Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
I have recently found another cause for maximum iterations exceeded: fluctuations in airloop mass flow due to two different fans in the airloop.
The example is as follows:
AirLoop constructed with OpenStudio containing UnitarySystem consisting of a Fan (On/Off), a WAHP cooling coil, heating coil etc.; i.e. OpenStudio creates an air loop with a VariableFlow-Fan and an OnOff-Fan in sequence. Whenever the OnOff-Fan switches On or Off, there can be significant deviations in mass flow between successive air loop nodes, which apparently is numerically difficult for the EnergyPlus solver.
My solution has been to eliminate the VariableFlow-Fan, so that the air loop only contains only one fan, i.e. the Fan of the UnitarySystem. This way the convergence problems were eliminated.
| | 2 | No.2 Revision |
I have recently found another cause for maximum iterations exceeded: fluctuations in airloop mass flow due to two different fans in the airloop.
The example is as follows:
AirLoop constructed with OpenStudio containing UnitarySystem consisting of a Fan (On/Off), a WAHP cooling coil, heating coil etc.; i.e. OpenStudio creates an air loop with a VariableFlow-Fan and an OnOff-Fan in sequence. Whenever the OnOff-Fan switches On or Off, there can be significant deviations in mass flow between successive air loop nodes, which apparently is numerically difficult for the EnergyPlus solver.
My solution has been to eliminate the VariableFlow-Fan, so that the air loop only contains only one fan, i.e. the Fan of the UnitarySystem.
This way the convergence problems were eliminated.
