Instruction Manual
D200156X012
4194HA, HB, HC Controllers
July 2018
39
Table 5‐1. Troubleshooting Chart
Fault
Possible Cause
Check
Correction
1. Process wanders or
cycles about set point.
1.1 Proportional band and
reset settings.
1.1 Refer to the Start‐up section for
controller settings.
1.1 If stable control cannot be attained, and all
other elements of the loop are functionally
correct, examine other possible causes related to
the controller.
1.2 Supply pressure
varying.
1.2 Monitor the supply pressure with an
external gauge. Ensure that it is set correctly
and does not fluctuate. Note the number of
instruments being supplied by the regulator.
1.2 Correct as necessary. One regulator per
instrument is recommended.
1.3 Process pointer
rubbing on cover or scale.
1.3 Note if the pointer is bent.
1.3 Bend pointer to provide clearance.
1.4 Failure of differential
pressure unit.
1.4 Inspect the differential pressure unit.
Using a soap solution, check for leaks. Refer
to the differential pressure unit instruction
manual.
1.4 Replace the differential unit as necessary.
1.5 Linkage failure.
1.5 Check for links bent or not connected
properly, or pivots broken.
1.5 Replace or repair as necessary.
1.6 Relay malfunction.
1.6 By changing the process differential
pressure in the sensor and observing the
output, verify that the output will move at
about the same speed in both directions.
1.6 If the output moves fast in one direction and
sluggishly in the other, replace the relay.
1.7 Differential relief valve
set too low.
1.7 The minimum relief valve setting is
dependent on the loop dynamics and the
controller settings. If, under normal load
changes, the relief valve opens, instability
can occur. Check by observing the controller
reaction to a set point or load change under
closed loop conditions.
1.7 If the differential relief valve appears to be set
too low, refer to the section of this instruction
manual that covers the anti‐reset windup option.
2. Controlling off set
point as reflected by
process and set point
indicators.
Note: Some offset is
inherent with
proportional‐only
controllers (4194HA
controllers). The
amount of offset is a
function of the
proportional band
setting.
2.1 Supply pressure not
set correctly.
2.2 Flapper not aligned.
2.3 Linkage not aligned
correctly.
2.4 Leak in differential
pressure unit or tubing.
2.5 Indicators out of
calibration.
2.6 Linkage not connected
correctly.
2.7 Leak in feedback
system.
2.8 Reset valve leaks.
2.9 Leak in remote set
point system.
2.1 Check with an external source.
2.2 Refer to the Flapper alignment
procedure.
2.3 Refer to the Maintenance Calibration
section.
2.4 Using soap solution, check for leaks.
Refer to the differential pressure unit
instruction manual.
2.5 Refer to the process (and remote set if
applicable) zero and span adjustment
procedure.
2.6 Inspect for loose screws, links or pivots.
2.7 Open the reset valve to .01 minute/
repeat. Adjust output pressure to 1.4 bar (20
psig). Using soap solution, check for leaks in
the proportional and reset bellows in the
tubing that connects these bellows.
2.8 Adjust output to 1.0 bar (15 psig) for a
0.2 to 1.0 bar (3 to 15 psig) output or 2.0 bar
(30 psig) for a 0.4 to 2.0 bar (6 to 30 psig)
output. Close the reset valve. If the controller
output varies as reset valve is closed and no
leaks were found in the rest of the feedback
system (Step 2.7), the reset valve is leaking.
2.9 Adjust remote set point pressure to 1.0
bar (15 psig). Using soap solution, check for
leaks in the remote set point and tubing
assembly.
2.1 Reset the supply pressure if necessary. If the
condition occurs again, the regulator should be
rebuilt or replaced.
2.2 Align the flapper as necessary.
2.3 Adjust as necessary.
2.4 Repair or replace parts as necessary.
2.5 Adjust as necessary.
2.6 Repair or replace parts as necessary.
2.7 Repair as necessary.
2.8 Replace the reset valve.
2.9 Repair or replace parts as necessary.
