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  1. #14
    Join Date
    Jul 2009
    Location
    Wa
    Posts
    113
    I took a class on PCT awhile back. The instructor was a ex JCI tech support guy for 20 years, and now works for our local distributor. When he started on PRAC tuning the first paragraph said PRAC doesn't work 60 to 70 % of the time, I have had nightmare's with the stupid control loops, and feel your pain. Wish I had a way of getting his manual tuning lesson to you it has worked for me. I have also let PRAC run for a day or two and then taken it off. The last one, that gave me problems, was a static pressure PID if it is something where the valve is too big, damper don't close right, these pid's will tune, tune, then do nothing. It was 100% all the time on that one. They suck, and manual tuning is the only way to go in your case. A PID should just adjust to correct for error until they melt the AO'S down. I hate to rant but CCT,PCT is a pure debacle in my opinion. I have programmed, with honeywell care, spyder tool, hvac pro, some GX9100, and I'm currently righting my own custom programs, just get away from the Q&A, state based, setpoint determination, output control CRAP. It's like what turn's this thing on??Let me look view logic, OH!! 500 layer's of JCI pre programmed modules, now it all makes sense. That view logic button makes me laugh when I press it. So logical!! It make sense, if you don't think about it!!

  2. #15
    Join Date
    Jan 2008
    Location
    Near Philly
    Posts
    501
    [QUOTE=dhoyt;14263051]They where set up for auto tuning and would work great in till you changed the setpoint then they would freak out and go out of control. This seems to be the common issue with auto tune from what I have read. I had the Hx's running at 140 deg F for weeks then they where having some issues and they wanted me to bump them up to 180 deg F. The loops never quite came under control and when I set them back down to 140 deg F at the end of the day that was it. They couldnt recover and the valves would open close open close... It ended up over heating and I had to have a guy cycle power to the control as I wasnt onsite anymore. I have been dealing with crazy logic to limit the outputs of the PID's and resetting there tuning based off of this and that and honestly its ridiculous... At this point I would just rather tune them out myself like every other control software I deal with and be done with it... Unfortunately these loops are not cooperating... I can get them close with my prop band but as soon as I try to add any integral at all they go out of wack. I had the temp almost right at setpoint so I figure perfect a little integral will get me right there. I put in 600 as preciously suggested in an above post and the valves go closed and still have opened 15 mins later and Im 15 deg F below setpoint... I dont understand its like the dont work anything like any other loop I have tuned in the 5 other software's im familiar in... What am I doing wrong here.

    I've been using these controllers with great respect to the auto-tune feature. To be honest I'm always within the JCI realm, meaning DAT control or duct pressure control etc. etc. I'm really not a big fan of it but so far so good. I can see where it maybe suspect or fragile. What you are trying to control doesn't seem to out of the normal, maybe it just doesn't fit in the JCI box. I know eventually I'd would have to cross this bridge, you just beat me to it. I'd love to see your program file, please, please, please forward it my way. It's only a matter of time before I'm in same boat as you. Either way, please let me be included with your resolve.

  3. #16
    Join Date
    Jul 2008
    Posts
    1,422
    Quote Originally Posted by dhoyt View Post
    process range: 60
    Time constant: 300
    Process Dead Time: 300
    Prop Band: 25
    Integral Time: 600
    Interval: 120
    http://cgproducts.johnsoncontrols.co...F/12011147.pdf

    Interval: Sets the Eff Period. This value is the time period between normal PID algorithm executions -- 120 is TOO BIG

    ...do you want this thing controlled in near-real-time ... or only evaluated every 2 minutes?
    1 + 1 = 3 ( *** for very large values of 1)

    ...everybody wants a box of chocolates and long stemmed rose

  4. #17
    Join Date
    Feb 2011
    Posts
    37
    Quote Originally Posted by Norriski Tech View Post
    I took a class on PCT awhile back. The instructor was a ex JCI tech support guy for 20 years, and now works for our local distributor. When he started on PRAC tuning the first paragraph said PRAC doesn't work 60 to 70 % of the time, I have had nightmare's with the stupid control loops, and feel your pain. Wish I had a way of getting his manual tuning lesson to you it has worked for me. I have also let PRAC run for a day or two and then taken it off. The last one, that gave me problems, was a static pressure PID if it is something where the valve is too big, damper don't close right, these pid's will tune, tune, then do nothing. It was 100% all the time on that one. They suck, and manual tuning is the only way to go in your case. A PID should just adjust to correct for error until they melt the AO'S down. I hate to rant but CCT,PCT is a pure debacle in my opinion. I have programmed, with honeywell care, spyder tool, hvac pro, some GX9100, and I'm currently righting my own custom programs, just get away from the Q&A, state based, setpoint determination, output control CRAP. It's like what turn's this thing on??Let me look view logic, OH!! 500 layer's of JCI pre programmed modules, now it all makes sense. That view logic button makes me laugh when I press it. So logical!! It make sense, if you don't think about it!!
    I agree with pretty much everything you have said here. O&A is a joke I have never used it for anything but VAV programs. You have to write your own stuff or you will never know whats going on or will will never get everything you need for the sequence of operations. Johnson is definitely my least favorite of all the control systems I work on. I would rather do alerton or invensys any day... hell I would almost rather do reliable! hahaha Everything has good things and bad things about them, auto tune loops in johnson is for the birds. They made it so they could keep hiring new guys that dont know a lot about what there doing because they are a revolving door. People come and go like crazy. Sorry if you work for johnson but you know its true, at least in new england it is...

    Anyway final resolve is hook up prop band and integral to your PID and not your pre processor, everything else hook up per usual and adjust prop and integral as you would with any other software. In other applications adjusting everything else that I was trying ie process dead times, time constants etc may be necessary but for me the defaults have worked just fine. Reaper has also sent me a loop he has made that Im going to play with and see how she goes. Thanks again.

  5. #18
    Proper valve sizing is critical for steam. no matter what you do may not be good enough if sized incorrectly.

  6. #19
    Join Date
    Dec 2006
    Posts
    186
    Quote Originally Posted by Norriski Tech View Post
    I hate to rant but CCT,PCT is a pure debacle in my opinion. I have programmed, with honeywell care, spyder tool, hvac pro, some GX9100, and I'm currently righting my own custom programs, just get away from the Q&A, state based, setpoint determination, output control CRAP. It's like what turn's this thing on??Let me look view logic, OH!! 500 layer's of JCI pre programmed modules, now it all makes sense. That view logic button makes me laugh when I press it. So logical!! It make sense, if you don't think about it!!
    I guess I don't seem to see the big issue with the PCT logic view. Just my opinion.

    It's kind of similar to Workbench wire sheet.

    All you see with HvacPro is inputs, outputs, and parameters. None of the underlying logic is shown. Are you saying you don't want to see all of the logic in the std app?

    Note: I'm not familiar with care or spyder, so I don't know how their apps can be examined any better. Do they show their underlying logic?

  7. #20
    Join Date
    Feb 2011
    Posts
    37
    The logic view is an absolute necessity when you write the logic yourself. I think he was referring to when you do the Q&A (which is the worst thing you could possibly attempt) and then look in the logic of those modules... **** show... If you cant write the programs yourself you need more training or you should think of another career path.

  8. #21
    Join Date
    Jul 2008
    Posts
    1,422
    Quote Originally Posted by wherzamizat View Post
    Proper valve sizing is critical for steam. no matter what you do may not be good enough if sized incorrectly.
    ...that is exactly where my mind was on this matter yesterday ... maybe the valves are simply too big
    1 + 1 = 3 ( *** for very large values of 1)

    ...everybody wants a box of chocolates and long stemmed rose

  9. #22
    Join Date
    Feb 2011
    Posts
    37
    Valve I have are fine. Loops are manually tuned to perfection and holding temp to within half a degree and less. Oh and if i change the set point it doesn't freak out and need to be reset... it just works..

  10. #23
    Join Date
    Jul 2008
    Posts
    1,422
    Quote Originally Posted by dhoyt View Post
    ...Loops are manually tuned to perfection and holding temp to within half a degree and less. Oh and if i change the set point it doesn't freak out and need to be reset... it just works..
    ...so what settings did you use in the end?
    1 + 1 = 3 ( *** for very large values of 1)

    ...everybody wants a box of chocolates and long stemmed rose

  11. #24
    Join Date
    Jul 2009
    Location
    Wa
    Posts
    113
    Yes I was talking about after the Q&A what the logic view is. It does look like a wire sheet?? When no Q&A is done maybe. I guess the discussion is more about the Q&A. I have watched guys who I would consider very good control guys, Q&A something then scratch there head for hours trying to figure out what is happening. The fact is when you program it yourself, you can find your error's fix them move on. I believe the earlier statement about the Q&A trying to dumb it down, so maybe the 24 year computer geek, can just answer all these questions and walk away. Translation chiller goes BOOM!!

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