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  1. #1
    Join Date
    Dec 2006
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    ASHRAE Guideline 36P - High Performance Sequences of Operation for HVAC Systems

    Anyone else using this guideline to program their systems? I have used the trim and respond reset logic for a few years now and find it very functional.

    ASHRAE 36P

    I hadn't heard about it till today, but had a project years ago that specified the reset logic exactly like it is in 36P and have used it since (appears to be what ALC has been doing for 15+ years). Going to go over it over the next couple of weeks and see if there are anymore diamonds in the rough I can implement.

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  3. #2
    Join Date
    Mar 2008
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    Thanks for posting.

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  5. #3
    Join Date
    May 2012
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    Excuse my soapbox...? My personal thoughts on Trim and Respond. No doubt it will work but you might want to consider other means.

    Example, if you want the VAV with the greatest opening to remain at 90% why not make this the setpoint for a PID. Compare the VAV with greatest opening against a setpoint of 90%. As the output of the PID varies reset the static pressure setpoint from a minimum of say .75" to a maximum of say 1.5". With a bit of tuning you'll get nice smooth control.

    Got a humidifier that you want to control? Reset the discharge humidity setpoint based on a PID using return (or space) humidity as the process variable. Spend a little time with a psych chart to gauge the maximum and minimum discharge setpoints. You can get nice smooth control without bumping into the high limit.

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  7. #4
    Join Date
    Jan 2015
    North Carolina
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    I was required to do this on a few jobs last year. I agree with craftyringwiseveteran, just use the greatest damper % as your process variable and call it a day. No need for all the extra crap.

    Either way, this whole "new, eco-friendly, ground-breaking" control strategy can easily be compromised with a shotty maintenance program.

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  9. #5
    Join Date
    Jan 2003
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    90.1 reset as they describes works well. Exactly as they say, its more forgiving on tuning than using a straight PID. Since most techs don't seem to bother properly tuning things these days, I would lean to their method simply for that reason.

    PID would accomplish the same, though are you only kicking in the PID when there is more than one or two calls for damper or whatever they call for and backing it off on the same? Being able to kill off problem boxes is a must to make it work or it will just end up at the max setpoint constantly.

    Never really understood what the thinking was behind ignoring the first few boxes calling for more static. They must not understand when its the CEOs office or packed conference room being ignored, its a problem. A big one. So PID straight up on damper position, if you can kill out undersized boxes, clean and easy. Assuming, someone actually tunes it and makes the PID slow enough not to cause a constant damper repositions with duct static changing constantly.

    The DAT reset in 90.1 is crap IMO. All the nonsense alarms they call out in this are a perfect recipe to get a customer to ignore everything. There some good ideas, but less is more with alarms IMO.
    Propagating the formula.

  10. Likes gregcmar liked this post.

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