[Equest-users] eQuest Users Group - Setting outside air minimum

Li, Lan lli at sbmce.com
Tue Feb 23 13:17:26 PST 2010


I thought this min. is for heating season. See below.

 


MIN-OUTSIDE-AIR


The minimum outside air flow divided by the supply air flow during
winter heating periods. You may alternatively, or additionally, specify
outside air quantities at the zone level using the ZONE keywords
OA-CHANGES, OA-FLOW/PER or OUTSIDE-AIR-FLOW. The default is calculated
from zone loads and ZONE input. 

If  you enter MIN-OUTSIDE-AIR as well as the ZONE keywords
OUTSIDE-AIR-FLOW, OA-CHANGES, OA-FLOW/PER or EXHAUST-FLOW, the ZONE
values take precedence. If no zone-level values are specified,
MIN-OUTSIDE-AIR will be used. If MIN-AIR-SCH is specified,
MIN-OUTSIDE-AIR, or the corresponding ZONE values, should be entered. 

The program will not allow MIN-OUTSIDE-AIR to be less than the sum of
the EXHAUST-FLOWs for all zones divided by the sum of all supply flows
for all zones. That is, the exhaust fan operation will override
MIN-OUTSIDE-AIR if MIN-OUTSIDE-AIR is set too low. 

The minimum outside air ratio reported on SV-A is based on the design
calculated supply air flow and not on the value input for SUPPLY-FLOW,
which overrides the design flow rate. 

When evaporative cooling is in effect, the outside air dampers are 100%
open. When outside air is able to cool the building without the aid of
evaporative cooling, the outside and return air dampers modulate open.

 

Lan

 

________________________________

From: Tomlinson, Scott [mailto:stomlinson at smma.com] 
Sent: Tuesday, February 23, 2010 4:11 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] eQuest Users Group - Setting outside air minimum

 

Hello folks,

 

Hopefully someone knows how to deal with outside air.  I can't seem to
figure out how to set my minimum outside air on my HVAC systems.  When I
set my OA minimum on my Air system , and adjust the minimum OA fraction
in my schedule I still get ventilation results below my set minimum.  It
seems, no matter what I do to the outside air setting on the system side
the program sizes the OA ventilation based solely on what my outside air
ventilation rates of the individual spaces and ignores any setting I put
in my system.  Does anyone have experience on how to remedy this?

 

 

 

 

 

 

 

-        Thank you,

 

__________________________________________

Scott Tomlinson, PE, LEED-AP

Mechanical

Symmes Maini & McKee Associates, Inc.

1000 Massachusetts Avenue, Cambridge, MA 02138

t: 617.520.9438

 

 

f: 617.354.5758

stomlinson at smma.com

www.smma.com <http://www.smma.com/> 

 

 

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