[Equest-users] outside air ratio

[Bishop, Bill]

I have also noticed that you have to be careful about how you specify OA
for induction systems. If I enter zone-level OA cfm and also enter
system-level SUPPLY-FLOW, I end up with NO outside air even though the
MIN-OUTSIDE-AIR is set to 1.00. The problem goes away if I enter a
system MIN-AIR-SCH (whether or not I have the SUPPLY-FLOW entered) or if
I leave the SUPPLY-FLOW blank (default).
 
To get a better idea of what the OA is actually doing, I create an
Hourly Report Block and select the following options under the "HVAC
System" variable type:
"Ratio of outside air to total supply air" 
"Total system supply air flow rate"
 
There are a ton of other variables available in the hourly reports that
you can use to troubleshoot your models.
 
Regards,
 
William Bishop, EIT, LEED(r) AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Please strive to live sustainably.
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Verena
Kindl
Sent: Friday, September 11, 2009 9:13 AM
To: Bouchard, Jordan; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] outside air ratio
 
Thank you, but i already thought about that and i have nothing specified
there. But now I tried to specify the flow to each zone instead of doing
it for the whole system and then the outdoor air ratio is calculated
correctly. Of course I considered the induction ratio so I specified for
each zone 1962 cfm supply flow (induction ratio of 2) then I get an
outdoor air ratio of 1 and 918 cfm OA per zone. Do you think I can do
that? It is strange so as the other way should work as well. 
 
________________________________

Von: Bouchard, Jordan [mailto:Jordan.Bouchard at stantec.com] 
Gesendet: Freitag, 11. September 2009 15:08
An: Verena Kindl; equest-users at lists.onebuilding.org
Betreff: RE: [Equest-users] outside air ratio
 
Hi Verena,
 
Check your zone level OA values. If you want to specify 100% OA at the
system level you have to clear the zone level inputs as they will
override the system level OA inputs.
Regards,
 
Jordan Bouchard, LEED(r) AP
Mechanical Engineer In Training
Stantec Consulting Ltd.
Ph: (416) 596-6686
Fx: (416) 596-6680
Jordan.Bouchard at stantec.com 
stantec.com <http://www.stantec.com>  
 
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________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Verena
Kindl
Sent: Friday, September 11, 2009 8:57 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] outside air ratio
 
Hi all,
 
I have an induction unit for the whole building, supplying 204000 cfm
outside air to the building. So I specify the supply flow of the system
(204000 cfm) and set the min outside air ratio =1. In the SV-A report it
shows on the system level 0 outside air and therefore no cooling/heating
capacity and for the zone it shows about 800-1100 cfm outside air. Only
if I do not specify the supply flow on the system level then I also get
an outside air ratio of 1 for the system level. Why is it not possible
to tell equest that the 204000 cfm it supplies is only outside air. I
have not specified an economizer so it should be outside air all the
time ??
Have a nice weekend.
 
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