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Installation Guide
9.
Troubleshooting
SYMPTOM
Control displays an alert code on
the screen.
Display will not come on
Indoor temperature display is
incorrect.
Indoor humidity display is
incorrect.
Room temperature overshoots
when the Heat/Cool setting is
changed more than 2°.
Heating will not come on.
Cooling will not come on.
Heating or Cooling is displayed,
but no warm or cool air is coming
from the registers.
Fan runs all the time
"+" symbol appears on Home
Screen beneath Indoor
Temperature readout
Fan is set to ON but not running.
Cooling or Heating cycles too
fast or too slow (narrow or wide
temperature swings).
Heat pump is not turning on; only
furnace or electric heat strips are
running.
Cannot change system mode to
desired setting.
Screen does not respond
properly to a button press
22
POSSIBLE CAuSES
A critical or major alert is present.
Loss of 24VAC between R & B at the Control.
1) Control requires one hour to acclimate to
environment.
2) Indoor temperature display needs calibration.
3) Heat from touch screen is being trapped
within the thermostat body. See section 3.1 for
mounting location guidelines.
Indoor humidity display needs calibration.
1) Oversized heating/cooling equipment under
current conditions. Control cannot respond fast
enough to prevent overshooting.
2) Improper location of Control.
1) System mode is not set to Heat/Auto or
setpoint is set too low.
2) Minimum off time delay is being enforced.
3) Heating system may require service.
1) System mode is not set to Cool/Auto or the
setpoint is too high.
2) Minimum off time delay is being enforced.
3) Cooling system may require service.
1) There is a fan delay as the heating or cooling
equipment turns on.
2) Equipment is not working properly.
1) Fan mode is set to On, Circulate or Clean
mode
2) There is a failure in the indoor unit
Both compressor heat and indoor heat are being
called simultaneously
1) Humidity Control is engaged.
2) Blower motor is not functioning.
1) Check the location of the Control for drafts.
2) Cycles per hour or aggressive recovery is
improperly set.
1) Outdoor temperature is below compressor
lockout temperature setting.
2) Compressor heating lockout is enabled and
outdoor temp sensor is out of calibration or
failed.
3) The outdoor unit is not reporting (Err.126.00)
Equipment is not configured properly.
1) Screen is out of calibration.
2) Internal Control fault
ACTION
Navigate to the Diagnostic screen on the 850 Control
for a Problem Description and Possible Cause.
1) Check wiring between R & B to see if R & D, or B &
D have been reversed.
2) Check transformer for 24VAC output.
3) Check for broken or shorted thermostat wire.
1) Allow one hour before proceeding with
troubleshooting process.
2) Calibrate temperature sensor from Control menu.
3) Move thermostat away from competing air stream or
use a remote temperature sensor
Calibrate humidity sensor from the Control menu.
1) Compare heat load calculation to equipment chosen.
2) Relocate Control (or use remote sensor) if Control is
in "dead" spot (poor or no air circulation).
1) Set mode to heat and raise the setpoint above the
room temperature.
2) Wait for 5 minutes and recheck heating equipment.
3) Check/repair system.
1) Set mode to cool and lower the setpoint below the
room temperature.
2) Wait for 5 minutes and recheck cooling equipment.
3) Check/repair system.
1) Wait a minute for blower delays and recheck
registers.
2) Check/repair system.
1) Check Control settings to see if fan is set to On,
Circulate or Clean mode.
2) Check indoor unit for failures (such as tripped
heating limit).
No action required, symbol is for informational purposes
only
1) If indoor humidity is higher than desired setpoint,
the blower will cycle off with the equipment. A humidity
icon will be displayed on the Fan Mode button when
the blower operation is being inhibited due too high
humidity.
2) Check/repair system.
1) Seal air leaks behind Control. Relocate Control or
apply remote indoor temperature sensor.
2) Adjust cycle rates and aggressive recovery features
in the advanced installer set up.
1) Adjust the compressor lockout temperature setting
if desired.
2) Check/repair outdoor sensor or wiring.
3) Check communication status of outdoor unit.
Check the standard installer set up screen to ensure
equipment is properly configured.
1) Remove Control from sub base and reset. Follow the
calibration instructions when the Control reboots.
2) Remove Control from sub base and reset.
18-HD73D1-9E-EN
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