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Thread: Carrier ccn

  1. #1
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    Carrier ccn

    V3 system i had a issue today of a damper vibrating bad today and found that the system had high static 1.25 inches wc. its only a 5 ton ac unit with a bypass damper whats the likely hood that the board that controls the bypass damper the psi transducer went bad or fell out of calabration

  2. #2
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    Go into your system pilot,touch pilot or service tool and perform a bypass damper commissioning and calibration procedure and see if the damper operates and static transducer is working. Could be something as simple as a loose tubing.

  3. #3
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    Check and see what the Static pressure setpoint is , could have a bad damper motor for the bypass. Check actual static pressure.

  4. #4
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    1.25" on a 5 ton?Sounds like the boxes are closing and the bypass isnt opening

    Usually on a 5 ton i see somewhere around .5" with all the vav's open

    Is the bypass motor 0-10 or floating?

    You can always use a squeeze bulb and put in a tee with a magnehelic to simulate and see if and at what static the bypass will open

  5. #5
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    well ok i did check the static using a magahelic and it is at 1.25" i honnestly think at this point in time the sensor is out of calabration. i did check tha damper motor it works good

  6. #6
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    Could someone have reversed the rotation in the software. Is it a 3V bypass controller?

  7. #7
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    yes

  8. #8
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    Can you verify that the motor is turning? I think when you put it calibration mode it turn the blower fan off. So watching duct static when this happens is useless.

  9. #9
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    If you check the duct static at the bypass and find it low you need to recalabrate the duct pressure sensor. If you find it won't recalabrate to the value in the duct it is toast. I have changed a great many carrier duct pressure sensors in a system having 43 units and 150 addresses

  10. #10
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    Also on the vibrating damper.If after solving the duct pressure the damper is still vibrating it may be out of adjustment. When it goes to the close position it will try to overdrive ( drive close farther than the damper will allow ) and it will sit there and vibrate. A quick fix is to set the minimum damper position to 1 or 2 on a closed damper call and see if the vibration stops. Be sure to readjust the damper. I have never been a fan of minimum damper settings. More trouble than worth. Does this make sense?

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