Product Overview

Master Catalog 125
Pressure Controls Section P
Product Bulletin P32
Issue Date 0190
© 1990 Johnson Controls, Inc.
1
Code No. LIT-125435
P32 Series
Sensitive Differential Pressure Switch
Application
The P32 differential pressure
switch is used to sense flow of air
in ducts. When used with electric
strip heaters, the switch can be
wired to open the circuit and de-
energize the heaters when air flow
stops.
Typical applications include:
•
Air proving with electric duct
heaters.
•
Maximum air flow controller for
variable air volume systems.
•
Reheat duct powered systems.
•
Detection of icing of air
conditioning coils and initiation
of defrost cycle.
•
Clogged filter detection.
For a P32 sensitive differential
pressure switch for combustion air
applications, see LIT-125430.
All P32 pressure switches are
designed for use
only
as
operating controls. Where an
operating control failure would
result in personal injury and/or
loss of property, it is the
responsibility of the installer to
add devices (safety, limit
controls) or systems (alarm,
supervisory systems) that
protect against, or warn of,
control failure.
Features
•
Easy-to-read set point scale.
•
Small and compact.
•
Versatile mounting options.
Fig. 1 -- The P32AC Differential
Pressure Switch with “U”
mounting bracket and a direct
mounted sensing probe
assembled.
• Durable construction.
• Sensitive switching differential.
General Description
This switch senses a change in
the differential pressure (either
velocity pressure or pressure drop
across a fixed restriction in the
duct) as air flow in the duct
changes.
The differential pressure, as
sensed by the two sensing ports,
is applied to the two sides of a
diaphragm in the control. The
spring loaded diaphragm moves
and actuates the switch.
The P32 can be also be used to
detect small positive gage
pressure by using only the high
pressure connection and leaving
the low pressure connector open,
or to detect a vacuum by using
only the low pressure connection
and leaving the high pressure
connector open to ambient
pressure.
Switches are factory set at the
bottom of the operating range with
the diaphragm in a vertical plane.
Specifications