Ariston OpenTherm / Bus Communication Error

Boiler displays 801, communication error with external Ariston Net / Cube thermostat

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Incorrect bus wiring, Faulty Ariston Net/Cube device, Damaged communication cable, PCB bus interface fault

Safety: Isolate power before working on low-voltage wiring.

Check wiring: Verify the bus connections (e.g. terminals + and -) are correctly wired between boiler and control, with no shorts.
Inspect cable: Look for damage or water ingress along the cable route.
Test with simple control: Temporarily connect a basic on/off room thermostat (if supported) to see if the boiler responds. If it does, the bus device may be faulty.
Firmware / reset: Reset the Ariston Net/Cube device according to its manual and ensure firmware is up to date.

Medium 3/5

Ariston Cube / Net Thermostat

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