[BLDG-SIM] eQuest 100% OA

Brandon Nichols BrandonN at Hargis.biz
Mon Nov 19 12:50:42 PST 2007


Taylor,
 
On pages 431-432 of the DOE2.2 Vol. 2 Dictionary manual, under the definition for the keyword OUTSIDE-AIR-FLOW, is in part the following statement:
 
"... Note that specifying outside ventilation air at the zone level takes precedence over specifying it at the system level."
 
This has tripped me up more than once... basically it's saying be sure to remove all outside air assignments at the zone level, either per person or per square foot, else whatever you do at the system level is ignored.
 
HTH...
 
Brandon Nichols, PE, LEED® AP
Mechanical
HARGIS ENGINEERS

600 Stewart Street

Suite 1000

Seattle, WA 98101

www.hargis.biz

 

d | 206.436.0400  c | 206.228.8707

o | 206.448.3376  f  | 206.448.4450

 
 

  _____  

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Kathryn Lee
Sent: Friday, November 16, 2007 6:41 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] eQuest 100% OA


I am modeling a 100% OA system for a hospital to compare the energy usage of constant volume and variable volume. I have entered in the appropriate OA minimum air change rates specified by code and am currently using the "Variable Air Volume" system type to model both systems. The only change that I am making between the two systems is the Min-Flow-Ratio; for CV it is set to 1.0 and for VAV it is set to 0.2 (we are using high turndown Phoenix valves). 
 
Our results are showing that the system is recirculating air. We have set OA economizer control as "fixed fraction" and 1.0 and have created a "min-air-sch" for ventilation air that is always set at 1.0. We have also tried setting the economizer control as "drybulb" and setting the boundary conditions to 100°F and 20°F. 
 
Do you have any suggestions regarding how to prevent recirculation? We still need to be able to define OA minimums for code compliance.
 
Thanks for the help.
 
Taylor


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