Bulletin AFS953.00
Model
AFS–953
DESCRIPTION &
OPERATION
The
Cleveland Controls AFS-953 Dif-
ferential Pressure Sensing Switch
is
designed to provide precise operation
and convenient features for industrial
and commercial air handling applica-
tions. The
AFS-953
can monitor posi-
tive, negative, or differential pressure
(flow) of air and noncombustible gases,
and is commonly used to monitor com-
bustion air, furnace pressure, ventilat-
ing blower operation, inflatable struc-
ture pressure, fume hood operation, bag
house air flow, dirt accumulation in air
filters, and heat-transfer air flow. The
AFS-953
has a field–adjustable set
point range of 0.05"wc to 12.0"wc with
a 20-second pre-purge delay and an
8-second (± 3 seconds) time delay re-
lay sequence. The time delay prevents
nuisance shutdowns due to normal draft
fluctuations.
COMMON
APPLICATIONS
The most common specific application
for the
AFS-953
is as a
Low Draft
(Negative Pressure) Cutoff Safety
Switch
for combustion draft control
systems where individual pre-purge is
needed. In general, the
AFS-953
can
be applied as follows:
• Low Positive Pressure Cutoff
.
(Shutdown upon insufficient pres-
sure.)
• Low Negative Pressure Cutoff
.
( S h u t d o w n u p o n i n s u f f i c i e n t
draft.)
• Low Differential Pressure Cutoff
.
(Shutdown upon insufficient dif-
ference between two samples.)
MOUNTING
Three NEMA-rated enclosures, de-
signed for surface mounting on any flat,
relatively stable surface free of vibra-
tion, are available for the
AFS-953
. The
s t a n d a r d e n c l o s u r e h a s m o u n t i n g
flanges with four mounting holes
(9/32") as shown in drawing on page 3.
The NEMA-4 rated model has mount-
ing flanges with four 5/16" mounting
holes as shown at top of page 4. The
NEMA-7/NEMA-9 rated enclosure has
two mounting slots as shown at bottom
of page 4. With any of the enclosures,
t
he AFS-953 must be mounted with
the diaphragm in a vertical plane, to
obtain the lowest operating set point
specification.
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
;
L
remains open
to the atmosphere.
Negative Pressure only:
Connect
sample line to
L
:
H
remains open
to the atmosphere.
AFS-953-1
in NEMA-4 rated
Enclosure.
A F S - 9 5 3
in Standard
Enclosure, rated NEMA-1.
AFS-953-2
in NEMA-7 and
NEMA-9 rated Enclosure.
Cleveland Controls
Division of UniControl Inc
.
Adjustable Set Point Air Pressure Sensing Switch with 20-Second Pre-Purge and 8-Second Time Delay
Tel:
216-398-0330
Fax:
216-398-8558
Email:
Web page:
http://www.clevelandcontrols.com
Cleveland Controls
Division of UniControl Inc.
1111 Brookpark Rd
Cleveland OH 44109
