To determine size requirements, follow Step 1 to Step 3. See the flowcharts in V46 flowcharts to locate a point on a flowchart that satisfies all the requirements.
Use tables that the manufacturer of the condensing unit
provides to determine the maximum water flow that you need, or calculate the
flow with the following formula:
If you do not know the outlet water temperature, assume it to be 10°F below the condensing temperature.
Example: A 9-ton capacity system has an inlet water temperature of 65°F and an outlet water temperature of 95°F. The maximum required water flow is:
Determine the refrigerant head pressure rise above the valve
- To assure closure under all conditions, choose the valve closing point that is the equivalent refrigerant pressure to the highest ambient air temperature that the equipment experiences in the off cycle. Read this in psig from a saturated vapor table for the selected refrigerant.
- To determine the valve opening point, add approximately 7 psig (48 kPa) to the closing point.
- From the same table, read the operating head pressure that corresponds to the selected condensing temperature.
- Subtract the valve opening point from the operating head pressure. This gives the head pressure rise.
Determine the water pressure drop across the valve. This is the
true pressure available to force water through the valve.
- Determine minimum water pressure available from city mains or other sources.
- From the condensing unit manufacturer’s tables, read the pressure drop through the condenser that corresponds to the flow that you need.
- Add the estimated or calculated drop through installed piping to the value from the previous step.
- Subtract the total pressure drops in the condenser, piping, and static head if applicable, from the available water pressure value in 3a. This is the available pressure drop across the valve.
- To select the correct valve size from the V46 flowcharts, locate a point on a chart that will satisfy the flow, the head pressure rise above opening point, and the pressure drop across the valve.