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  1. #1
    Join Date
    Feb 2013
    Posts
    13

    Virtual point speed

    Hi guys,
    I have a question to you ; I work with AHU units,Power Process Control program,but I am new in the field.My problem is,Virtual point at the loop is moving too slow,the damper is moving slow too and the freezstat shutdown the unit. Please help me to correct this problem.Also if you have information about Siemens application 2463-Tracking boxes. Il appreciate your help. All the best to you. Ghita

  2. #2
    What are the gains in your LOOP statement, and what type of panel is it?

  3. #3
    Join Date
    Feb 2006
    Location
    Float'N Vally, MS
    Posts
    1,825
    Quote Originally Posted by Ghita View Post
    Hi guys,
    I have a question to you ; I work with AHU units,Power Process Control program,but I am new in the field.My problem is,Virtual point at the loop is moving too slow,the damper is moving slow too and the freezstat shutdown the unit. Please help me to correct this problem.Also if you have information about Siemens application 2463-Tracking boxes. Il appreciate your help. All the best to you. Ghita
    This is part of a Lab or fume hood system?
    This stuff is sensative and in "some" areas you have to be certified to adjust it? Adjusting one part could have an adverse effect somewhere else.

    Just saying....
    Life is too short, Behappy!
    TFMM

  4. #4
    Join Date
    Feb 2013
    Posts
    13
    Behappy or others, if you have the application Simens 2463-traking boxes help me please, I promise, nothing bad will happen here.I have to read about (min.cfm, max cfm) and set point cfm, what is the connection between ? All the best to you
    Nave_ dude, I have to look in the program and I will reply to you. Thank you

  5. #5
    Join Date
    Jun 2006
    Location
    Des Moines
    Posts
    285
    The loop speed may not be the issue. Is the unit tripping off on startup or when it's been running and OA temp drops?

    Is it a new issue? Have you checked temps during trouble periods (look for stratification in the AHU) and what temp does the automation system show at the time of LTD trip?
    Dingman from Iowa~
    "A lie gets halfway around the world before the truth has a chance to get its pants on."
    - Sir Winston Churchill (1874-1965)

    The Dingman's webpage, featuring the Ding_Z

  6. #6
    Join Date
    Feb 2013
    Posts
    13
    Dingman,
    Thank you for the reply,We have Units and the virtual point is moving faster than virtual point at other Units. At this unit the virtual point is moving, but slow. For example; If the Setpoint temperature in the mixtbox is 55 F and the actual temperature is 45 F the damper should close and the heating valve should open.The damper close but slow and the unit go down on low temp. I was thinking how to speed up the loop. Thank you and all the best

  7. #7
    Join Date
    Jun 2006
    Location
    Des Moines
    Posts
    285
    Quote Originally Posted by Ghita View Post
    Dingman,
    Thank you for the reply,We have Units and the virtual point is moving faster than virtual point at other Units. At this unit the virtual point is moving, but slow. For example; If the Setpoint temperature in the mixtbox is 55 F and the actual temperature is 45 F the damper should close and the heating valve should open.The damper close but slow and the unit go down on low temp. I was thinking how to speed up the loop. Thank you and all the best
    That sounds pretty straightforward. The virtual point should be controlled by a PID loop in the PPCL. Find the PID values in a unit that is working properly and copy those values into the offending PID loop.

    That should get you close.
    Dingman from Iowa~
    "A lie gets halfway around the world before the truth has a chance to get its pants on."
    - Sir Winston Churchill (1874-1965)

    The Dingman's webpage, featuring the Ding_Z

  8. #8
    Join Date
    Feb 2013
    Posts
    13
    I will do that,I will make comparison between PID values. We use only P and I from PID
    Dingman, Thank you

  9. #9
    Join Date
    Apr 2006
    Location
    North Carolina
    Posts
    12
    "That sounds pretty straightforward. The virtual point should be controlled by a PID loop in the PPCL. Find the PID values in a unit that is working properly and copy those values into the offending PID loop.

    That should get you close. "

    Only if the units are simular in size/design. A 40,000 CFM unit with return fan doesn't react like a 5,000 CFM unit with out a return fan. Tread carefully when adjusting PID loops. Try increasing the P gain 25% as a start then bump up the I gain 5%.

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