User Guide

F-24384-1 © Copyright 2006 TAC All Rights Reserved. 5
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-7221 series valves.
Table-5 Water Capacity in Gallons Per Minute for VB-7221 Series.
C
v
Equation
Where:
C
v
= Coefficient of flow
GPM = U.S. gallons per minute (60°F, 15.6°C)
ΔP = Differential pressure in psi (pressure drop)
Steam Two-position
Two-position zone valves and direct radiation valves are normally sized using a minimum of
10% of inlet pressure (psig).
Proportional
Proportional control valves are normally sized using:
• For low pressure (15 psig or less), use ΔP of 80% of gauge inlet pressure.
• For steam pressures greater than 15 psig, use ΔP of 42% of absolute (gauge plus
14.7 psig) inlet pressure.
• When the C
v
required is between two valve sizes, select the larger size. Do not size
steam valves using a pressure drop greater than 42% of the absolute inlet pressure.
Steam Capacity
See Table-6 for steam capacity of VB-7221 series valves.
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-7221-0-4-1 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-7221-0-4-2 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-7221-0-4-3 2.22.23.13.84.44.95.45.86.26.67.08.59.8 13
VB-7221-0-4-4 4.4 4.4 6.2 7.6 8.8 9.8 11 12 12 13 14 17 20 26
VB-7221-0-4-5 5.5 5.5 7.8 9.5 11 12 13 15 16 17 17 21 25 33
VB-7221-0-4-6 7.5 7.5 11 13 15 17 18 20 21 23 24 29 34 44
VB-7221-0-4-7 10 10 14 17 20 22 24 26 28 30 32 39 45 59
VB-7221-0-4-8 14 14 20 24 28 31 34 37 40 42 44 54 63 83
VB-7221-0-4-9 20 20 28 35 40 45 49 53 57 60 63 77 89 118
C
v
=
GPM
ΔP=
GPM
C
v
()
GPM = C
v
ΔP
2
ΔP