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  1. #1
    Join Date
    Feb 2010
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    New York City
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    Commander SK Variable frequency Drive for boiler single Phase

    Have an Aerco Benchmark Boiler which is
    rated at 120 Volts Single phase
    The Aerco Benchmark manual only states the the
    The furnace Inducer blower motor / single phase 120 Volts / fractional H.P.

    with four leads attached,
    two for the 120 Volts power
    Two for the 0 to 10 Volt D.C. Speed signal
    is fed its speed control signal
    From an Emerson Commander SK V.F.D.
    It does not show How the Boiler control board sends a signal to the V.F.D
    nor THE V.F.D wiring diagram

    the Emerson site list them as controlling Three phase motors

    Any info would be helpful

  2. #2
    Join Date
    Oct 2010
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    Its likely done thru a modbus serial command

  3. #3
    Join Date
    Oct 2010
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    It has a USB stick in front of it don't remove it , it can cause problems

  4. #4
    Join Date
    May 2004
    Location
    SE Pennsylvania
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    What is the model number of the one you are working on? You may be looking at two different sets of literature for two different models. The larger BTU models have VFDs and the smaller ones have ECM motors from what I remember. Either way it is a 0-10VDC command from the control board to either the drive or the motor.

  5. #5
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    Feb 2010
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    Quote Originally Posted by hvac69 View Post
    What is the model number of the one you are working on? You may be looking at two different sets of literature for two different models. The larger BTU models have VFDs and the smaller ones have ECM motors from what I remember. Either way it is a 0-10VDC command from the control board to either the drive or the motor.
    This definetely has a Commander SK Drive
    The drawing shows that
    The boiler,"C More" board sends an analog
    Speed signal to the Drive
    The drive only sends an Analog output
    Signal to the actual blower motor
    I am guessing that the speed is varied with the
    O2 levels
    Why not have the boiler controls directly control the motor speed
    This motor has only four leads
    Two for power which are controlled by
    An onboard relay
    And two for the analog speed signal

  6. #6
    Join Date
    May 2004
    Location
    SE Pennsylvania
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    What is the model and serial number? The only VFD I can find listed in any 120VAC model parts list and wiring diagram is a Vacuum Fluorescent Display which is part of the C More controller. The C More control sends a signal through the IO module and to the 0-10VDC input of either the motor or a drive depending on BTU output of the boiler and is drawn on their diagrams that I have looked at. This may not be the same on your boiler. J3 terminals 7, 8 at the IO module and the 24 pin connector 23, 24 on the control board. Without model and serial the rest is guessing.

  7. #7
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    Feb 2010
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    It appears that the new model PMC board
    eliminates the drive altogether and
    sends the 0 to 10 Volt signal directly
    to the Blower motor's electronics
    the drive is a Commander SK
    Strangely enough the Benchmark 1.5
    does not have an O2 sensor
    It varies the speed based on the air valve position and it has a
    combustion air intake temperature
    sensor the regulates a voltage input to the "T4" /analog in 2 port
    on the SK Drive
    terminal on the SK Drive
    It seems that this sensor will "Bias" the Drive's output
    as the temperature increases
    the air is
    less dense and
    more air is needed
    as the air cools it is More dense
    and less air/Slower speed is required
    Commander SK Model # SK B 1100075

    a new problem with the identical drive on another unit
    no matter what I do i cannot prevent the driver from out putting the maximum frequency output
    regardless of how ,and how many times I adjust
    Parameter #2 "maximum speed (HZ)
    I do not want the drive to exceed 34 HZ regardless
    if it receives a speed input signal of 100%

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