AquaStar 250SX Troubleshooting and Online Tech Support from Bosch Water Heaters

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250SX Technical Support

Online Tech Support from Bosch Water Heaters

This model is for indoor installation only.

Please note: If you are unable to perform the tasks listed below or need additional assistance, please contact your original installer/licensed gas technician. Visit our Service Installer Locator.

For information on where to purchase our product, please visit our Where to buy page.
For information on where to purchase parts, visit the Parts List/Purchase Parts page specific to your model.

250SX Troubleshooting

Q. Burners Do Not Ignite When Hot Water Is Turned On?

Q. Water Is Too Hot?

Q. Water Is Not Hot Enough?

Q. Low Water / Flow Pressure?

Q. Hot Water Temperature Fluctuates At Tap?
Note: Temperature fluctuations from hot to cold during use are typically caused by a restriction in the hot water plumbing. This slows the flow within the tankless heater, decreasing it below the activation flow rate, which shuts off the burners. The end result is nothing but cold water coming out of the outlet. Follow each step below before proceeding to the next. After each step, test the hot water flow to see if it remains constant without turning cold.

Q. Noisy Burner / Heater During Operation?

Troubleshooting Error Codes

Please note: If there is a problem with the installation, venting or operation of the unit, the heater will communicate the source by these error codes.

Q. A2 - Fault in the flue gas limiter

Q. A7 - Hot water temperature sensor fault

Q. A9 - Hot water temperature sensor not sensing expected output temperature

Q. C1 - Fan rotation too low on startup

Q. C6 - Fan rotation too low in operation

Q. C7 - No rotaional speed sensor from fan

Q. CA - Water flow signal over specified maximum value

Q. E1 - Over-temperature detected by temperature sensor on hot water pipe

Q. E2 - Cold water temperature sensor fault

Q. E9 - Temperature limiter (ECO) open circuit

Q. EA - No flame ionization detected with water flow

Q. EC - Ionization failure during operation

Q. E0 - Internal hardware/software failure

Q. F7 - Ionization error at standby

Q. FA - Gas leakage error, gas valve circuit not closing properly

Q. 8E - Electronic noise on control unit

250SX Tech Support

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Note: Specifications and product information subject to change without notice.

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