Furnace shows E17, often after a brownout or surge, unit may be completely unresponsive or erratic.

Safety: Turn off power at the breaker before inspecting electrical connections.

• Check mains supply: Verify that the circuit breaker is not tripping and that other appliances on the same circuit operate normally.
• Inspect terminal block: Open the electrical compartment and check that L, N, and earth connections are tight and correctly wired.
• Use a surge protector: If your area has unstable power, consider installing a surge protector or voltage stabilizer as recommended by Termet.
• Power cycle: Leave the furnace off for 10 minutes, then restore power and check if E17 clears.

If E17 persists, the internal power supply on the control board may be damaged and should be replaced by a Termet service technician.