User Guide
4 © Copyright 2008 TAC All Rights Reserved. F-24381-2
Figure-2 Temperature and Pressure Ratings for VB-7212 Series Valve Bodies.
VALVE SIZING AND SELECTION
Water Two-position
Two-position control valves are normally selected “line size” to keep pressure drop at a
minimum. If it is desirable to reduce the valve below line size, then 10% of “available
pressure” (that is, the pump pressure differential available between supply and return mains
with design flow at the valve location) is normally used to select the valve.
Proportional
Proportional control valves are usually selected to take a pressure drop equal to at least 50%
of the “available pressure.” As “available pressure” is often difficult to calculate, the normal
procedure is to select the valve using a pressure drop at least equal to the drop in the coil
or other load being controlled (except where small booster pumps are used) with a minimum
recommended pressure drop of 5 psi (34 kPa). When the design temperature drop is less
than 60°F (33°C) for conventional heating systems, higher pressure drops across the valve
are needed for good results (Table-4).
Table-4 Conventional Heating System.
Secondary Circuits with Small Booster Pumps: 50% of available pressure difference
(equal to the drop through load, or 50% of booster pump head).
Water Capacity
See Table-5 for water capacity of VB-7212 series valves.
Table-5 Water Capacity in Gallons Per Minute for VB-7212 Series.
50
(345)
250 (121)
200 (93)
150 (65)
100 (38)
50 (10)
300 (149)
150
(1034)
250
(1724)
350
(2458)
100
(689)
Pressure — psig (kPa)
321 psig
(2218 kPa)
Temperature — °F (°C)
200
(1379)
300
(2068)
400
(2758)
Maximum Media
Temperature
281°F (138°C)
Minimum Fluid
Temperature
20°F (-7°C)
VB-7212-0-4-P
Design Temperature
Load Drop °F (°C)
Recommended Pressure Drop
a
(% of Available Pressure)
Multiplier on
Load Drop
60 (33) or More 50% 1 x Load Drop
40 (22) 66% 2 x Load Drop
20 (11) 75% 3 x Load Drop
a
Recommended minimum pressure drop = 5 psi (34 kPa).
Valve Body
Part Number
C
v
Rating
Differential Pressure (
ΔP in psi)
12345678910152035
VB-7212-0-4-1 0.4 0.40 0.57 0.69 0.80 0.89 0.98 1.06 1.13 1.20 1.26 1.55 1.79 2.37
VB-7212-0-4-2 1.3 1.30 1.84 2.3 2.6 2.9 3.2 3.4 3.7 3.9 4.1 5.0 5.8 7.7
VB-7212-0-4-3 2.22.23.13.84.44.95.45.86.26.67.08.59.8 13
VB-7212-0-4-4 4.4 4.4 6.2 7.6 8.8 9.8 11 12 12 13 14 17 20 26