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[EnergyPlus_Support] Re: Exceeding maximum iterations problem
Rahul,
Thank you for your help. I have made several simulation runs with
different convergence tolerances (both increased and decreased
values) on the cooling coil controller and reheat controllers but
these changes have had no effect on the number of iterations reported
in the error file. Does anybody have any other suggestions?
Thanks, David
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Rahul Chillar
<chillarrahul@y...> wrote:
> Hello
> This same problem had occured with a user earlier , ........... Max
> Iteration errors can be eliminated by increasing the convergence
tolerance
> on your controllers
>
> For example look at the controller information below and you will
easily figure out how to solve that. If it does not kindly let us
know so that we can look at your file which you uploaded.
>
> EARLIER CASE with problems:
>
> CONTROLLER:SIMPLE,
> Central Cooling Coil Contoller 1, !- Name
> TEMP, !- Control variable
> Reverse, !- Action
> FLOW, !- Actuator variable
> VAV Sys 1 Outlet Node, !- Control_Node
> Cooling Coil Water In, !- Actuator_Node
> 0.002, !- Controller Convergence Tolerance: delta
> temp from setpoint temp {deltaC}
> autosize, !- Max Actuated Flow {m3/s}
> 0.0000001; !- Min Actuated Flow {m3/s}
>
>
> CONTROLLER:SIMPLE,
> Central Heating Coil Contoller 1, !- Name
> TEMP, !- Control variable
> Normal, !- Action
> FLOW, !- Actuator variable
> VAV Sys 1 Outlet Node, !- Control_Node
> Main Heating Coil 1 Water Inlet Node, !- Actuator_Node
> 0.002, !- Controller Convergence Tolerance: delta
> temp from setpoint temp {deltaC}
> autosize, !- Max Actuated Flow {m3/s}
> 0.0000001; !- Min Actuated Flow {m3/s}
>
> These values created over 350 Max Iteration warnings. Then the
values were
> changed to:
> CONTROLLER:SIMPLE,
> Central Cooling Coil Contoller 1, !- Name
> TEMP, !- Control variable
> Reverse, !- Action
> FLOW, !- Actuator variable
> VAV Sys 1 Outlet Node, !- Control_Node
> Cooling Coil Water In, !- Actuator_Node
> 0.001, !- Controller Convergence Tolerance: delta
> temp from setpoint temp {deltaC}
> autosize, !- Max Actuated Flow {m3/s}
> 0.0000001; !- Min Actuated Flow {m3/s}
>
>
> CONTROLLER:SIMPLE,
> Central Heating Coil Contoller 1, !- Name
> TEMP, !- Control variable
> Normal, !- Action
> FLOW, !- Actuator variable
> VAV Sys 1 Outlet Node, !- Control_Node
> Main Heating Coil 1 Water Inlet Node, !- Actuator_Node
> 0.001, !- Controller Convergence Tolerance: delta
> temp from setpoint temp {deltaC}
> autosize, !- Max Actuated Flow {m3/s}
> 0.0000001; !- Min Actuated Flow {m3/s}
>
> The errors were reduced to over 50 Max iteration warnings.
>
> When Values Changed to
> CONTROLLER:SIMPLE,
> Central Cooling Coil Contoller 1, !- Name
> TEMP, !- Control variable
> Reverse, !- Action
> FLOW, !- Actuator variable
> VAV Sys 1 Outlet Node, !- Control_Node
> Cooling Coil Water In, !- Actuator_Node
> 0.0001, !- Controller Convergence Tolerance: delta
> temp from setpoint temp {deltaC}
> autosize, !- Max Actuated Flow {m3/s}
> 0.0; !- Min Actuated Flow {m3/s}
>
>
> CONTROLLER:SIMPLE,
> Central Heating Coil Contoller 1, !- Name
> TEMP, !- Control variable
> Normal, !- Action
> FLOW, !- Actuator variable
> VAV Sys 1 Outlet Node, !- Control_Node
> Main Heating Coil 1 Water Inlet Node, !- Actuator_Node
> 0.0001, !- Controller Convergence Tolerance: delta
> temp from setpoint temp {deltaC}
> autosize, !- Max Actuated Flow {m3/s}
> 0.0; !- Min Actuated Flow {m3/s}
>
>
> ALL MAX ITERATION ERROR ELIMINATED.
> Try the same procedure in your file , i am sure they will go away.
These occur because outer loop has higher tolerance set than inner
loop . Hence it is unable to converge.
> If they go away with above change you need not worry about the
results even if you loosen up the tolerance.
>
> Thanks
> Rahul Chillar
> Graduate Research Assistant
> Building Systems Laboratory
> Univerisity of Illinois UC
>
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> bsiengineer <arch_engel@h...> wrote:
> My simulation is having a problem of exceeding the maximum
iterations
> on the HVAC system. I am simulating two interior rooms served by a
> single-duct VAV reheat system. This model has previously been run
> successfully with a single-duct constant volume system. The system
> is electric preheat and reheat, and purchased chilled water
cooling,
> so it's fairly simple.
>
> I will upload my file, Iterations.idf, to the
> folder "Problem_Submittals". Can anyone help me figure out what is
> going wrong?
>
> Thanks!
>
>
>
>
> The primary EnergyPlus web site is found at:
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>
>
> Thanks
> Rahul Chillar
> Grad Student
> Building Systems lab
> Univ Of Illinois Urbana Champaign
>
>
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