1 Standard Direct Expansion (DX) Cooling Air Conditioning System Condensing Air: The ambient condensing air enters the condenser at 95 F and leaves at 115 F. Compressor: Condenser Fans: Draw ambient Moves the air across the condensing coil. refrigerant Discharge Line through the Condenser Coil: Rejects heat system. absorbed from the air along with the heat added to the system during the compression process. Condenser Tubes Expansion Device: Causes Liquid Line Expansion Cooling by creating a HIGH SIDE pressure loss between the high and low side of the system. Sight Glass / Moisture Indicator: LOW SIDE Provides a view into the system.
2 Evaporator Tubes Indicator is green normally, yellow when high in moisture. Evaporator Coil: The evaporator coil transfers heat from the warm air Supply Air: Enters the evaporator Filter-Dryer: Removes to the cool refrigerant. coil warm and leaves cool. Design water, debris and other condition for outdoor air is 95 F contaminants from the Suction Line dry bulb 75 F wet bulb. Typical refrigerant. leaving air design condition is 55 F dry bulb, 54 F wet bulb. SYSTEM TEMPERATURES AND PRESSURES. Refrigerant State T, F R-410A, psig Superheat/Subcool LOAD CALCULATIONS. Low Pressure Saturated 45 Condenser Qout (Btu/hr) = x SCFM x Temperature Low Pressure Superheated Vapor 53 Superheat = T - Tsat = 53 - 45 = 8 F Evaporator Qin (Btu/hr) = x SCFM x Enthalpy High Pressure Gas 180 High Pressure Saturated 125 R1 9-2010 RG.
3 High Pressure Liquid 110 Subcool = Tsat - T = 125 - 110 = 15 F. Copyright 2010 Greenheck Fan Corp. Air Cooled Packaged Refrigeration Options Hot Gas Bypass Hot Gas Reheat Digital Scroll Compressors Hot gas bypass consists of a pressure-operated Hot gas reheat includes a condenser coil (located in Condenser Digital scroll compressors adjust to the Cooling Coil valve located on the discharge line and additional the supply airstream) and a modulating refrigerant demand by separating (engaging and disengaging). refrigerant piping from the valve to the evaporator valve to control the supply air temperature and the compressor's scrolls.
4 When the scrolls are (DX) coil. Hot refrigerant vapor enters the hot gas relative humidity. separated, or disengaged, no thermodynamic bypass valve from the compressor and is routed to Benefit: HotHotgas reheat Gas Bypass Line controls the supply air work is done on the refrigerant. The compressor the DX coil inlet as suction line pressure decreases. temperature and relative humidity without the need resumes the normal Cooling cycle when the scrolls Suction line pressure decreases as the Cooling load for auxiliary post heat ( an electric heater). Hot are engaged. Cycle times between the disengaged decreases (indicating a part-load condition).
5 Gas reheat is often referred as free reheat as and engaged states are varied by a controller and Benefit: Prevents the DX coil from freezing and the refrigeration system needs to reject theEvaporator heat pressure valve to adjust the compressor output to reduces compressor cycling at part-load conditions. absorbed Suction by the refrigerant to the ambient air Coilor meet the Cooling demand. Line Availability: Standard on all MPX, ERCH and VER supply air for proper operation. This configuration Benefit: Digital scrolls offer capacity control from models with packaged DX Cooling . provides a means to provide dehumidified air 10 to 100% of the rated compressor capacity.
6 This without overcooling the space. turndown provides leaving coil temperature control Availability: Optional on all MPX, ERCH and VER as precise as F. Digital scrolls also save energy Condenser models. by eliminating hot gas bypass as the compressor Coil output can be adjusted to meet Cooling demands at Air Conditions after Reheat Coil part load conditions. 70 F DB / 60 F WB. 56% Relative Humidity Availability: Optional on the MPX, ERCH, and VER. Hot Gas Bypass Line models (up to 30 tons). Reheat Coil Evaporator Coil Air Conditions after Evaporator Coil Suction Line 55 F DB / 54 F WB. 94% Relative Humidity Models MPX ERCH VER.
7 Airflow Range Min. CFM 1,000 1,000 2,000. Max. CFM 10,000 10,000 10,000. Evaporator Coil Cooling Performance 5 -Coil Air Conditions after Reheat 30 4 - 30 4 - 30. Cooling Capacity 70 FRange DB / 60 F WB. 56% Relative Humidity tons tons tons Hot Gas Bypass Std. Std. Std. Hot Gas Reheat Optional Optional Optional Digital Scroll Compressors Optional Optional Optional Additional Cooling Options Chilled Water . Reheat Coil Water Source Heat Pump . Air Conditions after Evaporator Coil Heating Options 55 F DB / 54 F WB. Indirect Gas 94% Relative Humidity . Hot Water . Electric . Water Source Heat Pump . Evaporator Coil