Warnings When Modeling Walk-in Freezer Using Air-Chiller Object - Internal Temperature Fluctuations

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Hello everyone,

I am currently working on modeling a walk-in freezer using the air-chiller object and have encountered some warnings that I am struggling to understand and resolve.

IDF file is accessible here: IDF file

I use E+V9.2 you can find it here

Here are the key points of my model:

1. Objective: I am attempting to model a walk-in freezer using the air-chiller object.
2. Setpoint: The walk-in setpoint is -22°C ± 2K. To account for internal temperature fluctuations, I have used the "Temperature difference between cutout and setpoint" approach, setting the temperature at -18°C and the cutout at 2K.
3. Material Construction: I have utilized Polystyrene High Density as the construction material with a thickness of 0.2m and a thermal conductivity of 0.036 W/m.K.
4. Defrost Cycles: Three defrost cycles are defined in the model.

The figure below plots the internal temperature fluctuations over a 3-hour period. it can be seen the the fluctautions exhibit a high frequency.

Upon checking the error and warning file, I found some warnings, but I am unsure about their causes.

The warnings (File.err):

EnergyPlus V9.2

Program Version,EnergyPlus, Version 9.2.0-921312fa1d, YMD=2024.01.05 15:54,
   ** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR NTZ108-9B" unused. 
   ** Warning ** GetRefrigerationInput: : Refrigeration:Compressor="COMPRESSOR VTZ038-G" unused. 
   ************* Testing Individual Branch Integrity
   ************* All Branches passed integrity testing
   ************* Testing Individual Supply Air Path Integrity
   ************* All Supply Air Paths passed integrity testing
   ************* Testing Individual Return Air Path Integrity
   ************* All Return Air Paths passed integrity testing
   ************* No node connection errors were found.
   ************* Beginning Simulation
   ** Warning ** Zone Air Heat Balance is out of balance for zone named WALK-IN ZONE
   **   ~~~   ** Zone Air Heat Balance Deviation Rate is more than 163.7 {W}
   **   ~~~   **  Occurrence info: Environment=RUN PERIOD, at Simulation time=08/10 00:00 - 00:01
   ************* Simulation Error Summary *************
   ** Warning ** The following fluid names are "Unused Fluids".  These fluids are in the idf
   **   ~~~   **  file but are never obtained by the simulation and therefore are NOT used.
   ************* Refrigerant=NH3
   ** Warning ** The following schedule names are "Unused Schedules".  These schedules are in the idf
   **   ~~~   **  file but are never obtained by the simulation and therefore are NOT used.
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=ZONE CONTROL TYPE DUAL SET POINT SCHED.
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=WORK EFF. SCHEDULE
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=REF SYSTEM WORK SCH
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=ZONE CONTROL TYPE SCHED DUAL YEARROUND
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=NO DEFROSTSCHED
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=NO DRIPDOWNSCHED
   ************* Schedule:Year or Schedule:Compact or Schedule:File or Schedule:Constant=INFILTRATIONSCHEDULE
   *************
   ************* ===== Recurring Error Summary =====
   ************* The following recurring error messages occurred.
   *************
   *************  ** Warning ** Refrigeration:System chilling WarehouseCoils WALK-IN LOWTEMPSYSTEM - Refrigeration system unable to meet load of warehouse coils chilled by system ... continues by derating coil load
   *************  **   ~~~   **   This error occurred 25 total times;
   *************  **   ~~~   **   during Warmup ...