Why does my FX-5 show a NAC circuit trouble even though all appliances are wired and the EOL resistor is installed?

A NAC trouble on the FX-5 is typically caused by a wiring fault, a programming mismatch, or the circuit being manually disabled. First, check the NAC Trouble LED: if it is double-flashing, the circuit is simply disabled and can be restored by pressing the NAC Disable button (Page 15, 21) [1].

If the LED is steady, the panel is detecting a physical open or short circuit (Page 15) [1].

Common technical causes include:

1. Programming Mismatch: Ensure the NAC Class setting (Class A or Class B) in programming matches your actual field wiring (Page 15, 42) [1].

2. Ground Fault: Check if the Ground Fault LED is on, indicating a short between the NAC wiring and ground (Page 2) [1].

3. Polarity: Verify wiring polarity at the terminals; markings indicate polarity when the NAC is active (Page 93) [1].