C645A-E
Pressure Switches
PRODUCT DATA
FEATURES
•
C645A,B models are for use on natural gas, LP gas,
or air.
•
C645B1047 includes a scaleplate stop to meet
American Gas Association (AGA) requirements for
gas-fired boilers with inputs over 2-1/2 million Btuh.
•
•
•
C645C,D models are for use on air only.
C645E for use with distillate fuel oil.
C645A,B,D,E
C645C
Spring-loaded diaphragm actuates snap-acting
Micro Switch.
•
•
Switch can be wired to turn on alarm.
C645A,C and D models break control circuit on
pressure fall.
•
•
•
C645B models break control circuit on pressure rise.
Lockout and manual reset optional in A and C models.
Removable, zinc-plated cover protects scaleplate and
adjusting screw.
C645A,B with Window
•
•
Lockout models have external manual reset lever.
Pipe tappings allow selection of positive pressure,
differential-pressure, or venting connections.
•
•
Optional switch position indicator available.
Models of C645A,B available with cover window for
setpoint visibility.
GENERAL
•
•
Buna-N fiber-reinforced material for increased control
diaphragm strength.
The C645 pressure switches are safety devices used in
positive-pressure or differential-pressure systems to sense
gas or air pressure changes.
Two seal-off diaphragms for added reliability.
Contents
General ...............................................................................
Features ..............................................................................
Specifications ......................................................................
Ordering Information ...........................................................
Installation ...........................................................................
Settings and Adjustments ...................................................
Operation and Checkout .....................................................
1
1
2
2
4
6
7
Copyright © 1995 Honeywell Inc.
•
All Rights Reserved
60-2159-8
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C645A-E PRESSURE SWITCHES
Switching:
Canadian Standards Association listed: C645A-E, File no.
LR1620-369, Guide no. 140-A-2; for use subject to
same ambient temperature restrictions as Underwriters
Laboratories Inc.
Spdt Micro Switch snap-acting switch (Fig. 3).
Minimum Ambient Temperature:
-20°F (- 29°C).
Factory Mutual Approved.
Industrial Risk Insurers: C645A-D models with window in
cover approvable for applications on burners over
5 million Btuh (5 thousand cfh) input.
Maximum Ambient Temperature:
125°F (52°C).
Connections:
Optional Specifications:
1/4-18 NPT female tapping for main or high pressure
connection.
1. C645A with position indicator and manual reset.
2. C645A operation to 1.5 in. WC with position indicator
and manual reset.
1/8-27 NPT female tapping for venting or low-pressure
connection.
3. C645B with position indicator and manual reset.
4. C645C with position indicator and manual reset.
5. C645D with 2 in. (50.8 mm) differential.
Approvals:
Underwriters Laboratories Inc. listed: C645AE File
no. MP2168, Guide no. MFHX; for use in ambient
temperatures normally prevailing in occupiable spaces,
which usually are not higher than 77°F (25°C) but can
occasionally be as high as 104°F (40°C) for brief periods.
Accessories:
1. C645A,B,D: Mounting Bracket: part no. 15865AC.
2. C645C: Mounting Bracket: part no. 112657A.
3. C645A: Cover with Window: part no. 137637B.
4. C645B: Cover with Window: part no. 137637C.
3-1/2 (88.9)
MOUNTING
2-7/8 (73)
BRACKET
(OPTIONAL)
3/16 (2)
(4.8)
4
(101.6)
3-1/2
(88.9)
4-3/4
(120.6)
1/4-18 NPT
1/8-27 NPT
3/8 (9.5)
5/8
(15.9)
1
3/8
(9.5)
1-1/8
(28.6)
1-5/16
(33.3)
2-1/2 (63.5)
M7564
1
IMPORTANT: FOR MODELS WITH LOCKOUT, DO NOT OBSTRUCT MANUAL RESET LEVER.
Fig. 1. Dimensions of C645A,B,D, and E in in. (mm).
3
60-2159—8
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C645A-E PRESSURE SWITCHES
3-7/8
(98.4)
MOUNTING BRACKET
(OPTIONAL)
1-1/8
(29)
MANUAL
RESET
LEVER
5/16
(7.9)
1/4-18 INCH
NPT
3/16 (4.8)
DIA.
1
3-5/8
(92)
3/4
(19)
3
5
(76.2)
(127)
1-13/16
(46)
2-5/8
(66.7)
9/32 (7.1)
DIA. (2)
1-1/4
(31.7)
1
(25.4)
1/8-27 INCH NPT
M7563
3/4
(19)
7-7/8 DIA. (200)
2-1/4
(57.1)
2-3/4
(69.8)
1
IMPORTANT: FOR MODELS WITH LOCKOUT, DO NOT OBSTRUCT MANUAL RESET LEVER.
Fig. 2. Dimensions of C645C in in. (mm).
INSTALLATION
When Installing this Product . . .
Mounting
ᕡ Read these instructions carefully. Failure to follow them
could damage the product or cause a hazardous
condition.
The C645 has a hexagonal fitting with a 1/4 in. NPT tapping,
which is the high pressure connection in differential
applications. The bleed fitting is 1/8 in. NPT female tapped. In
differential pressure control applications using air, connect the
lower pressure to the bleed fitting (Fig. 3 and 4). In
applications using combustible gases, vent the bleed tapping
according to applicable standard code or jurisdictional
authority.
ᕢ Check the ratings given in the instructions and on the
product to make sure the product is suitable for your
application.
ᕣ Installer must be a trained, experienced service
technician.
ᕤ After installation is complete, check out product
operation as provided in these instructions.
The C645A,B,D can be mounted in any position but are more
accurate when mounted horizontally. The C645C is mounted
with the diaphragm vertical and the bleed fitting at the bottom.
CAUTION
Disconnect power supply before beginning installation
to prevent electrical shock or equipment damage.
60-2159—8
4
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C645A-E PRESSURE SWITCHES
OPENING
FOR 1/2 INCH
CONDUIT
The C645E1002 Distillate Fuel Oil Pressure Switch is the
same as the C645A1006 Gas Pressure Switch except that it
does not have a 0.015 in. (0.38 mm) diameter (nominal)
orifice in its 1/4 in. NPT main (high pressure) connection.
(This orifice is required in a C645A Gas Pressure Switch to
restrict gas leakage, but it is too small for oil applications.)
The C645E1002 has a 0.125 in. (3.18 mm) diameter
(nominal) opening in its 1/4 in. NPT main connection into its
pressure chamber.
MANUAL RESET
LEVER
ON LOCKOUT
MODELS ONLY
CAUTION
Vent the bleed tapping back to the oil supply tank—
not to the combustion chamber.
COVER
SCREW
SET POINT
ADJUSTMENT
SCREW
Wiring
Disconnect power supply before connecting wiring to prevent
electrical shock and equipment damage.
SCALE
PLATE
BLEED
M7561
FITTING
All wiring must agree with applicable codes, ordinances, and
regulations. An opening is provided to accommodate rigid
conduit or armored cable for line voltage operation (Fig. 3
and 4). Do not overload the switch contacts (see Switch
Ratings in Specifications section). The switching schematic is
shown in Fig. 5.
Fig. 4. C645C with cover removed.
SET POINT
SCALE
BLEED
FITTING
ADJUSTMENT
SCREW
PLATE
COVER
SCREW
OPENING
FOR 1/2 INCH
CONDUIT
W
2
B
1
MICRO
SWITCH
R
C645A,C,D BREAKS R-W, MAKE R-B ON PRESSURE FALL.
MANUAL RESET MODELS LOCK OUT.
1
2
M7560
MANUAL RESET LEVER
ON LOCKOUT MODELS ONLY
C645B BREAKS R-B, MAKES R-W ON PRESSURE RISE
AND LOCKS OUT.
M7565
Fig. 3. C645A,B,D with cover removed.
Fig. 5. Schematic showing switch in zero
pressure condition.
5
60-2159—8
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C645A-E PRESSURE SWITCHES
SETTINGS AND ADJUSTMENTS
Table 4. C645C Control Points.
Pressure
Pressure Setpoint Adjustment
Tables 2 through 4 give the pressure and switching for each
setpoint. To adjust the pressure setting, turn the setpoint
Pressure
kPa
Setpoint
Switching
R-W makes
R-B makes
R-W makes
R-B makes
R-W makes
R-B makes
R-W makes
R-B makes
in. of Water
adjustment screw (Fig. 3 and 4) clockwise
the pressure setting and counterclockwise
the pressure setting.
to increase
to decrease
1a
1
0.8
3
0.25
0.2
3b
5b
0.75
0.64
1.24
1.2
Table 2. C645A,D,E control points.
Pressure
2.6
5
Pressure
kPa
Setpoint
Switching
R-W makes
R-B makes
R-W makes
R-W makes
R-W makes
R-B makes
R-W makes
R-B makes
in. of Water
3a
3
0.8
0.5
2.2
3.7
5.2
4.5
8.7
7.7
4.3
6
Top Scalec
1.50
1.3
2
9b
15b
21c
9
5.2
a Nominal differential—0.2 in. of water (0.05 kPa).
15
21
18
35
31
b Differential between 0.2 and 0.8 in. of water (0.05 and
1.2 kPa).
c Maximum differential—0.8 in. of water (0.2 kPa).
35d
C645B1047 Scaleplate Stop Adjustment
a Nominal differential—1 in. of water (0.2 kPa).
The C645B1047 is the same as the C645B1013 except for a
scaleplate stop.
b Differential between 1 and 3 in. of water (0.2 and 0.7 kPa).
c Maximum differential—3 in. of water (0.7 kPa).
d Maximum differential—4 in. of water (1.0 kPa).
Specifications
Scaleplate Stop:
Limits maximum setting, factory-set at 5-1/4 in. of water
(1.31 kPa).
Table 3. C645B control points.
Scale Range:
3 to 21 in. of water (0.75 to 5.23 kPa).
Pressure
in. of Water
Pressure
kPa
Setpoint
Switching
R-W makes
R-B makes
R-W makes
R-W makes
R-W makes
R-B makes
R-W makes
R-B makes
R-W makes
R-B makes
3a
3
0.8
0.5
2.2
3.7
5.2
4.5
8.7
7.7
11.2
9.8
AdjustingWrench:
Part no. 23466 included with the C645B1047.
2
9b
15b
21c
9
To Adjust Scaleplate Stop
15
21
18
35
31
45
39
ᕡ Remove cover.
ᕢ Loosen scaleplate stop locking screw about 1/2 turn
counterclockwise
Wrench.
ᕣ Move scaleplate stop until bottom edge is aligned with
desired maximum setting.
ᕤ Tighten scaleplate stop locking screw clockwise
ᕥ Replace cover.
with the 23466 Adjusting
35d
45e
.
a Nominal differential—1 in. of water (0.2 kPa).
b Differential between 1 and 3 in. of water (0.2 and 0.7 kPa).
c Maximum differential—3 in. of water (0.7 kPa).
d Maximum differential—4 in. of water (1.0 kPa).
e Maximum differential—5.7 in of water (1.4 kPa).
60-2159—8
6
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C645A-E PRESSURE SWITCHES
23466 ADJUSTING
WRENCH
The C645B spring-loaded diaphragm actuates the Micro
Switch snap-acting switch which breaks a control circuit, locks
out, and turns on an alarm (if so wired) when the pressure
rises to the scale setting. When pressure falls to the scale
setting minus the differential, the switch lockout can be
manually reset, turning off the alarm
LOCKING
SCREW
Checkout
C645A,B—Gas or Air Switch
ᕡ Set cutoff pressure.
ᕢ Open main supply line. Depress reset lever on lockout
models until switch makes R-W.
ᕣ Set controller and limit switch to call for heat.
ᕤ For C645A—close main shutoff valve. Valve should
close when pressure reaches cutoff point.
For C645B—wait a few minutes for the pressure to rise;
then lower the scale setting until the switch makes R-W
and locks out.
SCALEPLATE
STOP
M7562
SET POINT INDICATOR
Fig. 6. Adjusting C645B1047 scaleplate stop.
NOTE: To more accurately check C645A, use slow
bleedoff. For C645B, jumper other limit and let
pressure rise to cutoff setting.
Manual Resetting
ᕥ For C645A—reconnect the control valve, open the
shutoff valve, press the reset lever (if necessary), and
return the pressure switch to its original setting.
For C645B—raise setting to normal. Depress reset
lever.
ᕦ Allow system to operate through at least one complete
cycle to make certain all components are functioning
properly.
The C645A,C manual reset models lock out at scale setting
minus the differential and require manual resetting after the
pressure rises to scale setting to resume normal operation.
The C645B locks out at scale setting and requires manual
resetting after the pressure falls to scale setting minus the
differential to resume normal operation. To reset, push the
reset button as far as it will go; then release.
IMPORTANT
C645C,D—Air Switch Only
Lockout models cannot be made to recycle
automatically by permanently holding in the reset
lever.
ᕡ Set cutoff pressure.
ᕢ Turn on fan.
ᕣ If using a manual rest C645, depress and hold lever
until switch makes R-W.
ᕤ Block fan inlet or filter area. Switch should break R-W,
make R-B when pressure drops to cutoff point. Manual
reset models lock out.
ᕥ Remove obstruction. Depress reset lever and allow
system to operate through at least one complete cycle
to make certain all components are functioning
properly.
OPERATION AND CHECKOUT
Operation
The C645A,C,D,E spring-loaded diaphragm actuates the
Micro Switch snap-acting switch to break a control circuit
when pressure falls to scale setting minus differential. The
switch can be wired to turn on an alarm at the same time.
When the pressure rises to the scale setting, the control
circuit requires manual resetting to reset and turn off alarm.
Optional C645A model will recycle automatically when the
control circuit returns to scale setting.
C645E1002—Distillate Fuel Oil Switch
ᕡ The C645E1002 is the same as the C645A1006 Gas
Pressure Switch except the C645E1002 has a 0.125 in.
NPT main connection in its pressure chamber.
ᕢ See Checkout for C645A.
7
60-2159—8
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Home and Building Control
Honeywell Inc.
1985 Douglas Drive North
Golden Valley, Minnesota 55422
Home and Building Control
Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Scarborough, Ontario
M1V 4Z9
60-2159—8 F.P. Rev. 5-95
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