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Bradford White M-2-TW-75T6SX User Manual

Page 41

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41

Troubleshooting continued-

Six flashes-four
flashes, three second
pause

Undesired-false pilot
flame sensed.
System auto resets.

Seven flashes, three
second pause

Simulated Resistive
Device Harness out of
specification or
disconnected.

Eight flashes-one flash,
three second pause

Simulated Resistive
Device Harness out of
specification possible
short.

Eight flashes-two
flashes, three second
pause

T'stat well & sensor
damaged or unplugged

Eight flashes-three
flashes, three second
pause

Gas valve electronics
fault detected

LED Status

Control Status

Probable Cause

1. Pilot valve stuck in open position.

Simulated resistive load out of specification

Simulated resistive load out of specification

1. Damage to thermowell wire.
2. Thermowell sensor resistance out of range.

1. Verify control is not wet or physically damaged
2. Reset control on/off switch.
3. Replace electronic module if 8-3 error persists

Eight flashes-four
flashes, three second
pause

Gas valve fault
detected.

1. Verify control is not wet or physically damaged
2. Reset control on/off switch.
3. Replace gas control if 8-3 error persists

Six flashes-three
flashes, three second
pause (Soft lockout)

Pilot flame
extinguished.
System resets after 5
minutes.

1. Unstable pilot.
2. Pilot tube blocked or restricted.
3. Oxidation build up on pilot electrode.
4. Wire damage to pilot assembly or bad
connection at gas valve.
5. Insufficient combustion air.

Control Sequence of Operation

Start up Sequence
Upon powering up, the control checks for the presence of the resistive plug, if the
resistance is in the expected range the control will begin normal operation after 5 to 8
seconds.

Normal Heating Sequence
1. The thermostat senses a need for heat.
2. The control checks the pressure switch condition.
3. If the pressure switch is open, the control sends power to the blower motor.
4. The blower starts moving combustion air through the combustion system.
5. The pressure switch closes.
6. The control senses the closed pressure switch and starts the ignition process by

providing a spark at the pilot electrode and allowing gas to flow to the pilot.

7. When the pilot is lit the gas control senses the pilot flame and opens the main gas

valve.

8. The main burner is lit.
9. The main burner and blower continue to operate until the thermostat is satisfied.
10. When the thermostat is satisfied the main and pilot gas valves close.
11. The blower operates for a short post purge period before shutting down.

12.

The water heater remains in the stand-by mode until the next call for heat.

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