I am guessing this is a VAV system. Check the temperature at the inlet of the cooling coil and see if it is below 12.8C.
Output:Variable, CoilInletNodeName here ,System Node Temp,detailed;
There also may be nothing wrong with the results since the tolerances you show do imply convergence. A good check of the results would be necessary to convince yourself of that (i.e., make sure the HVAC system are operating correctly).
On 9/30/2010 9:05 AM, grandocu wrote:
Yes I am and yes they are set to always available. It only happens on the hour when I go from cycling on any zone at 18 C to running the airloop system at a setpoint at 12.8 C. Coincidentally, there is no OA allowed during night as well so when it starts, the system has a load to deal with and now OA ventilation. Will this lead to a problem? Should I try to modify the OA and warmup schedule to get rid of it or might it be another reason.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> 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
> >
> >
>
> --
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL 32922-5703
> Phone: (321) 638-1454
> Fax: (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
>
> UCF - From Promise to Prominence: Celebrating 40 Years
>
-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 40 Years
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