Bosch Tankless Water Heater: Run gas and air auto adjust (UC)
Run gas and air auto adjust (UC) on a Bosch tankless water heater: Automatic gas and air adjustment inside the combustion adjust menu; takes about 15 minutes. Needed after an LPG conversion, repeated unresolved errors, or replacing the control unit, fan or gas valve.
Applies to: Greentherm T9800 SE 160/199 and T9900 SE 160/199 tankless water heaters
How to fix run gas and air auto adjust (uc): step by step
- Enter AU Technical Settings and open the combustion adjust menu
- Select UC Auto Adjust
- Open hot water taps when Open Taps shows
- Wait for the green check mark
If the unit shows an error code, look it up: Bosch Tankless Water Heater codes
Models
Bosch Greentherm T9800 SE
Greentherm T9800 SE 160Greentherm T9800 SE 199Greentherm T9800 SEC 199
Bosch Greentherm T9900 SE
Greentherm T9900 i 199Greentherm T9900 SE 160Greentherm T9900 SE 199
Source: Bosch Greentherm T9800 SE 160-199 installation 6720816815 (06.2023), 8.11 Gas and Air Adjustment pp.60-61; T9900 SE 160-199 installation 6 720 813 635 (2024-06) same section. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.