Boiler displays E17, no response to room thermostat or controller

Safety first: Isolate power before altering control wiring.

• Check controller power: Ensure the ACV room controller or thermostat has power (screen on, batteries good).
• Verify demand: Set the room thermostat to a higher temperature than the room. Confirm it is actually calling for heat.
• Inspect wiring: Check that the low-voltage control wires are firmly connected at both the boiler and the controller. Look for damage or signs of rodents.
• Parameter check: On the boiler menu, confirm that the control mode (e.g., On/Off, OpenTherm, ACV controller) matches the installed device. Refer to the ACV manual.
• Professional help: If E17 persists, a technician should test the controller and boiler interface circuits.