Utility - Generator Panel InterLock

This is a 3D printed version of the Square D Interlock. It allows you to use a generator to power your home during utility power outages restricting the power supplied to the circuit panel to a single source -- Utility Power OR Generator Power..

This interlock is designed for a Square D breaker panel but could be modified to work on most circuit breaker panels. The concept is simple: The main breaker must be switched OFF so the Auxiliary breaker that is connected to the Backup Power (generator) can be switched ON. This interlock prevents more than one of these sources to be ON, or powering the circuit panel, at any time.

NOTE: This Instructable is limited to fabricating the actual interlock. Please refer to other Instructables for the actual wiring requirements.

Basic usage: when you lose utility power (once wired properly):

1. Attach the generator.
2. Start the generator.
3. Switch the Main Breaker OFF.
4. Slide the interlock UP.
5. Switch the Aux breaker ON.

Your home is now powered by the generator.

3D printed Interlock.
3 each 4-40 taper head screws with t-nuts

Included are both the Sketchup18 source file and the STL file for the Square D panel.
You can modify the Sketchup file to fit your circuit panel and recreate the STL.
This interlock is printed with ABS.

You might want to consider electrician to perform or assist with the following:

1. Carefully remove the safety panel shield cover from the circuit panel. Usually, 6 exposed screws. Be very careful around the exposed live panel.

2. Drill and taper the backside of the shield panel with 3 holes using the printed interlock as a guide.

3. Secure the interlock to the front of the shield panel using 3 4-40 screws and t-locks. Make sure it slides up and down freely. Slide it to the down position.

4. Switch AUX breaker OFF.

5. Re-install the safety front panel with the interlock DOWN and the MAIN breaker ON. (AUX OFF).

See INTRO for operating instructions, repeated below.

So when you lose utility power:
1. Plug the generator (or aux) into the L5-30r plug.
2. Start the generator.
3. Switch the Main Breaker OFF.
4. Slide the interlock UP and
5. Switch the Aux breaker ON.

Your home is now powered by the generator.