Viessmann 29

Medium

Vitocal — Secondary return temp sensor — open circuit.

Viessmann 29: Secondary return temp sensor — open circuit. This fault usually isn't an immediate stop, but should be checked soon.

Possible causes

Sensor (Pt 500) interrupted.

Check steps

Check resistance (Pt 500) at F9 / X5.10-X5.11.
Check/replace lead & sensor.

Affected parts

Rücklauf-Temperatursensor (Pt 500)

Safety note

Isolate power.

Source: Viessmann resmi servis kılavuzu — Manual p.28-29: '29 Rücklaufsens. sekundär' = 'Unterbrechung Rücklauftemperatursensor Sekundärkreis' (open-circuit variant of code 21's Kurzschluss). This matches Enthalio DB's 'Rücklauftemperatursensor Sekundärkreis — U

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

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