A18
Beretta
Room Thermostat / Demand Signal Fault
A18 error; heater may not detect demand correctly
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Safety Warning
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.
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Possible Causes
Open or shorted room thermostat circuit, Incorrect wiring of external controls, Faulty room thermostat, PCB input failure
How to Fix / Troubleshooting
Safety: Isolate power before altering control wiring.
- 1. Check control settings: Ensure the Beretta heater is configured for the type of external control used (on/off thermostat, OpenTherm, etc.).
- 2. Inspect thermostat wiring: At the heater's terminal block, verify that the room thermostat wires are securely connected and not shorted.
- 3. Bypass test (technician): Temporarily bridge the thermostat terminals at the heater to simulate a demand. If the heater starts without A18, the external thermostat or its wiring is faulty.
- 4. Replace faulty thermostat: Install a compatible Beretta-approved room thermostat if the existing one is defective.
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Repair Difficulty
Medium
3/5
Required Part
Room thermostat
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