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Selection To make a rough field estimate of the size of valve for an application, find the valve size by locating a point on a flow chart that satisfies these requirements: • Water flow required by the condenser (Flow) • Refrigerant head pressure rise (P RISE ) • Available water pressure (P AVAIL ) Follow these steps, and use the information obtained to locate a point on one of the flowcharts that satisfies all three steps. 1. Take the water flow required by the condenser (Flow) from information provided by the manufacturer of the condensing unit. If the manufacturer's information is unavailable, use the following information to make a rough approximation of maximum water flow in gallons per minute (gpm) (cubic meters per hour [m 3 /hr]): - System Capacity (Tons of Refrigeration) - Outlet Water Temperature (Temp. Outlet ) - Inlet Water Temperature (Temp. Inlet ) Calculate the flow using the following formula: Figure 78: Flow Required Note: If the outlet temperature is unknown, assume it to be 10F° (5.6C° ) above the inlet temperature. 2. Determine refrigerant head pressure rise above the valve opening point (P RISE ) using the following steps: a. The Valve Closing Pressure (P CLOSE ) is equal to the refrigerant pressure at the highest ambient temperature the refrigeration equipment experiences in the Off cycle. Use a Pressure- Temperature Chart for the refrigerant selected to find this pressure. b. To approximate the Valve Opening Pressure (P OPEN ), add about 7 psi (0.5 bar) for EK and AL models or 10 psi (0.7 bar) for GL1 or GK1 models to the Valve Closing Pressure. Figure 79: Valve Opening Pressure, EK and AL Models (Top) or GK1 and GL1 Models (Bottom) c. From the Pressure-Temperature Chart for the refrigerant selected, read the Refrigerant Condensing Pressure (P COND ) (operating head pressure) corresponding to the selected condensing temperature. d. Subtract the Valve Opening Pressure from the Refrigerant Condensing Pressure. This gives the head pressure rise. Figure 80: Refrigerant Head Pressure Rise 3. Determine the available water pressure to the valve (P AVAIL ) using the following steps. This is the actual water pressure available to force water through the valve. a. Determine the minimum inlet pressure (P IN ). This is the water pressure from city water mains, pumps, or other sources. b. Pressure drop through condenser (ΔP COND ) is the difference in water pressure between the condenser inlet and the condenser outlet. Obtain this information from the condenser manufacturer. c. Estimate or calculate the pressure drop through all associated piping (P LOSS ). d. Subtract the ΔP COND and P LOSS from P IN . The result is P AVAIL . 257 Refrigeration Products Catalog

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