Fireye NX6100 F15: Air pressure detected when off, what to check?
I'm getting an F15 fault on our Fireye NX6100 burner controller. It's happening either before the fan starts or after shutdown while the fan is winding down. What should I check first?
The Fireye NX6100 F15 fault indicates that the main combustion air pressure switch detected air pressure when it should not have. This can occur before the fan starts (Status 01) or if the switch registers air for more than three minutes after the burner turns off. It can also appear if the air-switch option (Opt 6.x) is not correctly set in the controller.
Likely causes and checks
1Air pressure switch contacts stuck or jumpered
- Points to it
- The switch contacts may be physically stuck in a closed position, or a jumper could have been left in place from previous maintenance, causing the controller to falsely detect air pressure.
- Check
- With the fan off and isolated, check the main combustion air pressure switch. Also, look for any jumpers that might have been left in place from prior work.
2Fan still running or windmilling
- Points to it
- If the fan continues to turn after shutdown, or if there's a strong stack draft or shared breeching causing it to windmill, the air pressure switch will correctly detect air when the controller expects none.
- Check
- Confirm that the fan completely stops after shutdown. Measure the pressure at the sensing point with the fan off to verify no residual air pressure.
3Air switch option parameter not set
- Points to it
- The F15 fault can occur if the optional air switch parameter (Opt 6.x) in the NX6100 controller is not configured correctly, especially after a new installation or parameter changes.
- Check
- Have the commissioning engineer verify the settings for the Opt 6.x air switch in the controller's parameters.
Next check: First, check the main combustion air pressure switch with the fan off and isolated for stuck contacts or any jumpers. This is the most common cause for F15.
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