The air loop can fail convergence for reasons other than tolerance. Are you getting many of these errors?
Are you using chilled water coils? If so try setting the availability schedules for the water coil to always on and see if the message disappears.
On 9/30/2010 8:50 AM, grandocu wrote:
Hello everyone,
I have a warning that keeps popping up saying "Maximum iterations (20) exceeded" and the message below says the airloop failed, but all tolerance values below are 0. Does anyone know why this message is showing up if all the tolerance values are 0?
** Warning ** SimHVAC: Maximum iterations (20) exceeded for all HVAC loops, at ANNSIM, 01/02 05:10 - 05:11
** ~~~ ** SimFlags=[TFFFFFFF] AirLoops[T],ZoneEq[F],NonZoneEq[F],PlantLoops[F],CondLoops[F],ElecCircuits[F],PlantDemandLoops[F],CondDemandLoops[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=[724 - AHU-B-6 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=[723 - AHU-B-3 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=[720 - AHU-B-5 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=[719 - AHU-B-4 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=[722 - CB AHU-B-2 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=[390 - CB CONDENSER DEMAND OUTLET NODE]
** ~~~ ** 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=[347 - CHW_LOOP 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=[383 - CB CONDENSER DEMAND INLET NODE]
** ~~~ ** 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=[342 - CHW_LOOP CNDW DEMAND INLET]
** ~~~ ** 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=[314 - HW_LOOP HW DEMAND OUTLET]
** ~~~ ** Plant Flow Tolerance Values, Most Recent listed first
** ~~~ ** PlantFlowFlowTol=0.000
** ~~~ ** PlantFlowFlowTol=0.000
** ~~~ ** PlantFlowFlowTol=0.000
** ~~~ ** PlantFlowFlowTol=0.000
** ~~~ ** PlantFlowFlowTol=0.000
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