About this task
Each application is unique and requires specific engineering data to properly size and design a system to fulfill the appropriate requirements. Typically, a valve is replaced with another valve of the same size in a properly sized and engineered system.
In North America, contact Johnson Controls/PENN® Refrigeration Application Engineering at 1-800-275-5676 to obtain specific engineering data. In other areas, contact the local Johnson Controls® sales office to obtain specific engineering data.
To make a rough field estimate of the size of valve for an application, find the valve size needed by locating a point on a flow chart that satisfies these requirements:
- Water flow required by the condenser (Flow)
- Refrigerant head pressure rise (PRISE)
- Available water pressure (PAVAIL)
Follow these steps, and use the information obtained to locate a point on one of the flowcharts that satisfies all three steps.
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
water flow in gallons per minute (gpm) [cubic meters per hour
- System Capacity (Tons of Refrigeration)
- Outlet Water Temperature (Temp. Outlet)
- Inlet Water Temperature (Temp. Inlet)
Calculate the flow using the following formula:Figure 1. Flow Required
Note: If the outlet temperature is unknown, assume it to be 10F° (6C° ) above the inlet temperature.
Determine refrigerant head pressure rise above the valve opening point
(PRISE) using the following steps:
- The Valve Closing Pressure (PCLOSE) 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.
To approximate the Valve Opening Pressure (POPEN), add about
10 psig (0.7 bar) to the Valve Closing Pressure.
Figure 2. Valve Opening Pressure
- From the Pressure-Temperature Chart for the refrigerant selected, read the Refrigerant Condensing Pressure (PCOND) (operating head pressure) corresponding to the selected condensing temperature.
Subtract the Valve Opening Pressure from the Refrigerant Condensing
Pressure. This gives the head pressure rise.
Figure 3. Refrigerant Head Pressure Rise
Determine the available water pressure to the valve (PAVAIL) using
the following steps. This the actual water pressure available to force water
through the valve.
- Determine the minimum inlet pressure (PIN). This is the water pressure from city water mains, pumps, or other sources.
- Pressure drop through condenser (ΔPCOND) is the difference in water pressure between the condenser inlet and the condenser outlet. Obtain this information from the condenser manufacturer.
- Estimate or calculate the pressure drop through all associated piping (PLOSS).
Subtract the ΔPCOND and P LOSS from P
IN. The result is PAVAIL.
Figure 4. Available Water Pressure
- Select the proper valve size from the flowcharts by locating a point on a chart that satisfies the flow, the head pressure rise above opening point, and the pressure drop across the valve.