Fault F9 (Detailed 151 or 152) — Burner fault: fan speed too low during start

What does F9 mean?

The burner is in fault mode because the fan speed is too low during the burner start sequence. The fan is essential for proper combustion air supply and flue gas exhaust, so low speed prevents safe operation.

• Fan speed too low during burner start

Click steps to track your progress.

1. 1

   Check the fan unit for any obstructions or unusual noises.

2. 2

   Inspect the fan cables and power supply connections for tightness and damage.

3. 3

   Verify the fan control unit for proper function.

4. 4

   Press the reset button R on your boiler.