259
Table 50 — Humidifier Troubleshooting (cont)
AHU — Air-Handling Unit
SYMPTOM POSSIBLE CAUSES POSSIBLE REMEDIES
Steam valve will not open
There is no power. Verify and, if necessary, correct power or air pressure to the valve
actuator.
There is no control signal. Verify and, if necessary, correct control signal or pressure range to the
valve actuator.
Control polarity has been reversed. Verify and, if necessary, correct c
ontrol signal polarity to the valve
actuator.
Actuator is not working. Remove actuator to verify that it is operational. Clean or replace
jammed valve.
There is high steam pressure. Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Valve has been installed incorrectly. Verify proper valve orientation. Electric valves must face upward.
Steam valve will not
close
There is no control signal. Verify and, if necessary, correct control signal to the valve actuator.
Control polarity has been reversed. Verify and, if necessary, correct control signal polarity to the valve
actuator.
Actuator is not working. Remove actuator to verify that it is operational. Clean or replace
jammed valve.
There is high steam pressure. Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Valve has been installed incorrectly. Verify proper valve orientation. Electric valves must face upward.
Steam valve is leaking
Control signal is not at full range. Verify and, if necessary, correct full-range control signal to the valve
actuator.
Control polarity has been reversed. Verify and, if necessary, correct control signal polarity to the valve
actuator.
Actuator is not working. Remove actuator and test to verify that it is operational. If not, clean or
replace jammed valve.
There is high steam pressure. Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Humidity exceeds set
point
Control signal is not at full range. Verify and, if necessary, correct compatibility of the full range control
signal to the valve actuator.
There is no control signal. Verify and, if necessary, correct control signal polarity to the valve
actuator.
The controller is out of calibration. Check and, if necessary, correct calibration of controller.
Humidity sensor is not installed properly. Ensure that humidity sensors are installed correctly and not located in
drafts (wall). If necessary, correct sensor installation.
Actuator is not working. Remove actuator and test to verify that it is operational. If not, clean or
replace jammed valve.
There is high steam pressure. Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Boiler is not operating correctly. Verify stable boiler pressure. Wide swings in pressure could affect the
humidity controls.
Humidity remains below
set point
Control signal is not at full range. Verify and, if necessary, correct compatibility of the full range control
signal to the valve actuator.
Control polarity has been reversed. Verify and, if necessary, correct control signal polarity to the valve
actuator.
Controller is out of calibration. Check and, if necessary, correct calibration of controller.
Humidity sensor is not installed properly. Ensure that humidity sensors are installed correctly and not located in
drafts (wall). If necessary, correct sensor installation.
Actuator is not working. Remove actuator and test to verify that it is operational. If not, clean or
replace jammed valve.
There is high steam pressure. Verify that the steam pressure has not changed. Excessively high
pressure could jam the valve.
Boiler is not operating correctly. Verify stable boiler pr
essure. Wide swings in pressure could affect the
humidity controls.
There is an airflow switch fault. Ensure that airflow switch is not fluttering. If necessary, correct
fluttering airflow switch.
The high limit controller is not in
the correct location.
Verify that high-limit controller is not located too close to steam
discharge manifolds. If necessary, correct location of controller.
The humidifier
is too small. Humidifier is undersized. Check humidity load calculations.
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