Det-Tronics 505 Combustible Gas Detector Transmitter with Combustible Gas Sensor CGS - Manual (Page 15)

12 95-8472 3.1
Section III —
System Maintenance
TROUBLESHOOTING
Table 3 is intended to serve as an aid in locating the
cause of a malfunction.
The transmitter is not designed to be repaired in the field.
If a problem should develop, first check for proper wiring,
calibration and sensor sensitivity. If it is determined that
the problem is caused by an electrical malfunction in the
transmitter, the unit must be returned to the factory for
repair.
NOTE
Record all faults on the Fault Record Sheet
supplied at the back of this manual.
ROUTINE MAINTENANCE
The Model 505 Transmitter requires no routine
maintenance, except for periodic checks to ensure
proper calibration. The frequency of these checks
is determined by the requirements of the particular
installation. Calibration gas kits are required for these
checks.
CHECKOUT IN NORMAL MODE
The entire gas detection system should be checked
periodically to ensure that the presence of gas at the
sensor will result in the proper system response.
SENSOR INSPECTION
Since a dirty or plugged sensor filter can adversely affect
the response time of the sensor by restricting the flow of
gas to the sensing element, it should be inspected on a
regular basis. If a dust cover or splash shield is used, it
should also be checked.
SENSOR SENSITIVITY
If sensor response to 50% LFL methane is less than 15
millivolts, the sensor should be replaced. Refer to Table
2, “Calibration Procedure” for information regarding
calibration and sensor sensitivity.
SENSOR REPLACEMENT
De-classify the area prior to replacing the sensor and
secure any output devices connected to the system
to prevent unwanted actuation of this equipment. To
replace the sensor:
1. Verify that no hazardous levels of combustible gas
are present at the sensor, then remove the cover
from the junction box.
2. Unplug the sensor from the circuit board and unscrew
it from the junction box.
3. Coat the threads of the new sensor with silicone free
grease, then screw the sensor into the junction box
and plug it into the circuit board.
4. Allow the sensor output to stabilize under power
(about two hours minimum for best results), then
perform the calibration procedure described in the
“Calibration” section of this manual.
5. For the highest degree of calibration accuracy,
perform a second calibration after 24 hours.
A Recommended Test Form is supplied at the back of
this manual for recording maintenance performed on the
system.