Low Warning
77:2 to 77:99 on Viessmann Vitodens 050-W

Your boiler's internal communication system has identified an addressing conflict between different control units on the network.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

LON user number, adjustable from 1 to 99: 1-4=boiler, 5=cascade, 10-...=Vitotronic 050, 99=Vitocom

What causes this fault?

This fault occurs when two or more components on the boiler's internal communication network are trying to use the same identification number. It is usually caused by a technician incorrectly configuring the settings during a repair or by a digital glitch that has scrambled the control unit's memory. Because the system cannot distinguish between the different parts, it struggles to send and receive commands correctly.

Engineer required

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

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Related fault codes

77:1View →DAView →BCView →

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