Controller displays E20, generator shuts down with ground fault indication

Safety first: Ground faults can be dangerous. Turn the controller to OFF, open the generator main breaker, and disconnect the battery. Do not re-energize until the fault is located.

• Inspect output wiring: Check the generator output lugs, junction boxes, and conduit for signs of insulation damage, water intrusion, or rodent damage.
• Dry moisture: If condensation or water is present in the output compartment, dry thoroughly and correct any leaks or missing gaskets.
• Isolate loads: Have an electrician disconnect branch circuits from the transfer switch and reconnect them one at a time to identify a faulty load or circuit causing the ground fault.
• Megger test (technician): A technician can perform insulation resistance testing on the alternator windings to determine if internal damage exists.

If the alternator windings are compromised, the alternator assembly may need replacement.