Bosch C 950 ES Installation Manual page 50

Problem solving
Display Cause
Primary fan rotation too low in
operation.
No rotational speed sensor signal
from primary fan.
(Flashing) Water flow signal over specified
maximum value.
Water flow > 10 gallon/min.
(Status message).
Over-temperature
outlet temperature sensor.
Temperature > 185°F
Cold water temperature sensor
fault.
Table 29
* By installer or service technician only.
50
Solution
1. Disconnect power supply cord and check wire connection on
back side of fan and the connectors on the control board, see
84 page 65
,
2. Check supply voltage. It must be 120VAC and properly
grounded.
3. Check venting specifications are met. Long vent lengths,
venting with more than three elbows, blocked vent or combination
venting may cause this failure.
4. Ensure intake and exhaust terminations maintain the required
clearances stated in the manual. Cross contamination between
intake and exhaust may cause the fan to alter its rotational speed.
5. Check gas pressure. Low gas pressure may cause the fan to
change its speed to meet desired temperature.
6. Possible defective control unit call Bosch Water Heating for
further instructions.
1. Disconnect power supply cord and check wire connections on
back side of fan and the two connectors on the control board, see
Fig. 84 page 65
,
2. Check supply voltage. It must be 120VAC and properly
grounded.
3. Possible defective component in fan or defective control unit
call Bosch Water Heating for further instructions.
1. Disconnect power supply cord and check wire connections on
water valve and the two connectors on the control board, see
84 page 65
,
2. Excessive water pressure and flow. Ensure water pressure is
less than 150psi and flow rate is below 10 gallons per minute.
detected by 1. Check that the sensor is firmly attached to the horizontal section
of the hot water pipe, see
2. Check red wire connections at hot water temperature sensor.
Clean terminals with an eraser. If badly corroded, replace sensor
and wire harness.
3. In areas where water has a high mineral content, periodic
descaling may be necessary. See chapter
directions.
4. Check sensor (ref.
1. Check connector on wires coming from top of watervalve for a
secure connection. See
2. Sensor may trip if water temperature drops below 36°F (2
Protect heater from freezing conditions as any damage due to
freezing conditions is not covered under warranty.
3. Check sensor (ref.
.
.
.
Fig. 83 page 64
,
page 53, chapter 9).
Fig. 77 page 57
,
page 54, chapter 10).
Fig.
Fig.
.
6.3 page 42
, for
.
°
C).
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