UniControl Cleveland Controls AFS-952 User manual

BulletinAFS952.01
Model
AFS–952
Description & Operation
The Cleveland Controls AFS-952
Differential Pressure Sensing
Switch is designed to provide precise
operation and convenient features for
industrial and commercial air han-
dling applications. The AFS-952 can
monitor positive, negative, or differ-
ential pressure (flow) of air and non-
combustible gases, and is commonly
used to monitor combustion air, fur-
nace pressure, ventilating blower op-
eration, inflatable structure pressure,
fume hood operation, bag house air
flow, dirt accumulation in air filters,
and heat-transfer air flow. The AFS-
952 has a field–adjustable set point
range of 0.05"wc to 12.0"wc with an
8-second (± 3 seconds) time delay
relay sequence. The time delay pre-
vents nuisance shutdowns due to nor-
mal draft fluctuations.
Common Applications
The most common specific applica-
tion for the AFS-952 is as a Low
Draft (Negative Pressure) Cutoff
Safety Switch for combustion draft
control systems.
The general applications of the AFS-
952 are:
•Low Positive Pressure Cutoff.
(Shutdown upon insufficient pres-
sure.)
•Low Negative Pressure Cutoff.
(Shutdown upon insufficient draft.)
•Low Differential Pressure Cutoff.
(Shutdown upon insufficient differ-
ence between two samples.)
Mounting
The AFS-952 is available in 3 enclo-
sures designed for surface mounting
on any flat, relatively stable surface
free of vibration. To obtain the low-
est operating set point specification,
the control must be mounted with the
diaphragm vertical (Fig 1).
The standard enclosure has mounting
flanges with four 9/32" mounting
holes as shown on page 3. The
NEMA-4 rated model has mounting
flanges with four 5/16" mounting
holes as shown on page 4. The
NEMA-7/NEMA-9 rated enclosure
has two mounting slots as shown on
page 4.
AFS-952-1 in NEMA-4 rated
Enclosure.
AFS-952 in Standard Enclosure,
rated NEMA-1.
AFS-952-2 in NEMA-7 and
NEMA-9 rated Enclosure.
Cleveland Controls
Division of UniControl Inc.
Adjustable Set Point Air Pressure Sensing Switch with 8-second Time Delay

Piping
The field sample line connectors, two
1/4" - 18 NPT female fittings, labeled
H (high) and L (low), are located on
the side of the enclosure as shown in
Figure 1.
Positive Pressure only:
Connect sample line to H;
Lremains open to the atmosphere.
Negative Pressure only:
Connect sample line to L:
Hremains open to the atmosphere.
Two Negative Samples:
Connect higher negative sample to L:
Connect lower negative sample to H.
Two Positive Samples:
Connect higher positive sample to H:
Connect lower positive sample to L.
One Negative and One Positive
Sample:
Connect positive sample line to H:
Connect negative sample line to L.
For each right angle bend, add four
feet to the computed line length in order
to determine correct pipe or tubing size.
If either sample line connector is
vented to the atmosphere, attach an el-
bow to it so that the open end of the con-
nector points downward. This will help
protect the switch from contamination.
Electrical Connections
Five numbered terminals are provided
for field wiring. Terminals are pressure
clamp screw type.
Sequence of Operation
Before pressure and power are applied
to the AFS-952, the SPDT switch con-
tacts are in the normally closed posi-
tion as shown inFigure 3(“shelf” con-
dition), and relay contacts 3 and 5 are
closed (“alarm mode”).
When the sample lines are con-
nected as shown in Figure 1, and
power is applied to terminals 1 and 2,
the following sequence occurs.
Initially the red lamp is on, indi-
cating that differential pressure is less
than set point. The SPDT switch con-
tacts remain in the NC position for as
long as differential pressure remains
less than set point; the TD1 time delay
is not energized and the K1 load relay
circuit remains in alarm mode. When
differential pressure reaches set point,
the SPDT switch contacts change to
NO immediately so that the red lamp
goes out and the TD1 time delay is en-
ergized. If the TD1 time delay remains
energized for 8 ± 3 seconds continu-
ously, the TD1 contacts close, ener-
gizing the K-1 coil and opening K-1
load contacts 3 and 5. The circuit is
now in normal operating mode.
Whenever differential pressure
drops below the set point, the SPDT
switch contacts change to NC imme-
diately, turning the red lamp on, and
de-energizing the TD1 time delay. The
K-1 load contacts for terminals 3
and 5 remain open unless differen-
tial pressure remains less than set
point for 8 seconds continuously.
After this 8-second period, K-1 load
relay contacts 3 and 5 close while K1
contacts 3 and 4 open: the circuit is
now in alarm mode.
When the differential pressure be-
comes greater than set point, the SPDT
switch contacts change to NO imme-
diately, turning the red lamp off, and
energizing the TD1 time delay. The dif-
ferential pressure must remain greater
than set point for 8 seconds continu-
ously before the K-1 load relay con-
tacts open contacts 3 and 5.
Field Adjustments
Field adjustments to the operating set
point are made by removing the protec-
tive plug button on the side of the con-
trol enclosure and inserting a standard
blade-type screwdriver, at least 3 inches
long*.
The adjustment range is 0.05 ± .02"
w.c. to 12.0" w.c. To adjust the set point,
Model AFS-952
Air Pressure Sensing Switch
Mounting Position: Mount with the
diaphragm in any vertical plane.
Set Point Range: 0.05 ± 0.02" w.c. to
12.0"w.c. (1.3 to 305 mm wc; 0 to 0.43
psi).
Field Adjustable “Operate Range”:
0.07"w.c. to 12.0" w.c.
Field Adjustable “Release Range”:
0.04"w.c. to 11.2" w.c.
Approximate Switching Differential:
Progressive, increasing from 0.02± 0.01"w.c.
at minimum set point to approximately 0.8"
w.c. at maximum set point. (0.5 ± .25 mm to
approximately 20.3 mm).
Operating Temperature Range: 0Fto 130F
(-18 to 54.4C).
Measured Media: Air or combustion by-
products that will not degrade silicone.
Maximum Pressure: ½ psi (0.03 bar).
Life: 100,000 cycles minimum at 1/2 psi
maximum pressure each cycle and at
maximum rated electrical load.
Electrical Rating–Relay Switching
Capacity:
720 va at 120 vAC at 50/60 Hz.
10 amps at 120 vAC,
5 amps at 240 vAC resistive load.
Power consumption: 4.5 watts at 120 vAC.
Contact Arrangement: SPDT NC (single
pole, double-throw snap action switch;
contacts are in normally closed position
before pressure is applied to the diaphragm.)
Electrical Connections: 5 numbered
terminals, pressure clamp screw type.
Conduit Opening: 7/8" diameter opening
accepts 1/2" conduit.
Sample Line Connectors: Two ¼"—18
NPT female fittings.
Approval: FM approved.
Shipping Weight:
AFS - 952 (std. enclosure): 5 lbs.
AFS - 952 - 1 NEMA 4 enclosure: 8 lbs.
AFS - 952 - 2 NEMA 7/9 enclosure: 18 lbs.
*Standard enclosure only.
L
H
H
L
H: L:
HIGH POSITIVE LOW POSITIVE
POSITIVE NEGATIVE
LOW NEGATIVE HIGH NEGATIVE
Figure 1
12 345
G
K1 Load
Relay Contacts
120 V
Common
(Load)
Control
with Delay
Alarm
with Delay
Ground
12910
1234
Typical Draft Control System Connections
Series 7700
Draft Control Terminals:
:
AFS-952 Terminals:
Series 9500
Draft Regulator Terminals wire in series with
the safety limits.
turn the adjusting screw counterclockwise
until motion has stopped. Next, turn the
adjusting screw 4 complete turns in a
clockwise direction to engage the spring.
For the next 10 turns, each full turn
represents approximately1.2" w.c. At
higher operating pressures, there is a
slight increase in the switching differ-
ential. Pleasenote: To properly calibrate
an air pressure sensing switch, a digital
manometer or other measuring device
should be used to confirm the actual set
point.
Figure 2: Electrical Connections

Contact Position
Condition K-1 Load Relay Contacts
3 - 4 3 - 5
Red
Lamp
On Shelf (Figure 3). Open Closed Off
Power Applied;
Differential Pressure above
Set Point (Immediate). Open Closed Off
Power Applied; Differential
Pressure above Set Point
(After 8 seconds). Closed Open Off
Power Applied; Differential
Pressure below Set Point
(Immediate). Closed Open On
Power Applied; Differential
Pressure below Set Point
(After 8 seconds). Open Closed On
Model AFS-952 in Standard NEMA-1 rated housing:
•Coated steel finish.
•Shipping Weight: 5 lbs.
K1
L
2
1
TD-1
TD - 1
(8 SEC)
C
NC NO
LOW
PRESSURE
HIGH
PRESSURE
4
3
5
CONTROL
WITH
DELAY
10 A MAX 720 VA
@ 120 vAC
K1
Figure 3: "Shelf" Condition
CLEVELAND CONTROLS
DIVISION OF UNICONTROL INC.
MODELAFS-952-B
Remove Plug Button to Adjust
Turn Clockwise to Increase
Operating Set Point.
TD -1
K - 1
Load
Relay
Red
Signal
Lamp
Enclosure
Cover
Low Pressure Inlet
¼ NPT
High Pressure Inlet
¼ NPT
0.281” (7 mm)
mounting holes (4)
AFS-952
.875" hole
accepts
.5" conduit
Plug Button
to access
adjusting
screw
1.75"
(44 mm)
4.38"
(111 mm)
3.59"
(91 mm)
5.88"
(149 mm)
5.25"
(133 mm)
1.00"
(25 mm)
6.00"
(152 mm)
2.31"
(59 mm)
1.25"
(32 mm)
8.00"
(203 mm)
3.56"
(90 mm)
1.44"
(37 mm)

ENCLOSURE SPECIFICATIONS & DIMENSIONS
ModelAFS-952-1:
14-gauge grey hammertone enameled steel with
neoprene gasketed clamped cover hinged on the
left side. NEMA 4 rated: provides protection
from dust, dirt, oil, and water.
Shipping Weight: 8 lbs.
ModelAFS-952-2:
Red lamp not available.
Cast aluminum alloy, nonmagnetic, non-sparking, and non-rusting. NEMA 7 and NEMA 9 rated. UL approved for Class 1, Group D; Class II,
Groups E, F, G.
Piping: Either pressure inlet, if not connected to a pressure sample, must be piped and vented to a nonhazardous area.
Shipping Weight: 18 lbs.
Timed
e
l
a
y
r
e
l
a
y
i
s
notfie
l
d
r
e
p
l
a
c
e
a
b
l
e
.
TD -1
(8 sec.)
K-1
Weatherproof
Electrical
Connection
½ NPT
6.00"
(152 mm)
4.00"
(102 mm)
9.50"
(241 mm)
8.75"
(222 mm)
3.562"
(90 mm)
1.00"
(25 mm)
2.062"
(52 mm)
1.687”
(43 mm)
Red Signal
Lamp
Hinged
Cover
Low Pressure Inlet
¼ NPT
High Pressure Inlet
¼ NPT
Load Relay
0.313" (8mm)
mounting holes (4)
Timedelayre
l
a
y
i
s
notfieldrepla
c
e
a
b
l
e
.
TD -1
(8 sec.)
K-1
2.562"
(65 mm)
2.75"
(70 mm)
6.562"
(167 mm)
10.187"
(259 mm)
8.75"
(222
mm) 3.562"
(90 mm)
3.00"
(76 mm)
Low Pressure Inlet ¼ NPT
Mounting Slot for ½" Bolt (2)
High Pressure Inlet ¼" NPT
½" 14 NPT Electrical Connection