Cleveland Controls
Model
Division of UniControl Inc.
AFS–305
ADJUSTABLE AIR PRESSURE SENSING SWITCH WITH MANUAL RESET (SPDT)
APPLICATION
The Model AFS-305 is a general purpose
proving switch designed to require manual
operator reset following actuation. It can
be used to sense positive, negative, or differential air pressure in HVAC and Energy
Management applications which require
operator interface.
GENERAL DESCRIPTION &
OPERATION
The plated housing contains a diaphragm, a
calibration spring and a snap-acting SPDT
switch with manual reset button.
The sample connections located on each
side of the diaphragm accept 0.25" OD
metallic tubing via the integral compression
ferrule and nut.
An enclosure cover protects the operator
from accidental contact with the live switch
terminal screws and the set point adjusting
screw. The enclosure cover accepts a 0.5"
conduit connection.
MOUNTING (FIGURE 1)
Select a mounting location which is free from
vibration. The AFS-305 must be mounted
with the diaphragm in any vertical plane in
order to obtain the lowest specified operating
set point. Avoid mounting with the sample
line connections in the "up" position. Surface
mount via the two 3/16" diameter holes in
the integral mounting bracket. The mounting
holes are 3–7/8" apart.
(Figure 1)
AIR SAMPLING CONNECTION
(FIGURE 2)
The AFS-305 is designed to accept firm-wall
sample lines of ¼" OD tubing by means of
ferrule and nut compression connections.
An optional ¼" adapter, suitable for slip-on
flexible tubing is available: order part number
18311. 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 tubing.
Locate the sampling probe a minimum of
1.5 duct diameters downstream 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 on
page 2, and connect the sample lines as
recommended.
POSITIVE PRESSURE ONLY: Connect the
sample line to inlet H; inlet L remains open
to the atmosphere.
N
EGATIVE PRESSURE ONLY: Connect
the sample line to inlet L; inlet H remains
open to the atmosphere.
TWO NEGATIVE SAMPLES: Connect the
higher negative sample to inlet L. Connect
the lower negative sample to inlet H.
TWO POSITIVE SAMPLES: Connect the
higher positive sample to inlet H. Connect
the lower positive sample to inlet L.
ONE POSITIVE AND ONE NEGATIVE
SAMPLE: Connect the positive sample
to inlet H. Connect the negative sample to
inlet L.
Bulletin AFS-305.01
Cleveland Controls
DIVISION OF UNICONTROL INC.
(Figure 2)
ELECTRICAL CONNECTIONS
SPECIFICATIONS
(Figure 3)
(Figure 4)
(SEE FIGURE 3)
Before pressure is applied to the diaphragm,
the switch contacts will be in the normally
closed (NC) position.
The snap switch has screw top terminals
with cup washers. Wire alarm and control
applications as shown in Figure 4.
FIELD ADJUSTMENT
The adjustment range of an AFS-305 Air
Switch is 0.4" ± 0.02" w.c. to 12.0" w.c. To
adjust the set point, turn the adjusting screw
counterclockwise until motion has stopped.
Next, turn the adjusting screw four complete
turns in a clockwise direction to engage
the spring. From this point, the next ten
turns will be used for the actual calibration.
Each full turn represents approximately
1.16" w.c.
Please note: To properly calibrate an air
switch, a digital manometer or other measuring device should be used to confirm the
actual set point.
MODEL AFS-305 AIR
PRESSURE SENSING
SWITCH WITH MANUAL
RESET FEATURE
Mounting Position:
Mount with the diaphragm in any vertical plane.
Set Point Range:
0.40 ± 0.06"w.c. to 12.0"w.c.
Field Adjustable “Operate Range”:
0.46"w.c. to 12.0" w.c.
Field Adjustable “Release Range”:
0.46"w.c. to 11.2" w.c.
Approximate Switch Differential:
Progressive, increasing from approximately 0.06± 0.01"w.c. at minimum
set point, to approximately 0.8"w.c. at
maximum set point.
Measured Media:
Air, or combustion by-products that will
not degrade silicone.
Maximum Pressure:
½ psi (0.03 bar)
Life:
Exceeds mechanical endurance test
of 6,000 cycles minimum at 0.5 psi
maximum pressure each cycle and at
maximum electrical load.
Electrical Rating:
@ 60 Hz.
15 amp 125, 250, or 277 VAC
¼ hp 125 V AC, ½Hp 250 VAC,
½ amp 125 V DC,
¼ amp 250 V DC .
Contact Arrangement:
SPDT (manual reset).
Electrical Connections:
Screw top terminals with cup washers.
Conduit Opening:
7/8" diameter opening accepts ½"
conduit.
Sample Line Connectors:
Male, externally threaded 7/16" 24
UNS 2A thread, complete with nuts and
self-aligning ferrules.
Sample Line Connections:
Connectors will accept ¼" OD rigid or
semi-rigid tubing.
Shipping Weight:
1.2 lbs.
Accessories:
• P/N 18311 Slip-on ¼" OD Tubing Adapter, suitable for slipping
on flexible plastic tubing.
• Sample line probes.
• Orifice plugs (pulsation dampers).
Nominal Dimensions in Inches (Millimeters)
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