Problem Solving - Bosch C 950 ES Installation 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.
Temperature
(110°C) inside the cabinet.
Exhaust
happens if sensor is disconnected
or in short circuit or appliance
selection on "P7" mode is not
correct.
Backflow
defect - happens if sensor is
disconnected or short circuit.
Outlet temperature sensor fault
(Temperature below 36°F or above
210°F).
(Flashing) Outlet temperature sensor not
sensing
temperature.
(Status message, not an error).
Table 29
* By installer or service technician only.
6 720 646 812
above 230°F
temperature sensor -
temperature sensor
expected output
Solution
1. Check continuity of the flue gas limiter (see
Go to steps two and three to determine flue gas limiter fault and
repair it.
2. Check for flue gas leakage around the top and bottom seals of
heat exchanger, use mirror to check around the rear as well as the
viewing window.
3. Check that flue gas limiter connector and spade connections
are secure.
4. Unplug heater and check the wiring harness connections on the
control board.
1. Check exhaust temperature sensor connection. See
page 57
#1, .
page 54
2. Check sensor (ref.
water heater
3. Check "P7" mode: the
.
condensing appliances
1. Check backflow temperature sensor connection. See
page 57
#1, .
2. Replace exhaust temperature sensor.
page 54
3. Check sensor (ref.
1. Check red wire connections at hot water temperature sensor.
Clean terminals with an eraser. If badly corroded, replace sensor
Fig. 72
and wire harness. See
2. Sensor may trip if water temperature drops below 36°F to
protect heater from freezing conditions. Any damage due to
freezing conditions is not covered under warranty.
3. In areas where water has a high mineral content, periodic
descaling may necessary.
page 54, chapter 10).
4. Check sensor (ref.
1. Check that the sensor is firmly attached to the vertical section of
Fig. 83
the hot water pipe, see
2. Ensure that hot water sensor is not placed on any bends in the
hot water pipe or misreading may occur.
3. Check gas pressure. Low gas pressure may prevent the heater
from reaching desired output temperature.
4. Check supply voltage. It must be 120VAC and properly
grounded.
5. Possible defective control unit call Bosch Water Heating for
further instructions.
Problem solving
Fig. 77 page 57
,
Fig. 77
chapter 10
, ).
requires setting "Cd" for
Fig. 77
chapter 10).
,
page 53
, .
page 64
, .
).
,
,
49