Another method to control blower speed uses an ECM (electronically commutated motor) controlled via an external 3-phase inverter and the speed is controlled by varying the AC frequency. Another type of motor that uses an external inverter is the VSR (variable switched reluctance) motor. The VSR motor itself is very simple and has no windings on the rotor. It too is controlled via a variable frequency inverter.

    The shaded pole motor is horribly inefficient but cheap to manufacture. The PSC motor is considerably more efficient than the shaded pole motor. The other motors are considerably more efficient than the PSC motor at all speeds and, when the speed is controlled appropriately, will provide more satisfactory performance for the HVAC system. However, the initial cost is greater and it may be that the electronics involved could reduce the reliability. On the other hand, they've been around for a long time and it may be that that has provided sufficient time to work out the bugs and make them reliable.

    Others know more than I do about how these devices are used with HVAC systems.
    Anybody as a student who attended a good HVAC school knows all that theroy, but I think it is too deep to present to an HO>
    Last edited by hvaclover; 04-21-2008 at 09:36 PM.

  5. #18
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    Too much for some. Others would like to hear that info.

    In the end though, if the info makes or breaks the sale, is what matters.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #19
    Join Date
    Apr 2008
    Location
    Toronto, Canada
    Posts
    166
    Quote Originally Posted by beenthere View Post
    Too much for some. Others would like to hear that info.

    In the end though, if the info makes or breaks the sale, is what matters.
    exactly. im a home owner and i want this information. i have spend considerable time researching furnaces because i want to understand what is involved and make a decision i am comfortable with. i also want to have knowledge around some of these details to protect myself from false information or faulty opinions because after all, i am the one that is going to have to live with the machine and installation, not the contractor or manufacturer.

    i think buying an extended warranty is a good way to mitigate risks as well.

    brett

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    An extended parts and labor warranty are always smart investments.(factory/third party)
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #21
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    Quote Originally Posted by beenthere View Post
    Too much for some. Others would like to hear that info.
    I'd agree if the prospects you are servicing and selling to are all engineers and/or employed in technology based career.

    But that is not the case. Not every prospect is going to be a technically oriented person or engineer, just as every one is not going to be a doctor or lawyer.

    By saying "Too much for some. Others would like to hear that info" leads me to think you feel the majority of prospects would want this info.

    I go into great detail on equipment as my selling approach is based on selling the mechanic of the install. When a customer wants the theoretical workings
    of the equipment I will gladly indulge that person. Otherwise I stick to analoies that folks can relate to in every day life.

    Analogies work best on HOs who don't want to hear OHMS law or what the "Wet Time" of a furnace is, or how the AC current is converted to half wave DC current.
    Your market may be different than mine, but I don't think you use such technical speak on every sales call unless you are selling HVAC systems on the International Space Station
    Last edited by hvaclover; 04-21-2008 at 11:47 AM.

  9. #22
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Plexus:

    Here's some data for you to illustrate power consumption for a VS motor. I don't have example data for a PSC motor.

    This data is from a WaterFurnace 3-ton 2-speed compressor variable-speed fan motor Envision unit. It's a 230V ECM2 variable-speed motor.

    While the range of data is reflective of the ECM2 motor overall, the specific values are dependent on specific installation. Current draw is shown as a range, as the draw is dependent on static pressure. This data is from a zoned unit, and thus the static pressure varies as a function of the zone damper positions.

    ECM2 motor (only) current draw:
    0650 cfm: 0.15 - 0.36 amps (200-395 rpm)
    0750 cfm: 0.19 - 0.54 amps (263-465 rpm)
    0850 cfm: 0.24 - 0.76 amps (270-519 rpm)
    1000 cfm: 0.32 - 1.12 amps (308-625 rpm)
    1100 cfm: 0.43 - 1.54 amps (333-678 rpm)
    1200 cfm: 0.56 - 2.25 amps (363-779 rpm)
    1300 cfm: 0.67 - 1.04 amps (385-508 rpm)
    1400 cfm: 1.02 - 1.30 amps (472-555 rpm)
    1500 cfm: 1.02 amps (454 rpm)

    Again, this data should be used just to get an idea of power consumption for an ECM2 motor - the variability shown above is reflective of static pressure changes, and, the Intellizone controller limiting upper speeds to lower static pressure scenarios.

    Hope this helps.

    Best regards,

    Bill

  10. #23
    Join Date
    Apr 2008
    Location
    Toronto, Canada
    Posts
    166
    Quote Originally Posted by a0128958 View Post
    Plexus:

    Here's some data for you to illustrate power consumption for a VS motor. I don't have example data for a PSC motor.

    This data is from a WaterFurnace 3-ton 2-speed compressor variable-speed fan motor Envision unit. It's a 230V ECM2 variable-speed motor.

    [snip]

    Hope this helps.

    Best regards,

    Bill
    yes thats very helpful! i see the current draw is quite low. lower than i expected actually. i understand that the static pressure affects these units but still as a guideline. i can see why its possible to run an ECM motor on low 24/7 without too much utility cost.

  11. #24
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    As I said in my post, its too much for some.

    You have to feel out each individual customer. You can't group all customers together, no more then you can group all HVAC contractors together
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  12. #25
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Quote Originally Posted by plexus View Post
    ... i can see why its possible to run an ECM motor on low 24/7 without too much utility cost.
    Yes, if I were to run my ECM2 motor "on low 24/7" it would cost me roughly .15A * 230V, or approximately 34 watts. Including the standby power consumption for the Envision, at about 30 watts, the total adds up to the advertised "run the fan on ON for about the cost of a 60 watt light bulb" (paraphrasing). So it can be measured, and verified, that yes, running an ECM2 motor on the lowest setting is about the same as the light bulb. So if this is what you were looking for independent confirmation of, you're all set. Indeed, the ECM2 motor is 'the real deal.'

    But, in my individual case, I don't run my blower motor 24/7 because I don't live in an arid climate (I live in Dallas area). See the numerous threads on this site that address the increased humidity levels that can occur when the blower motor is running with an evaporator coil all loaded up with water without the compressor simultaneously running. In fact, this was the case for me, and I actually measured the RH increase. So for my geographic location, while the advertising of a cost savings of a VS motor running 24/7 is 'catchy,' it's not as comfortable due to increased RH.

    Best regards,

    Bill

  13. #26
    Join Date
    Mar 2008
    Posts
    28
    Actually, I am a home owner and my degree is in business administration. So, if I can understand various types of electric motors, surely others can also.

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