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Symptom Cause
Miswiring – Check wire colors to verify A at ADHC is connected to ZA at
thermostat and B is connected to ZB.
No RH display, no outdoor ADHC power source – When wired to the Model 8570 thermostat, the ADHC
temperature display must be wired to a continuously ON power source. Use voltmeter to verify
presence of 24VAC (nominal) at ADHC.
ADHC not operating correctly – check red diagnostic light on ADHC.
No RH display, outdoor temperature OK No valid reading available – run fan for at least 40 seconds.
RH display, outdoor temperature @ 20°F ADHC set for manual mode of operation. Wire an outdoor sensor to the
ADHC or wire an outdoor sensor to the thermostat.
No display, weak text in display, Readjust contrast of display to an optimum level. See “Adjust Contrast”
or too dark of a display Section 7.8 in the Owner’s Manual.
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TROUBLESHOOTING – ADHC CONNECTION6. CHECK FAN OPERATION
1. Turn on the fan (set to ON).
• The thermostat G terminal will energize and the
system blower will start. The Fan Status on the display
will show “FAN ON.”
2. If an ADHC has been installed, allow the fan to
operate for no less than 40 seconds. If an ADHC is
not part of this installation, you can turn the fan off at
any time. A humidity value can be displayed only after at
least 40 seconds of blower run-time to ensure the
humidity reading is representative of the room air.
3. Turn the fan off (set to AUTO).
7. VERIFY ADHC CONNECTION (if optional Automatic Digital
Humidifier Control installed).
1. Ensure that the ADHC has power (the green status light
on the ADHC should be on) and make sure the ADHC is
functioning properly – see ADHC installation procedure
for start up and diagnostics.
2. From the Main Screen, press the “INFO” button.
• The outdoor temperature and relative humidity will be
displayed for five seconds after which the contact
screen will be displayed.
3. Press the BACK button to return to the Main Screen.
• When the humidifier is operating, the message
“HUMIDIFIER ON” appears at the message center,
alternating with the time and date and any other
currently active messages.