Fluid Cooler / Refrigeration Condenser Loop Turns Off Mid-Year in EnergyPlus (with persistent “No Cooling Water Flow” warnings)

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Hi everyone,

I'm trying to model a water-cooled condenser loop for my supermarket integral cabinets in EnergyPlus. The loop contains water-cooled condensers on the supply side for the medium-temp and low-temp compressor racks, and a variable-speed pump and a fluid cooler on the demand side to reject heat to ambient air.

However, I consistently get the following warnings in the ERR file:

** Warning ** Refrigeration:CompressorRack:MEDIUMTEMPRACK. Water-cooled condenser has no cooling water flow. Heat is not being rejected from compressor rack condenser.
 This error occurred 96,780 total times;
 during Warmup 8 times;
 during Sizing 0 times.

** Warning ** Refrigeration:CompressorRack:LOWTEMPRACK. Water-cooled condenser has no cooling water flow. Heat is not being rejected from compressor rack condenser.
 This error occurred 96,780 total times;
 during Warmup 8 times;
 during Sizing 0 times.

The strange thing is that the entire water loop shuts down after July 21st and stays off until December. During this period, water flow rate = 0, refrigerant mass flow = 0, and pump power = 0, even though:

• All my schedules are active year-round
• I also set the loop minimum flow rate > 0
• The refrigeration racks are operating normally in the load reports
• The fluid cooler setpoint is fixed and the outdoor conditions should not force the loop to shut down

It’s as if something triggers the loop to turn off after July and it never comes back on.

I have checked the setpoint managers, schedules, availability managers, and node temperatures but cannot identify the cause. Does anyone know what might make an EnergyPlus plant loop stop flowing for several months, even though the refrigeration system still requires condenser cooling?

Any ideas would be greatly appreciated. Thanks!