U4 Daikin — Refrigerant addressing error
At a glance
- Severity
- FAULT STOP
- Domain
- VRV_VRF_system
- Reference standard
- EN 378-1:2016, F-Gas EU 517/2014, ISO 5149
- Product / context
- Transmission error indoor-outdoor
What it means
The VRV/VRF system cannot correctly route refrigerant to the requesting indoor units. The distribution valves (branch controller / BS box) do not switch or receive incorrect signals from the main board, causing units that do not cool/heat despite an active demand.
Probable causes
- Branch controller solenoid valve stuck or with burned coil
- Indoor unit addressing error on the communication bus
- Communication cable between branch controller and outdoor unit broken
- Incorrect system configuration after board replacement
- Address conflict between indoor units on the same branch
Where to start
Check communication between outdoor unit and branch controller. Inspect the main F1-F2 cable. Verify communication voltage with an oscilloscope. If absent, check the outdoor unit board.
Full guided diagnosis in the app
The diagnostic tree for this fault has 6 guided steps with measurements, checks and resolutions. You'll find it in HVACIQ, one of the five IndexOS apps: free, works offline.
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