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  1. #1
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    Aug 2006
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    Beachwood, NJ
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    Digital Scroll Compressors with FEC/PCT Controllers

    I am hoping someone can help with this.
    I am looking to see if anyone may have a caf.file they would not mind sharing, or a digital scroll operation module.
    I have a few AAON Units and those familiar with them know that WATTMASTER controls the first stage compressor with an enable and a dc volt signal (1.5 to start to 5 vdc) that ramps up the voltage per load demands. At 50% compressor 1 shuts down and compressor 2 enables (no unloading operation comp 2). At 51% Compressor 2 runs and compressor 1 enables again and dc voltage ramps up the unloader operation.
    I have ran across some files attempting to control the copeland digital compressor controller but they do not work properly. These AAONS came from the factory with FEC controllers and the ABCS contractor did not program them correctly. Best I see is just basically enabling compressor and sending 100% signal to fully load compressor operation. I know its difficult but i am guessing someone by now has figured it out.
    I have been attempting to figure this out myself but i keep hitting rock bottom and pulling my hair out.
    Any help would be appreciated.
    Thank you.
    Just when I thought I knew it all, I realize that I am still learning something new everyday!

  2. #2
    Join Date
    Sep 2007
    Location
    edmonds wa
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    Does your BMS send a sat setpoint or does it drive thru the wattmaster to the digi scroll controller? From units i have seen, we send a setpoint temp to the unit and then it decides on how to get there with the comp, although i am not a fan of how short the unloader goes back and forth when unloading, seems like a lot of wear and tear on the comp. 1 unit lost the digi comp within 8 months of start up, had the most loud noise like it was grinding away inside, the sight glass had a gray metal coating on the inside and the comp was to hot to touch on the shell. Still at times short cycles on the unloader, is there a way to adjust the interval on the unloader as it seems like it is controlling to as very tight discharge air temp.
    UA Local 32

  3. Likes bigguy158 liked this post
  4. #3
    Join Date
    Jan 2003
    Location
    USA
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    Bare Aaons don't have any smarts,they plan on you bringing them. You need to figure out demand, and drive compressor staging and loading directly. You typically have enable points, a modulation input and a suction pressure feedback off memory.
    Propagating the formula. http://www.noagendashow.com/

  5. #4
    Join Date
    Sep 2015
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    Yea, I just went through this about a year ago.

    Aaon's digital variable scroll compressor is always in the lead position and should never shut off during mechanical cooling. The digital scroll modulates from minimum 10% to 100% capacity. When the second "on/off" compressor energizes at full capacity, the digital backs off to 10% or as required to satisfy sum total load. As the load increases, the digital will modulate to 100% and between the two refrigerant circuits the total nameplate capacity is delivered. The evaporator coil is row split so the digital scroll circuit is in series with the on/off compressor.

    On the four compressor units we had, the evaporator coil was both face and row split. One digital variable scroll compressor was mated to one "on/off" compressor in series or row split coil on one face and the second of each was similarly configured on the second face. The control sequence ran both variable scroll compressors simultaneously in the lead position and simultaneously cycled the "on/off" compressors.

    The trick is a dead band range in the cooling set point so that the second compressor does not short cycle. In other words, the second compressor engages at 78 degrees and disengages at 74 degrees. The digital compressor continually ramps between minimum 10% and full its capacity.

    If the digital variable scroll compressor is not maintained in the lead position, humidity control suffers and similar short cycling results.

    If these are new, I suggest you check the purchase order for the aaon units for factory start-up services. You can also engage a factory tech and pass their charges to the owner.

    Hope this help, please keep us posted.

  6. #5
    Join Date
    Apr 2014
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    I think I can put something together that will exceed your expectations.
    Give me a couple hours

  7. #6
    Join Date
    Aug 2006
    Location
    Ohio
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    Hey JCIman , if you end up getting something together for this I would love to be copied on it!

  8. #7
    Join Date
    Apr 2014
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    Let me know if you got it

  9. Likes hvacpilot liked this post
  10. #8
    Join Date
    Aug 2006
    Location
    Beachwood, NJ
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    Quote Originally Posted by JCIman View Post
    Let me know if you got it
    Got it. Thank you.
    Just when I thought I knew it all, I realize that I am still learning something new everyday!

  11. #9
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    Aug 2006
    Location
    Ohio
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    My email had issues. I sent you a respone, if it was possible to send it to the other emailI appreciate it!

  12. #10
    Join Date
    Apr 2014
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    Well, did it work out for you?

  13. #11
    Join Date
    Aug 2006
    Location
    Ohio
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    Im assuming your talking to hvacpilot, howeverI received it just fine thanks. Also it was in CCT and hvacpilot was kind enough to recreate it in pct for me. Thanks alot guys! Greatly appreciate it.

  14. #12
    Join Date
    Aug 2006
    Location
    Beachwood, NJ
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    Quote Originally Posted by JCIman View Post
    Well, did it work out for you?
    JCIman, yes it worked great.
    Thanks a million. Still trying to take apart program module and figure it out entirely, i am kind of a slow learner but eventually i can figure it all out. I am very appreciative of your time and effort with this issue which has haunted me personally for a few years now. ( I am very particular about doing the right thing for both customers and manufacturers), and i am disturbed when i see programmers not doing their job right or even close for that matter or mechanics not starting and maintaining equipment properly. I cant see why they just don't ask for help, I am never too proud to ask for help and I do take my job seriously and I have pride in the work I do. There is a sense of satisfaction when I can walk away from a job not having to look back.
    I probably wrote more than I should but what the heck, I felt like letting it all out.

    Again thank you for the program and thank you all on this site for your responses.
    Just when I thought I knew it all, I realize that I am still learning something new everyday!

  15. #13
    Join Date
    Apr 2014
    Posts
    335
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    Thank you. Keep trying to right all of the poor quality work out there! We can "Make America Great Again" One CCT program at a time!

  16. Likes hvacpilot liked this post
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