C437D,E GAS PRESSURE SWITCHES
5 68-0286
WIRING
WARNING
Electrical Shock Hazard.
Can cause severe injury, death or property damage.
Disconnect all power to the pressure switch before
connecting wiring to prevent electrical shock and
equipment damage.
All wiring must comply with local electrical codes, ordinances,
and regulations. Do not exceed the switch ratings given in the
Specifications section.
Wiring diagram for the C437D,E is shown in Fig. 3. The
switches make or break as indicated in the diagram. Connect
the wiring to the screw terminals on the terminal strip after
removing the cover glass. Route the wires through the conduit
tapping.
Fig. 3. Wiring diagram for C437D,E.
SETTING AND CHECKOUT
Setting
In the C437D, the differential is subtractive. The upper
operating point is determined by the setpoint, while the lower
operating point is determined by the setpoint minus the
differential. In the C437E, the differential is additive. The lower
operating point is determined by the setpoint, while the upper
operating point is determined by the setpoint plus the
differential. Operating points are shown in Fig. 4.
Remove the retainer and adjust the setpoint for the desired
operating pressure (cutout pressure) by turning the setting
screw (Fig. 2) clockwise to increase the setpoint and
counterclockwise to decrease it.
Trip-Free Manual Reset Feature (C437D,E
only)
The C437D breaks contact between terminals when the
pressure rises to the setpoint. The C437E breaks contact
between terminals when the pressure falls to the setpoint.
None of these pressure switches will automatically return to
their former positions.
To reset one of these pressure switches, wait until the pressure
falls to the setpoint minus the differential (C437D), or rises to
the setpoint plus the differential (C437E). Then depress the
manual reset button (Fig. 2) and release it. The pressure
switch will not be reset until you release the manual reset
button. This prevents the switch from becoming an automatic-
reset device if the reset button is stuck, held in, or tied down.
Checkout
Adjust the setpoint for normal operation and check to see that
the gas pressure switch performs as intended. Use a
manometer or accurate pressure gauge connected upstream
from the switch to measure the actual pressure.
C437D (Subtractive Differential)
1. Put the system into normal operation, and set the
pressure switch at the normal setpoint (above the normal
operating pressure). Turn the setting screw (Fig. 2)
slowly toward a lower pressure setting
(counterclockwise ) to simulate a pressure
increase.
2. When the setpoint is approximately equal to the pressure
indicated on the pressure gauge, the C437D should
break contact and turn off the controlled equipment;
locking out.
Fig. 4. C437 operating points.
Turn the setting screw toward a high pressure setting
(clockwise ) to simulate a pressure decrease greater than
the differential.
3. Push the manual reset button (Fig. 2) on the C437D; the
C437D should make contact.
C437E (Additive Differential)
1. Put the system into normal operation and gradually close
the upstream gas shutoff valve to cause a pressure
decrease.
2. When the pressure gauge indicates that the pressure is
approximately equal to the setpoint, the C437E should
break contact and turn off the controlled equipment,
locking out.
3. Open the gas shutoff valve to increase the pressure
again. When the pressure rises to the setpoint plus the
differential, push the manual reset button (Fig. 2) on the
C437E; the C437E should make contact.
TERMINAL
STRIP
M23673
C437D: BREAKS ON PRESSURE RISE
C437E: BREAKS ON PRESSURE FALL
PRESSURE
RISE
PRESSURE
FALL
SET POINT
(SWITCH BREAKS, LOCKS OUT)
SUBTRACTIVE
DIFFERENTIAL
SET POINT MINUS
DIFFERENTIAL (SWITCH MAKES)
SET POINT PLUS
DIFFERENTIAL (SWITCH MAKES)
ADDITIVE
DIFFERENTIAL
SET POINT
(SWITCH BREAKS, LOCKS OUT)
C437D
C437E
C437D IS A MANUAL RESET MODELS; IT CAN BE MANUALLY
RESET WHEN THE PRESSURE FALLS TO THE SET POINT
MINUS THE DIFFERENTIAL.
C437E IS A MANUAL RESET MODELS; IT CAN BE MANUALLY
RESET WHEN THE PRESSURE RISES TO THE SET POINT
PLUS THE DIFFERENTIAL.
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M22763
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