Complications with my situation, options?

Hello! I just came across this project and I am VERY interest.

At my house (near Seattle) I have a very large solar array and various other electric devices (including two electric vehicles) that I wish to monitor the usage of. I currently have a TED 5000 monitoring my overall net usage from the utility, but that's not enough for me.

I have played with Arduinos in the past and I'm an experienced software developer, so OpenEnergyMonitor caught my eye when I started searching for something to use instead of the TED.

My energy monitoring needs are made very difficult by the particular layout of my electrical system, so most off-the-shelf monitors aren't going to meet my needs. I'm hoping that OpenEnergyMonitor is something I can use to get what I want, even if I have to do a bit of coding myself, without spending too much money.

Here's an overview of my electrical layout:

I have placed red arrows pointing to the circuits I wish to monitor, ideally.

As you can see, I have a 200 A panel in my house, which feeds a number of subpanels (in addition to all the stuff in the house). On the house panel, I have two electric vehicle charging stations, each on a 40A circuit (max draw is 30 A on one and 32 A on the other) and a 100 A feeder circuit to the subpanel for the HVAC (a heat pump with electric auxiliary). There's also a 70 A feeder circuit for everything else in the diagram...

Most important is the "shed", which is about 30 meters (100 ft) from the house. This is where the solar PV feeds in to the rest of the system, and where I'd need to place a CT to measure my solar PV output. I can't place the CT inside the house panel because there are other loads on that same circuit which would subtract from PV output.

This is what has complicated my search for a metering device. Because it's so far from the house, the TED 5000 can't pick up its powerline networking signal; it's very picky about its PLC, for some reason, even though I've got HomePlug AV powerline networking for ethernet working over 100 meters (wire distance) away with about 30 Mbps.

From what I've seen so far, it looks like the OpenEnergyMonitor transmits information via radio. However browsing the forums, it sounds like the range of this might be quite limited, certainly not near the 30 meters I'm talking about (which includes probably 6 wood-framed walls in the way).

So I'm seeking opinions about the best way to approach this. Would my only choice be to have a base station in my "shed", in addition to one in the house?

Let me know what you think. Please ask if you have questions I might be able to answer to help you formulate your own answer.

Thanks!

sumnerboy's picture

Re: Complications with my situation, options?

Can you, or do you, have ethernet cabling between the house and shed? It is relatively easy to build an Arduino + ethernet shield + EmonTX shield and modify the sketches to publish sensor values over ethernet, rather than RF. This is what I am doing, not because of a situation like yours but because I prefer hard wiring than RF.

octagon's picture

Re: Complications with my situation, options?

sumnerboy I would be very interested in an ethernet one - but that can do 12 inputs as well... 

Robert Wall's picture

Re: Complications with my situation, options?

I wouldn't write off radio quite so quickly. The old RFM12B radio modules allegedly can work over 100 m given a clear line of sight, and I've had no trouble receiving data from a battery-powered emonTH over a clear line of sight of 30 m, nor over about 12 m then through a 2 feet thick stone wall. The new RFM69CW modules can have a higher transmit power than the RFM12B, so if you are able, it would be well worth trying the radio option first.
But like Ben, I too would prefer hard wired if it's convenient and cost is not an obstacle.

JD's picture

Re: Complications with my situation, options?

I've installed a setup similar to yours, except there are 3 solar arrays around the property instead of one solar array an electric car and generator.  There are 3 emonTX's supporting 12 CT's measuring the various circuits, and lots of calculated feeds created by subtracting one thing from another as you have proposed.  The feeds are created on the server side in emonCMS, and there is little modification of the Arduino code needed (only calibration and changes to accomodate 600A CT's for the main).

One of the solar arrays is on a subpanel in the back of the property, about 600ft from the base station in the barn.  The standard antenna setup didn't have the range to bridge this gap, but a trip to the ham radio store returned a 7 element 440mHz yagi antenna, which blasts through with range to spare.

On another customer's site I used a second emonBase to solve the distance problem as there was internet available at the remote building - works fine and cost about the same as the $100 ham radio antenna.

Atttached is a pic of the antenna setup.

Dashboard for the property:

http://data.peakmonitor.com/proto3

yagi antenna

Computerizer's picture

Re: Complications with my situation, options?

Thanks everyone for your helpful responses.

I do have Ethernet in the shed (via PLC), so if the Ethernet shield works then that sounds like a great option for me if the wireless doesn't work. Is there a link that describes what changes would need to be made to the Arduino sketches to make that work?

Also, it sounds like there are changes that need to be made to make an enomTX work in the US. Is there a step by step guide for this somewhere?

Ideally I'd not like to have to spend too much time on this project myself.

Thanks again!

Robert Wall's picture

Re: Complications with my situation, options?

I can't answer the bit about Ethernet, Ben (summerboy) should be able to help there.

As for the emonTx, you probably need a larger CT, both for current rating and the aperture, and that implies changing the burden resistor(s) on the emonTx PCB. I've written about this very many times in the forums, try searching here for "USA" and "Magnelab".

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