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Thread: Honeywell

  1. #1
    Join Date
    Nov 2005
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    13
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    Angry Honeywell

    hey guys this may be an easy one but I've never seen it before.
    I've got a air handler with a heating coil the coil is feed by a Honeywell valve with a ML7984A3001 actuator controlled by a W793b controller. the way it is wired it is only using two wires off r and b and there tied into the mod terminals of the 793 one the diagram it calls this super mod? what it doesn't tell me is if the power is created by the actuator or the controller. 0 volts dc across the controller with no heat call, 2 volts dc with a call and no wires hooked up. any ideas?

  2. #2
    Join Date
    Oct 2005
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    Don't know but you can get literature here. http://customer.honeywell.com

  3. #3
    Join Date
    Aug 2006
    Location
    New England
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    I believe what you have is a W973B. Its signal is sometimes called electronic series 90. It should be wired R on W973 to W on ML7984 and W on W973 to R on ML7884. Power comes from 24V AC or DC on T5 and T6. Dip switches should be 1, 2, 4 up and 3 depends on valve action. I think the actual signal is 0 to -2VDC. T5 and W are internally connected.

  4. #4
    Join Date
    Nov 2005
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    Smile thanks

    that makes all lot of sense sounds like of got a bad acuator, thank you

  5. #5
    Join Date
    Aug 2016
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    Hi,

    Good Day,

    Got a ML7984A4009 here but i can't run or modulate this unit.
    I've tried to set the DIP switch setting aside from the recommended one (from manual) into other settings just to make another test but still it doesn't move at all.

    I've been trying to test the unit using a DDC Controller with 0-10 VDC but still fails.

    Does the unit requires higher current rating from 0~10 VDC?
    Any similar experience?

    Any work around for this?

    Thanks.

  6. #6
    Join Date
    Oct 2007
    Location
    England
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    Im on a train at the moment so cant check, but you have 24V ac wired to it yes?

  7. #7
    Join Date
    Aug 2016
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    Yes, I have followed the recommended wiring in the manual.
    What i have not verified if the 0.5A is the required current at 0-10VDC?

  8. #8
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    1,539
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    .5 requirement is the transformer requirement for the 24vac. Verify 24 vac to actuator. Verify you have expected vdc signal at R and W. Is the controller and actuator powered by same transformer.

  9. #9
    Join Date
    Aug 2016
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    3
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    Quote Originally Posted by hvac69 View Post
    .5 requirement is the transformer requirement for the 24vac. Verify 24 vac to actuator. Verify you have expected vdc signal at R and W. Is the controller and actuator powered by same transformer.

    1st Test - the controller (with 0-10vdc) used the same 24 VAC with the valve actuator (parallel Connection). but the actuator does not move..only during power up.
    By the way the power supply (24VAC) that i've been using is 3A.

    Can you confirm that 0.5A is the minimum rating?
    Or this one is the recommended current rating?

    2nd Test - the controller and actuator uses different 24VAC supply. Result is that actuator does not move with signal 0-10 vdc. It only moves/rotates in one direction during power up.
    (Also the 24VAC used is 3A).


    Thanks.
    Christian

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