Here are a couple of things to consider:
· You must have an exhaust fan in the zone. Its airflow rate must match the amount of outdoor air introduced to the zone by each air loop. Normally that zone outdoor airflow rate is controlled in the Controller:OutdoorAir object, but it is also influenced by the outdoor air fields in Sizing:Zone. If you have an ERV or other zone object which introduces outdoor air, that also affects the balance.
· If your zone fan is not operating at the exact same times as the exhaust fan(s), the ?unbalanced exhaust? message will occur when the zone fan is off (and exhaust is on)
· Finally if your zone fan is the OnOff style, the warning will occur during times that the zone fan cycles off and the exhaust fan remains on.
p.s., Most of this information is from having the same problem and getting excellent assistance from Mike Witte
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of grandocu
Sent: Friday, September 24, 2010 10:52 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Airloop Error
Hello,
I'm getting the following error:
** Warning ** In AirLoopHVAC AHU-B-5 there is unbalanced exhaust air flow.
** ~~~ ** During Warmup, Environment=SUMMERSIZINGDAY, at Simulation time=07/20 19:40 - 19:50
** ~~~ ** Unless there is balancing infiltration / ventilation air flow, this will result in
** ~~~ ** load due to induced outdoor air being neglected in the simulation.
I don't see a problem with my connections but I did supply airflow rate myself. I am also getting a "maximum iterations" error for this airloop. Has anyone ever had this problem before? Thank you.
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