Sierra Monitor Corporation 4105 manual Service

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.

Model	Gas Module
4105-02	Combustible
4105-03	Oxygen
4105-04	CO
4105-05	H2S
4105-06	Cl2
4105-07	H2
4105-10	SO2
4105-12	NO2
4105-21	HCl
4105-22	HCN
4105-25	NH3
4105-26	HF

Table 6.1

Model Numbers

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.

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.

6.4Sensor 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.

Page: 6 Model 4105 Gas Sensor Module (12/02)