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24 | schneider-electric.com Selection Guide
January, 2019 tc © 2019 Schneider Electric. All rights reserved. All trademarks are owned by Schneider Electric Industries SAS or its affiliated companies.
Document Number: F-27086-14
Insulation of Ball Valve Assembly
The ball valve should be completely insulated to minimize the effect of heat transfer and condensation at the actuator.
Caution: The actuator itself must not be insulated. Doing so can result in excess heat or condensation within the actuator.
Temperature Limits for Ball Valve Assembly
When installing the ball valve assembly, observe the minimum and maximum temperature limits. Refer to the valve and actuator
specifications..
Water System Maintenance
All heating and cooling systems are susceptible to valve and system problems caused by improper water treatment and system
storage procedures. Durability of valve stems and packings is dependent on maintaining non-damaging water conditions. Inad-
equate water treatment or filtration, not in accordance with chemical supplier or ASHRAE handbook recommendations, can result
in corrosion, scale, and abrasive particle formation. Scale and particulates can cause scratches in the stem and packing, and
can adversely affect packing life and other parts of the hydronic system. Consult EN-205, Water System Guidelines Engineering
Information, F-26080, for futher details.
Sizing and Selection
Flow Coefficient (Cv)
When sizing a valve, you must select a flow coefficient (Cv), which is defined as the flow rate in gallons per minute (GPM) of 60 °F
water that will pass through the fully open valve with a 1 psi pressure drop (DP). It is calculated according to this formula:
Cv =
gpm
∆P
where DP is measured in psi.
Since the flow rate through the heat exchanger is usually specified, the only variable normally available in sizing a valve is the
pressure drop. The following information in this section can be used to determine what pressure drop to use in calculating a valve
Cv. Once you have calculated the Cv, consult Table-1 and Table-2 to select the valve body having the nearest available Cv.
NOTE: Metric equivalent
The metric measure of flow coefficient is kvs, which is calculated according to the formula:
kvs =
m3/h
∆P
(where DP is measured in bar; 1 bar = 100 kPa).
If the Cv is already known, it may be converted directly to its kvs equivalent:
Cv
1.156
kvs
=
Two-position Control
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.
VB-2000 Series Ball Valves
with SmartX Actuators
8. VBB/VBS and VB-2000 Series
Ball Valve Assemblies
8. VBB/VBS and VB-2000 Series
Ball Valve Assemblies