Airflow network CalcAirflowNetworkMoisBalance error [closed]
We are running a detailed EnergyPlus simulation of a house. The purpose is to have a detailed duct and airflow model for assessing the performance of HVAC air delivery components. We are currently in the process of defining and hooking up all of the zone nodes and ductwork, however I keep getting the following fatal error after the simulation has run for ~1 month: "A diagonal entity is zero in AirflowNetwork matrix ZONE3OUTLETNODE." ZONE3OUTLETNODE is currently defined as a leakage path from one of the bedrooms to the adjacent hallway, acting as the return air path.
Digging into the source, it appears the error is based off an integer comparison which should not be changing during simulation. I'm not that familiar with C++ or the E+ code so I may be mis-understanding what is occurring. I'm also not sure what the MA() command does.
// Check singularity
for ( i = 1; i <= AirflowNetworkNumOfNodes; ++i ) {
if ( MA( ( i - 1 ) * AirflowNetworkNumOfNodes + i ) < 1.0e-6 ) {
ShowFatalError( "CalcAirflowNetworkMoisBalance: A diagonal entity is zero ...
The relative humidity in both zones is something normal (10%-50%).
So far we have connected 6 of the 30 thermal zones into the AFN. I am hoping to troubleshoot errors and gain a better understanding of the simulation in this more simplified state before setting up the entire model in the AFN.
Has anyone encountered this error before? Are there known causes and fixes?
Other background: Initial model is created using Rhino and Honeybee. 1 minute simulation timestep Thermostat is being modeled by using an EMS to over-ride the fan airflow. (since E+ can't model an actual thermostat by default) Heating is from an electric coil, and cooling is from a simple DX coil.
@spqr, is your favorite movie Gladiator? :)
I have updated the model to include a complete airflow network, however continue to get the error message. Sometimes a simulation will run for an entire year with no problem, sometimes it will run for a day or a month before kicking back with the error. I am modifying various HVAC system parameters such as fan flow rate, supply temp set point, total system capacity, duct length, duct U value, etc. The error is coming from a different thermal zone each time, but always seems to come from the zone outlet.
What values are feeding into the MA array? Is the model calculating 0 RH for a node?