Bradford White TW4-75S-76B-3N - Manual (Page 37)

37
Troubleshooting continued-
LED Status Control Status Probable Cause
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.
Six flashes‐four
flashes, three second
pause (Soft lockout)
Undesired‐false pilot
flame sensed.
System auto resets.
Pilot valve stuck in open position.
Seven flashes, three
second pause
Flammable vapor
sensor fault detected,
see warning label
1. Flammable vapor present
2. Flammable vapor sensor exposed to excessive
moisture
3. Flammable vapor sensor exposed to extreme
ambient temp
4. Simulated resistive device removed or out of range
(if applicable).
Eight flashes‐one flash,
three second pause
Flammable vapor
sensor out of
specification. Possible
short.
1. Flammable vapor sensor out of specification
2. Possible short
Eight flashes, two
flashes, three second
pause
Temperature sensor
fault
1. Damage to sensor or wire in control’s well.
2. Control’s sensor resistance out of range.
3. Replace Control.
Eight flashes‐three
flashes, three second
pause
Electronics fault
detected
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 8‐4 error persists
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.