3 phase solar setup

Is there a guide to setup “my solar” app view with 3 phase solar, or someone there can help me with the setup over teamviewer?

Hi Bruno,
I am looking to do this soon, so will be interested to see what is done - so no guide per say.

I have been running my three phase OpenEmon with an emonPi and a couple of EmonTX units, getting the vrms feeds for all phases. It took a while to work out, but I have the power input from the EmonPI going to a number of feeds, one of which collates the two other power inputs from the TX units, for a total use figure, and another one that collates the kWh totals. These then are used for the app inputs. Doesn’t give a separate phase graphing, but it allows a total picture to be seen.

This seems to be working - although I am getting some occasional negative use figures off the phase with the lowest (almost non-existent) use - filtered out as >0 for the feeds. I am also getting the kWh drop off a cliff result when the power is interupted, i.e the incremental kWh count drops to zero again and starts rising when the power is turned on.

I am anticipating doing the same feed setup for the solar input as well.

As an aside, it is fascinating seeing the voltage feeds, as two are floating around the high 240v to 250v range and one is dropping into the 215v range. I am presuming that the houses around with solar are on the two high feeds. I am in Australia, so 230v is the target.


Did you successfully set up the solar feed in part?

I’m asking because I’m part way through a similar setup myself. 3ph from grid with a single phase PV system and I’m contemplating adding another single phase PV on one of the other phases soon, so I thought I might as well go the whole journey and monitor everything.

I’m currently monitoring one phase input and the PV output using an Emon Pi. If I add the next PV, I was planning on adding 2 x TX units with one phase on each of the TX or Pi units and one PV each on the TX’s. All 3 units will have their own voltages from the phase being measured.

Are you using the standard single phase sketch on each of your units (ie monitoring each phase as a separate item and adding the feeds for a total) or are you using the 3 phase sketch?

Thanks in advance.

Hi Geoff,
Yes, I have it monitoring all three phases. It is using the standard single phase sketch. I have an emonpi and two emontx units, each one monitoring a phase of both grid and solar, as well as the voltage. Given the voltage off my local sub-station is running one phase below spec and two phases above spec, I was glad I did.

It took a while to work through the input processing to feeds, but I can now bring up an aggregate solar App view, as well as for each individual phase (I have solar feeding all three phases separately). I have probably more feeds than I need, but it was useful to work out the correct connection of the CTs to the appropriate paired solar/grid phase.

Here are my input feed process lists

Phase 1 Grid process list setup (Power 1 input on EmonPI)
1 Log to feed log emonpi: Phase 1 raw
2 Allow positive > 0
3 Log to feed log emonpi: Phase 1 Import
4 Power to kWh kwh emonpi: Phase 1 Import kWh
5 + feed + feed emontx3: Phase 2 Import
6 + feed + feed emontx4: Phase 3 Import
7 Log to feed log emonpi: All-Import
8 Power to kWh kwh emonpi: All-Import-kWh

Phase 1 Solar generation process list setup (Power 2 on EmonPI)
1 Log to feed log emonpi: Phase 1 Solar generation
2 Power to kWh kwh emonpi: Phase 1 Solar generation kWh
3 + input + inp Node 8:2 Phase 2 Solar generation
4 + input + inp Node 7:2 Phase 3 Solar Generation
5 Log to feed log emonpi: ALL Solar generation
6 Power to kWh kwh emonpi: ALL Solar generation kWh
7 + input + inp Node 5:1 Phase 1 Grid
8 + input + inp Node 8:1 Phase 2 Grid
9 + input + inp Node 7:1 Phase 3 Grid
10 Log to feed log emonpi: All-Use
11 Power to kWh kwh emonpi: All-Use-kWh
12 Reset to Original ori
13 + input + inp Node 5:1 Phase 1 Grid
14 Log to feed log emonpi: Phase 1 Use
15 Power to kWh kwh emonpi: Phase 1 Use kWh

Phase 1 vrms process list setup (power wall wart input on EmonPI)
1 Log to feed log emonpi: Phase 1 vrms

Phase 2 Grid process list setup (power 1 on emonTX 1)
1 Log to feed log emontx3: Phase 2 raw
2 + feed + feed emontx4: Phase 3 Raw
3 + feed + feed emonpi: Phase 1 raw
4 Log to feed log emontx3: All - Raw
5 Reset to Original ori
6 Allow positive > 0
7 Log to feed log emontx3: Phase 2 Import
8 Power to kWh kwh emontx3: Phase 2 Import kWh

Phase 2 Solar generation process list setup (power 2 on emonTX 1)
1 Log to feed log emontx3: Phase 2 Solar generation (573.00)
2 Power to kWh kwh emontx3: Phase 2 Solar generation kWh (29.96)
3 + input + inp Node 8:1 Phase 2 Grid (-372.00)
4 Log to feed log emontx3: Phase 2 Use (201.00)
5 Power to kWh kwh emontx3: Phase 2 Use kWh

Phase 2 vrms process list setup ((power wall wart input on EmonTX 1)
1 Log to feed log emontx3: Phase 2 vrms

Phase 3 feeds are the same as Phase 2, minus the “All - Raw” feeds, and are fed off emontx 2.

Emonpi is attached to the front of the main power board and the two tx units are behind the board (swings out on a hinge). Very crowded, as the enphase monitoring CTs are huge.

Happy to go into more detail if needed.


If it’s not too hard to construct, I’d be interested in a plot of your 3 phase voltages laid on top of each other. I’ve always been a proponent of measuring all 3, although I know in some installations that can be hard to achieve. Any data on just how different they can be is always welcome to help other decide if it’s worth the effort.

I second that. For a long time I’ve been advocating the introduction of a 3-phase unit, with sufficient capabilities to at least monitor two currents on each phase. When such a thing might appear, I don’t know.

Until that does appear, the solutions are as @garnhedryn has done, build your own front end for an Arduino, or live with the assumption that all three phase voltages are equal and use two emonTx’s.

Graph of the three phases.

I have longer logging but disrupted power and mixed up measurements make for slightly messy graphing.

The significant difference between the emonpi and the 2 emonTx’s is probably largely due to the calibration rather than being entirely down to actual difference in line voltage.

Despite the same AC input circuitry and AC adapter, the emonpi and emontx apparently have different Vcal values.

Once upon a time they were both 276.9, possibly each has been independently “fixed” at some point.

This alone could result in around 5% difference regardless of any difference in line voltage or component tolerances etc. I couldn’t say which if any is correct for your setup (in Australia) have you measured any line voltages by any other means to cross ref?

Are they all using identical AC adapters? Are they Aus specific or OEM shop supplied UK ones with an adapter? (I don’t think the shop does Aus AC:AC adapters)

The voltage calibration coefficients for the 3 a.c. adapters from the shop are:

Adapter Type Voltage calibration coefficient for
EmonTx V3, EmonTx Shield V2.5 & emonPi
Ideal Power 77DB-06-09 (UK Plug type) 268.97
Ideal Power 77DE-06-09 (EURO Plug type) 260.0
Ideal Power 77DA-10-09 (US Plug type) 130.0

Note: The values are derived from manufacturer’s data and are subject to normal manufacturing tolerances. The coefficient might be in error by up to ±6% (77DA-10-09 & 77DE-06-09) or ±4% (77DB-06-09) when resistor tolerances are added.

For any other a.c. adapter, the voltage calibration coefficient is the mains voltage that would give 13 V at the low voltage output of the adapter with no load. The latter is important because the adaptor’s output voltage is specified at full load, the no-load voltage can be much higher (it’s 11.6 V rather than 9 V for the 240 V UK one). If the no-load voltage is not specified, then it and the mains voltage must be measured and their ratio used to determine the nominal mains voltage that would give 13 V out.

Under no circumstances must a higher than normal mains voltage be applied to an adapter in order to obtain an output voltage of 13 V.

Correct, but this one has been recommended:
I don’t know the calibration coefficient for it, unfortunately.

Jaycar advise me that the no-load voltage is 10.4 V. That means that the nominal voltage calibration constant is 300.0

That’s the one I used in those early stm32 emonTX shield experiments last year. The one I have (single sample) has a V ratio of pretty much exactly 23. 230V in gives 10V out. I’m not sure how you turn that into a Vcal value, but hopefully you can.

More recently I’ve been doing some dynamic range tests on my energy monitor. It’s designed for direct grid connection with an upper limit of about 270Vrms. I’ve long known it can easily measure all the way down to 90Vrms without changing the dividers, but I was curious just how low that could go. I happened to have one of these at hand so hooked up two monitors sync’d to each other within a few mains cycles, one connected to the mains, the other connected to the output of that transformer. The results were impressive; with 24-bit ADCs you can accurately measure from ~14V up to ~270V with the one set of dividers. But back on this topic, it showed the ratio for that transformer is about 16.58 (again just a single sample).

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Dead simple: The Vcal value is the mains voltage that gives 1 V at the ADC input. There’s a 13:1 divider inside the emonTx / Shield / Pi, so 13 × 230 ÷ 10 = 299.0

[Edit: Jaycar advise me that the no-load voltage is 10.4 V, so the nominal calibration constant is 300.0 ]

That’s the voltage calibration coefficient for the Jaycar adapter - 299.0 300.0

I can’t recommend the M9265A until I’ve checked the input rating of the emonTx power supply - at 14.8 V (with 246 V in), it might be exceeding the rating.

And 246V is relatively low for my 'hood, so you might want to build a bit more of a buffer into that calculation:

The old UK spec was 240 V ± 6% = 225.6 – 254.4 V, so I’d have assumed much the same. It looks as if I wouldn’t have been far wrong. Do you know the nominal centre voltage and the tolerance (and is it the same for the entire continent)?

There’s an Aus/NZ standard centered around 230V for EU harmony, but each state gets to decide when it migrates. Here I found:

The Queensland Government recently confirmed a change in voltage from 240 volts (+/-6%) to 230 volts (+10/-6%) across the state.

That sounds awfully high, that would mean Brian’s corrected voltages would be 257(ish) / 268.97 * 299 = 285.69V for the emonTx’s and 222(ish) / 256.8 * 299 = 258.48V for the emonPi, even the latter is high but 286V sounds way too high, surely?

Is that 10V definitely with no load @dBC ?

It was plugged into the emonTxshield… so pretty close to no load.

I don’t think we’ve confirmed that @garnhedryn is using that VT though. Your analysis makes me think he probably isn’t.

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Hi Brian

Thanks for that information - should save me a lot of setup time.

Out of curiosity with your voltages, are you using a JayCar 9VAC or the OEM UK one or something else?

Just looking at your graph posted later, the voltages for the EmonPi look pretty much the same as when I first plugged in EmonPi with a JayCar MP3027 9VAC transformer. Compared to voltage measurements from PV Inverter, multimeter and logging from a UPS, the JayCar unit was coming up with about 12% lower voltage reading than ‘real’. Plugging the UK one in gave about 4% lower. Real voltage is typically between 235 and 245 for my connection.

Also of note if anyone else is using the JayCar unit, seems that something is wired differently in that compared to UK unit. When calculating Vrms*I using JayCar unit giving +ve value, changing to the UK version without changing anything else comes up with -ve value (ie I also had to reverse the CT after I plugged the UK unit in to get a correct feed value).

I will post on voltages using the TX’s in my installation when they arrive as some comments later on in this thread note differences in calibrations between Pi & Tx - that may explain large voltage differences between phases.

That’s something that there’s no standard for - even (according to @pb66) amongst supposedly identical UK adapters.

Also, we don’t know the phase error of most adapters, so for best accuracy that needs adjusting too.

Due to space constraints I am using one of the JayCar 9VAC recommended (they are huge) with the emonPI, and two of the OEM UKs (smaller but with an adapter for AU plugs). Looks like I need to go through a calibration. I had a quick look early on, but was more interested at the time in getting the appropriate feed processors correct. Looks like I need to read the calibration doco more closely.

I know the high phases are actually high, as my solar cuts out at 255V and and is supposed to come back on <253V. They are cutting out pretty much daily, hence I have the local energy supplier monitoring my feeds at the moment. I am not sure I will get a copy of the results. (EvoEnergy for any Australian’s here).

I don’t know about the low phase, other than I used to blow a lot of incandescent bulbs when the house was running only on that phase, and that is considered a bit of a warning sign that the voltage is low. I changed to fluro and now LEDs, so don’t have that problem

That sounds like an old wives tale to me. Lamp life for an incandescent lamp is proportional to something like the inverse 4th power of voltage (I forget the actual number) - so reduce the voltage by about 10% and the lamp life goes up significantly. Likewise, removing the inrush current has much the same effect.