20.Ignition System (cont’d)

Fault Modes (cont’d)

Lockout

21.Gas Valve

22.Fan Motor

If the gas valve was sensed as closed when it should be open, and has not de- energized after the venter motor was shutoff for 15 seconds, then the venter motor is re-energized to vent the unburned gas.

Soft Lockout - The control shall not initiate a call for heat or call for continuous fan while in lockout. The control will still respond to an open limit and undesired flame. Lockout shall automatically reset after one hour. Lockout may be manually reset by removing power from the control for more than one second or removing the thermostat call for heat for more than one and less than 20 seconds.

Hard Lockout - If the control detects a fault on the control board, the status LED will be de-energized, and the control will lockout as long as the fault remains. A hard lockout will automatically reset if the hardware fault clears.

Power Interruption - During a momentary power interruption or at voltage levels below the minimum operating voltage (line voltage or low voltage) the system will self-recover without lockout when voltage returns to the operating range.

Power interruptions of less than 80mS shall not cause the control to change operat- ing states. Power interruptions greater than 80mS may cause the control to inter- rupt the current operating cycle and re-start.

The main operating gas valve is powered by the 24-volt control circuit through the thermostat and safety controls. The main control valve is of the diaphragm type providing regulated gas flow preset at the factory. (For location, see FIGURE 18, page 31.)

WARNING: The operating valve is the prime safety shutoff. All gas supply lines must be free of dirt or scale before connecting the unit to ensure positive closure. See Hazard Levels, page 2.

The fan motor is equipped with thermal overload protection of the automatic reset type. Should the motor refuse to run, it may be because of improper current char- acteristics. Make certain that the correct voltage is available at the motor.

NOTE: If the unit is equipped with an optional totally enclosed motor or optional voltage, the horsepower may be larger than the standard motor. Refer to the motor nameplate to verify horsepower.

Form RZ-NA I-UDA, P/N 195673 Rev 5, Page 22

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Thomas & Betts UDAS, UDAP dimensions Gas Valve Fan Motor, Fault Modes cont’d Lockout
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UDAP, UDAS specifications

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