RE: [EnergyPlus_Support] Heat Recovery Problem

Dear Omer,

I have had the same warning recently. Apparently the design parameters of the HX model cause it’s accuracy to degrade significantly below 50% air flow. This seems inappropriate to me, but it’s part of the program presently.

You can check for your own project, but I don’t think it affects my model too much. It does generate a LOT of warnings, though!

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 O. Tugrul Karaguzel
Sent: Tuesday, June 22, 2010 3:42 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Heat Recovery Problem

Hi all,
I'm repeatedly having the following warning for my Energy Plus model in which i tried to simulate a heat recovery system (using HeatExchanger:AirToAir:SensibleAndLatent).

   ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent "OA HEAT RECOVERY 3"
   **   ~~~   ** Average air volume flow rate is <50% or >130% of the nominal HX supply air volume flow rate.
   **   ~~~   ** Air volume flow rate ratio = 0.494. Occurrence info= HEADMASTER'S RESIDENCE, 01/01 08:00 - 08:15

Does anyone have experience with such a warning? I tried to overcome it by changing input parameters in objects of Controller:OutdoorAir or Fan:VariableVolume or Sizing:System but unfortunately I cannot manage to solve it.
Many Thanks.

Omer T. Karaguzel
Center for Building Performance & Diagnostics
Carnegie Mellon University
5000 Forbes Ave. Pittsburgh, 15213 PA

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