NX6300 F15: Air pressure detected when off
I'm getting an F15 fault on my NX6300 burner control. It happens right after shutdown, and the main combustion air pressure switch shows air pressure when the fan should be off. What should I check first?
The Fireye NX6300 F15 fault indicates that combustion air pressure was detected when it should not have been. This can occur either before the fan starts (Status 01) or more than three minutes after the burner turns off (subset 2). It also appears if the air-switch option (Opt 6.x) is not correctly set.
Likely causes and checks
1Stuck switch contacts or jumper
- Points to it
- The main combustion air pressure switch contacts may be stuck closed, or a jumper could have been left in place from previous maintenance, causing the controller to detect air pressure constantly.
- Check
- Isolate and check the main combustion air pressure switch with the fan off. Look for any jumpers that might have been left in the wiring.
2Fan still running or windmilling
- Points to it
- The combustion fan might continue to run or 'windmill' due to shared breeching or a strong stack draft, maintaining air pressure even after the burner has shut down (subset 2).
- Check
- Confirm that the combustion fan completely stops after shutdown. Measure the pressure at the sensing point with the fan off to verify no residual pressure.
3Option parameter not set
- Points to it
- The F15 fault can occur if the air-switch option parameter (Opt 6.x) is not correctly configured in the NX6300 controller, especially after a new installation or parameter changes.
- Check
- Have the commissioning engineer verify and confirm the settings for the Opt 6.x air switch parameters in the controller.
Next check: After checking the physical switch and fan operation, review the controller's option parameters for the air switch settings.
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