Medium
477 on Viessmann Vitodens 100-W B1HF-25

Your boiler's solar hot water panels on the roof aren't producing heat as they should, but your central heating and main hot water should still work normally.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Limited solar thermal system functionality. No solar yield. Cause: Fault, differential temperature monitoring, solar, collector/cylinder, difference outside tolerance. Air in the solar circuit. Sensor not positioned correctly. Pump faulty.

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 100 W B1hf B1kf 6167586 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

476View →478View →

All 151 fault codes on the Vitodens 100-W B1HF-25

Seeing a different code? Every code this model can display, in one place.

78111213141516293049505758596263646567686970717273747577788789919295100102103104142161162163176182183184185299345346347348349350351352353354355357359361364365366367368369370371372373374375376377378379380381382383384385386387388395396399400401402403404405406408410416417418425446447448449451452453454455456457458461462463464467468471474517527528540544545574575576577578579682683684694738766767799979980981982E10E12

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