Emerson Rosemount OCX8800 - Fault Isolation

Instruction Manual
IM-106-880C, OI
Fault Isolation
April 2017
Fault
Isolation
16
9
O
2
cell degraded or failed
Check O
2
cell impedance by reading the O2 Snsr R value via the LOI (see Figure
4-5, sheet 2), or the O2 Snsr value via Field communicator (see Figure 6-4, sheet
1). If cell impedance is zero, replace O
2
cell with cell replacement kit. If cell
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
2
cell with cell replacement kit.
Ref Current Err (RTD excitation current error) (reference current should be 5.02 mA)
Probable Cause Recommended Corrective Action
O2 Sensor R High (Oxygen sensor resistance high, > 5000 Ohms)
O2 Sensor Open (Oxygen sensor disconnected)
Probable Cause Recommended Corrective Action
O2 Temp Hi (Oxygen sensor heater temperature high, > 750 ºC)
Probable Cause Recommended Corrective Action
COe Temp Hi (Combustion sensor heater temperature high, 310 ºC)
Probable Cause Recommended Corrective Action
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 Table 8-1.
If a fault is indicated on the Field Communicator or LOI, locate the fault indication in Table 8-2.
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
Loose or open O
2
cell circuit connection Check O
2
cell circuit wires for breaks or loose connections. Repair lead wire break
or loose connections.
Loose or open lead or circuit wire
connection for COe sensor or CJC sensor
current loop
Check all COe and CJC sensor current loop wiring per Figure 8-5 and Figure 9-
10. Correct wiring faults.
COe sensor grounded Check resistance of COe sensor leads to ground per . Replace COe sensor if
resistance is less than 10M Ohms.
COe sensor failed Check resistance of both COe sensor elements per . Replace COe sensor if
resistance of sensor element is not between 100 and 250 Ohms.
CJC sensor grounded Check resistance of CJC sensor to ground per . Replace CJC sensor if resistance is
less than 10M Ohms.
CJC sensor failed Check resistance of CJC sensor per . Replace CJC sensor if resistance of sensor is
not between 100 and 150 Ohms.
High noise in OCX power supply Check power supply for line noise or voltage fluctuations. Install power line filter
kit
(PN 6A00171G01) or high quality line filter for input power.
High noise in OCX power supply Check power supply for line noise or voltage fluctuations. Install power line filter
kit
(PN 6A00171G01) or high quality line filter for input power.
Table continued on next page