I'm getting 972 Earth Ground Fault on my Honeywell VISTA-128FBP. What should I check?
A 972 Earth Ground Fault indicates the FACP has detected an unintended electrical path between the system's circuitry and earth ground, or there is an issue with the required physical ground connection (Page 60) [2].
Steps to troubleshoot:
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Verify Terminal 30: Ensure a dedicated earth ground wire is securely connected to terminal 30 on the main circuit board and bonded to a proper earth ground, such as a cold water pipe or grounding rod (Page 102) [1].
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Inspect for Pinched Wires: Check the main cabinet and all junction boxes for wires with stripped insulation or pinched points touching the metal enclosure or conduit.
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Isolate Field Circuits: Disconnect field wiring (such as NAC or SLC loops) one at a time. If the 972 code clears after removing a specific circuit, the Ground Fault is located on that run.
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Check for Moisture: Inspect outdoor devices or underground conduits for water ingress, which commonly causes ground leakage.
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Test with Multimeter: With the wires disconnected from the panel, use a multimeter to measure resistance (Ohms) between each conductor and the metal cabinet. A reading other than "Infinite" or "Open" confirms a fault on that wire.
Verify with current documentation before making changes.