Home Generator Sub-Panels

Generator Sub-Panels

Various options for connecting a portable generator, and installing a generator sub-panel with an interlock kit to temporarily power your home

Installed Interlock kit on a Cutler Hammer Circuit Breaker Panel

CH Generator Interlock Kit

Dear Mr. Electrician:  How do I install a main breaker CH generator interlock kit on my main electrical panel? Answer:  A main breaker CH generator interlock kit is great if you want to supply power to your entire circuit breaker panel and can be an economical choice compared to installing a separate external transfer switch.  NOTE: Some text links below go to applicable products sold on Amazon.  As an Amazon Associate I earn from qualifying purchases. Below are step by step photos depicting a main breaker interlock kit installation on an older Cutler Hammer main circuit breaker panel.  On the last page is a short YouTube video of this installation. Before beginning the work of installing an interlock kit on your main electrical panel, you should obtain an electrical permit from your town's building department.  Submit a copy of the interlock kit installation instructions with your permit application.  In addition I always write a short "Scope of Work" and include that with my permit applications so that the inspector has a clear understanding of the work being done before hand. I had submitted documentation about the interlock kit and the PB30 generator inlet along with my application for an electrical permit for this job.  I also made a simple drawing depicting the location of the generator inlet in relation to the basement electrical panel.  The work was inspected by the town electrical inspector. When the work is completed you will arrange to have an electrical inspector look over the job to make sure that it is compliant with the electrical code.  This is very important to ensure that your installation is safe and not hazardous to someone connecting the generator during a power outage. HOW TO INSTALL A MAIN BREAKER GENERATOR INTERLOCK KIT Above is what the Cutler Hammer circuit breaker panel looked like prior to the installation of the interlock kit.  Fortunately there were five available spaces in this 30 circuit panel.  The interlock kit for this particular Cutler Hammer panel requires three spaces on the top right. To install a main breaker interlock kit you will need a few extra spaces in your main electrical panel as a two pole 30 amp or two pole 50 amp circuit breaker will need to be installed adjacent to the main breaker. The new two pole breaker will be connected to the incoming power from the portable generator.  Usually two or three spaces are required for the generator two pole circuit breaker. Main breaker generator interlock kits are available for many new electrical panels from the original manufacturer.  However for older electrical panels it is sometimes necessary to use an interlock kit from a third party manufacturer.  The interlock kit depicted in the photos on this page is from a third party manufacturer (www.interlockkit.com).  It is approved by a certified testing laboratory for use on this particular electrical panel. The homeowner had typed up a panel directory for most of the circuits years before this installation.  It came in handy when identifying critical circuits to run off of the portable generator....
A Completed Main Breaker Interlock Kit Installation on an Existing GE Circuit Breaker Panel

GE Interlock Kit

Dear Mr. Electrician: How can I install a GE Interlock Kit on a GE main breaker panel so that I can connect a portable generator to it safely? Answer: In order to install a GE interlock kit on a main breaker, You first must determine if you have the needed circuit breaker spaces for a generator circuit breaker and interlock kit in your main electrical panel.   NOTE: Some text links below go to applicable products on Amazon.  As an Amazon Associate I earn from qualifying purchases. Usually two, but sometimes three circuit breaker spaces are needed to accommodate the interlock kit.  It varies according to interlock kit and the circuit breaker panel. CHOOSING AN INTERLOCK KIT FOR THE MAIN BREAKER Some existing circuit breakers near the main will need to be moved to make room for the generator breaker.  Then you need to order the correct generator interlock kit that is approved for your circuit breaker panel. On newer electrical panels many manufacturers make an accessory interlock kit.  If you read the labeling inside of the panel carefully you should see a part number for the interlock kit for your panel.  You may need a magnifying glass to read the label. If your main circuit breaker panel is older you might be able to obtain a third party manufacturer interlock kit.  The interlock kit shown on this post was made and sold by InterlockKit.com.  The photos below depict the interlock kit installation onto a GE main circuit breaker panel that was originally installed in the 1980's. Before beginning the job of installing an interlock kit on an existing main electrical panel, you should apply for an electrical permit at your local building department.  Include a copy of the interlock kit installation instructions with your permit application.  I always include a brief one page description of the work being done with my permit applications if I cannot fit all of the information on the permit application form. Wording such as "Electrical work consists of the installation of a third party manufactured interlock kit on an existing 150 amp, 30 circuit GE main electrical panel.  A new 50 amp sub-panel is to be installed for relocated circuits.  Generator inlet to be installed outside next to garage door" is something that I probably used with the permit application for the installation depicted in this post. I had a permit application for an interlock kit installation rejected once.  After I submitted the paperwork, I received a call from the electrical sub-code official.  He said that the state was no longer accepting the laboratory testing results of the third party interlock kit.  Consequently I was not allowed to install that particular interlock kit as it would never pass inspection. I contacted the manufacturer and it was confirmed that my state was the only one that was no longer accepting the laboratory testing results from this one particular testing laboratory.  The testing laboratory had stopped doing electrical testing, but their previous tests were good. My state would no longer accept even the previously accepted testing.  The...