Sierra Monitor Corporation 4105 - Manual (Page 9)

Model 4105 Gas Sensor Module (12/02) Page: 6
Instruction Manual
6. SERVICE
6.1 Sensor Module Configuration
The gas sensor module is comprised of the following
sub assemblies:
4105-XX Gas Sensor Module
-SPM25002 Transmitter Assembly
-SPT25013
Combustible Gas Sensor
Module Transmitter Assembly
-SPM25003 Oxygen and Toxic Gas Sensor
Module Transmitter Assemby
(must specify gas type)
-4205-XX Sensor Assembly
[Where "xx" is the suffix to the gas sensor
module number (Table 6.1)]
There is no field servicable components below
the sub assembly level.
Warning: Prior to removal of the trans-
mitter assembly, remove system power at
the controller or other power source.
6.3 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:
1. Remove the cover of the main enclosure.
2. Remove the front panel by loosening the two cap-
tive thumb screws in the 4105-XX front panel and
remove the PANEL/CPU PCB assembly as far as is
allowed the by the ribbon cable.
3. Unscrew the sensor harness from the transmitter
(TB1).
4. Remove the three wires from the P,S,G terminals
(TB2).
5. Remove the I/O PCB.
6. Reverse the preceding steps to install the new
transmitter.
7. Restore power and allow a minimum of 30 minutes
for stabilization before re-calibration.
6.4 Sensor Replacement
The sensor should be replaced when it is determined
that:
- It is no longer possible to obtain correct Zero and
Span values at the test points or at the controller.
- The sensor output signal is noisy, causing errone-
ous gas level readings.
To replace the sensor:
1. Remove the gas sensor module enclosure lid.
2. Remove the front panel by loosening the two cap-
tive thumb screws in the 4105-XX front panel and
remove the PANEL/CPU PCB assembly as far as is
allowed the by the ribbon cable.
3. Unscrew the sensor wires from the transmitter..
4. Unscrew the old sensor assembly from the enclo-
sure conduit hub. Remove the sensor assembly
with its harness.
5. Reverse the preceding steps to install the sensor
assembly.
6.2 Enclosure Replacement
The enclosure should be replaced if the lid threads or
conduit threads have been damaged, or if the enclo-
sure has corroded sufficiently that it no longer meets
the required NEMA classification.
To replace the enclosure follow the transmitter and
sensor assembly removal instructions, remove the
damaged enclosure from it’s conduit or wall mount-
ing, install a new enclosure and continue the trans-
mitter and sensor assembly replacement instructions.
Model Gas Module
4105-02 Combustible
4105-03 Oxygen
4105-04 CO
4105-05 H
2
S
4105-06 Cl
2
4105-07 H
2
4105-10 SO
2
4105-12 NO
2
4105-21 HCl
4105-22 HCN
4105-25 NH
3
4105-26 HF
Table 6.1
Model Numbers