Powers 596 Series Flowrite II Heavy Duty Control Valves - Type MI Mixing - Manual (Page 3)

NOTE: Supply pressures (inlet) are affected by piping sched-
ule, internal surface conditions, and vertical runs (back pres-
sure) so the actual flowing pressure is best measured at the
point of valve use.
Proportional to Mix Supply Flows
Proportional valves when used to blend two water flows con-
trol the output by varying the water temperature to the heat
exchanger at constant flow. These valves require high pres-
sure drops for good control results. They can be sized for a
pressure drop of 20% of the flowing pressure or equal to 25% of
the pressure drop through the heat exchanger at full flow.
Proportional to Bypass Flow
Proportional mixing valves when used to bypass flow are piped
on the outlet side of the hot water source to throttle the water
flow and thereby control heat output. These valves are usually
selected to take a pressure drop up to 50% of the flowing pres-
sure through the valve.
Valve Sizing and Selection
n
3
Table - 1 Water Capacity in Gallons Per Minute
Valve Cv
Size Rating Differential Pressure (∆ in psi)
5 10 15 20 25 30 35 40 45 50
2.5 74 165 234 287 331 370 405 438 468 496 523
3 101 226 319 391 452 505 553 598 638 678 714
4 170 380 538 658 760 850 931 1006 1075 1140 1202
5 290 648 917 1123 1297 1450 1588 1716 1834 1945 2051
6 390 872 1233 1510 1744 1950 2136 2307 2467 2616 2758