Generator Interlock Kit for a Cutler Hammer Loadcenter

 

Dear Mr. Electrician: How do I install a generator inlet box to supply portable generator power to my Cutler Hammer main circuit breaker panel so that I can power all of my circuits.

AnswerA generator interlock kit works best 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 Below are step by step photos depicting an interlock kit installation on an older Cutler Hammer main circuit breaker panel.  A YouTube video depicting the same installation is at the bottom.

This 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 CH panel requires three spaces on the top right.
This 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 CH panel requires three spaces on the top right.
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
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 circuit tracer is handy for tracking down circuits throughout the house.
This is the location that the homeowner chose to have his portable generator sit and operate during a power outage.
This is the location that the homeowner chose to have his portable generator sit and operate during a power outage. The open door is the entrance to the garage
The hole in the wood siding was made using two spade drill bits. First a 7/8" bit was used to drill an 1/8" deep hole to allow for the button connector. A 1/2" drill bit was used to drill all the way through into the basement.
The hole in the wood siding was made using two spade drill bits.  First a 7/8″ bit was used to drill an 1/8″ deep hole to allow for the button connector. A 1/2″ drill bit was used to drill all the way through into the basement.

 

The 10/3 Romex which will be entering the rear of the generator inlet box.
The 10/3 Romex which will be entering the rear of the generator inlet box.
Duct Seal was used to seal the hole from air and moisture.
Duct Seal was used to seal the hole from air and moisture.
A button type Romex connector was used to prevent the 10/3 Romexfrom being pulled out. The generator inlet box was secured to the wood siding using #8 x 1-1/2 inch pan-head sheet metal screws.
A button type Romex connector was used to prevent the 10/3 Romex from being pulled out.  The generator inlet box was secured to the wood siding using #8 x 1-1/2 inch pan-head sheet metal screws.
Note how the number 10 bare copper ground wire is shaped in the rear of the generator inlet box and then wrapped around the green ground screw using the included clamp.
Note how the number 10 bare copper ground wire is shaped in the rear of the generator inlet box and then wrapped around the green ground screw using the included clamp.
The PB-30 generator inlet box comes with a factory installed green grounding pigtail. Consult article 250 in the National Electrical Code for information on grounding.
The PB-30 generator inlet box comes with a factory installed green grounding pigtail. Consult article 250 in the National Electrical Code for information on grounding.
Here is the finished generator inlet. It just needs a small bead of clear caulk at the top to keep water from getting behind it. Article 702 in the National Electrical Code pertains to generator installations, but other articles in the code book also apply to the wiring methods used in this installation.
Here is the finished generator inlet. It just needs a small bead of clear caulk at the top to keep water from getting behind it.  Article 702 in the National Electrical Code pertains to generator installations, but other articles in the code book also apply to the wiring methods used in this installation.
You can see the 10/3 Romex as it penetrates through the drilled hole in the rim joist in order to come into the back of the generator inlet mounted outside.
You can see the 10/3 Romex as it penetrates through the drilled hole in the rim joist in order to come into the back of the generator inlet mounted outside.
Duct Seal was also used inside where the 10/3 Romex penetrates through the rim joist to prevent air from coming into the basement.
Duct Seal was also used inside where the 10/3 Romex penetrates through the rim joist to prevent outside air from coming into the basement.
The 10/3 Romex is secured to the rim joist using BX staples.
The 10/3 Romex is secured to the rim joist inside of the basement using BX staples.
This is an older house. The orange 10/3 Romex stands out against some of the original wiring and pipes.
This is an older house. The orange 10/3 Romex stands out against some of the original wiring and pipes.
The 10/3 Romex is stapled along the rim joist using BX staples.
The 10/3 Romex is stapled along the rim joist using BX staples.
See the 10/3 Romex cable fit in between the existing cables leaving the Cutler Hammer loadcenter.
See the orange 10/3 Romex cable fit in between the existing cables leaving the Cutler Hammer loadcenter.
A two screw metal Romex connector was used to secure the10/3 Romex to the CH circuit breaker panel.
A two screw metal Romex connector was used to secure the10/3 Romex to the CH circuit breaker panel.
Note how tightly twisted together the #8 wires are before the blue wire connector is screwed on.
Note how tightly twisted together the #8 wires are before the blue wire connector is screwed on.  The existing #8 copper conductors for the stove were too short.  Pigtails were added so that the stove circuit breaker could be located further down to make room for the generator circuit breaker.
Here's a close shot of two Ideal 30-454 Wing-Nut Blue Wire Connectors being used to splice short pieces of #8 copper wire to the existing stove feed wire. This was necessary in order to relocate the existing stove circuit breaker down a few spaces to make room for the generator circuit breaker.
Here’s a close shot of two Ideal 30-454 Wing-Nut Blue Wire Connectors being used to splice short pieces of #8 copper wire to the existing stove feed wire. This was necessary in order to relocate the existing stove circuit breaker down a few spaces to make room for the generator circuit breaker.
The generator circuit breaker with the wires attached. The space below the generator breaker is needed for the operation of the interlock kit. Note the label above the Ideal 30-454 Wing-Nut Blue Wire Connectors. It is attached to a strap that is holding the generator circuit breaker in place and is required as per the interlock kit instructions. Without the label attached, this interlock kit installation would fail the electrical inspection
The generator circuit breaker with the wires attached.  The space below the generator breaker is needed for the operation of the interlock kit.  Note the label above the Ideal 30-454 Wing-Nut Blue Wire Connectors.  It is attached to a strap that is holding the generator circuit breaker in place and is required as per the interlock kit instructions.  Without the label attached, this interlock kit installation would fail the electrical inspection.
An inexpensive circuit tracer comes in handy when trying to identify important circuits before you have a need to turn on the generator.
An inexpensive circuit tracer comes in handy when trying to identify important circuits before you have a need to turn on the generator.  You could also just flip the circuit breakers off and on to see what goes out.
The upper red arrow points to the generator ground connection. The lower red arrow indicates the white neutral wire connection. This is the main panel so the ground and neutral are connected on the same terminal bar. In a sub-panel the ground and neutral would be kept separate.
The upper red arrow points to the generator ground connection.  The lower red arrow indicates the white neutral wire connection.  This is the main panel so the ground and neutral are connected on the same terminal bar.  In a sub-panel the ground and neutral would be kept separate.  Only a generator with an unbonded internal neutral/ground can be used to temporarily power this house.
These are the holes that were made using the included drill bit. It is also required to scrape and file the perimeter of the holes so that the screws can make good contact for grounding of the interlock kit.
These are the holes that were made using the included drill bit.  It is also required to scrape and file the perimeter of the holes so that the screws can make good contact for grounding of the interlock kit.
Here are the holes with the screws in them and the interlock kit mounted on the front side.
Here are the holes with the screws in them and the interlock kit mounted on the front side.
This is the completed interlock kit installation on an older Cutler Hammer type CH circuit breaker panel (AKA Loadcenter). The interlock kit functions as a transfer switch without having to install a separate box with additional wiring that also requires additional wall space.
This is the completed interlock kit installation on an older Cutler Hammer type CH circuit breaker panel (AKA Loadcenter).  The interlock kit functions as a transfer switch without having to install a separate box with additional wiring that also requires additional wall space.
The red tape marks on some of the circuit breakers are there so that the homeowner can easily identify some of the critical circuits that will require generator power. These include the heating system, the well pump, and the refrigerator. The bathroom and kitchen lighting circuits are also identified.
The red tape marks on some of the circuit breakers are there so that the homeowner can easily identify some of the critical circuits that will require generator power. These include the heating system, the well pump, and the refrigerator. The bathroom and kitchen lighting circuits are also identified.
Installed Interlock kit on a Cutler Hammer Circuit Breaker Panel
Installed Interlock kit on a Cutler Hammer Circuit Breaker Panel. The interlock kit prevents the generator circuit breaker, located in the upper right column, from being “On” at the same time as the main circuit breaker. The labeling is an integral part of the installation and must be in place to pass inspection.