Viessmann · Boiler

S.154 Internal flow switch open

Normal status Vitodens 200-W B2HE

What the display is showing

The boiler's internal flow switch is in the open position.

Applies to: Vitodens 200-W B2HE 85, 120, 150, 199

Models that show this code

4 models in Vitodens 200-W B2HE

B2HE-120B2HE-150B2HE-199B2HE-85

Other codes on the same units

I.59 Parameters restored
P.1 Service interval reached
P.4 Top up heating water
P.8 Service due after burner hours
S.60 Summer mode active
S.74 Heating suppression
S.75 DHW recirculation pump active
S.94 No demand, external hook-up HC1

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

Source: Viessmann Vitodens 200-W B2HE 85/120/150/199 Service Instructions 6167 813-24 (09/2026), Further messages, p.74. 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.