Geek On The Hill

First, a disclaimer: This is not an instructional article. It’s just the way I personally connected a portable generator to use to power my house in the event of an outage. It’s not a “how-to” article. It’s a chronicle of a day in my life. Please consult a licensed electrician for all your electrical needs.

This setup was to use an A-iPower 12,000-watt portable generator to power my entire house during power outages. Note that when I say “entire house,” I mean that I can power everything in my house. I don’t mean I can power it all simultaneously. For example, if I want to use a high-draw appliance like the electric range, I can’t use any other high-draw appliances at the same time. But critical things like the lights, the well pump, and the furnace can run all the time.

I decided to wire the generator into the house using a 50-amp circuit to maximize the generator’s usefulness. That meant that every item used in the job had to be rated at or above 50 amps. I consulted my friend (who’s an electrician) as well as the National Electrical Code to make sure that everything I did would meet or exceed national and local code requirements.

If you’re thinking about doing this job yourself, I suggest that you have your electrician run wire capable of carrying 50 amps (which means using 6-gauge wire in most homes and jurisdictions) even if you’re only planning to use a 30-amp portable generator. Heavy wire is very very difficult to snake through conduit once the conduit is cemented. It’s much better to install the higher-capacity wire from the get-go in case you decide to upgrade in the future, and the difference in cost is trivial.

I have a lot of experience doing wiring and I have a friend who’s an electrician whom I could call if I needed help, so I decided to do the job myself. Here’s what I did.

1. I drilled a hole and ran a piece of PVC electrical conduit through it. Then I fished enough wire through the conduit to wire the riser and inlet box. The wire I chose for the hots and common was AWG-6 THWN in red, white, and black, which are the standard colors for 240V installations in the United States. I used green AWG-10 THWN  for the ground.

I used THWN because the codes require wire used in outdoor conduit to be rated for wet areas, and THWN is a lot less bulky and easier to work with than UF-B 6/3. Most THNN wire is also rated as THWN.

2. I dry-fitted the conduit body to the stub of conduit and ran the wires through it, one at a time.

3. I dry-fitted the riser and 50-amp generator inlet box housing and ran the wires through them.

4. I connected the wires to the generator inlet box and the receptacle itself, including the ground.

5. I cemented all the PVC conduit together, attached the inlet box to the wall, and screwed the box closed. I had to notch out the siding to get the cover on. But had I moved the box lower, the screw holes wouldn’t have hit a firm backing. Sometimes life is a compromise.

6. I connected the THWN that I used outside to the 6/3 NM-B (aka “Romex”) wire that I used inside using a standard electrical junction box and wire nuts. The Romex goes to a 240V / 50-amp breaker in the distribution panel.

7. I installed the generator safety interlock in the panel (with the power disconnected, of course). This is extremely important. Every year, linemen die because of idiots who backfeed their generators into their houses without using an approved transfer switch or generator safety interlock. The current energizes the utility power lines while the linemen are trying to fix the problem, and they get electrocuted. So don’t be an idiot. If you’re going to do a job like this, do it right.

What the interlock switch does is physically prevents the main breaker (which is fed by the utility power) and the backfeed breaker (which is fed from the generator) from being “ON” at the same time. That way, when you’re feeding power to the panel from the generator, it can’t energize the line to the pole. It’s simple and inexpensive, but it can save a life.

8. After double-checking all my wiring for flaws and faults, I started up and load-tested the generator, connecting it to the house with a 50-amp generator cord. It worked great. I’m very happy with the generator and the setup. You might even say I feel energized.

Richard