Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual page 238

SYMPTOM
There is no power.
There is no control signal.
Control polarity has been reversed.
Steam valve will not open
Actuator is not working.
There is high steam pressure.
Valve has been installed incorrectly.
There is no control signal.
Control polarity has been reversed.
Actuator is not working.
Steam valve will not
close
There is high steam pressure.
Valve has been installed incorrectly.
Control signal is not at full range.
Control polarity has been reversed.
Steam valve is leaking
Actuator is not working.
There is high steam pressure.
Control signal is not at full range.
There is no control signal.
The controller is out of calibration.
Humidity sensor is not installed properly.
Humidity exceeds set
point
Actuator is not working.
There is high steam pressure.
Boiler is not operating correctly.
Control signal is not at full range.
Control polarity has been reversed.
Controller is out of calibration.
Humidity sensor is not installed properly.
Actuator is not working.
Humidity remains below
set point
There is high steam pressure.
Boiler is not operating correctly.
There is an airflow switch fault.
The high limit controller is not in
the correct location.
The humidifier is too small.
AHU — Air-Handling Unit
Table 50 — Humidifier Troubleshooting (cont)
POSSIBLE CAUSES
238
POSSIBLE REMEDIES
Verify and, if necessary, correct power or air pressure to the valve
actuator.
Verify and, if necessary, correct control signal or pressure range to the
valve actuator.
Verify and, if necessary, correct control signal polarity to the valve
actuator.
Remove actuator to verify that it is operational. Clean or replace
jammed valve.
Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Verify proper valve orientation. Electric valves must face upward.
Verify and, if necessary, correct control signal to the valve actuator.
Verify and, if necessary, correct control signal polarity to the valve
actuator.
Remove actuator to verify that it is operational. Clean or replace
jammed valve.
Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Verify proper valve orientation. Electric valves must face upward.
Verify and, if necessary, correct full-range control signal to the valve
actuator.
Verify and, if necessary, correct control signal polarity to the valve
actuator.
Remove actuator and test to verify that it is operational. If not, clean or
replace jammed valve.
Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Verify and, if necessary, correct compatibility of the full range control
signal to the valve actuator.
Verify and, if necessary, correct control signal polarity to the valve
actuator.
Check and, if necessary, correct calibration of controller.
Ensure that humidity sensors are installed correctly and not located in
drafts (wall). If necessary, correct sensor installation.
Remove actuator and test to verify that it is operational. If not, clean or
replace jammed valve.
Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Verify stable boiler pressure. Wide swings in pressure could affect the
humidity controls.
Verify and, if necessary, correct compatibility of the full range control
signal to the valve actuator.
Verify and, if necessary, correct control signal polarity to the valve
actuator.
Check and, if necessary, correct calibration of controller.
Ensure that humidity sensors are installed correctly and not located in
drafts (wall). If necessary, correct sensor installation.
Remove actuator and test to verify that it is operational. If not, clean or
replace jammed valve.
Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Verify stable boiler pressure. Wide swings in pressure could affect the
humidity controls.
Ensure that airflow switch is not fluttering. If necessary, correct
fluttering airflow switch.
Verify that high-limit controller is not located too close to steam
discharge manifolds. If necessary, correct location of controller.
Humidifier is undersized. Check humidity load calculations.