VAV Fume hood exhaust with Energy Recovery

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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.



Bouchard, Jordan's picture
Joined: 2011-09-30
Reputation: 0

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 Porter's picture
Joined: 2011-09-30
Reputation: 0

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.

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?


William Bishop, EIT, LEED(r) AP

Bishop, Bill2's picture
Joined: 2011-09-30
Reputation: 0


I am trying to construct the various schedules for my eQuest project.
In order to ensure that I understand what everything means and to avoid the
automatic creation of superfluous schedules, etc., I am composing entirely
in the .inp file using notepad and using eQuest-generated code as a guide.
I noticed that eQuest generates twelve (12) day schedules for exterior
lighting, the U-name of each of which is formatted like this:
"Ext Lighting W1 All "
Can anyone tell me what the twelve such schedules signify? Does each
belong to a particular month? Are they even necessary? If all of my
external lighting is photocell-controlled, can't I just set all such daily
external lighting schedules to ( 1 ) (always on), then apply photocell
control per the DOE2-2 dictionary?

Lars Fetzek, EI

Lars Fetzek's picture
Joined: 2011-09-30
Reputation: 0

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Scott Criswell's picture
Joined: 2011-09-30
Reputation: 0

You might find it easier to do, and understand if you made your schedules in the detailed mode rather than with note pad.

Charles Land's picture
Joined: 2011-09-30
Reputation: 0