UHD LOW PROFILE DUCT FURNACE INSTALLATION OPERATION AND SERVICE MANUAL
Figure 17: Manual Reset Limit Switch
Reset Button
To reset manual reset limit switch, press reset
button. NOTE: To reset, the switch must be cool.
Description | Part Number |
Manual Reset Limit Switch | 90412106 |
12.3Lighting Instructions 12.3.1 To Turn On Heater
1. Ensure that the electrical and gas supplies to the heater are on. Check that the on site controls are "ON".
IMPORTANT: The thermostat setting must be above the ambient temperature for the heater to operate.
2.The automatic firing sequence will begin as described on Page 27, Figure 15. The heater will now operate automatically under the control of the on site controls.
12.3.2 To Turn Heater Off
Set the thermostat to the "OFF" position. The burner will turn off immediately.
To restart, turn the thermostat above room temperature.
12.4 Simple Troubleshooting
Some possible reasons for the heater not operating are:
1.Gas supply not "ON".
2.Electricity supply not "ON".
3.The time and/or temperature controls are not "ON".
4.A limit switch may have operated. This may be caused by an interruption of the electrical supply, failure of the distribution fan or vent or heat exchanger blockage.
If a temperature limit switch persistently trips, there is a fault which must be investigated by a contractor qualified in the installation and service of
12.4.1 Simple Troubleshooting (Burner Faults)
If the burner fails to ignite for any reason, it will retry for ignition (four trials total). After four unsuccessful ignition trials, the control will put the heater into lockout for one hour.
Lockout should not occur during normal operation of the heater and indicates there is a fault condition which must be corrected. There is an LED light on the ignition control that flashes codes to assist in fault correction. See Page 30, Figure 18 for LED indication codes.
Figure 18: LED Diagnostic Codes
LED INDICATION | FAULT MODE |
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Slow Flash | Normal Operation - No call for heat. |
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Fast Flash | Normal Operation - Call for heat. |
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2 Flashes | Ignition Lockout - No flame detected. |
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3 Flashes | Airflow Fault - Pressure switch open or closed. |
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4 Flashes | Temperature Limit or |
| Manual Reset Limit Switch Open |
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5 Flashes | Flame Sense Error - Gas valve not energized. |
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Steady On | Internal Control Failure |
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