Problem Solving - Bosch GWH 2400 ES NG Manual

8

Problem solving

8.1 Error code diagnostics
To remove error code from the
i
display, press the reset button.
Display Cause
Fault in the flue gas limiter.
Jumper connection is not correct.
Backflow
defect - happens if sensor is
disconnected or short circuit.
Outlet temperature sensor fault
(Temperature below freezing or
above 210°F).
Table 22
* By installer or service technician only.
6 720 608 782
Solution
1. Check continuity of the flue gas limiter (see Fig.
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
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.
1. Check jumper connection on connector at upper right hand cor-
ner of heat exchanger.
2. Check jumper and connection on sensor at upper right hand
corner of heat exchanger.
3. Measure jumper resistance, must be 115-125 ohms
temperature sensor 1. Check backflow temperature sensor connection and resistance.
See
2. Replace backflow temperature sensor.
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.
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.
Fig. 63 page 47 Fig. 65
, and
65
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Problem solving
65 49
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3.3
49
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49.
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