Bosch A01 (5246)

Critical

Compress — Booster heater limiter (STB) or pressure switch tripped.

Bosch A01 (5246): Booster heater limiter (STB) or pressure switch tripped. This fault typically halts operation and needs immediate attention.

Possible causes

Low system pressure / air in system.
Poor circulation, clogged filter ball.

Check steps

Reset STB button (click).
Bleed, refill pressure, clean filter ball.

Affected parts

STB
Filterball
Umwälzpumpe PC0

Safety note

Electric heater 230/400 V – de-energise.

Source: Bosch resmi servis kılavuzu — Alarm List 8754, code 5246, Display Code A01, Customer: "Alarm Z1 electric booster heater E2 manual reset high limit (STB) or pressure switch tripped — Alarm is given when the overheating protector of the electrical heater is tripped, which happens at 95 degrees." Causes list als…

Reviewed by Anıl Güzeldemir — in the refrigeration machine room since 2006, developer of Enthalio.

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