MTU Onsite Energy
Generator Breaker Fails to Close
Generator starts and runs but main circuit breaker does not close to supply load
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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.
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Possible Causes
Breaker close coil failure, Interlock or permissive not satisfied, Low control voltage to breaker, Mechanical binding in breaker mechanism
How to Fix / Troubleshooting
Safety first: Never force a breaker closed. Ensure proper synchronization and interlocks are in place.
- Check controller status: Confirm that all breaker close permissives (voltage, frequency, phase sequence) are satisfied.
- Measure control voltage: Verify that the breaker close coil receives the correct voltage when a close command is issued.
- Inspect wiring and interlocks: Check wiring from the MTU controller to the breaker, including any auxiliary contacts or key interlocks.
- Breaker mechanism: With power isolated, manually operate the breaker (if design allows) to check for mechanical binding. Service or replace the breaker if it does not operate smoothly.
- Functional test: After repairs, perform a controlled close under no-load conditions, then test with load.
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Repair Difficulty
Professional Required
5/5
Required Part
Generator Main Circuit Breaker
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