Bulletin AFS442.02
1
Model
AFS–442
Air Pressure Sensing Switch with Adjustable Set Point Range
Dimensions in Inches
(Millimeters)
Application
The
Model AFS-442
is a general pur-
pose proving switch designed for
package burner, furnace, fuel-burning
equipment, HVAC and other Energy
Management applications. It may be
used to sense positive, negative, or
differential air pressure.
General Description &
Operation
The plated housing contains a dia-
phragm, a calibration spring and a
snap-acting SPDT
switch.The sample
connections located on each side of
the diaphragm accept
1
/
8
" pipe.
An enclosure cover guards against ac-
cidental contact with the live switch
terminal screws and the set point ad-
justing screw. The enclosure cover will
accept a ½" conduit connection.
Mounting (see Figure 1)
Select a mounting location which is
free from vibration. The
AFS-442
must
be mounted with the diaphragm in any
Cleveland Controls
Division of UniControl Inc.
(Figure 2)
(Figure 1)
vertical plane in order to obtain the
lowest specified operating set point.
Avoid mounting with the sample line
connections in the "up" position. Sur-
face mount via the two
3
/
16
" diameter
holes in the integral mounting bracket.
The mounting holes are 3-
7
/
8
" apart.
Air Sampling Connection
(see Figure 2)
The
AFS-442
is equipped with two
1
/
8
" – 27 NPT female connectors. For
sample lines of up to 10 feet,
1
/
8
" pipe
is acceptable. For lines up to 20 feet,
use ¼" pipe. For lines up to 60 feet,
use ½" pipe. For each right angle
bend, add 4 feet to the computed
sample line length to determine correct
pipe size.For sample lines of up to 10
feet, ¼" OD tubing is acceptable. For
lines up to 20 feet, use ¼" ID tubing.
For lines up to 60 feet, use ½" ID tub-
ing. Locate the sampling probe a mini-
mum of 1-½ duct diameters down-
stream from the air source. Install the
sampling
probe as close to the center
of the airstream as possible. Refer to
Figure 2 to identify the high pressure
inlet (H) and the low pressure inlet
(L). Select one of the five application
options listed below (on page 2), and
connect the sample lines as recom-
mended.
