[Equest-users] VAV Fume hood exhaust with Energy Recovery

Bishop, Bill wbishop at pathfinder-ea.com
Thu Sep 10 07:05:37 PDT 2009


Jordan,
One way you can model variable hood exhaust and allow for energy
recovery is to use a MIN-AIR-SCH at the system level to vary the
percentage of outside air, in combination with MIN-FLOW-SCH at the zone
level, provided your system is VAV.
 
Fred,
Are you sure you can get energy recovery from zonal exhaust? The help
menu for EXHAUST-FLOW is pretty specific about this not being the case,
and help for ERV-FAN doesn't say anything about it. As for an ERV-FAN
bug, are you keeping in mind that the ERV fans will not operate when the
system fans are off?
 
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 Fred
Porter
Sent: Thursday, September 10, 2009 9:13 AM
To: equest-users at lists.onebuilding.org; Jordan Bouchard
Subject: Re: [Equest-users] VAV Fume hood exhaust with Energy Recovery
 
I'm fairly certain that if the ERV-FAN command is set to SELF-CONTAINED,
then the ERV is modeled as receiving both the "general" exhaust (RETURN
or RELIEF) fan airflow, and, the zone exhaust airflow. This works fine
as long as the none of the other zones on the system have actual return
air.
 
It seems the ERV-FANs has a modest bug. Even if the all its keywords are
set to enable 24/7 fan operation, these fans are only simulated as
running when energy recovery is occurring, which is only about 1/2 to
2/3 of the hours of the year, when the ERV controls are set properly.
Happy Modeling
Fred

>>> "Bouchard, Jordan" <Jordan.Bouchard at stantec.com> 9/3/2009 1:08 PM
>>>
Hello,
 
I am currently trying to model a laboratory with VAV fume hoods in
eQUEST. The lab exhaust is tied to the general exhaust. When the fume
hood demand goes up, the general exhaust goes down, all to maintain a
constant overall exhaust and a negative pressure relationship to the
neighboring offices. 
 
My problem is that the project is incorporating glycol run-around loops
into the exhaust and that heat is routed back to the AHU. If I input the
exhaust into the Zone, I understand that I will not realize any heat
recovery because only the central exhaust can do that. Is there a way to
model this properly or do I have to model the fume hoods in the zone
with air-flow tracking and not capture any of the heat recovery savings.
 
Thanks,
Jordan
 
 
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