[Equest-users] Air side HVAC

[Seun Odukomaiya]

John and Sambhav,
You are absolutely correct. If you specify exhaust CFM that exceeds OSA cfm, the OSA cfm is indeed increased to prevent negative pressurization of the zone. This is true if the Exhaust Air Source is specified as "Air Handler" (see screenshot). The other options are "Infiltration" and "Balanced Infiltration". If either of these latter two options are selected, the OSA cfm is not increased, but the exhaust air is made up through outside air infiltration into the zone (note: this is different than zonal infiltration, or space-to-space air transfer). I personally have been unsuccessful using either the "Infiltration", or "Balanced Infiltration" options because my unmet load hours tend to skyrocket when either option is selected. Again, my interpretation is that eQuest is making up the exhaust air with unconditioned outside air, which then dramatically impacts the temperature of the space. If anyone has had any success using these other methods, or some work-around to simulate space-to-space air transfer, I would be very interested in hearing about it.
As John has already stated, with any of the three options, eQuest will account for fan power based on your input KW/cfm or a combination of Static Pressure and Efficiency.

Seun Odukomaiya, LEED AP  -  Mechanical Engineer
L'Acquis Consulting Engineers
9229 Delegates Row, Suite 550
Indianapolis, IN 46240
voice:  (317) 706-2075 Ext. 255
fax:     (317) 706-2076
email: sodukomaiya at laceindy.com<mailto:sodukomaiya at laceindy.com>
web:  www.laceindy.com<http://www.laceindy.com/>
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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
Sent: Thursday, April 01, 2010 3:00 AM
To: sambhav tiwari; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Air side HVAC

Sambhav:

If you want Exhaust CFM Fan energy, then I believe you need to specify Exhaust CFM.

OK, eQuesters, I think I have this straight. If you specify an Exhaust CFM LESS THAN OSA CFM, nothing airwise changes, and Exhaust CFM translates to an Exhaust fan HP. If Exaust CFM EXCEEDS OSA CFM, the OSA CFM is increased to account for no negative airflow. And Exhaust CFM STILL creates and Exhaust HP.

Comments from our studio audience, please..

________________________________
From: sambhav tiwari <tiwari.sambhav at gmail.com>
To: equest-users at lists.onebuilding.org
Sent: Wed, March 31, 2010 10:47:32 PM
Subject: [Equest-users] Air side HVAC

Hi  All,
              In the AIR side HVAC under zone when we go to outdoor air tab there it asks about exhaust fan cfm for each zone so do we have to specify it exhaust cfm zonewise or the program assumes it that what ever is the fresh air cfm for each conditioned zone same will be the exhaust cfm.

Any response will be appreciable.

Thanks
Sambhav Tiwari.

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