A.O. Smith SGS - 100 Installation & Service Manual page 85

Code + Description Cause
F04 (lock out error) No gas
Three unsuccessful
ignition attempts.
Air in the gas pipes
No burner pressure
Defect in the hot
surface igniter circuit
Defect in the ionisation
circuit
Supply voltage too low Check the supply voltage, this must be 230 VAC (-15%, +10%).
F05 (lock out error) Incorrect roof or wall
conduit.
Too many flame errors Recirculating flue
have been signalled. gases.
Instruction manual SGS
Solution
1. Open the main gas valve and/or the manual gas valve supplying
the water heater
2. Check the supply pressure to the gas control
3. If necessary, repair the gas supply
Bleed the air out of the gas pipe
1. Check the burner pressure to the gas control
2. Check that the gas valve(s) open and shut correctly
3. If necessary, replace the gas control.
1. Check that the hot surface igniter is correctly connected (JP2).
2. Check the wiring of the hot surface igniter.
3. Measure the resistance across the hot surface igniter. This must
lie between 2 and 5 ohms.
4. Check that the hot surface igniter lights up during ignition.
5. If necessary, replace the hot surface igniter.
1. Check that the flame probe is correctly connected (JP2)
2. Check the wiring of the flame probe
3. Measure the ionisation current. This must be at least 1.5
microamps.
4. Replace the wiring if necessary.
1. Check that the correct roof or wall flue conduit
and flue") has been fitted.
2. If necessary, install the correct roof or wall conduit.
3. Check that the roof or wall conduit discharges into a permitted
area.
Remark
To repair the gas supply, contact your installation engineer
See Checking the supply pressure and burner pressure
bleed air from the gas line, and measure the supply pressure and
burner pressure.
To replace the necessary parts, you must contact your installation
engineer
If the error persists, contact your installation engineer.
To replace the necessary parts, you must contact your installation
engineer
(3.10 "Air supply If the error cannot be resolved or is persistent, contact your
installation engineer
is
for how to
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