Emerson Rosemount OCX 8800 Reference Manual page 211

Table 8-1: Troubleshooting
COe Htr Failure (Combustibles sensor heater could not reach final temperature)
Probable cause
COe heater circuit wiring open
COe heater open
Heater electronics failure
SB Htr Failure (Sample block heater could not reach final temperature)
Probable cause
Sample block heater circuit wiring open
Sample block heater open
Heater electronics failure
Sensor housing exposed to high wind and/or extreme cold
temperatures
Cal Warning (Calibration warning)
Cal Failed (Calibration failed)
Probable cause
Calibration gas supply low or gas connection leaking
O cell degraded or failed
2
O slope error (slope < 34.5 mV/Dec or > 57.5 mV/Dec)
2
Reference Manual
(continued)
Recommended corrective action
Check COe cell heater circuit for broken wire or loose con-
nection per Figure 8-1. Repair broken wire or loose connec-
tion.
Check resistance of COe heater per
heater resistance is 97.7 Ohms. Replace COe heater if
heater is open or has a large resistance.
Check heater fuse F3 in electronics housing per
If open, locate and correct cause of overload. If F3 is not
open, or if cause of overload cannot be found, replace elec-
tronics package.
Recommended corrective action
Check sample block cell heater circuit for broken wire or
loose connection per Figure
loose connection.
Check resistance of sample block heater per
Normal sample block heater resistance is 36.4 Ohms each
(18.2 Ohms with both heaters in parallel). Replace COe
heater if heater is open or has a large resistance.
Check heater fuse F4 in electronics housing per
If open, locate and correct cause of overload. If F4 is not
open, or if cause of overload cannot be found, replace elec-
tronics package.
If above probable causes are not causing the SB heater fail-
ure, install flange insulator (PN 6P00162H01)
Recommended corrective action
Check calibration gas supplies and connections. Adjust gas
pressure and flow. Replenish low calibration gas supplies
and tighten or repair loose or leaking connections. When
calibration gas supplies are adequate, recalibrate.
Check O cell impedance by reading the O
2
ue via the LOI (see Figure 4-4, sheet 2) or the O
ue via Foundation Fieldbus menu tree
2)HART menu tree (see Figure
dance is zero, replace O cell. If cell impedance is less than
2
5000 Ohms and no ground fault is indicated, replace O
cell.
Troubleshooting
Figure 9-7. Normal COe
Figure 8-1.
8-3. Repair broken wire or
Figure 8-1.
Figure 8-1.
Cell Imped val-
2
Snsr R val-
2
(Figure 6-3, sheet
6-3, sheet 2).. If cell impe-
2
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