Solar Monitoring

by Ben N on July 9, 2018

I LOVE my garage solar array! The only thing I don’t like is the fact that I can’t see how much power it’s making RIGHT NOW! Sure, I have software which gives me TONS of info about the system, but it requires a computer or smart phone, internet access, and username and password. Can’t I just have something simple to show how much power I’m making?

A while back, I saw that a friend installed a simple an inexpensive panel meter to track how much power his electric car charing connection was using. It sounded like a great solution for me to display my solar power in real time. So, I went on Amazon and ordered a versatile 100A display. (https://amzn.to/2zzkuLh) This unit displays Voltage, Current, Power, and Energy – all in real time on a nice little back lit display.

Not only that, but the dimensions are pretty close to fitting right inside a single-gang metal electrical box cover. By grinding away a little of the tabs on the box cover, the multi-meter display should snap right into place.

I started the installation by turning off the power – Solar AC Disconnect, 30A load-side connection breaker, and my 100A main breaker. Next, I took off the breaker panel cover so that I could get at the wiring. The current transducer (CT) goes around a wire to measure the current going through it. It works on the principal that the flow of electricity (current) creates a magnetic field. The CT picks up this magnetic field and converts it to an electrical signal. I disconnected one of the legs of power from my solar circuit breaker, slipped the CT over the wire, and then connected the wire back up.

On the side of the breaker box, I removed a 1/2″ knock-out and installed a short connector. On the 4″ metal box, I removed a matching 1/2″ knockout and connected the box to the breaker panel. Since the box was a bit away from the wall, I slid a wood block behind it for support.

I ran the small and short CT wires into the 4″ box.

Next, I added a 15A 2-pole breaker to the breaker panel. This supplies the 240V power for the multimeter. I connected two pieces of 14 AWG wiring from the breaker into the 4″ box.

Next, it was time to make the panel meter fit the single gang metal cover. I used a Dremel rotary tool to grind away almost all of the two tabs which would normally take the screws of a single-gang device. Once done, the panel meter can snap into place.

Back at the 4″ box, I connected the two small CT wires and the two 14 AWG power wires to the meter. I then pushed it through the single-gang cover, snapped it in place, and then screwed down the cover.

Finally, it was time to turn the power on. I turned on the outdoor AC disconnect, the 30A load-side connection breaker, and the 100A main breaker. Other than realizing that I installed the panel upside-down, everything was working well. I killed the power, spun the meter right-side up, and turned power back on again. At this point, the solar STILL wasn’t making any power. That’s because of the Anti-Islanding safety feature. With a “Grid-Tie” inverter system, the inverters will NOT send out power if they do not sense utility power. This prevents sending out power during a blackout and injuring or killing utility workers trying to fix the problem. Even after power is restored, the system waits five minutes before outputting power. (Often, when power is restored after a blackout, it immediately fluctuates in frequency goes out again, etc.)

After the five minutes were up, I the meter displayed the power I was now outputting. Unfortunately, it had turned into a cloudy afternoon, and I was only making about half the power I could on a sunny day. Still, I KNEW EXACTLY how much power I was making, and could watch it change in real-time as the clouds came and went!

I’m very happy with this display so far. The panel meter itself was very inexpensive, the backlight makes the display very readable, and it fixed the ONE thing I didn’t like about my solar array!

I’ve also played around a bit with using an Arduino to read current. The neat thing about that is an Arduino also has the ability to control outputs and run “IF…Then” statements. It wouldn’t be too hard to design a setup with a micro-controller which could turn power ON and OFF to an EVSE (Electric Car Charging Station) based on if the solar was making enough power to run it or not. Even more exciting, and Arduino could actually generate the signal that the EVSE sends to an electric car telling it how much current it could draw. Instead of a simple ON/OFF, a car could charge at a varying rate, depending on how sunny it was!

Make sure to subscribe to this blog and my videos so you don’t miss that future project!

Until next time, stay charged up!

-Ben

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