Bosch GWH 2700 ES LP - Manual (Page 41)

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Problem solving
41
8 Problem solving
8.1 Error code diagnostics
i
To remove error code from the
display, press the reset button.
Display Cause Solution
Fault in the flue gas limiter. 1. Check continuity of the flue gas limiter (see Fig. 64 , page 49 ).
Go to steps two and three to determine air box temperature
sensor fault and replace it.
2. Check for flue gas leakage around the top and bottom seals of
heat exchanger as well as the viewing window.
3. Check that venting is within specifications (see Section
3.3 ).
Long vent lengths, venting with more than three elbows, blocked
vent or combination venting may cause this failure.
4. Check that flue gas limiter connector and spade connections
are secure.
5. Unplug heater and check the two main plug connections inside
the control board.
Appliance selection on “P7” mode
is not correct. 1. Check “P7” mode: water heater requires setting “NC”.
2. Check jumper and connection on sensor at upper right hand
corner of heat exchanger.
3. Measure jumper resistance, must be 115-125 ohms.
Backflow temperature sensor
defect - happens if sensor is
disconnected or short circuit.
1. Check backflow temperature sensor connection and resistance.
See
Fig. 62 , page 47 and Fig. 64 , page 49 .
2. Replace backflow temperature sensor.
Outlet temperature sensor fault
(Temperature below freezing or
above 210°F). 1. Check red wire connections at hot water temperature sensor.
Clean terminals with an eraser. If badly corroded, replace sensor
and wire harness. See Fig.
64 , page 49.
2. Sensor may trip if water temperature drops below freezing to
protect heater from freezing conditions. Any damage due to
freezing conditions is not covered under warranty.
3. Clean inlet filter screen and clear any debris out of shower
heads, faucet aerators and whole house filters.
4. In areas where water has a high mineral content, periodic
descaling may be necessary.
Table 20
* By installer or service technician only.