Should large refrigerated spaces over 30,000 sqft with setpoints ranging from -20°F to 35°F be modeled using the refrigeration tab of the HVAC Systems side tab of OpenStudio 1.9, or by using an air loop with schedules to apply setpoints to each zone? Or should it be both, that is, should the refrigeration system (see screenshot) or the zones they are in have an HVAC loop?
I currently have the refrigerated spaces drawn as unique spaces and thermal zones, and have applied a refrigerated walkin case for each zone. I then applied constructions, racks, zones, etc under the system grid view. I can run ideal air loads, but when I turn them off and run the model I get several severe errors.
"Severe * GetRefrigerationInput: Refrigeration:WalkIn="COOLER 132" System Node Number not found for Zone 1 Name = THERMAL ZONE: L1 II COOLER 132 * ~~~ ** .. Walk Ins must reference a controlled Zone (appear in a ZoneHVAC:EquipmentConnections object."
"Severe ** GetRefrigerationInput: Refrigeration:System="REFRIGERATION SYSTEM", System Node Number not found for Suction Piping Zone Name = THERMAL ZONE: L1 II COOLER 132 even though Sum UA Suction Piping is greater than zero. Suction piping heat gain cannot be calculated unless a Zone is defined to deterimine the environmental temperature surrounding the piping."
