Bosch Therm 8000 S Installation And Operating Instructions Manual page 42

42 | Problem solving
Display Cause
(Flashing) Outlet temperature sensor not
sensing expected output
temperature. (Status message,
not an error)
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 > 37 l/min.
Software/hardware failure.
Table 25
* By installer or service technician only.
6 720 680 174 (2014/05)
Solution
1. Check that the sensor is firmly attached to the vertical section of the
hot water pipe.
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.
5. Possible defective control unit, call the Technical Assistance.
1. Disconnect power supply cord and check wire connections on back
side of fan and the two connectors on the control board.
2. Check supply voltage.
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 the Technical Assistance.
1. Disconnect power supply cord and check wire connections on back
side of fan and the two connectors on the control board.
2. Check supply voltage.
3. Possible defective component in fan or defective control unit, call the
Technical Assistance.
1. Disconnect power supply cord and check wire connections on water
valve and the two connectors on the control board.
2. Excessive water pressure and flow. Ensure water pressure is less
than 10 bar and flow rate is below 37 Litters per minute.
1. Disconnect power supply cord and check the two wire and ground
connections on control board as well as ground connection on heater
chassis.
2. Pressing the wrong combination of buttons on the control unit can
create confusion among the microprocessors inside. In this case, the
error code should not happen more than once or twice. Turn off the
water heater. Turn water heater back on and try resetting error code.
Use the reset button (
3. Possible defective control unit, call the Technical Assistance.
) to reset any error codes.
Therm 8000S