Error while modeling radiant underfloor cooling system

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Hello guys! I'm a student in Technical University in Crete and I've been struggling a couple of weeks in a project, in which I would like to model a radiant floor cooling system using "Low Temperature Radiant Variable Flow" and I'm getting the following warnings every time:

Error file results:

 Program Version,EnergyPlus, Version 9.0.1-bb7ca4f0da, YMD=2019.01.18 18:50,
   ************* Beginning Zone Sizing Calculations
   ** Warning ** ProcessScheduleInput: Schedule:Constant="ALWAYS ON DISCRETE", Blank Schedule Type Limits Name input -- will not be validated.
   ** Warning ** ProcessScheduleInput: Schedule:Constant="ALWAYS OFF DISCRETE", Blank Schedule Type Limits Name input -- will not be validated.
   ** Warning ** ProcessScheduleInput: Schedule:Constant="ALWAYS ON CONTINUOUS", Blank Schedule Type Limits Name input -- will not be validated.
   ** Warning ** GetHTSurfaceData: Surfaces with interface to Ground found but no "Ground Temperatures" were input.
   **   ~~~   ** Found first in surface=SURFACE 16
   **   ~~~   ** Defaults, constant throughout the year of (18.0) will be used.
   ** Warning ** CheckUsedConstructions: There are 1 nominally unused constructions in input.
   **   ~~~   ** For explicit details on each unused construction, use Output:Diagnostics,DisplayExtraWarnings;
   ** Warning ** Calculated design heating load for zone=THERMAL ZONE 4 is zero.
   **   ~~~   ** Check Sizing:Zone and ZoneControl:Thermostat inputs.
   ** Warning ** Calculated design heating load for zone=THERMAL ZONE 8 is zero.
   **   ~~~   ** Check Sizing:Zone and ZoneControl:Thermostat inputs.
   ************* Beginning Plant Sizing Calculations
   ** Warning ** GetElectricEIRChillerInput: Chiller:Electric:EIR="CHILLER - AIR COOLED"
   **   ~~~   ** Adding OutdoorAir:Node=CHILLER - AIR COOLED INLET NODE FOR CONDENSER
   ** Warning ** GetElectricEIRChillerInput: Chiller:Electric:EIR="CHILLER - AIR COOLED"
   **   ~~~   ** Energy input ratio as a function of temperature curve output is not equal to 1.0 (+ or - 10%) at reference conditions.
   **   ~~~   ** Curve output at reference conditions = 0.850
   ** Warning ** Output:Meter:MeterFileOnly requested for "Electricity:Facility" (TimeStep), already on "Output:Meter". Will report to both eplusout.eso and eplusout.mtr
   ************* 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 ** ZoneHVAC:LowTemperatureRadiant:VariableFlow [LOW TEMP RADIANT VAR FLOW 1]
   **   ~~~   ** Surface [SURFACE 28] temperature below dew-point temperature--potential for condensation exists
   **   ~~~   ** Flow to the radiant system will be shut-off to avoid condensation
   **   ~~~   ** Predicted radiant system surface temperature = 33.33
   **   ~~~   ** Zone dew-point temperature + safety delta T= 33.79
   **   ~~~   **  Environment=SOUDA/KHANIA ANN CLG .4% CONDNS DB=>MWB, at Simulation time=07/21 00:00 - 00:10
   **   ~~~   ** Note that a 1.0000 C safety was chosen in the input for the shut-off criteria
   **   ~~~   ** Note also that this affects all surfaces that are part of this radiant system
   ** Warning ** ZoneHVAC:LowTemperatureRadiant:VariableFlow [LOW TEMP RADIANT VAR FLOW 6]
   **   ~~~   ** Surface [SURFACE 49] temperature below dew-point temperature--potential for condensation exists
   **   ~~~   ** Flow to the radiant system will be shut-off to avoid condensation
   **   ~~~   ** Predicted radiant system surface temperature = 32.67
   **   ~~~   ** Zone dew-point temperature + safety delta T= 38.23
   **   ~~~   **  Environment=SOUDA/KHANIA ANN CLG .4% CONDNS DB=>MWB, at Simulation time=07/21 00:00 - 00:10
   **   ~~~   ** Note that a 1.0000 C safety was ...