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  1. #1
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    Fluid Cooler Sequencing

    Hello Guys,

    Is the following workable for fluid cooler sequencing?

    Also what is the typical minimum allowable condenser water temperature?

    There is also a requirement in the sequence that during heating season water has to pass through both towers to prevent freeze up, what will be the best way to implement it?



    C START THE LEAD FLUID COOLER PUMP WITH ASSOCIATED TOWER FAN TO RUN AT 50% SPEED
    C IF THE CONDENSER WATER SUPPLY TEMPERATURE SETPOINT CAN NOT BE REACHED FOR AN OPERATER ADJUSTABLE PERIOD OF TIME,
    C THEN START THE SECOND FLUID COOLER PUMP WITH ASSOCIATED TOWER FAN TO ALSO RUN AT 50% SPEED
    C IF THE CONDENSER WATER SUPPLY TEMPERATURE CAN NOT STILL BE MAINTAINED FOR AN OPERATER ADJUSTABLE PERIOD OF TIME
    C THEN ALLOW BOTH TOWER FANS TO BE RAMP UP TO 100%
    C ASSUME LEAD LAG OF TWO FLUID COOLERS AT 100 HRS
    C IFL_HO_CHILLERSYS_ENA IS CHILLER DEMAND
    C FC_STG_OPER_TIME_1(OPERATOR ADJUSTABLE) IS THE TIME AFTER WHICH THE SECOND FC IS RAMPED UPTO 50% WHEN FIRST ONE IS
    C FC_STG_OPER_TIME_2 (OPERATOR ADJUSTABLE)IS THE TIME BETWEEN STAGING OF THE FIRST FLUID COOLER
    C CWP_1 AND CWP_2 ARE CONDENSER WATER PUMPS
    C VFD SPEED CONTROL IS THROUGH 0-10 V DC MODULATING COMMAND

    ------- LEAD LAG STRATEGY FOR THE FLUID COOLERS --------------

    C ATLEAST ONE FC IS RUNNING FOR ONE CHILLER. THE LEAD LAG OF THE FLUID COOLER SYSTEM IS CONSIDER AFTER 100 HOURS

    0270 SAMPLE (60) IF("FC_1_SS".EQ. ON .AND. "FC_1_STS" .EQ.ON) THEN "FC_1_SYS_RT" = "FC_1_SYS_RT" + 1
    0280 IF("FC_1_SYS_RT") .EQ. 6000 THEN SET($LOC2, 1) ELSE SET($LOC2, 0)
    0290 IF("FC_1_SYS_RT") .GE. 6000 THEN SET(0,"FC_1_SYS_RT")
    0300 C
    0310 C
    0320 SAMPLE (600000) IF $LOC2.EQ.1 THEN $LOC4= $LOC4+ 1
    0330 $LOC5= $LOC4
    0340 CH_1_SYS_CYCLE =$LOC5
    0350 C
    0360 SAMPLE (60) IF("FC_2_SS".EQ. ON .AND. "FC_2_STS" .EQ.ON) THEN "FC_2_SYS_RT" = "FC_2_SYS_RT" + 1
    0370 IF("FC_2_SYS_RT") .EQ. 6000 THEN SET($LOC3, 1) ELSE SET($LOC3, 0)
    0380 IF("FC_2_SYS_RT") .GE. 6000 THEN SET(0,"FC_2_SYS_RT")
    0390 SAMPLE (600000) IF $LOC3.EQ.1 THEN $LOC7 =$LOC7+1
    0400 $LOC8 =$LOC7
    0410 C
    0370 "FC_2_SYS_CYCLE" = $LOC8
    0380 C
    0390 IF("FC_1_SYS_CYCLE" .LE. "FC_2_SYS_CYCLE" .AND. "FC_1_SYS_FAULT" .NE. ON .AND. "IFL_HO_CHILLERSYS_ENA" .EQ. ON) THEN ON("FC_SYSTEM_1")
    0400 IF( "FC_2_SYS_CYCLE" .LE."FC_1_SYS_CYCLE" .AND. "CHILLER_2_SYS_FAULT" .NE. ON .AND. "IFL_HO_CHILLERSYS_ENA" .EQ. ON) THEN ON("FC_SYSTEM_2")

    ------ LEAD SYSTEM FIRST STAGE START ---------
    0410 IF(FC_SYSTEM_1" .EQ. ON .AND. "IFL_HO_CHILLERSYS_ENA" .EQ. ON ) THEN ON ( "CWP_1_SS")
    0420 IF ("CWP_1_SS") .EQ. ON .AND. ("CWP_1_STS").EQ. ON .AND. ("CWP_1_FAULT").EQ. OFF THEN SET $LOC1 =1 ELSE $LOC1=0
    0430 IF $LOC1 .EQ. 1 THEN TABLE(SECND2,$LOC10,0,0,150,50)
    0440 SET($LOC 10,"FC_1_VFD_SPD_VRT")
    0450 TABLE( "FC_1_VFD_SPD_VRT", "FC_1_VFD_SPD",0,0,100,10)
    0460 C IF THE SYSTEM 2 IS THE LEAD SYSTEM
    0470 IF(FC_SYSTEM_2" .EQ. ON .AND. "IFL_HO_CHILLERSYS_ENA" .EQ. ON ) THEN $LOC9= 1 ELSE $LOC9 =0
    0480 IF $LOC9 .EQ. 1 .AND. ("CWP_2_STS").EQ. ON AND. ("CWP_2_FAULT").EQ. OFF THEN TABLE(SECND2,$LOC11,0,0,150,50)
    0490 C
    0500 C
    0510 SET($LOC2,"FC_1_VFD_SPD_VRT")
    0520 TABLE( "FC_1_VFD_SPD_VRT", "FC_1_VFD_SPD",0,0,100,10)

    C LINE 410: IF THE FC SYSTEM 1 IS THE LEAD SYSTEM THEN ON THE CONDENSER WATER PUMP 1 SS COMMAND (VFD SS COMMAND)
    C LINE 420: IF THE CONDENSER WATER SS IS ON AND THERE IS NO FALUT ON THE PUMP THEN SET PLACE HOLDER $LOC1 TO 1 ELSE IT IS ZERO
    C LINE 430,440 AND 450: RAMP THE VFD TO 150 SECONDS FROM 50 SECONDS THEN RAMP THE VFD TO 50 PCT (5V)
    C LINE 460: IF THE FC SYSTEM 2 IS THE LEAD SYSTEM THEN ON THE CONDENSER WATER PUMP 2 SS COMMAND (VFD SS COMMAND)
    C LINE 470: IF THE CONDENSER WATER SS IS ON AND THERE IS NO FALUT ON THE PUMP THEN SET PLACE HOLDER $LOC9 TO 1 ELSE IT IS ZERO
    C LINE 480: SIMILIAR TO LINE 420
    C LINE 480,510,520: RAMP THE VFD TO 150 SECONDS FROM 50 SECONDS THEN RAMP THE VFD TO 50 PCT (5V)



    ----- STAGING OF FLUID COOLER SECOND STAGE AND BETWEEN STAGES ------

    0530 IF (" FC_1_VFD _SPD" .NE. 50 ) THEN SET (SECND3,0)
    0540 IF ("FC_SYS_CWRT" .GT. "FC_SYS_CWRT_STPT" ) .AND. SECND3. GE."FC_STG_OPER_TIME_1" .AND. "CWP_2_SS" .EQ. OFF THEN ON " CWP_2_SS"
    0550 IF ("FC_SYS_CWRT" .GT. "FC_SYS_CWRT_STPT" ) .AND. SECND3. GE."FC_STG_OPER_TIME_1" .AND. "CWP_2_STS" .EQ. ON .AND."CWP_2_FAULT".NE. ON THEN TABLE (SECND4,$LOC12,0,0,150,50)
    0550 SET($LOC12,"FC_1_VFD_SPD_VRT")

    0560 IF (" FC_1_VFD _SPD" .NE. 50 ) THEN SET (SECND4,0)
    0570 IF ("FC_SYS_CWRT" .GT. "FC_SYS_CWRT_STPT" ) .AND. SECND4. GE."FC_STG_OPER_TIME_1" .AND. "CWP_1_SS" .EQ. OFF THEN ON " CWP_1_SS"
    0580 IF ("FC_SYS_CWRT" .GT. "FC_SYS_CWRT_STPT" ) .AND. SECND3. GE."FC_STG_OPER_TIME_1" .AND. "CWP_1_STS" .EQ. ON .AND."CWP_1_FAULT".NE. ON THEN TABLE (SECND4,$LOC4,0,0,150,50)
    0590 SET($LOC4,"FC_1_VFD_SPD_VRT")


    0600 IF (" FC_1_VFD _SPD" .NE. 50 .AND. " FC_2_VFD _SPD" .NE.50 ) THEN SET (SECND7,0)
    0610 IF ("FC_SYS_CWRT" .GT. "FC_SYS_CWRT_STPT" ) .AND. SECND7. GE."FC_STG_OPER_TIME_2".THEN TABLE (SECND4,$LOC13,0,50,150,100)
    0620 SET($LOC13,"FC_1_VFD_SPD_VRT")
    0630 IF ("FC_SYS_CWRT" .GT. "FC_SYS_CWRT_STPT" ) .AND. SECND8. GE."FC_STG_OPER_TIME_2" THEN TABLE (SECND4,$LOC14,0,50,150,100)
    0640 SET ($LOC14, "FC_2_VFD_SPD_VRT")

    C LINE 530: IF FC1 VFD SPEED IS NOT 50 (PCT) THEN SET TIMER(SECOND 3) AS ZERO OTHERWISE START TIMER
    C LINE 540: IF RETURN WATER TEMPERATURE OF THE CONDENSED WATER IS GREATER THEN CONDENSED WATER RETURN TEMPERATURE THEN ON VFD 2 (CWP2) SS CMMAND
    C LINE 540 AND 550: RAMP THE VFD( FC2) TO 50 PCT TO 50 HZ IN 2.5 MIN TO MEET CONDENSER WATER TEMPERATURE
    C LINE 560 : SIMILIAR TO LINE 530
    C LINE 570: SIMILIAR TO LINE 540
    C LINE 580 AND 590 : RAMP THE VFD( FC1) TO 50 PCT TO 50 HZ IN 2.5 MIN TO MEET CONDENSER WATER TEMPERATURE
    C LINE 600: IF FC1 VFD SPEED IS NOT 50 (PCT) AND FC2 VFD SPEED IS NOT 50 (PCT) THEN SET TIMER(SECOND 7) AS ZERO OTHERWISE START TIMER
    C LINE 610 TO 640 : RAMP UP THE VFD TO 100 ( PCT) FOR BOTH FLUID COOLERS TO MEET CONDENSED WATER TEMPERATURE

  2. #2
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    I have a question.

    Every time I see one of your posts it has to do with confirming code writing. Are you in a job that requires code writing? Are you not capable of debugging your own code?
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"

    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

    Jtrammel - "I’m going to sell hvac systems derp derp derp"
    BBeerme - "every time he opens his mouth, he reminds me of a cow without the fart bag."

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  4. #3
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    I'm reminded of our long lost member matrix who said once.

    "Some of us are coin operated around here"
    Propagating the formula. http://www.noagendashow.com/

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  6. #4
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    Ghufran, couple of questions. You start out with "fluid cooler sequencing", then you mention needing to run water through "both towers". What type of a fluid cooler/tower are you working with? What's the definition of "heating season" for where this to be implemented, in terms of expected Outside Air Temperature range?

    Is it cold enough outside that simply turning on the pump would get the needed temperature drop as a first 'stage'? If it does, why not bring on the standby (lag) pump as the next step if there is a concern about the cooler/tower freezing up? I'm making the presumption that these two coolers/towers are piped in true parallel fashion.

    Once you have the water moving, I'd be concerned about taking the fan(s) straight to 50% & jumping from that point to 100%, particularly since you have VFD's, depending on ambient air temperature it's way too easy to starting forming ice on an open tower (been there, done that, didn't get a t-shirt) and/or overshoot your condenser water temp setpoint. IMHO, running a fan motor as 0/50/100% off of a VFD doesn't really gain much beyond having a "soft start" for what is basically being run as a two-speed motor. Why not start the VFD on the lead unit to run the fan at the higher of the minimum motor and cooler/tower fan speed recommended by their manufacturers, and then ramp it up to 50% as needed to maintain the water temperature at setpoint, then follow with the second cooler in a similar manner before ramping them any higher?

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  8. #5
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    Thread Starter
    @ dolson, thanks!

    see below the piping configuration for the fluid coolers, it does look like they are in true parallel configuration. the intent for running the water through both towers in "heating season" ( seem to be ) to have enough flow so as to not prevent freezing. In terms of OAT, it will get cool enough that only turning a pump ( with spray pump and fan turn off) may cause freezing.

    IMHO Turning on one FC only and then if it starts freezing ( say coil temperature falls below the minimum of 8C) then start the second FC to prevent freezing is a good suggestion.

    Yes I agree that the current sequence does translate the VFD/motor setup into two speed Motor control and might actually risk freezing in the FC specially at Low Load Conditions.

    starting the VFD on the lead unit to run the fan at the higher of the minimum motor and cooler/tower fan speed recommended by their manufacturers( Trane), and then ramp it up to 50% as needed to maintain the water temperature at setpoint, then follow with the second cooler in a similar manner before ramping them any higher is a good idea IMO.
    Attached Images Attached Images  

  9. #6
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    The quality of the responses is epic. I could be highly motivated to deal with that job if enough coins were to be deposited in the correct slot.

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  11. #7
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    Im just waiting for the next new thread...
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"

    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

    Jtrammel - "I’m going to sell hvac systems derp derp derp"
    BBeerme - "every time he opens his mouth, he reminds me of a cow without the fart bag."

  12. #8
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    Ghufran, the diagram helps, but also muddies the water as well. Your initial post asked about "typical minimum allowable condenser water temperature", condenser water for what? That should be information found in the equipment manual or equipment submittal package. On the diagram it shows piping associated with the heating water of two air handling units, by my interpretation of the acronyms. The overall operation of the systems likely were designed by a mechanical engineer, and if the sequence is unclear they should be contacted directly to discuss your questions with them.

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  14. #9
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    Thread Starter
    yes, we are in discussion to sort it out.

    typical minimum / maximum condenser water temperature was in context of the return water temperature from another set of FCs(not on this diagram) to the condensers of a set of Chillers. I will go through the mechanical package to get those numbers. thanks, again.

  15. #10
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    Thread Starter
    for those waiting for new thread, I have few other things that I will be posting soon. always good to have keen readers !

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