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  1. #1
    Join Date
    Jul 2002
    Location
    NorthEast
    Posts
    811

    Johnson UNT controller is faulty

    Johnson UNT controller # AS UNT 1144-0


    There is a steady and reliable 24 volt supply-
    All connections are tight.
    The address and analog output dip switches are properly set.
    This is a recent problem.
    The controller is constantly going on and off.

    All outputs are constantly turning on and off

    It cycles between on line and off line on the N2 network.

    Is it time for a new controller?

    Thank you

  2. #2
    Join Date
    Mar 2003
    Location
    Washington,NJ
    Posts
    504
    I'd try cycling power to controller, if that doesn't work I'd disconnect N2, then try all load wires off of inputs and outputs. If that still doesn't solve problem then sell the customer a new UNT.
    Hope that helps!!
    Chris

  3. #3
    Join Date
    Jan 2005
    Location
    Miami, Florida
    Posts
    40
    Yes it is time for a new controller.
    I had a 141-1 do the same thing about 6 months ago. Tried everything to eliminate the controller itself. I replaced the controller and that solved the problem.


    Quote Originally Posted by cleancondenser View Post
    Johnson UNT controller # AS UNT 1144-0


    There is a steady and reliable 24 volt supply-
    All connections are tight.
    The address and analog output dip switches are properly set.
    This is a recent problem.
    The controller is constantly going on and off.

    All outputs are constantly turning on and off

    It cycles between on line and off line on the N2 network.

    Is it time for a new controller?

    Thank you
    Do the best you are capable of, be totally honest, die with a smile on your face!

  4. #4
    Join Date
    Sep 2007
    Location
    Michigan
    Posts
    290
    Watch yourself... See if you have a solid neutral supplying your 24v transformer. I did 150 UVs over the summer and had some mis-wiring by the MFG, guy traced down the wiring and said it wasn't a solid neutral. The controller only cycled when the BO energized. I have had others that just fail and do the same thing though.
    "Yeah I can figure out whats wrong with it, but you were here first and there isn't room for two, plus it's cold up here, I'll be in the van"

  5. #5
    Join Date
    Jul 2002
    Location
    NorthEast
    Posts
    811
    This is why I like this site very much
    I always get very good advice

    I am aware that I may have a faulty wire condition or components
    on the HVAC unit itself.

    Then again Tlrsr may have a good point also

    We do have the fan and the compressor jumped out at the terminal board and so far so good ,
    I purchased a new UNT ,and comes Tuesday it will be the moment of truth,as the customer is looking over my back.

    If the UNT solves the problem OK,
    If not then I will be doing a major wire and transformer overhaul

    I will post the results

    Thank you

  6. #6
    I have seen these symptoms alot in noisy enviroments. Particularly in rooftops in the winter when the heating ignition on a gas trane fires. If you still have problems try adding a isolation transformer and some line filters. and also with the 1100's never mount the unt in the same compartment as the the ignition device.

  7. #7
    Join Date
    Jan 2007
    Posts
    735
    I'm curious,

    Did you disconnect all of the I/O and just put power on it and see what happens? And then start adding all of the I/O back on one by one? I agree, it's easier to change the controller and see what happens, but I would hope you're not getting feedback from some source that might be causing the problem.

  8. #8
    Join Date
    Jan 2005
    Location
    Miami, Florida
    Posts
    40
    Quote Originally Posted by cleancondenser View Post
    This is why I like this site very much
    I always get very good advice

    I am aware that I may have a faulty wire condition or components
    on the HVAC unit itself.

    Then again Tlrsr may have a good point also

    We do have the fan and the compressor jumped out at the terminal board and so far so good ,
    I purchased a new UNT ,and comes Tuesday it will be the moment of truth,as the customer is looking over my back.

    If the UNT solves the problem OK,
    If not then I will be doing a major wire and transformer overhaul

    I will post the results

    Thank you

    cleancondenser: What was the result when you went back to the job? Did you change the control?
    Do the best you are capable of, be totally honest, die with a smile on your face!

  9. #9
    Join Date
    Jul 2002
    Location
    NorthEast
    Posts
    811
    It has been a busy week
    The controller is still on my desk.

    It is warm we have the air conditioning running.

    In the mean time I have PLC Modbus problems.

    Will post the results as soon as I get there.
    Thank you

  10. #10
    Join Date
    Jul 2002
    Location
    NorthEast
    Posts
    811
    Installed the new UNT today.
    So far so good but
    I also installed iso relays on the fan and all stages

    Thank you

  11. #11
    Join Date
    Jan 2007
    Posts
    735
    Good idea on both fronts.

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