Electric Boxes for Solar Roof

by Ben N on May 28, 2017


I had to double-check and saw that it’s been over TWO WEEKS since my last solar garage update. I’ve just been busy, working out of town and on the weekends.

In the time that I’ve had, I’ve chipped away at getting the racking installed over the course of several evenings. After that, I also installed the micro-inverters and trunk cable.

Today, I got to take a look at what I plan to do for the electrical junction boxes on the roof. I have three sections of 240V trunk cable – one for each row of eight solar panels. Each of those cables needs to go into a junction box where it can connect to plain 12 ga wires and get routed through conduit down to the side of the building. From there, it will go into an AC Disconnect and then finally into the building to the main circuit breaker panel.

I purchased several outdoor rated plastic electric boxes. One was a plain double-gang box. The other two were 6″x6″x4″. The nice thing about the double-gang box is that it already has threaded holes on it for conduit adapters to thread right in. However, it’s a relatively small box, but big enough to connect my Enphase trunk cable to some standard 12 ga wire and send it down the conduit.

At the other two boxes, I need a little more space. There will be more total wires coming through and two of the three rows will be connected in parallel. Connecting them all together would be too much current for the 12 gauge wiring, whereas having each on its own would require another circuit. Those boxes are also deeper. That will allow space for connecting the conduit and having it run UNDER the racking.

IMG_4807The larger boxes are plain, there’s no holes in them. I drilled two 1 inch holes so that I could insert a threaded 3/4″ conduit connection. I also drilled a 3/4″ hole so that I could add a 1/2″ watertight connector for the trunk cable to enter. I also made sure to use silicon sealant at all the ports and the drilled holes to make sure they stay weather-proof.

Each of the three boxes just gets mounted to the Iron Ridge racking with self-tapping screws. This past Thursday, I attended some solar training sponsored by Iron Ridge and Enphase. I asked the Enphase representative about the “proper” way to attach junction boxes to the racking for their system and mentioned that I had trouble finding the right brackets. His response was that they used to make those but stopped because “Everyone just screwed the boxes right to the racking anyways…”

So, while just using a few screws to connect the boxes feels like a very low-tech solution and perhaps not the “correct” way, it turns out that’s how everyone was ┬ádoing it anyhow!

I also cut two pieces of 3/4″ plastic conduit to run from the top box to the middle one and from the middle to the bottom box. I’m still trying to figure out the best way to wrap the conduit around the edge of the roof and have it visually look okay. I might just buy some spare PVC conduit parts to have handy so that when I do get the electrician over, we can come up with a solution together while minimizing the time (and thus cost) of having the electrician there.

I also need some blocking to which I can attach my AC Disconnect. We don’t have the siding up yet , and we will want a nice flat surface for the disconnect. My brother (who is the one with all the construction experience, and acting as my general contractor for the garage) said that he would make up some blocking for me for the disconnect. Then we can put up the siding around it when we get to that point.

IMG_4809I haven’t cemented the PVC conduit yet. First, I just want to make sure that everything lays out right. I also ran into a problem with the 1/2″ waterproof connectors I was using for the trunk cable. The connectors are rated for cable thickness up to exactly the thickness of the cable that I’m using. When I was at the store, I even tested one on a sample piece of my cable. It worked fine in the store and again at home later. Of course, once I was on the roof, it was nearly impossible to thread on the connector. It was as though the cable was just a little too thick, and I couldn’t get the threads started. Even when I did, the plastic connectors would cross-thread and distort. I was able to get two of the three connectors to tighten down, although I wasn’t real confident with them. I might have to head back to the store and see whether or not the 3/4″ version of the same connector will work or not.

As it is right now, I’m expecting the electrician to come out at the end of the week. (Unfortunately, the weather report suggests thunderstorms that day!)

I’ve also been trying to nail down my roofer on a date. He did a fantastic job on the metal roof and has a man-lift which would be perfect to get the solar panels up. With my experience so far, I really don’t feel that there’s any good safe way to install the panels on the roof WITHOUT some sort of power equipment. The roofer would be able to provide both the equipment and the experience to operate it. He would also transport it to and from my property. Add that all up, and it makes more sense to hire a guy and his gear for a day then try to go rent something and transport it myself.

I talked to him last week. He’s been very busy too, but has promised me a day to work on my project. I’m hoping to hear back from him after the Memorial Day Weekend.

At this point, the solar project feels like it’s in a holding pattern. I’m also trying to think of the best way to make sure the solar panels go on STRAIGHT and LEVEL when I put them up. In my experience with things like shingling, we usually used measurements and chalk lines. With the solar panels up on the racking, there’s no easy way to compare them to a chalk line. (No idea how well that would work on a metal roof anyways!) Perhaps I’ll just stick a large square behind the panels and make sure it’s at a right-angle to the racking. I’m pretty confident on the overall racking installation. One other reason why I’d like to hire the roofer is not just for his man-lift, but also for the experience he has making things square and level.

The MREA Energy Fair is coming up real soon and my goal has always been to have the solar up and running by then. Besides the installation, I still need the electrical inspection AND have the Power Utility to do a test before I can commission the system. Who knows how long THOSE take to happen!

I hope that THIS becomes the week that I REALLY get something done on my solar, but it is heavily dependent on other people’s schedules…


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