resolving "Plant temperatures are getting far too cold"

Hello,

I connected a boiler to the generator side of an absorption chiller (Chiller:Absorption:Indirect) by combining some of the example files that come along with Energy Plus 8.2. It's the first time I've done manual loop construction, and I've gotten the branch integrity to check out and set some extra sizing:plant loop objects so that I can autosize the chiller and boiler. But during warmup the inlet and outlet nodes of the demand side of the generator loop crash (-89.4C and -90.1C respectively). As the .err file suggests, I've manually increased operating capacity (boiler size = 6MW for a 130m2 building) and checked the operation schemes, although this is my first time working through these objects. I can't locate the source of the problem, although it does look there's 0W power getting from the supply to the demand side - the full 3MW of heating demand are unmet.

Any ideas about the next thing to look at (and maybe a good way to look at it?) would it be helpful if I included some of the code, or the .err file?

Thanks!

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Nick N

asked 2015-06-01 08:25:42 -0500

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updated 2015-06-12 10:32:09 -0500

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To diagnose a problem like this, I would add output variables to confirm if the boiler is operating and also look at the system node temperatures and mass flow rates on the plant loop to see what is happening. For example, is the pump operating on the boiler loop? I assume you've found example file IndirectAbsorptionChiller to reference. And it sounds like you may have already added outputs like these:

Output:Diagnostics, ReportDuringWarmup;
Output:Variable,*,Plant Supply Side Cooling Demand Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Plant Supply Side Heating Demand Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Plant Supply Side Inlet Mass Flow Rate,hourly; !- HVAC Average [kg/s]
Output:Variable,*,Plant Supply Side Inlet Temperature,hourly; !- HVAC Average [C]
Output:Variable,*,Plant Supply Side Outlet Temperature,hourly; !- HVAC Average [C]
Output:Variable,*,Plant Supply Side Not Distributed Demand Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Plant Supply Side Unmet Demand Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Boiler Heating Rate,hourly; !- HVAC Average [W]
Output:Variable,*,Boiler Mass Flow Rate,hourly; !- HVAC Average [kg/s]
Output:Variable,*,Pump Mass Flow Rate,hourly; !- HVAC Average [kg/s]
Output:Variable,*,System Node Temperature,hourly; !- HVAC Average [C]

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MJWitte

answered 2015-08-21 18:18:40 -0500

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Hi!

I had the same issue: I was able to solve it changing the field "Design Generator Fluid Flow Rate" from the "Chiller:Absorption:Indirect" object from Autosize to a high flow rate.