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Re: [EnergyPlus_Support] Unbalanced exhaust air flow warning

Thank you very much, James!

On 8.01.2013 13:52, Jim Dirkes wrote:


1.       An exhaust fan which cycles will cause this warning, and there is nothing you can do about it (I am pretty sure)

2.       An exhaust fan which runs constantly will not normally cause this warning if:

·         It operates with the same schedule as the air loop fan and..

·         the air loop uses a mixing box with variable outdoor air ability and sufficient variability to stay balanced (e.g. maximum outdoor air + infiltration >= maximum exhaust air)

o   Infiltration is normally small, so it doesn’t affect the balance very much.


James V Dirkes II, PE, BEMP, LEED AP
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653


From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Miroslav Bratanov
Sent: Tuesday, January 08, 2013 5:41 AM
To: EnergyPlus Support
Subject: [EnergyPlus_Support] Unbalanced exhaust air flow warning



Hello Everyone,

I get the following warning:

** Warning ** In zone F006 there is unbalanced exhaust air flow.
** ~~~ ** During Warmup, Environment=SOFIA ANN HTG 99.6% CONDNS
DB, at Simulation time=01/21 00:00 - 00:15
** ~~~ ** Unless there is balancing infiltration / ventilation
air flow, this will result in
** ~~~ ** load due to induced outdoor air being neglected in
the simulation.

There is an exhaust fan in zone F006 which I modeled using the
Fan:Zoneexhaust. There is no infiltration or ventilation in the zone, so
no outdoor air. To balance the exhaust air I use a ZoneMixing object
which takes the necessary amount of air from another zone where fresh
air is supplied by means of mechanical ventilation. The mechanical
ventilation, exhaust fan and zonemixing use the same availability schedule.

Is there anything else that has to be done in order to get rid of this

Thank you,


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