Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
There are over 2 million warnings and only 2 maximum iteration warnings? I would check the bottom of the err file to see if there are recurring warnings listed there.
Maximum iteration warnings can be troubling. What they mean are that the simulation was unable to find a solution, and in most cases, the solution bounces from one result to another. Usually a different temperature or mass flow rate, or both. This means that the answer found during the iteration process is whatever the last iteration found. This answer may not necessarily be the correct result.
Over the years I have found two recurring reasons for maximum iteration warnings. There are certainly other reasons for these warnings. These are:
1) HX using the in the outdoor air system WITHOUT tight controls on the air loop supply air temperature 2) Multi-speed air loop systems that cannot decide how to meet a small load while bringing in outdoor air. The simulation begins by calculating an outdoor air quantity and mixed air temperature based on the last time step results. Then the multi-speed system is simulated and decides a different speed or mode (i.e., cooling or heating) is needed to meet the load. This changes the outdoor air mass flow rate and can result in oscillations or maximum iterations. This typically happens at low load conditions. 3) ??
Other users/developers feel free to edit this list as needed....
| | 2 | No.2 Revision |
There are over 2 million warnings and only 2 maximum iteration warnings? I would check the bottom of the err file to see if there are recurring warnings listed there.
Maximum iteration warnings can be troubling. What they mean are that the simulation was unable to find a solution, and in most cases, the solution bounces from one result to another. Usually a different temperature or mass flow rate, or both. This means that the answer found during the iteration process is whatever the last iteration found. This answer may not necessarily be the correct result.
Over the years I have found two recurring reasons for maximum iteration warnings. There are certainly other reasons for these warnings. These are:
1) HX using the in the outdoor air system WITHOUT tight controls on the air loop supply air temperature
temperature
2) Multi-speed air loop systems that cannot decide how to meet a small load while bringing in outdoor air. The simulation begins by calculating an outdoor air quantity and mixed air temperature based on the last time step results. Then the multi-speed system is simulated and decides a different speed or mode (i.e., cooling or heating) is needed to meet the load. This changes the outdoor air mass flow rate and can result in oscillations or maximum iterations. This typically happens at low load conditions.
conditions.
3) ??
Other users/developers feel free to edit this list as needed....
| | 3 | No.3 Revision |
There are over 2 million warnings and only 2 maximum iteration warnings? I would check the bottom of the err file to see if there are recurring warnings listed there.
Maximum iteration warnings can be troubling. What they mean are that the simulation was unable to find a solution, and in most cases, the solution bounces from one result to another. Usually a different temperature or mass flow rate, or both. This means that the answer found during the iteration process is whatever the last iteration found. This answer may not necessarily be the correct result.
Over the years I have found two recurring reasons for maximum iteration warnings. There are certainly other reasons for these warnings. These are:
1) HX using the used in the outdoor air system WITHOUT tight controls on the air loop supply air temperature
2) Multi-speed air loop systems that cannot decide how to meet a small load while bringing in outdoor air. The simulation begins by calculating an outdoor air quantity and mixed air temperature based on the last time step results. Then the multi-speed system is simulated and decides a different speed or mode (i.e., cooling or heating) is needed to meet the load. This changes the outdoor air mass flow rate and can result in oscillations or maximum iterations. This typically happens at low load conditions.
3) ??
Other users/developers feel free to edit this list as needed....
