Variable Speed Motors

Discussion in 'General Discussions' started by Bluecuda, Mar 23, 2009.

  1. Bluecuda

    Bluecuda New Member

    In my quest for Geothermal, I've heard various different slants on retrofitting my existing home. One thing that has me wondering is the variable speed blower motors.

    One installer claims that a variable speed blower will save me money in the long run because it's more efficient. Another claims that with the existing duct work in my home that there won't be enough volume on the lower speeds to heat the house evenly, and that it will end up at the higher speeds anyways.

    What do you guys think?

    Last edited by a moderator: Aug 29, 2010
  2. geo fan

    geo fan Member Forum Leader

    volume or pressure?

    the reality is ecm motors are more effecient as Im sure you know
    but if the ductwork is sub par the benifits decrease
    what it does insure is that you will move enough cfm ( rare exceptions excluded ) which is criticle to maintaining your heatpumps eff.

    Duct work issues should not be masked by an ecm they should be addressed , I have never heard of a psc motor masking anything
  3. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    ^^^pats Geo Fan

    on the back.

    Hands out one gallon cans of free ductape in a can to all that read this.

    I am sorry buy your own throw away paint brushes.

    Sealing duct work is imparative, since nobody installs it to the rules. Once sealed then insulate the sections in any non-conditioned spaces in the building.
  4. gabby

    gabby Member Industry Professional Forum Leader

    As Mark Custis and geofan stated, one starts with a good duct system.

    The speed of the fan is proportional to the load, heating or cooling. One will normally have lower fan speeds in stage 1 versus stage 2, or in a single stage system in the cooling mode versus the heating mode.

    If your system has a dehumidifier, you will note slow fan speeds for a longer period in the cooling cycle so you can pull more moisture out of the air even if set point is reached. This will allow your comfort level to be at a higher temperature than you are normally accustom saving you money. Those near large bodies of water, Lake Erie included, will see a definite benefit to this auxiliary option in a geo system. Those living in gator country, most anywhere in Florida, or coastal towns within 100 miles of this water mass, will benefit the most. Those living in the desert of Utah, Nevada, Arizona, or most of Texas really don't need this option.

    Those living in the Midwest, North, or Northeast where heating is a prime concern, should in my opinion have a two stage system. The load calculations will be heat dominated thus oversized for summer operation. The two stage allows for a reduced load in summer operation by running stage 1 most of the time, and stage 2 with emergency backup for winter or heating season.
    I have been assured more than once that 4 candles and a smoldering marshmellow will handle the heat requirements in Houston for winter operation.
  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I would add to Gabby' thoughts about power consumption,

    what I learned from Mark Hunt today. Mr. Hunt showed me/us how an ECM pump or blower will deliver the correct (think just enough just in time) amount of flow, be it water in the loops or air in the ductwork, to make the the heat transfer. Making the heat transfer at the lowest possible watts per hour is a good thing I think.

    Blue: Veriable speed speed motors are good if it keeps your elctric bill down. The best veriable speed motor is the DC train you had as a kid. Then comes an ECM motor. I think the best bit on how ECM's work I have seen is it the John Siegenthaler artical in Plumbing and Mechanical, march 2009. It is a push pull motor.

    Now I will answer what you asked. Yes and ECM motor is good for a heat pump.

    I will do more on why loops "ACT" short when they ar really poorly piped soon.
  6. Bluecuda

    Bluecuda New Member


    Thanks guys for the input. The reason I ask is because I've gotten quotes for split geo systems versus doing a complete swap of my existing furnaces. Odviously the price is going to be more expensive to do a complete unit with a variable speed motor, and the geo installers are all trying to justify their position on why they chose the equipment options they quoted.

    Just trying to be an informed consumer :)
  7. Valveman

    Valveman Guest

    I have heard from several people who had them, that variable speed motors save a lot of energy. They say that is because these systems are not dependable and won't work 1/2 the time. For this reason I did not go for the variable speed on my system. I believe simple is dependable, and dependable is green. It doesn't do any good to save an extra 200 bucks a year in energy, if you have to spend 300 bucks on maintenance. :eek:
  8. Looby

    Looby Member Forum Leader

    If you really believe that, you should prolly go short on
    WFI. (They're listed on the Toronto stock exchange.)

    ...'cause their standard ECM warranty is 10 YEARS,

  9. Bluecuda

    Bluecuda New Member

    Easy Kids...

    I'm not so much worried about motor failure as I am volume of air for the stack coming off my main furnace. If one could save say $200 a year in electric with an ECM, then it would more than pay for itself over a single speed blower, and with a 10 year warranty I'd feel pretty comfortable going that route. I just want to make sure that an ECM is going to provide consistent, even warmth in my home.

    Thanks again for all your input!
  10. gabby

    gabby Member Industry Professional Forum Leader

    1. Duct problems will point to a bad ECM.
    2. Properly designed systems have longer duty cycles, saving wear and tear on the ECM
    3. A system ECM that runs longer in stage 1 versus stage 2 saves you money. Stage 2 will operate at the upper end of the demand curve until the load requires additional emergency standby heat.
    4 Short cycle times ends the life of most any electrical/mechanical device sooner than expected, be it from friction or surges of mass or current.

    A lighted incandescent bulb may run 30 days (24/7) before dying. Turn it off and on 5-10 times a day and the useful life will be a small percentage of what is expected. The shock of on or off vibrates the filament (surge) that ends its life.

    The question comes down to one of choice. Would you rather have sex 25 times a day as some lions, or have an orgasm last 30 minutes like some pigs. If you are a Buddhist, reincarnation may have some choices to contemplate.:)
  11. Bluecuda

    Bluecuda New Member

    Would that be 25 times a day, lasting more than a minute each time???

  12. gabby

    gabby Member Industry Professional Forum Leader

    No, 10-20 seconds, depending on age.
  13. ECM

    vs variable speed. Generally vs refers to 3 different speed options. ECM is infinately variable. ECM = Electronically commutated motor. Sort of like the gas pedal in your car. Of which are we speaking?
  14. gabby

    gabby Member Industry Professional Forum Leader

    I believe he is referring to a whole new system with ECM versus a split system using his current air handler. This most likely would be a two speed induction motor. One speed for heat the other for cooling....that was not for your benefit but others reading this thread.:D

    I still want to see one of those experimental variable speed pumps we talked about....
  15. Jay

    The great thing about the new tax incentive is that you receive the credit for new ductwork as well as anything else you need to make the systems work well together: Egg Systems International Complete Rooftop Cooling Systems: Home The Variable speed motors do require custom sized ductwork for low cfm as well as other considerations.
  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I should have grabbed you butt Tuesday.

    Sorry I owe you, I now get why ECM are the most efficient.
  17. gabby

    gabby Member Industry Professional Forum Leader

    The most expensive?
    The most efficient?
    The most confusing?
  18. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Dear Friend:


    ECMs will only do what they are told to do. They deliver just enough, just in time.

    That saves money.
  19. Bluecuda

    Bluecuda New Member

    You are correct

    I was referring to a split system vs a whole knew ECM system. I didn't realize there was a difference between variable speed and ECM.

    I fully understand what you guys are talking about with a "JIT" delivery system, but what confused me was an installer telling me that my stack off my existing furnace was too large for an ECM to be effective without it running at a higher speed, similar to how my furnace runs now. I was just trying to determine whether or not he was just giving me a line of bull, or if he actually knew what he was talking about :)
  20. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I am not sure what you mean when you say stack. If you mean the duct work on the delivery end of the machine that does not matter what does matter is the size of the duct trunks leaving the plenum. An ECM blower, "feels" how much work it is doing and varies it speed accordingly.

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