[Equest-users] Unmet Hours

Matt Clough mclough at kme-inc.com
Fri Mar 16 08:00:55 PDT 2012


All right Folks,

It's time to do that thing again where we talk about unmet hours.  I'll give a little background first:  I'm new to equest and to the HVAC industry, so bear with me.  The project is a 1F school building (pre-k) with a clerestory, split into 10 zones and predominantly served by series VAV terminals using chilled water and hot water loops.  It's in Houston, TX so and are no economizers.  I've spent the majority of the past few days reading previous discussions and trying a variety of changes.  I have attached the INP and PD2 for convenience.

I initially tried to represent the system based on the mechanical/electrical schedules, but that yielded many unmet hours (99%), so it is currently set to auto-size, but am still at about 600 unmet hours (7%).  7 of the zones are series VAV, 2 are single-zone with reheat, and one is a packaged single zone for the MDF room.

  *   Changing to an auto-sized system provided a large reduction in UH.
  *   am trying to not manipulate the data by adjusting the cooling/heating ratio.
  *   The setpoints are 75c/72h.  I tried changing them a few degrees in either direction, but did not get a large enough reduction.
  *   have the fans cycling at night (no OA), which did help reduce the hours
  *   switched into DDE and set actual CFM from the mechanical plans.  This resulted in an increase

As I am looking through the LS-B report, it seems like some of my zone loads might be a little high with some of the heat generation loads at about 12kbtu/h.  I think my inexperience hampers my ability to troubleshoot some of the problems because I don't necessarily have a good sense for what a reasonable result/prediction is.

I appreciate any assistance on this matter and am open to suggestions as far as proper modeling techniques and troubleshooting methods.

Sincerely,
Matt Clough
Mechanical Designer
KME Engineering
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