Honeywell
VP522A, B
Sequencing Water Valve
GENERAL
Description
VP522 Sequencing Water Valves are pneumatically actuated,
three-pipe water valves that control both hot and cold water
flow to fan coil units in three- and four-pipe systems.
C O N T R O L
A I R
VP522A
V A L V E
Application
The VP522A controls the flow of hot or cold water to a fan coil
unit from the hot or chilled water supply piping.
The VP5226 is used in conjunction with the VP522A as a
diverting, return-water valve on four-pipe systems to ensure
isolation of the hot and chilled water circuits.
Operation
The VP522A (Fig. 1) is a proportioning valve that controls the
flow of first hot and then cold water to a fan coil unit as
branchline pressure increases and the reverse as branchline
pressure decreases. No flow occurs at mid-pressure. See
Table 1 for operating sequence.
The VP522B diverts the return water from the coil directly to
return piping of the system feeding the coil. During the dwell
period of the VP522A, when both ports are closed but the
valve is moving towards opening either the hot or cold port,
the VP522B is actuated to open the proper port before the
VP522A allows water to flow.
C O N T R O L
A I R
VP5220B
V A L V E
CH I LLEO
W A T E R
T O
C H I L L E R
H O T
W A T E R
To
C O I L
B O I L E R
Fig. 1. VP522A, B Typical Application.
Copyright 1992 Honeywell Inc.
l
All Rights Reserved
Ill II I
75-2598