Problem solving
Display | Cause |
|
| Solution |
(Flashing) | Outlet | temperature | sensor not | 1. Check that the sensor is firmly attached to the hot water pipe |
| sensing | expected | output | (see Fig. 70, page 55). |
| temperature. |
| 2. Clean inlet filter screen and clear any debris out of shower | |
|
|
|
| heads, faucet aerators and whole house filters. |
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.Check gas pressure. Low gas pressure may prevent the heater from reaching desired output temperature.
5.Check supply voltage. It must be 120VAC and properly grounded.
6.Possible defective control unit call Bosch Water Heating for further instructions.
7.Ensure that outlet temperature sensor is not placed on any bends in the hot water pipe or misreading may occur.
| Primary fan rotation too low on | 1. Disconnect power supply cord and check wire connections on | |
| operation. | back side of primary fan and the two connectors on the control | |
|
| board (see Fig. 71, page 56). |
|
|
| 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 | |
|
| minimum 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. |
|
| No rotational speed sensor signal | 1. Disconnect power supply cord and check wire connections on | |
| from primary fan. | back side of primary fan and the two connectors on the control | |
|
| board (see Fig. 71, page 56). |
|
|
| 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. | |
(Flashing) | Water flow signal over specified | 1. Disconnect power supply cord and check wire connections on | |
| maximum value. | water valve and the two connectors on the control board (see | |
| Water flow > 10 gallon/min. | Fig. 71, page 56). |
|
|
| 2. Excessive water pressure and flow. Ensure water pressure is | |
|
| less than 150psi and flow rate is below 10 gallons per minute. | |
| Internal hardware/software failure. | 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. Pushing 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 ( | ) to reset any error |
|
| codes. |
|
|
| 3. Possible defective control unit. Call Bosch Water Heating for | |
|
| further instructions. |
|
Table 20
* By installer or service technician only.
42 | 6 720 608 542 |
