Fault Isolation; Table 8-1 Troubleshooting - Emerson Rosemount OCX8800 Instruction Manual

Instruction Manual
IM-106-880C, OI
8.4

Fault Isolation

Faults in the Hazardous Area OCX 8800 Transmitter are indicated by messages displayed on the
375 Field Communicator or LOI. Fault indications that can appear are listed in
If a fault is indicated on the Field Communicator or LOI, locate the fault indication in
For each fault listed, there are related Probable Causes and Recommended Corrective Actions.
The Probable Causes are listed in the order of most probable to least probable. Starting with the
most probable cause, inspect and test the unit to isolate the actual cause, then use the
Recommended Corrective Action listed to correct the problem.

Table 8-1 Troubleshooting

O2 Sensor R High (Oxygen sensor resistance high, > 5000 Ohms)
O2 Sensor Open (Oxygen sensor disconnected)
Probable Cause
Loose or open O cell circuit connection
2
O cell degraded or failed
2
Ref Current Err (RTD excitation current error) (reference current should be 5.02 mA)
Probable Cause
Loose or open lead or circuit wire
connection for COe sensor or CJC sensor
current loop
COe sensor grounded
COe sensor failed
CJC sensor grounded
CJC sensor failed
O2 Temp Hi (Oxygen sensor heater temperature high, > 750 ºC)
Probable Cause
High noise in OCX power supply
COe Temp Hi (Combustion sensor heater temperature high, 310 ºC)
Probable Cause
High noise in OCX power supply
Table continued on next page
Fault
Isolation
Recommended Corrective Action
Check O cell circuit wires for breaks or loose connections. Repair lead wire break
2
or loose connections.
Check O cell impedance by reading the O2 Snsr R value via the LOI (see
2
4-5, sheet 2), or the O2 Snsr value via Field communicator (see
1). If cell impedance is zero, replace O
impedance is less than 5000 ohms, check for cell housing ground fault. Repair
ground fault. If cell impedance is greater than 5000 ohms and no ground fault is
indicated, replace O cell with cell replacement kit.
2
Recommended Corrective Action
Check all COe and CJC sensor current loop wiring per
10. Correct wiring faults.
Check resistance of COe sensor leads to ground per . Replace COe sensor if
resistance is less than 10M Ohms.
Check resistance of both COe sensor elements per . Replace COe sensor if
resistance of sensor element is not between 100 and 250 Ohms.
Check resistance of CJC sensor to ground per . Replace CJC sensor if resistance is
less than 10M Ohms.
Check resistance of CJC sensor per . Replace CJC sensor if resistance of sensor is
not between 100 and 150 Ohms.
Recommended Corrective Action
Check power supply for line noise or voltage fluctuations. Install power line filter
kit
(PN 6A00171G01) or high quality line filter for input power.
Recommended Corrective Action
Check power supply for line noise or voltage fluctuations. Install power line filter
kit
(PN 6A00171G01) or high quality line filter for input power.
Fault Isolation
Table
Figure
cell with cell replacement kit. If cell
2
Figure 8-5 and
April 2017
8-1.
Table 8-2.
Figure
6-4, sheet
Figure 9-
16
9