Results 1 to 6 of 6
  1. #1
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    213

    ECM blower motors responding to static pressure--how?

    I understand Bryant Evolution systems and a certain Lennox,
    (model G60UHV60C090X07) vary blower speed depending on,
    I think, static pressure. For zoned systems, I believe these
    units do not need bypass dampers. They can somehow sense
    if one zone is open versus two or more, and then adjust blower
    speed and CFM accordingly. I was hoping to determine whether
    that sensing is done entirely by the blower motor electronics
    or whether there is a sensor in the airstream somewhere and
    maybe the main control board tells the blower motor to adjust.
    Obviously, this knowledge would really help diagnosis in the event
    a blower motor was responding inappropriately to static pressure.

    For example, the motor slowing down to almost nothing every
    time one of the zones opens and then speeds up when the
    zone dampers are closed--I pulled the zone damper motor wires
    in that case.

    So this is not the typical ECM-motor-not-running problem. This motor
    runs at various speeds. It just does not do it consistently. It USED
    to do it fine, for years. Then it stopped. And then it supposedly started
    working after I left the house when the homeowner called for
    heat hours later.

    Thank you for any enlightenment.

  2. #2
    Join Date
    Mar 2010
    Location
    Rochester, NY
    Posts
    437
    The way the motor knows how to adjust speed is done electronically. The motor communicates the RPM to the board and the board inturpets this for CFM. If the motor still ramps up and down I would look for changes in the duct/house that would affect the air flow.

  3. #3
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,378
    The motor determines amp draw and rpm then calculates CFM based on it's internal programming.

  4. #4
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    213
    So are you guys in agreement or at odds as to whether the board of the motor or the board of
    the furnace would be the most likely cause of simply strange behavior? This unit stopped responding
    appropriately a month ago, then started working fine, then, a month later, started acting weird
    again, and then started working okay. The homeowner swears nothing is changing with respect
    to registers or filters or ductwork. Nobody is touching anything. I visually checked the zone
    dampers--peered at them via the open evap coil cover--so I know what they are doing. What I don't
    know is how to troubleshoot these motors very well except for basic working/not-working. I have
    a tester for that.

  5. #5
    Join Date
    Mar 2012
    Location
    New Hampshire
    Posts
    84
    I had a similar issue a few months back on a York. Pull the ECM head off the back of the motor and look at the board. The Yorks have 2 capacitors in them and one of them was leaking. In some cases they sound quieter when a 2nd zone opens up but the blower speeds up. If that isn't the case, I would pull both boards and look at the back of to see if anything is fried/shorted. If you aren't 100% sure which board is bad, call tech support.


    "I don't know why it be like it is, but it do"

  6. #6
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    5,708
    Quote Originally Posted by georgelass View Post
    So are you guys in agreement or at odds as to whether the board of the motor or the board of
    the furnace would be the most likely cause of simply strange behavior?
    The board in the motor ECM module is the cause of this behavior.

    The motor, and the equipment manufacturers, develop tabular data to relate torque and RPM to mass airflow. This data is then stored in the ECM microcontroller, and used to control the motor to a constant airflow.
    Instead of learning the tricks of the trade, learn the trade.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event