Service Manual

7. Steady State Operation.

Duringsteady state operation the gascontrol monitors:

Thermostat Temperature Sensor- When the setpoint temperature issatisfied, the gascontrol is shutdown

and the blower will postpurge for 15 seconds. The gascontrol LED flashes a short flash onceevery 4

seconds (idle) status code.

Pressure Switch / Blower Temperature Switch- If either switch opens the pilot valve and main valve are

shutdown. The blower continues to run for 30 seconds attempting to closethe circuit. The control LED

flashes 3 times followed bya3second pause.

Flame Sense- Ifflameis lost, the pilot & main valve are shutdown and the blower runsfor 15

seconds. The

gascontrol attempts to re-lightthe pilot 4 times.Ifunsuccessful, the blower is shutdown and the gascontrol

proceeds toa5minute lockout. The gascontrol re-attempts to lightthe pilot starting at normal heating

sequence#2.

8. Thermostat Satisfies.

9. Burner Off.

10. Blower Post-purge (15 seconds).

Sequence ofOperation

Abnormal Operation

1. Flammable Vapor Sensor Fault:

a) If the Flammable Vapor Sensor Resistance is Greater than 70,000 Ohms - the gascontrol immediately turns

off all outputs. The gascontrol waits and monitors resistance for 30 seconds.If theresistanceisgreater than

70,000 ohms after 30 seconds, the gascontrol proceeds

to verifyresistive delay for 2minutes and flashes 7 times

followed by a3second pause. This process is repeated 5 timesuntil the gascontrol either returns to normal

operation or proceeds toalockout mode flashing 7 times followed bya3second pause.

b) If the Flammable Vapor Sensor Resistance is Be

low 3000 ohms - The gascontrol immediately turns off all

outputs and proceeds to flash 8 times then 1 time followed bya3second pause. The error selfclears if the

resistance returns to the normal range for at least 15 seconds.

Normal Heating Sequence (continued)

2. Temperature Sensor Fault:

a) Temperature Sensor Detected Open Circuit - The gascontrol Immediately turns off all outputs and proceeds to

flash 8 times then3timesfollowed bya3second pause. The error selfclears if the fault clearsfor at least 15

seconds.

b) Temperature Sensors not Reading the Same Temperature Within ±5.5 °F - The ga

scontrol immediately turns

off all outputs and proceeds to flash 8 times then 3 times followed bya3second pause. The error selfclears if the

fault clearsfor at least 15 seconds.

c) Water Temperature in Excess ofECO(Energy Cut Out)limit - The gascontrol immediately turns off the pilot

and main

valve and proceeds to flash 4 times followed bya3second pause. Blower continues to run until the gas

control is reset. The set point knobshould beturned to the minimum temperature settingfor at least6seconds

and then turned clockwise by45

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UPDX Series