Why does my FX-5 show a NAC circuit trouble even though all appliances are wired and the EOL resistor is installed?
The most common cause for a NAC trouble on an FX-5 panel when an EOL is present is using the incorrect resistor value; the FX-5 requires a 15 kΩ EOLR (Page 4) [1].
If you used a 47 kΩ resistor (which is used for FX-NAC modules or IDCs), the panel will not supervise correctly (Page 5) [1].
Other potential causes include:
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Reverse Polarity: NACs use reverse polarity for supervision. Ensure all appliances are polarized and wired correctly, as the marking on the terminals indicates polarity only when the circuit is active (Page 20) [1].
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Ground Faults: The panel monitors for ground fault impedance between 0 and 5 kΩ (Page 20) [1].
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Manual Disable: Check if the NAC was manually disabled. If so, the NAC Trouble LED will double-flash and the common Disable LED will turn on (Page 21) [1].
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Wiring Shorts: A short circuit will cause the module to inhibit activation and report a trouble to protect the riser (Page 5) [1].