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[EnergyPlus_Support] Problem with CHILLER:CONST COP in Cooling Tower example



Dear Sankar,
I tested the example CoolingTower.idf which comes with E+1.2.3.
It runs without any problems in the delivered configuration (only one 
chiller is working). 
Now I tried to run 2 chillers in parallel, so I made the following 
changes: 
-) used 'All Chillers' instead of 'Electric Only' in the 'COOLING LOAD 
RANGE BASED OPERATION' object 'Peak Operation' and 'Off Peak 
Operation'
-) changed the order of equipments in the 'PLANT EQUIPMENT LIST' 'All 
Chillers': Now the 'Little Chiller' is the first element and the 'Big 
Chiller' is the second.

This results in following error:
   ** Severe  ** CalcConstCOPChillerModel: Condenser flow = 0, for 
ElectricChiller=LITTLE CHILLER
   **   ~~~   **  Occurrence info=CHICAGO_IL_USA ANNUAL COOLING 1% 
DESIGN CONDITIONS DB/MCWB, 07/21 07:10 - 07:20

Now this is very strange, because the AbsorbtionChilller.idf example, 
which have the same configuration, runs without any problems. The only 
difference is the used chiller type. The AbsorbtionChilller example 
uses a CHILLER:ELECTRIC in parallel to the CHILLER:ABSORPTION.

Therefore, I replaced the CHILLER:COP in the CoolingTower example with 
a CHILLER:ELECTRIC, and now the 2 chillers are working in parallel!!!

So it seems that the CHILLER:COP model have a problem to run in 
parallel with other chillers.


This is the same problem as reported by Patrik, an colleague at work, 
see post 'Re: How many condenser loops' from 21.Oct.2005. 
May be, the problem with CHILLER:COP is also the reason for the errors 
in the uploaded file chiller_09.30.2005.zip.

Christian











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