Viessmann 21

Medium

Vitocal — Secondary return temp sensor — short circuit.

Viessmann 21: Secondary return temp sensor — short circuit. This fault usually isn't an immediate stop, but should be checked soon.

Possible causes

Sensor (Pt 500) shorted.

Check steps

Check resistance (Pt 500) at F9 / X5.10-X5.11.
Replace sensor if faulty.

Affected parts

Rücklauf-Temperatursensor (Pt 500)

Safety note

Isolate power.

Source: Viessmann resmi servis kılavuzu — Serviceanleitung WO1C, section '21 Rücklaufsens. Sekundär' (p.90-91): 'Ursache: Kurzschluss Rücklauftemperatursensor Sekundärkreis.'

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

Look up in Enthalio →

Related fault codes

Compressor switched off, heating via alternatiA9 Safety high-pressure switch tripped, compressoC9 Low-pressure fault, compressor switches off.D3 Control high-pressure fault, compressor off.D4 Flow switch detects no flow, compressor off.D6 Utility lockout – compressor off (by energy suC5