Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
My understanding is that the <50% or >130% warning is because the HeatExchanger:AirToAir:SensibleAndLatent only provides inputs for heat exchanger effectiveness at 75% and 100% airflow. At higher and lower airflows, the effectiveness may vary significantly from that given. (wouldn't it be nice to have a curve, instead of a few inputs?) If your heat exchanger has a similar effectiveness at low and high airflows, this warning can be safely ignored.
The severe warning is more serious. Like high and low airflows, different types of heat exchangers will have different effectiveness with unbalanced airflows.
I would obtain the actual effectiveness of your heat exchanger at various airflow rates, and look at simulation detailed outputs:
Output:Variable,*,Heat Exchanger Sensible Effectiveness,hourly; !- HVAC Average
Output:Variable,*,Heat Exchanger Latent Effectiveness,hourly; !- HVAC Average
