Honeywell PDX65S65F(B,S,C)*(N,X) PDX Series, Sequence of Operation, Steady state operation

PDX Series

Sequence of Operation

Steady state operation.

7During Steady State Operation the Control Monitors:

Thermostat temperature sensor- When set point temperature is satisfied, gas valve is shut down and

blower will post purge for 15 seconds. Control LED flashes a short flash once every 4 seconds (idle) status code.

Pressure switch / Blower temperature switch- If either switch opens, pilot valve and main valve is shut

down. The blower continues to run for 30 seconds attempting to close the circuit. The control LED Flashes 3 times with 3 second pause.

Flame Sense- If flame is lost, pilot & main valve are shut down, blower runs for 15 seconds. Control attempts to re-light pilot 4 times. If unsuccessful, Blower is shut down and control proceeds to 5 minute lockout. Control re-attempts to light pilot starting at normal heating sequence #2.

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Thermostat satisfies.

Burner off.

Blower post purge (15 seconds).

1. Simulated Resistive Device Fault:

a)If the Flammable Vapor Sensor resistance is greater than 70,000 Ohms - the gas control immediately turns

off all outputs. Control waits and monitors resistance for 30 seconds. If the resistance is greater than 70,000 ohms after 30 seconds, the gas control proceeds to verify resistive delay for 2 minutes and flashes 7 times with a three

second pause. This process is repeated 5 times until the control either returns to normal operation or proceeds to a lockout mode flashing 7 times with a 3 second pause.

b) If the Flammable Vapor Sensor resistance is below 3000 ohms - The gas control immediately turns off all outputs and proceeds to flash 8 times then once with three second pause. The error self clears if the resistance

returns to normal range for at least 15 seconds.

2. Temperature Sensor Fault:

a)Temperature sensor detected open circuit - The gas control Immediately turns off all outputs and proceeds to flash 8 times then three times with three second pause. The error self clears if the fault clears for at least 15 seconds.

b) Temperature sensors not reading the same temperature within ±5.5 °F - The gas control Immediately turns off all outputs and proceeds to flash 8 times then three times with three second pause. The error self clears if the fault

clears for at least 15 seconds.

c) Water temperature in excess of TCO (Temperature Cut Off) limit - The gas control immediately turns off pilot & main valve and proceeds to flash 4 times with 3 second pause. Blower continues to run until gas control is reset.

Power needs to be cycled to remove gas control from TCO lockout.

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