OpenEnergyMonitor Community

Three phase & solar setup help


I have recently purchased and setup some emon gear and clearly need advice on how to set it up correctly. I have an emonpi and 2 x emontx. I purchased plenty of CT clamps (one for each device input) which is probably too many. When I ordered them, I requested both emontx be supplied with the three phase firmware and each has a unique nodeID.

I’m in Australia and have three phase mains power and also three phase off-peak/controlled load for in slab heating (both three phase setups have their own smart meter). I also have a 10kW solar system with two Sunny Boy inverters.

When I was ordering my emon gear I assumed that I needed the following:
1 x emonpi to monitor the Solar inputs - two CT’s (one to monitor each inverter)
1 x three phase emontx to monitor the main three phase usage - 4 CT’s (to monitor each of the three phases + neutral)
1 x three phase emontx to monitor the off-peak three phase usage - 4 CT’s (to monitor each of the three phases + neutral)

I was hoping to sum:

  • the two solar inputs to give the total solar generation
  • the three mains phases to give the total mains usage
  • the three off-peak phases to give the total off-peak usage
  • total mains usage + total off-peak usage to get total household usage

The goal was to feed the above data into the local emoncms My Solar App to provide a view of current use, solar generation and thus how much we were importing.

My electrician has kindly drawn up the attached diagram for me to help me get a view of the meter box wiring. As an initial start we have added the CT clamps as shown in the diagram.

I am getting readings from the CT’s but the numbers seem very low for both usage and solar generation.

To start simply, the other day the two CT’s that are monitoring the two solar feeds were showing a combined total of 410w:

At that time, the two inverters were showing 715w and 826w each:

I did see the Type 1 and Type 2 sensor installation diagrams (here but I don’t understand how they relate to my multi-three phase and solar wiring.

I am really unsure how I should be setting up the CT’s and I’m hoping the community can offer some guidance on the right way to setup my system.

OK, I’ll try my best. On the basis that your diagram uses red for the three phase conductors and blue for the neutral…

You bought two c.t’s too many. A c.t. on the neutral will only tell you the vector sum of the three phase currents - which doesn’t mean much to you. Ideally, when everything is balanced across your three phases, that current should be zero. You’d have saved some money if you’d asked first.

The PV infeed is single phase - is that correct?
Are there four cables there, or two twin cables? If you put your c.t. around a twin cable containing both line and neutral conductors (see the photo on that page you link to), you will not read anything except noise. What are the individual powers, and how do they relate to the inverter displays?

You don’t mention a.c. adapters? Do you have an a.c. adapter for each emonTx and for the emonPi? The a.c. adapter is absolutely essential for the emonTx’s, without it the software cannot lock to the mains wave and so cannot measure the powers. You might be able to get away without an a.c. adapter for the emonPi, but what you measure will be a best guess at the apparent power, based on an assumed constant value for the voltage, not the real power.

Have you read the documentation that comes with the 3-phase sketch and set up the emonTx’s according to that? Update to 3-Phase PLL sketch .
I take it you didn’t buy a programmer, so you won’t be able to make any changes to the software.

If your diagram is accurate, i.e. you are measuring the house consumption on the house side of the point where the PV is connected and you’re measuring the PV input entirely separately, you have a “Type 1” set-up.

If you were to move the three c.t’s so that they are on the grid side of where the P.V. connects, you would have a “Type 2”.

The names “Type 1” and “Type 2” are OEM’s own, and relate to the values you know and how you arrange the equation [Total Use] = [Grid] + [PV].
In a “Type 1”, you measure [Total Use] & [PV], and derive [Grid].
In a “Type 2”, you measure [Grid] & [PV], and derive [Total Use].
Note, we measure imported, used, and P.V. generated powers as positive.

In terms of the diagram, you must sum the set of three phase powers measured at “Main Sw house” to get [Total Use] or (power1) in the description, as a single Feed; and likewise sum the two PV powers to get [Total PV] or (power 2) before you can use them in emonCMS “My Solar”.