[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [EnergyPlus_Support] max iteration problem
Hello,
I have looked at this problem and found that all or many of your Max
Iteration errors can be eliminated by increasing the convergence tolerance
on your controllers. Here are the original values that you had for the
controllers:
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 I changed the values 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}
Then all of the Max Iteration warnings were eliminated. What was happening
was that on 1 iteration the controller converged on the air loop setpoint
at 12.998C and the next time it was 13.002. Both values are within the
0.002 convergence tolerance of 13.0C, but greater than the sub-loop
tolerances between the Air Loop and the Zone Equipment Manager. Since you
have an outside Air System the sensitivities of the loop mass flow rate can
be enhanced or decreased by the weather file and that is why it was not
there for Chicago, but there with Minneapolis. Once you have determined
that your Max Iteration warnings are due to controller convergence
tolerance you can be confident that these warnings will not effect your
results even if you loosen them up a little.
Thanks
Dr. Richard Liesen
Associate Director, Building Systems Laboratory
Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign
At 12:44 AM 6/23/2004, you wrote:
>I try to simulate a building with VAV single duct reheat system, and
>I use ¡°5ZoneAuto.idf¡± as example. I gave the exactly same system
>to my building and run it at Minneapolis, except that there is no
>plenum zone in my building.
>
>However, I always get ¡°** Warning ** SimHVAC: Maximum iterations
>exceeded for all HVAC loops, MINNEAPOLIS SUMMER¡±.
>
>I am sure there is no problem on control setpoints, schedules,
>active or passive braches because I just copied from the 5AutoZone.
>Since I used autosizing, there is no possibility that sum of
>terminal airflows is not equal to supply fan air flow. I double
>checked all the air loop and water loop connections. It should be Ok
>if I understand correctly.
>
>I don¡¯t know where else it might be wrong. I attach the idf
>file "MySingleDuctReheatwithEconomizer2 "and appreciate if someone
>could help me have a look the file. Thank you so much.
>
>Meng
>
>
>
>
>The primary EnergyPlus web site is found at:
>http://www.energyplus.gov
>
>The group web site is:
>http://groups.yahoo.com/group/EnergyPlus_Support/
>
>Attachments are not allowed -- please post any files to the appropriate
>folder in the Files area of the Support Web Site.
>
>Yahoo! Groups Links
>
>
>
>
------------------------ Yahoo! Groups Sponsor --------------------~-->
Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar.
Now with Pop-Up Blocker. Get it for free!
http://us.click.yahoo.com/L5YrjA/eSIIAA/yQLSAA/dkFolB/TM
--------------------------------------------------------------------~->
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/EnergyPlus_Support/
<*> To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/