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bennelson 07-12-18 09:53 AM

Simple Solar Instrumentation

Last summer, I built a 6.24kW solar array on my garage. It uses Enphase micro-inverters. Overall, I love it EXCEPT that there's no real-time power display!

The system uses power line communications for the individual micro-inverters to talk to an internet gateway called the "Envoy". That in turn feeds data out to Enphase's servers, where I can check my power production.

In fact, you can see my power production too. Look at it here:

However, the Envoy itself doesn't have a display on it. (It has a few LEDs indicating power, communications, etc., but not how much power I'm making.)

So, I set to work to add a basic Ammeter/Voltmeter to my setup. I bought one off Amazon for about $20, which comes with a current transducer. That's one of those ferrite rings with two wires coming off of it.

I turned off all the power, disconnected one of the solar power leads from the load-side connection breaker and slipped on the Current Transducer, then hooked it up again.

On the side of my breaker panel, I knocked out a 1/2" hole and connected a 4" metal box with a 1/2" conduit spacer.

I took a single-gang metal cover and ground away most of the tabs that would normally mount the screws for a switch or outlet. That made the hole in the cover almost exactly the right size for the panel meter.

The meter also needs power to operate. Instead of tapping power off some other circuit, I added a plain 15A dual-pole breaker dedicated to it, and then ran a pair of 14 awg stranded wires from the new breaker into the 4" box.

The multimeter has 4 screw-down terminals, 2 for the signal wires from the current transducer, and two for power. I made the connections, snapped the panel meter in place in the cover, and then screwed down the cover.

I turned the power on. Other than realizing how easy it is to install the meter upside-down, everything looked good. I re-installed the panel right-side-up, and called it a day.

With the power back on, I can now see in real-time Voltage, Current, Power, and Energy on the display. It's basically a permanently mounted 240V Kill-a-Watt. I like the blue backlight. Looks nice and is very easy to read.

More details at my blog:

I was also on Facebook and another user on a group there reminded me about It's a web page which you can push solar production data to, and then share from. I looked at it a while back, and meant to get back to it.

So, last night, I dug through and figured out how to get my Enphase Envoy to send data out to that web page. (I don't even know what an API is, but if it works, it works!)
You can now see live system data from my garage at:

What's neat about that is it's non-proprietary, and data can be pulled and displayed in different ways on web pages, shared, etc.

So, I now have a real-time meter in my garage which responds INSTANTLY to changes in power production AND a new way to add a solar production output graph to my blog!

pinballlooking 07-12-18 01:25 PM

1 Attachment(s)
Looks good.
You can login to the IP address of your Envoy. (You probably know this)
I have the older Envoy that shows how many microinverters are communicating and the output power being made.

I do like PVoutput it is a great way to share your solar output.

where2 07-18-18 06:07 PM

I've got two generations of the older Envoy with a display (one in FL, one in Maine). One can use a USB wifi stick to communicate, the other will not recognize it due to the age of the unit.

I'm also quite familiar with those display units Ben used, and that's a great implementation of how to use one.

I need to play in the world of API's one of these days...

bennelson 07-18-18 08:41 PM

I know! The OLDER Envoy HAD an LCD display on it, and the newer one (which I have,) DOESN'T!

In what world does it make sense to have FEWER options and information?!

Again, I love all the data I can get through the software, but I really just wanted a real-time display. That's it. Is that too much to ask for!?!? :D

where2 07-19-18 09:09 PM


Originally Posted by bennelson (Post 59528)
...but I really just wanted a real-time display. That's it. Is that too much to ask for!?!? :D

Would it not be possible to put a raspberry pi or arduino device on the network to query the API or envoy? I know both Pi's and Arduinos are available with wireless networking these days.

My envoy in FL lives in the laundry room, despite having the LCD display. Unfortunately, the whole envoy device isn't particularly suited for hanging on a wall for everyone to see. I'd love to have a better display front end for PV output. The TED5000 I have was intended to act as a better display, but it has some shortcomings...

bennelson 07-19-18 09:29 PM

Yes, you can have an internet device ping the Envoy for data, but it's still not real-time. It's five minute increment posts at best. And then that's actually an average of the power over that amount of time.

It all depends on what you are doing. If you want to track data, or if what the sun was doing 5 or 15 minutes ago is good enough for your application, then yes, pinging the Envoy through API works great.

Frankly, about the only thing I know about API is that it's a way to get data somewhere else. Still, I did manage to stumble my way through the settings to pull data from the Envoy and post it to I need to play around with that some more.

I would be fun to have just a giant display to put on your wall which simply shows how much solar power you are making right now. Seems totally doable with a micro-controller and wireless.

Elcam84 07-23-18 08:28 AM

How is it measuring 220v when it only has one inductive pickup? Is it just seeing one leg and just doubling the amp value?

Wendys used to have a system that monitored power usage into the main disconnect panel. Every remodel I found the inductors left in the panels because whoever took them out just snipped the wires and left them in. They ditched the system because yes it was neat to have that info but it was just an expense and had no energy saving value.
I wish I would have saved those inductive pickups. Might have come in handy... They had them on every breaker feeding each panel. 150 to 300 amp panels usually and normally 3 per store on the old ones.

bennelson 07-23-18 12:14 PM

On a 240V circuit on the U.S. split-phase system, a complete circuit has current flow moving through one hot wire and returning on the other hot wire. The Current Transducer just has to be anywhere on that circuit. (ie - it's just slid over the one wire.)

The two wires going to power the display connect to a 240V connection not only to power the display, but also to let it know the voltage. By multiplying voltage and current, power in watts can be known and displayed. Multiplying that by clock-time gives energy in watt-hours.

If you wanted to measure current on two different 120V circuits (each on the two legs of the 240V system), you would need a CT on each of the two hots. Most total home energy monitors include two CTs for exactly that reason.

Elcam84 07-23-18 02:48 PM

By only having one inductor you are assuming the load is balanced. Now this being a power supply and not a load the inverters should be putting out power balanced on both hots but when only monitoring one leg you don't know for sure.

I have three amp meters that I put on panels to see how imbalanced the loads are and move breakers around to balance out the loads on a panel. With a mix of 3 phase 220 and 110 its interesting. I wish everything everywhere was three phase...

bennelson 07-23-18 03:42 PM

No assumptions here.
It's 240V ONLY. There CAN'T be any imbalance. All the power flowing through the black wire is also flowing through the red wire.

If this was inside a breaker panel or someplace else mixing 120 & 240, then yes, a person would need two CTs.

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