V43/V243 Series Pressure-Actuated Water-Regulating Valves Product/Technical Bulletin
3
When the head pressure rises, and the refrigerant
pressure overcomes the spring force (pilot valve), the
valve begins to open (the disk lifts off of the seat). This
point is called the opening point.
The opening point is adjusted by increasing or
decreasing the spring force by using the adjustment
stem. If the head pressure continues to rise, the
refrigerant pressure further opens the valve until the
valve is fully open. The range from the point where the
valve lifts off the seat (the opening point) to the point
where the valve is fully open is called the throttling
range.
The throttling range is fixed and cannot be adjusted.
The throttling range is approximately 40 psig for the
low-pressure V43 Series Valves, approximately 50 psi
for the medium-pressure V43 Series Valves, and
approximately 60 psi for the high pressure V243 Series
Valves.
Head Pressure Rise Above the Opening Point
When the head pressure rises, the force of the
refrigerant head pressure overcomes the spring force
(plus any hysteresis) and pushes the disc off the seat,
allowing water to start flowing through the valve.
Anything above that point is head pressure rise above
the opening point. Typically, the opening point is
approximately 7 psi above the closing point.
Proper Valve Size
A properly sized valve meets the requirements of the
maximum water flow required yet functions at an
acceptable level when minimum flow is required (does
not water hammer, cut, or wire draw the seats and
seating discs). See Figure 3 and Figure 4 to select the
correct valve size for your application.
Use the following steps to help determine the
appropriate valve size for your application:
1. Locate the point where the valve is fully open on
the Refrigerant Head Pressure Rise Above Valve
Opening Point (y-axis).
2. Draw a horizontal line from this point to where the
line intersects with the Water Pressure Available
WPA curve. This is Point A.
3. Draw a vertical line from point A to where it
intersects with Maximum Water Flow Available line
(x-axis). This is Point B.
Point B is the maximum amount of water that the
valve can flow, when fully open, under the stated
conditions. See Figure 3.
4. Locate the Maximum Water Flow Required for your
application (x-axis). This is Point C.
5. Draw a vertical line from Point C to where the line
intersects with the WPA curve. This Point D.
6. Draw a horizontal line from Point D to the left
where it intersects with the Refrigerant Head
Pressure Rise Above Opening Point.
This is where the selected value meets the
maximum flow requirement of the application.
Use the flow charts to select the valve that is most
appropriate for your application.
Example
In this example, the required flow for an R-404A
system is 300 GPM. The cooling tower pump discharge
pressure is 30 psig, and the condenser manufacturer's
table gives a pressure drop through the condenser at
8 psid. The pressure drop through the installed piping,
fittings, and valves is approximately 12 psi.
Maximum Water Flow Required = 300 GPM
Water Pressure Available= 30 - (12 + 8)
Water Pressure Available= 10 psid
You need to select the proper valve size. The proper
size valve is indicated by the flow chart that slightly
exceeds the maximum required flow when the valve is
wide open.
Refrigerant
Head
Pressure
Rise Above
Opening
Point
Refrigerant Head
Pressure at
Opening Point
=
Refrigerant
Head Pressure greater
than Opening Point
-
Water Pressure Available Across Valve (psid)
Maximum Water Flow Required
Value Determined in Step 1
Difference ensures
that the valve
meets the maximum
flow rate required.
CAPACITY CHART REPRESENTING
THE PROPER VALVE SIZE
Refrigerant Head Pressure Rise Above
Valve Opening Point (psig)
Point B
WPA Curve
Point C
Point A
FIG:capacity chart
Point D
