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HE420A STEAM POWER HUMIDIFIER
769-1108—2
APPENDIX A
Table 3. Compensating Humidistat Troubleshooting Guide.
PROBLEM SOLUTION NOTES
Humidifier does not
operate in “Test”
mode.
• Confirm the outdoor temperature sensor is
connected to the correct terminals on the
humidistat. (For manual operation, ensure the
jumper pins are positioned correctly.)
• Check wiring diagram (Figure 1) for correct
installation.
• Check the voltage at the humidistat “24 VAC”
terminals. (Should be 22-30 VAC.)
• Ensure the control knob has not been left in the
“Test” position.
Humidifier only
operates in “Test”
mode.
• Check the resistance of the sensor by removing
the leads from the humidistat terminals and
measuring the resistance across the wires with
an ohmmeter. Compare the reading to the
temperature/resistance chart (right).
• For automatic applications, make sure the
outdoor temperature sensor is mounted
completely outside the house (i.e. not recessed
into the hole) on the North, Northeast or
Northwest side, away from direct sunlight. And is
mounted at least 3 feet away from all exhaust
vents.
• If the outdoor temperature sensor is mounted in
the fresh air intake duct, make sure the probe is
no further than 30 inches from an outside wall.
Temp/Resistance Chart
100°F 6000 ohms 38°C
90°F 7500 ohms 32°C
80°F 9500 ohms 27°C
70°F 11,500 ohms 21°C
60°F 14,000 ohms 16°C
50°F 18,000 ohms 10°C
40°F 23,000 ohms 4°C
30°F 28,500 ohms -1°C
20°F 37,000 ohms -7°C
10°F 46,500 ohms -12°C
0°F 61,500 ohms -18°C
-10°F 78,500 ohms -23°C
-20°F 105,500 ohms -29°C
-30°F 135,000 ohms -34°C
Notes:
In automatic applications, if the outdoor
temperature is greater than +50°F (+10°C)
or less than -32°F (-35.6°C), the
compensating humidistat will not operate
(except in “Test” mode).
In both automatic and manual applications,
if the relative humidity in the home is
higher than the knob setting, the
humidistat will not operate. Similarly, the
humidistat will not operate if the indoor RH
exceeds 45%.
Humidifier operates
constantly.
• Check the humidistat setting. If the RH in the
home is less than the knob setting, the humidifier
will operate until the humidity level is higher than
the knob setting.
• In “Test” mode, verify that the humidifier will shut
off after approximately one minute.
• Check the resistance of the sensor.
• See previous Problem/Solution, regarding
outdoor temperature sensor mounting locations.
• Turn the humidistat “OFF” and observe whether
the humidifier turns off. If operation continues,
check Figure 1 wiring diagram. Remove the
wires from the humidistat's “OUT” terminals. If
humidifier continues to operate, check the
humidifier.
Humidifier or
compensating
humidistat “chatters”
or clicks on and off
rapidly.
• Use a voltmeter to check for steady 22-30 VAC.
• Make sure the outdoor temperature sensor
wiring does not run alongside the wires carrying
high voltage (120 VAC or higher).
Furnace or heat
pump blower system
runs continuously;
condensation is
building up in
ductwork.
• It may be necessary to make a setting change on
the furnace or heat pump board to prevent the
blower from shifting down to lowest idling speed.
• Consult the furnace/heat pump operating manual
or contact the manufacturer for procedures to
prevent low air flow.