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

This is Part 2 of the “Connecting a Portable Generator to the Home Main Electric Panel” series. You may want to read Part 1 (click here) first to get the necessary parts.

REQUIRED PARTS / TOOLS

• ~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;

Wrap up

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!