Variable Speed Primary Chilled Water Pumps Operate Unexpectedly
 
  
 
  
 
 
 
 
 
 
    
        
        asked Feb 9  
 
 Keigo's avatar  
 
 
 
 
    
        
        updated Feb 10  
 
 
 
 
 
A bug report about chilled water pumps. The bug occurs when the following conditions are met.
 
     
  1. There are multiple chiller objects e.g.Chiller:Electric:EIR.
    2.  
  2. Each chiller has a primary chilled water pump.
    3.  
  3. The primary chilled water pumps are Pump:VariableSpeed, and Chiller Flow Mode of Chiller:Electric:EIR is set to LeavingSetpointModulated.
    4.  
  4. Design Minimum FLow Rate of Pump:Variable:Speed is not 0.
    5.  
  5. Load Distribution Scheme of Plant Loop is SequentialUniformPLR, SequentialLoad or Optimal.
    6.  
 
I expect that each chilled water pump is interlocked with each dedicated chiller, but actually all chilled water pumps operate when there is a cooling load even if the load is small enough to be handled by one chiller. That's the bug. Pump Control Type is set to Intermittent.
 
Since I can't find an ExampleFile which meets the coditions above, I reproduced the bug using HVACTemplate-5ZoneVAVWaterCooled.idf. I quickly revised the idf and expid files to meet the conditions above. The waterside schematic is shown below.
 
image description
 
The bug is easy to spot on 7 and 8 May in the charts below. Chiller2 to 4 do not operate but all the chilled water pumps operate on those days.
 
image description
 
The idf file is here. The version is V24-2-0.
 
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Comments
1
That's a great demonstration. Bug reports should ideally be reported at https://github.com/NREL/EnergyPlus/is... though.
Julien Marrec's avatar
                        Julien Marrec
                     (
    
        Feb 10
    )
1
@Julien Marrec If no one answers and this is more likely to be a bug, I'll post it on GitHub.
Keigo's avatar
                        Keigo
                     (
    
        Feb 10
    )
1
Reported on Github.
https://github.com/NREL/EnergyPlus/issues/10964
Keigo's avatar
                        Keigo
                     (
    
        Mar 4
    )
It seems the PLRs differ among the active chillers, which doesn’t align with the expected behavior of SequentialUniformPLR. Do you have any insights on why that might be happening?
yiyuan-jia's avatar
                        yiyuan-jia
                     (
    
        Apr 4
    )
I haven't looked into the code. It is beyond the scope of user's voluntary bug reporting.
Keigo's avatar
                        Keigo
                     (
    
        Apr 4
    )
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