Load Distribution with "Sequential Load" in E+

asked 2017-10-03 06:09:15 -0500

Fish Lee gravatar image

updated 2017-10-03 20:23:08 -0500

I have found this problem in EnergyPlus for quite a while already perhaps from v8.5.

I have set the load distribution scheme to "Sequential Load" as below.

PlantLoop,
ChilledWaterLoop Chilled Water Loop,  !- Name
Water,                   !- Fluid Type
,                        !- User Defined Fluid Type
ChilledWaterLoop Chiller Operation,  !- Plant Equipment Operation Scheme Name
ChilledWaterLoop ChW Supply Outlet,  !- Loop Temperature Setpoint Node Name
98,                      !- Maximum Loop Temperature {C}
1,                       !- Minimum Loop Temperature {C}
autosize,                !- Maximum Loop Flow Rate {m3/s}
0,                       !- Minimum Loop Flow Rate {m3/s}
autosize,                !- Plant Loop Volume {m3}
ChilledWaterLoop ChW Supply Inlet,  !- Plant Side Inlet Node Name
ChilledWaterLoop ChW Supply Outlet,  !- Plant Side Outlet Node Name
ChilledWaterLoop ChW Supply Side Branches,  !- Plant Side Branch List Name
ChilledWaterLoop ChW Supply Side Connectors,  !- Plant Side Connector List Name
ChilledWaterLoop ChW Demand Inlet,  !- Demand Side Inlet Node Name
ChilledWaterLoop ChW Demand Outlet,  !- Demand Side Outlet Node Name
ChilledWaterLoop ChW Demand Side Branches,  !- Demand Side Branch List Name
ChilledWaterLoop ChW Demand Side Connectors,  !- Demand Side Connector List Name
SequentialLoad,          !- Load Distribution Scheme
,                        !- Availability Manager List Name
SingleSetpoint,          !- Plant Loop Demand Calculation Scheme
CommonPipe;              !- Common Pipe Simulation

PlantEquipmentList,
ChilledWaterLoop 3 Chillers,  !- Name
Chiller:Electric:EIR,    !- Equipment 1 Object Type
WCC-101,                 !- Equipment 1 Name
Chiller:Electric:EIR,    !- Equipment 2 Object Type
WCC-102,                 !- Equipment 2 Name
Chiller:Electric:EIR,    !- Equipment 3 Object Type
WCC-103;                 !- Equipment 3 Name

PlantEquipmentOperation:CoolingLoad,
ChilledWaterLoop Chiller Operation All Hours,  !- Name
0,                       !- Load Range 1 Lower Limit {W}
1000000000000000,        !- Load Range 1 Upper Limit {W}
ChilledWaterLoop 3 Chillers;  !- Range 1 Equipment List Name

PlantEquipmentOperationSchemes,
ChilledWaterLoop Chiller Operation,  !- Name
PlantEquipmentOperation:CoolingLoad,  !- Control Scheme 1 Object Type
ChilledWaterLoop Chiller Operation All Hours,  !- Control Scheme 1 Name
HVACTemplate-Always 1;   !- Control Scheme 1 Schedule Name

At the beginning of the simulation run, the load distributed to WCC-101 (1st Chiller) seemed behaving normally with a gradual increase up to 0.99.

Once the cooling load exceeded the capacity of my 1st chiller, WCC-102 (2nd chiller) kicked in. Afterwards, both chillers operates continuously as uniform load distribution until the end of simulation run. The 2nd chiller would not stop operating even with the cooling demand can be handled by the 1st chiller.

Has any one experienced this and has an explanation to it? image description image description

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Comments

Can you add your IDF snippet for the "ChilledWaterLoop Chiller Operation" (PlantEquipmentOperationSchemes and the (probably) PlantEquipmentOperation:CoolingLoad)? I'm also confused on the graphs: what's the blue line? the red crosses?

Julien Marrec gravatar imageJulien Marrec ( 2017-10-03 17:38:11 -0500 )edit

Hi @Julien Marrec, I have added the code for those two classes.

The graphs are line graphs with red crosses marking the data points.

Fish Lee gravatar imageFish Lee ( 2017-10-03 20:25:01 -0500 )edit

Any chance you could share your whole IDF (upload it somewhere and link to it here)? Or at least a CSV with results for both chillers and timestamps + telling us what are Chillers Min/Max/Optimum PLR and Min Unloading Ratios? I'd like to be able to play with the data myself. It's an interesting question, I'm willing to have a look.

Julien Marrec gravatar imageJulien Marrec ( 2017-10-04 03:29:54 -0500 )edit