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Connecting a Portable Generator to the Home Main Electric Panel – Part 2


If you landed on this page from a search engine, you may want to read my first post, “Connecting a Portable Generator to the Home Main Electric Panel – Part 1″ by clicking (here).


  • ~10 ft of 12/2 (20 amps) or 14/2 (15 amps) cable;
  • Wire nuts
  • Wire cutter
  • One, 2 in. Non-metallic (NM) Sheathed Cable Clamp Connector
  • 36-in. drill bit

Step # 1 – Relocate Existing Breakers

The primary purpose of a backfeed circuit breaker is to stop electricity from your generator to the power grid.

I cannot stress enough that you absolutely need to make sure that your electricity is isolated from the general power grid.

During power outage, there may be multiple lineman working near your house and we want to protect them getting injured or killed by our portable generator.

For my main load panel (Square D, QO series, 200 amps), I needed to free up two 15 amp breaker slots on the right side (just below the main breaker) to install my 60 amp double pole circuit breaker. Because my panel was pretty full, I had to relocate these two breakers to the bottom, left side. This meant I had to splice the extra wires using wire nuts to extend the existing wires to the new location. Please note that not all towns allow this extension method. Contact your local inspector for his/her guidance;

Step # 2- Install Service Cable / Feedback Circuit Breaker

This step routes the service cable from the main panel to the power inlet box. Because I had to install this setup last minute, I simply tacked the cable on to the ceiling. At later time, I will re-route the service cable through the floor joists via the garage attic.

  • First, knock off a hole from the top of the main panel and install a 2-in NM Cable Clamp Connector;
  • Route the service cable through, making sure that it does not touch any parts that are still energized;
  • We want the extra length to be able to route it inside the main panel without any kinks (gentle curves);
  • Attach the white wire to neutral
  • Attach black and red hot wires to the circuit breaker
  • Insert the feedback circuit breaker to the main panel

Step # 3 – Install Power Inlet Box

  • The hole was drilled with a downward angle (approx 15 degrees) to ensure that water will not drip back in to the house (akin to drip loop);
  • Disassemble the inlet box and attach the back bracket to the wall. I inserted a leftover toilet plastic shim between the bracket and wall to angle down the inlet box to minimize water penetration;
  • Add some NOALOX into the wire receptacles and screw down the wires;
  • Space is rather tight inside the inlet box with thick wires. I had to juggle wires multiple times to make them fit;

Step # 4 – Install the Interlock Kit

  • Remove a single screw holding down the main circuit breaker shroud;
  • Attach the metal plate that identifies feedback circuit breaker;
  • Flip the cover panel and line up the screw hole template (making sure that right side is now left side because I reversed the cover panel);
  • Align the plate and lightly drill with a 3/16″ metal drill bit;
  • Flip the cover panel and re-drill the holes using a 5/8″ drill bit;
  • Remove the metal shards from the backside of the panel using a pair of pliers;
  • Line up the interlock slider on the cover panel and install 3 screws;
  • Apply the interlock notification sticker on the inside part of the cover panel door;
  • Test to make sure that the slider moves up and down without resistance;


That pretty much does it for this project. With a manual interlock kit, I am able to manage whichever circuit I want to supply power to without worrying about overloading the portable generator. Not as convenient as the standby generator, but I am not a big fan of all the electronics in such units so this setup works for me.

If you have any questions, please leave a comment below.

Thanks and good luck with your DIY project!


Monday 25th of April 2022


Dumb question of the day..... When I backfeed from my generator into the main panel via a 60 or 30 amp breaker on One side of the panel, I am not feeding power to all the circuits on the other side of the panel am I???? Aren't the two sides of a Main Panel Isolated/Separate? Or am I really missing something?

I want to wire my generator set-up this way, but just want to make sure I am setting it up and understanding it correctly. And yes, I have experience with basic electrical, wired my whole house, have added many breakers/lines into my panel, etc. Just want to understand how it feeds both sides of the panel, etc.


Sunday 26th of July 2020

Are the linemen safe having the neutral wire connected without any switch to isolate it? Also, you never mentioned the ground wire..

Chad P

Thursday 11th of June 2020

How did you deal with the bonded ground in your breaker box? I've got a similar setup and it causes a ground-fault condition in my generator. I've tried removing the ground bond in the generator, but that did not fix the problem.


Thursday 11th of June 2020

Hi Chad-

It's been some time since I did this project. I believe the setup was:

exterior plug - accepts 3-wire connection (black, red, white) main electric panel - neutral bonded to panel (ground) 4-wires connect from the main to sub subpanel - neutral bus bar is NOT bonded to panel (isolated from ground)

Working with subpanel and main panel is quite dangerous so if you are absolutely not sure what you are doing, please consult with an electrician.



Monday 6th of January 2020

It may have just been missed in writeup, but you did not mention grounding the cable in the breaker panel

Rick Conti

Friday 30th of August 2019

Jim, thanks for the article! I'll be using it to install a kit in my house. Here's a recap and a questions. So, the main function of the kit is to protect Power Company workers from getting electrocuted from a home owner backfeed. Secondly, to make it easier on the homeowner to power up needed appliances during a power outage. The scenario is you've lost main power to your house and the interlock kit is going to make you place the main breaker disconnect in the off position before placing the backfeed breaker in the "On" position. So, before you turn on the backfeed breaker, which will become the feed to the breaker box buss, wouldn't you want to turn off all the other breakers in the box first, then turn on your backfeed breaker and then sequentially turn on the breakers needed to support you emergency condition? It's my thought if you don't do it in that fashion you may cause a current surge and trip the backfeed breaker or overload the generator or both? Am I missing something in your article? I know that's the way I'd power up what I needed. Thanks, Rick