SDMO Failure to Close Generator Breaker

Generator runs but does not take load when ATS transfers; main breaker remains open.

Advertisements

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Advertisements

Possible Causes

Faulty SDMO main breaker closing coil, Interlock from controller preventing closure, Mechanical jam in breaker mechanism, Incorrect wiring from controller to breaker shunt trip/close coil

How to Fix / Troubleshooting

Safety first: Ensure both mains and generator sources are isolated before working on the breaker or ATS. Only qualified personnel should work inside power panels.

  • Check controller status: Confirm that the SDMO controller indicates generator ready and no active alarms. Some alarms inhibit breaker closure.
  • Test breaker manually: With power off, operate the breaker handle to ensure it moves freely. If it is stiff or jammed, service or replace the breaker.
  • Measure coil voltage: During a close command, measure voltage at the breaker closing coil terminals. If no voltage is present, trace control wiring and check the closing relay in the SDMO panel.
  • Inspect interlocks: Verify that mechanical and electrical interlocks with the mains breaker are correctly adjusted and not preventing closure.
Advertisements

Repair Difficulty

Hard 4/5

Required Part

Generator Main Breaker
Check Price on Amazon

We may earn a commission from links on this page.

Advertisements