Sierra Monitor Corporation 4501-05 - Manual (Page 21)

Model 4501-XX Toxic Gas Sensor Module
Page 17 of 35
7.3 TRANSMITTER REPLACEMENT
The transmitter assembly should be replaced when it is determined that it is unreliable, noisy or cannot be
adjusted for calibration. This may occur due to age, corrosion or failed components.
To replace the transmitter assembly:
a. Remove the cover of the main enclosure.
b. Unscrew the two thumb screws in the top of the cover plate, lift the assembly and rotate 90
o to relieve the
wiring service loop.
c. Remove the two wires from P1 terminals (see figure 4-3).
d. Unplug the sensor connector from the transmitter.
e. Reverse the preceding steps to install the new transmitter.
f. Restore power and allow a minimum of 30 minutes for stabilization before re-calibration.
7.4 SENSOR REPLACEMENT
NOTE: Refer to Appendix D for information on sensor electrolyte replacement for 4501-25.
The gas sensor which is located inside the sensor assembly housing can be replaced without replacement of
the housing. The gas sensor needs replacement when:
 It is no longer possible to obtain correct Zero and Span values.
 The “LOW SENS” message appears after calibration.
 The sensor output signal is noisy, causing erroneous gas level readings.
To replace the sensor:
a. Confirm that system power has been removed.
b. Remove the gas sensor module enclosure cover.
c. Unscrew the two thumb screws in the top of the faceplate, lift the transmitter assembly and rotate 90
o to
relieve the wiring service loop.
d. Unplug the sensor connector from the transmitter.
e. Unscrew the old sensor assembly from the enclosure conduit hub. Remove the sensor assembly with its
harness.
f. Unscrew sensor housing cover from the sensor.
g. Carefully pull the old sensor straight up from the socket.
h. Press the new sensor into the socket.
i. Reverse the preceding steps to install the sensor assembly.
j. Allow the new sensor to stabilize for a minimum of 30 minutes and then calibrate using the procedure in
Section 6.
7.5 INSTALLATION INSPECTION
Prior to system start-up or trouble shooting, the entire system should be visually inspected. The following are
guidelines for that inspection:
7.5.1 CONTROLLER INSTALLATION
• Controller installed in conformance to manufacturer’s instruction manual recommendations.
7.5.2 CABLING INSTALLATION
• All splices are soldered or via terminal block.
• Cabling is away from sources of electrical noise or RFI where possible.
7.5.3 SENSOR MODULE INSTALLATION
• Module installation in conformance with this manual.
• Modules accessible for calibration.
• Wiring terminations clean and correct.