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.12/2" WC, CLOSE-HI, Pneumatic Differential Pressure Switch

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Manufacturer: Johnson Controls

Description: .12/2"WC,CLOSE-HI,PNEU DIF #SW

Category: Electrical Controls

Sub Category: Pressure Controls

P40 Series
Pneumatic Differential Pressure Switch


The P40 pressure switch is used
to sense the flow of air in ducts.
The switch is a sensitive
pneumatic device which can be
used as a fan status sensor or a
differential pressure switch. The
switch has an adjustable
switching set point from .12 to
2.0 in. W.C. (.03 to .50 kPa).

! WARNING: The maximum
pressure applied to the low

pressure connection must
not exceed 1 in. W.C.
(.25 kPa).

All Series P40 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.


· Versatile mounting options.

· Durable and compact

· Easy-to-read set point scale,

General Description

The P40 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
The differential pressure, as
sensed by two sensing ports, is
applied to the two sides of a
diaphragm in the switch. The
diaphragm moves and actuates
the pneumatic switching unit.
The P40 can also be used to
detect small positive gauge
pressure by using only the high pressure connection and leaving
the low pressure connection
open for the atmosphere as a
Switches are factory set at the
bottom of the switching set point
range with the diaphragm in a
vertical plane. The setting will
change if mounted in other
positions. Mounting with the
steel housing (high pressure
connection) down will change
the set point by about
0.07 in. W.C. (0.017 kPa).

Note: The switch must not be
mounted with the steel housing

Replaces Part Numbers: P40AA-1, CARP40AA-1

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