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3
Troubleshooting
Table 3A Troubleshooting Chart - No Display
FAULT
- No power supplied to the unit.
- No LED's illuminated on the CON•X•US
Interface control board.
No Display
- Bad display, no LED's illuminated.
- Bad display.
- Main control board temperature set point
satisfied.
- Remote thermostat satisfied.
- Outside air temperature above Warm
No Burner
Weather Shutdown (WWSD) set point for
Operation
main control board.
- Unit locked out on fault.
- Ramp delay active.
Unit Does Not
Modulate
Up to 100%
- Boiler controlled by BMS.
42
CAUSE
CORRECTIVE ACTION
• Check external line switch, fuse, or breaker.
• Check position of ON/OFF switch. Turn switch to the
ON position.
• Check 120 vac through the ON/OFF switch.
• Check wiring harness connection between display
board
and
main
control
harness at both points.
• Check connection.
• Replace the display.
• Review temperature setting.
• Review remote thermostat setting.
• Check location of outside air sensor.
resistance of outdoor air sensor and compare to Table
3C of this manual.
• Consult display for specific fault.
descriptions in this manual for corrective actions.
• Check ramp delay parameter settings.
• Turn ramp delay feature off. See this manual for
instructions on how to turn this feature off.
• Check BMS parameter settings.
Service Manual
board.
Connect
Check
Refer to fault
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