Rosemount OCX 8800, Instruction Manual

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Instruction Manual
IM-106-880, Rev 2.1
April 2017
OCX 8800
8-3
FAULT ISOLATION
Faults in the 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, Troubleshooting.
If a fault is indicated on the Field Communicator or LOI, locate the fault
indication in Table 8-1. 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 8-3 and Figure 9-9.
Correct wiring faults.
COe sensor grounded Check resistance of COe sensor leads to ground per Figure 9-9. Replace COe sensor if
resistance is less than 10M Ohms.
COe sensor failed Check resistance of both COe sensor elements per Figure 9-9. 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 Figure 9-9. Replace CJC sensor if
resistance is less than 10M Ohms.
CJC sensor failed Check resistance of CJC sensor per Figure 9-9. 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
O
2
cell degraded or failed
Check O
2
cell impedance by reading the O2 Snsr R value via the LOI (see Figure 4-4,
sheet 2), or the O2 Snsr value via Field communicator (see Figure 6-3, 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, > 750ºC)
Probable Cause Recommended Corrective Action
COe Temp Hi (Combustion sensor heater temperature high, 310ºC)
Probable Cause Recommended Corrective Action