[Equest-users] Fixing unmet hours / outside of throttling rangewarnings

Jeremy Poling Jeremy.Poling at transwestern.net
Mon May 2 15:26:10 PDT 2011


Mark,
 
Your question seems to be less "how do I make these go away" and more "why is eQuest making it look like my engineer is wrong", correct?  The way you phrsed your question makes this sound like a design model question and not a question about a baseline model.
 
John Aulbach's advice is a good place to start: see if those items match the mechanical design.  At that point, I would then take the time to discuss the rest of the system inputs with the mechanical engineer to make certain the system is described the way he intended.  In addition, check the basic load conditions that he assumed compared to what is in eQuest: Occupancy, lighting, miscellaneous loads.  If you have a higher occupancy in eQuest than the engineer did when he selected the coils, that could cause the warnings you are seeing and the hours outside the throttling range if the discrepancy was large enough.  Make sure to confirm that the right system type was selected in eQuest - take a look in the help file for the system type.  A system in the model set to be a single-zone system will have large numbers of hours outside the throttling range if it has multiple zones assigned to it.  If you have every room setup in eQuest, but the engineer is designing single-zone systems and grouping rooms into common thermal zones, that may very well be the cause of your problem.
 
Another tip: look at the SS-K and SS-O reports to get an idea of where the system (SS-K) temperatures and zone (SS-O) temperatures are at.  The SS-O report logs 0 hours in a temperature band when the fans are not on.  Those two reports will give you an idea of how far outside of the temperature zone the system is operating.  The SS-R report will show you more detailed information on hours where the space temperatures are not being met.
 
When you do discuss this, make sure you approach it from a "we have a difference here that I want to make sure we figure out together" approach: both eQuest and the engineer's load calculations take into account a large number of variables.  While each variable has a greater or lesser impact on the results, they all do affect the calculations.
 
Good luck with the tweaking of the model!
 
Jeremy R. Poling, PE, LEED AP+BDC


________________________________

From: equest-users-bounces at lists.onebuilding.org on behalf of Mark Darrall
Sent: Mon 5/2/2011 8:21 AM
To: equest-users
Subject: [Equest-users] Fixing unmet hours / outside of throttling rangewarnings



Good Morning, eQUESTers,

 

I'm working on my design case model. Here's my ATTN report:

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys1 (PSZ) (G.NNW1)          may have inadequate cooling capability

             Check COOLING-CAPACITY and MIN-SUPPLY-T for consistency

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys2 (PSZ) (G.WSW2)          may have inadequate cooling capability

             Check COOLING-CAPACITY and MIN-SUPPLY-T for consistency

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys3 (PSZ) (G.N3)            may have inadequate cooling capability

             Check COOLING-CAPACITY and MIN-SUPPLY-T for consistency

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys4 (PSZ) (G.S4)            may have inadequate cooling capability

             Check COOLING-CAPACITY and MIN-SUPPLY-T for consistency

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys5 (PSZ) (G.N5)            may have inadequate cooling capability

             Check COOLING-CAPACITY and MIN-SUPPLY-T for consistency

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys6 (PSZ) (G.E6)            may have inadequate cooling capability

             Check COOLING-CAPACITY and MIN-SUPPLY-T for consistency

 

**WARNING**********************************************************************

             SYSTEM EL1 Sys7 (PSZ) (G.C7)            has zero outside air for design calculations

 

 

This last one I can answer as this system is a R/A only computer room cooler. For the others:

 

COOLING-CAPACITY comes directly from the HVAC designer and is the capacity of the installed units. I've tried adjusting MIN-SUPPLY-T from 55 to 50 (and this seems to jive with information the coil manufacturer provides) to get a larger delta-T and it only seemed to make things worse somehow. Minimum OSA is 20%, but again, this is a design condition. These units do have enthalpy-controlled economizers.

 

I'm also getting WAY too many hours outside of throttling range - 15%. My baseline model only has a 3%. I'm way out of whack with Appendix G requirements.

 

Any suggestions as to settings to modify to clear these? Thank you!

 

MARK DARRALL, AIA, LEED AP BD+C, NCARB
Senior Project Manager

 

 

 

DESIGN ENRICHING LIFE // LIFE ENRICHING DESIGN

 

A2SO4 Architecture, LLC

Union Station
300 South Meridian Street / 250
Indianapolis, Indiana 46225
TEL  317 388 8850

FAX  317 280 0692

MOB 765 749 0841
www.a2so4.com

 

Please consider the environment before printing this e-mail.  

 

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