Error: Too many iterations in Airflow Network simulation (calculated natural ventilation)
Posted by Andy Tindale on 14-Mar-19 10:46 AM
When using calculated natural ventilation with very large airflow openings (relative to the size of the rest of the zone) an EnergyPlus error can occur:
"Too many iterations (SOLVZP) in Airflow Network simulation"
This is caused by EnergyPlus failing to solve an equation internally due to the presence of very high airflow heat transfer between zones. The usual cause is a large horizontal hole between stacked zones. It is often possible to solve the problem by increasing the size of the tolerances as described in the program help on advanced calculation options. For example try multiplying both the "Relative airflow convergence tolerance" and the "Absolute airflow convergence tolerance" model option values by 10 until the simulation is able to proceed. In most cases it is sufficient to multiply both by 100.