Quick answer
A breaker interlock ensures safe generator use by preventing backfeeding. Install it by aligning the interlock kit with the main and generator breakers, securing it in place, and verifying that it blocks both breakers from being on simultaneously.
Confirm the symptom
- Generator trips the main breaker when connected
- Main breaker and generator breaker can both be on at the same time
- No power to home when generator is running
- Generator backfeeds into the grid
- Breaker interlock mechanism is loose or damaged
Tools and prep
- Voltage tester
- Screwdrivers (flathead and Phillips)
- Lockout/tagout kit
- Breaker interlock kit
- Safety gloves and goggles
- Turn off main power supply before starting
- Verify no power is present with a voltage tester
Step-by-step troubleshooting
- Turn Off PowerDo: Shut off the main breaker to disconnect power from the utility grid.Observe: The home’s electrical system is de-energized.Means: You can now work safely without risk of electric shock.Next: Install the interlock kit
- Install the Interlock KitDo: Align the interlock bracket with the main and generator breakers. Secure it using the provided screws.Observe: The interlock physically prevents both breakers from being on at the same time.Means: The interlock is properly installed and functional.Next: Test the interlock
- Test the InterlockDo: Attempt to turn on both the main and generator breakers simultaneously.Observe: The interlock prevents both breakers from being on at the same time.Means: The interlock is working correctly.Next: Connect the generator
- Connect the GeneratorDo: Plug the generator into the transfer switch or connect it directly to the generator breaker.Observe: Power flows from the generator to the home’s electrical system.Means: The generator is supplying power safely.Next: Verify operation
- Verify OperationDo: Turn on the generator breaker and check for power in the home.Observe: The main breaker remains off, and the generator powers the home.Means: The system is operating as intended.Next: Final inspection
- Final InspectionDo: Double-check all connections and ensure the interlock is securely fastened.Observe: All components are properly installed and secure.Means: The system is ready for use.Next: Complete
Common causes
| Cause | Likelihood | Difficulty | Part often needed |
|---|---|---|---|
| Improper installation The interlock may not be aligned correctly or secured tightly. | Common | Easy–Medium | Breaker interlock kit |
| Worn or damaged interlock Over time, the interlock mechanism can become loose or broken. | Sometimes | Easy | Replacement interlock |
| Incorrect breaker size Using a breaker that is not compatible with the interlock can prevent proper function. | Sometimes | Medium | Correct-sized breaker |
| Generator not grounded Improper grounding can cause electrical issues and prevent safe operation. | Rare | Medium | Grounding kit |
| Faulty transfer switch A malfunctioning transfer switch can interfere with the interlock’s operation. | Rare | Hard | Transfer switch repair or replacement |
| Loose connections Loose wiring connections can cause power interruptions or prevent the generator from supplying power. | Sometimes | Easy–Medium | Wire connectors or terminal blocks |
| Incorrect generator setup The generator may not be properly configured for use with the interlock system. | Sometimes | Medium | Generator manual or setup guide |
Parts matching
Match your symptoms to the most likely parts needed for a breaker interlock system:
- Breaker interlock kit for your specific panel
- Correct-sized generator breaker
- Voltage tester
- Safety gloves and goggles
- Lockout/tagout kit
- Grounding kit (if needed)
- Wire connectors or terminal blocks
Always verify the compatibility of the interlock kit with your electrical panel and generator model before purchasing.
When to call a professional
- You are unsure about the correct installation procedure
- The interlock does not prevent both breakers from being on simultaneously
- You detect a burning smell or sparks during operation
- The generator does not supply power to the home despite proper installation
- You are not confident in working with electrical systems
- You encounter unexpected electrical issues or errors
FAQ
What is a breaker interlock for a generator?
A breaker interlock is a mechanical device that prevents the main utility breaker and the generator breaker from being on at the same time, ensuring safe operation and preventing backfeeding into the grid.
Can I install a breaker interlock myself?
Yes, if you have basic electrical knowledge and follow safety procedures. However, it is recommended to consult a licensed electrician if you are unsure.
Do I need a permit to install a breaker interlock?
Local codes may require a permit for electrical work. Check with your local authorities before installation.
How do I know if my interlock is working properly?
Test the interlock by attempting to turn on both the main and generator breakers. If the interlock prevents this, it is functioning correctly.
Can I use any generator with a breaker interlock?
The generator must be compatible with the interlock system and sized appropriately for your home’s electrical needs.
What are the safety risks of not using an interlock?
Not using an interlock can result in backfeeding, which can damage the generator, cause electrical fires, or endanger utility workers.