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RE: [EnergyPlus_Support] Max Iterations exceeded?





The reporting time is June 01 at 08:00 am.  If this is the first time the cooling is turned on, you can ignore the warning.
 
If you get lots of these, there may be some incorrect sizing or scheduling program. 
 
The zone mean temperature  and system cooling and heating rate  usually will give the clue.
 
The long report simply says that the cooling plant is not turned on at that time, which could be at the heating and cooling change over point, if you have mixed thermostat types in use.
 
I cannot tell the problem by looking the error message alone.

 Dr. Li  

 

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: gch2j2006@xxxxxxxxx
Date: Thu, 2 Feb 2012 18:10:54 +0000
Subject: [EnergyPlus_Support] Max Iterations exceeded?

 
I've been getting messages like this a lot. Wondering if anyone could help me out (Dr Li? Anyone?)

** Warning ** SimHVAC: Maximum iterations (20) exceeded for all HVAC loops, at SDD, 06/01 08:00 - 08:06
** ~~~ ** SimFlags=[TFFFF] AirLoops[T],ZoneEq[F],NonZoneEq[F],PlantLoops[F],ElecCircuits[F]..F=ok,T=fail
** ~~~ ** HVAC Tolerance Flags=[0000000] Enthalpy[0],MassFlow[0],HumRat[0],Pressure[0],FlowQual[0],Energy[0],Temp[0]..0=ok,1=fail
** ~~~ ** HVAC Tolerance Values, Most Recent listed first
** ~~~ ** HVAC EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** HVAC side outlet node=[610 - 0 CLASSROOMS RETURN AIR OUTLET]
** ~~~ ** HVAC EnthalpyTol=0.000, MassFlowTol=1.478E-011, HumRatTol=1.7347E-018, PressureTol=3.E-011
** ~~~ ** FlowQualTol=0.00, EnergyTol=3.135E-007, TempTol=3.55E-015
** ~~~ ** HVAC side outlet node=[609 - 5 OTHERS RETURN AIR OUTLET]
** ~~~ ** HVAC EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** HVAC side outlet node=[608 - 5 LABS RETURN AIR OUTLET]
** ~~~ ** HVAC EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** HVAC side outlet node=[607 - 5 CLASSROOMS RETURN AIR OUTLET]
** ~~~ ** HVAC EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** HVAC side outlet node=[606 - 4 OTHERS RETURN AIR OUTLET]
** ~~~ ** Plant Tolerance Flags=[00000000] Enthalpy[0],MassFlow[0],HumRat[0],Pressure[0],FlowQual[0],Energy[0],Temp[0],PlantFlowMassFlow[0]..0=ok,1=fail
** ~~~ ** Plant Tolerance Values, Most Recent listed first
** ~~~ ** Plant EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** Plant side outlet node=[337 - CHILLED WATER PLANT CNDW SUPPLY OUTLET]
** ~~~ ** Plant EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** Plant side outlet node=[345 - CHILLED WATER PLANT CNDW DEMAND OUTLET]
** ~~~ ** Plant EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** Plant side outlet node=[327 - CHILLED WATER PLANT CHW SUPPLY OUTLET]
** ~~~ ** Plant EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** Plant side outlet node=[301 - HOT WATER PLANT HW SUPPLY OUTLET]
** ~~~ ** Plant EnthalpyTol=0.000, MassFlowTol=0.000, HumRatTol=0.0000, PressureTol=0
** ~~~ ** FlowQualTol=0.00, EnergyTol=0.000, TempTol=0.00
** ~~~ ** Plant side outlet node=[333 - CHILLED WATER PLANT CHW DEMAND OUTLET]
** ~~~ ** Plant Flow Tolerance Values, Most Recent listed first

I've tried changing different setpoints and messing with my schedules but nothing seems to work. The result of this is mostly that none of my zones receive the proper cooling (all the cooling coils have a nominal capacity of 0) and I see no end uses in cooling after the simulation.




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