Service Manual

Page 61
8. Trouble Shooting
Display
Description
Solution
A0
Either cold or hot water temperature
sensor fault
Check temperature sensors and associated connections.
A1
Temperature inside the cabinet is above
158 °F.
The appliance automatically regulates the performance of
the appliance to avoid overheating.
▶ External air temperature is above 140 °F.
▶ Check for flue leakage inside the appliance or in
concentric vent.
AA
Flue gas temperatures above 356 °F after
the primary heat exchange and/or 176 °F
at the exhaust sensor.
The appliance is protected against overheating.
▶ Descale appliance. 1)
▶ Check if inlet water temperature is above maximum
limit.
A2
External Tank temperature sensor is not
installed properly. Temperature sensor
fault.
Check temperature sensor and associated connections.1) 2)
▶ Check SA-A1 menu in HMI and select OFF if tank
loading application is not in use
A3
Flue gas temperature sensor fault.
Check connections or replace sensor.
A4
Cabinet air temperature sensor fault.
Check connections or replace sensor.
A5
Primary or Secondary heat exchanger gas
temperature sensor fault.
Check connections or replace sensor.
A6
Inlet water temperature sensor fault.
Check connections or replace sensor.
A7
Heat exchanger temperature sensor fault.
Check connections or replace sensor.
A8
Outlet water temperature sensor fault.
Check connections or replace sensor.
A9
Incorrect output power. Hot water
temperature sensor is not installed
properly. Incoming gas pressure too low
(below 3.5" W.C. for NG or 8" W.C. for
LP).
▶ Check incoming gas pressure.1)
▶ Check hot water temperature sensor.
▶ Check manifold solenoids are operating
C5 Fault in the bypass valve.
▶ Check bypass valve connections.
▶ Perform calibration in submenu bP in PA
C7 Fan not working
▶ Check fan connections.
▶ Close and open a hot water tap.
C8
Main Water valve disconnected
Check water valve connections
C9
Barometric pressure sensor fault
Replace electronic control unit
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