Bosch · Tankless water heater

P9 P9 purge menu

Menu / mode display Bosch Greentherm T9800 SEBosch Greentherm T9900 SE

What the display is showing

Purges the exhaust circuit. About 2 seconds after it is entered the fan starts and keeps running until the menu is left.

Applies to: Greentherm T9800 SE 160/199 and T9900 SE 160/199 tankless water heaters

What to do

Open Information / Adjustments, touch until P9 Purge shows
Touch the symbol to start; the fan starts after about 2 seconds
Exit the menu to stop the fan

Models that show this code

6 models in Bosch Greentherm T9800 SE, Bosch Greentherm T9900 SE

Greentherm T9800 SE 160Greentherm T9800 SE 199Greentherm T9800 SEC 199Greentherm T9900 SE 160Greentherm T9900 SE 199Greentherm T9900 i 199

Other codes on the same units

F7 Control unit internal error
F8 Control unit internal error
F9 Gas valve driver fault
P4 P4 Information menu
AA Flue gas temperature too high, power limited
AC AC consumption
AD Power derate warning
AU AU technical settings (service mode)

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Source: Bosch Greentherm T9800 SE 160-199 installation 6720816815 (06.2023), 6.5.4 P9 Purge p.52; T9900 SE 160-199 installation 6 720 813 635 (2024-06) same section. Summarized in our own words; check the original manual for your model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.