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Troubleshooting - Bosch Pro Tankless GWH-450-ES Series Manual

Temperature modulated with electronic ignition - normal duty suitable for recirculating potable water only
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Fault Indication
Orange LED + 100°F flashing
Orange LED + 110°F flashing
Orange LED + 125°F flashing
Orange LED + 140°F flashing
Orange LED + 100°F + 140°F flashing
Orange LED + 110°F + 140°F flashing
LED of the appliance doesn't start up,
no function.
Noise; boiling noise (over heating), no
correct function.
Low temperature (sanitary water).
Insufficient water flow.
Table 9
Error codes and diagnostics
The following table is a diagnostic indicator and it does not solve all the technical problems that may occur with the
appliance. It is very important to retain a good working knowledge of the appliance , its electrical and hydraulic layout
and functional operation.
Possible Cause
Shut down by the temperature limiter
(over temperature).
No Flame detected (no ignition).
"false flame" (error during self check of
Shut down because of low voltage.
Shut down by pressure switch.
NTC defect (no function)
No mains voltage supply, fuse blown,
transformer etc. defect
Low circulation, air inside installation,
bad heat transfer.
To low burner power, burner ON / OFF.
• Low water pressure
• Filter, taps or heat exchanger with
• Check position of heating NTC
• Check temperature limiter, cables
• Check system with air, air vent
• Check gas inlet pressure, gas type,
air inside gas pipe
• Check flame, ignition
• Check burner pressure, injectors
• Check ionisation sensor, cable
• Check electronic unit.
• Check humidity at Electronic
• Check
• Check flame inside Burner chamber
• Check electronic unit.
• Check power supply
• Check electronic unit.
• Check chimney, fresh air tube and
combustion gas tube
• Check ventilator, Venturi / silicone
• Check
• Check cables, electronic.
• Check NTC
• Check cable (opened, short)
• Check electronic unit.
• Check mains voltage supply
• Check fuse
• Check electronic unit.
• Check air in system, air vent
• Check circulation
• Check heat exchanger
• Check gas type, injectors, gas valve.
• Check air vent
• Check Adjustment of gas, gas valve
• Check NTC
• Check electronic unit.
• Check inlet pressure
• Check filter, taps, heat exchanger
and clean
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