GE CGA 351, User Manual

Page: 95 / 133

Service and Maintenance 5-17
December 2004
Replacing the
Thermocouple
The thermocouple is mounted on the bottom of the sensor furnace and
extends approximately 2–3 in. into the sensor furnace.
Note:
For information regarding component locations and/or wiring
connections in an optional enclosure, see Appendix C.
Caution!
To prevent damage, the oxygen sensor must cool for
about two hours after the unit is powered down before the
sensor enclosure door may be opened. Then, replace the
thermocouple and reconnect the power as quickly as
possible to prevent corrosion of the analyzer components
due to acid condensation.
IMPORTANT:
These symbols indicate Caution - dangerously hot
surfaces and risk of electric shock, respectively:
A standard screwdriver is the only tool needed for replacement of the
thermocouple. Complete the following steps, in the order shown, to
remove the defective thermocouple:
1.
Disconnect the main power to the CGA 351.
!WARNING!
Failure to cut the main power at the external
disconnect device before proceeding will result in
serious personal injury.
2.
Open the cover on the sensor and electronics enclosures.
!WARNING!
The sensor furnace may still be hot. Always use
heat-resistant gloves when handling it.
3.
Remove the oxygen sensor/manifold assembly, as described in the
previous section.
4.
Disconnect the thermocouple leads from
TB2
in the electronics
enclosure (make a note of the terminal pins for each lead), and pull
the leads through the conduit and into the sensor enclosure.
5.
Remove the screw that secures the integral thermocouple clamp to
the bottom of the sensor furnace.
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