Germany 3+N Household with additional 1Phase PV and planned EV Car

Hi all,
i have a house in germany with 3phase + N supply and a 1phase PV generator. In future I plan to have a EV car charging box. Further I have a AVM Fritz Box.
I plan to have this all monitored. Maybe, I add gas heating to this monitoring.
3 phase consumption and 1 phase PV generation are strictly parallel and have their own Counters due to german regulations.
Not to forget, I have to measure it all on the basement and my fritzbox is on the ground floor.
Now I wonder if I should buy a IotaWatt with 3 +1 CTs and 1 ACAC voltage sensor or a emonTXv3 with wifi module or a emonTXv3 with emon base?

your help would be appreciated.


There are few people here with detailed knowledge of Iotawatt. I suggest The IoTaWatt forum is a better place to ask a question that is specifically about the operation and use of IoTaWatt. That is managed by Bob Lemaire, its creator, and he and the other users there are more likely to have the specific knowledge to help you.

Regarding the emonTx solution, the first point is that unless you have a solid concrete floor, there should not be a problem with WiFi or with the RFM radios built in to the emonTx - but for that you would need an emonBase (Raspberry Pi + receiver) to receive and save the data.

The second point is you can have optical sensors on your meter (zähler), but it is likely that the LED on the grid connection will pulse only on import, therefore it will not tell you when energy is exported, nor how much.

Will your EV charger be 1-phase or 3-phase? If 3-phase, I would expect that it will only be necessary to measure 1 phase and multiply by 3, but there will be a small error when you do that because the control electronics will load one phase by a tiny amount.

If you have an emonTx with WiFi, what will you do with the data? You can send it to (which will require a subscription at some time in the future), or you can have emonCMS on your own server (which could be the same Raspberry Pi as the emonBase). You can do more with your own emonCMS than you can with, especially if you know Linux & PHP.

One of our contributors in Germany (@Simsala) is very happy with the 3-phase emonTx. He might be able to comment .

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Thank you, I appreciate your help!
There are indeed some open questions. Maybe, I start with the and then switch to my own one.
The probes will be Curent sensors for all phases. Will it be necessary, to use 3 emonTx to have the voltage of all phases for calculation? This is writen in another thread here.

For EV charger, I think, 3 phases will be necessary in future.

Elias (@Simsala) can probably tell you whether you need to measure the voltages of all three phases for accuracy. If your phase voltages are reasonably well balanced, it is probably not necessary.

The same is true for the EV charger. If it takes power equally from the three phases, then it is not necessary to measure all three.

I did not write about your gas heating last time. I think (and I might be wrong) that the Iotawatt cannot count pulses. Each emonTx can count pulses, but from only one source. That is usually optical (from your electricity meter). If your gas meter is compatible, it might also be a magnetic reed switch or a reflective optical sensor attached to your gas meter.

Do you have WiFi in the basement? (Your smartphone might be useful for testing, or can you take a laptop down and put it close to where the meter is, to get an indication of signal strength?)

If you have an emonTx with ESP8266, then you must use either or your own emoncms on a (standard) Raspberry Pi or on another server somewhere (which might be a NAS box).

If you have an emonTx using 433 MHz RFM radio (not WiFi) then you must add a RFM69Pi radio module to your raspberry Pi, then you can use, or your own emoncms, or both.

again, thx Robert!

EV charger will be future. I think, with emonTx or EmonEVSE it will be easy to add.
Unfortunately, the gas counter is in a different room in the basement. So it will need an extra emonTx.

In the electrics room in basement I already have LAN by PowerLAN for my PV inverter. So WLAN will be easy to add.

As Base I would prefer a emonBase. It coould be positioned nearby in basement and from there connected to my home LAN. In this I have a QNAP NAS, which should be capabale for hosting the data.

So for now my biggest question is wether to use 1 or 3 emonTx. Maybe, I start with 1.

Or emonTH, which also can have a pulse input. It is normally battery-powered, but you can supply it with 5 V. Although I think it should be able to work with an ESP8266, I have never heard of anyone doing that. It normally sends to an emonBase.
However, if you can run a cable, then you can use the emonTx in the other room. A 2-wire ‘telephone’ cable is all that is needed, if your gas meter has a magnet that will operate a reed switch. If you need an optical detector, then you might need 3 wires.

If you start with one emonTx and ESP8266, and you can run emonCMS on your NAS, you do not need the emonBase. You can adjust (in software) the calibration of your emonTx, and then decide whether it is good enough compared to your energy supplier’s meter.

[I think Elias must be busy or on holiday.]

Sorry for the late answer! I can’t add much more to @Robert.Wall’s good answers. Personally I am very satisfied with the three-phase firmware which only measures one voltage. The power data on the other two phases are nevertheless very good. But it is of course a question of what exactly one wants to achieve with the measurement. Is it about exact numbers or is it about getting a feeling for how high the consumption of the individual devices is. I can’t give exact numbers yet, but one customer said that the accuracy on the energy was 5% compared to his official electricity meter.

For the measurement of the gas consumption I also use an emonth and have adapted the firmware for a gas meter with reed contact. This is now absolutely reliable.

As Robert has already mentioned, emonCMS might indeed run directly on your NAS, a jeelink would be recommended as receiver for the radio transmission: The JeeLabs Shop - JeeLink (v3c) (this is a kind of rfm2pi, only that it can be plugged into a USB input).
This allows you to use emontx and emonth without emonESP.

Whether emontx or iotawatt is a matter of taste. If you want to build more yourself and you can compile and upload Arduino firmware yourself then emontx. What I like about the iotatwatt is that the data is stored locally on an SD card directly at the measuring device and that you can simply connect different current transformers. Both emontx and Iotawatt can be operated at three-phase connection with only one voltage reference. For the Iotawatt there is also an adapter with which you can connect two more power adapters, but I have no experience with it yet.

I hope this helps a little bit with the decision.

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Thank you guys. You helped a lot.

I will think about IoTaWatt vs emonTX. The option of 3phase coltage reference may be interesting.

As I have a QNAP, it seems not so easy for me to setup emonCMS on it. There is only few help in the net.
So the bucks for a emonBase seem to be a good solution for me.

I was curious myself how exactly the three-phase measurement with only one voltage reference (using the emontx) matches the official electricity meter. I only have a short period now, but the result is really impressive: measuring period 1.5 days, consumption according to emontx 19.9 kWh and according to the official meter 20.1. That’s a 99 % match, not bad!

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Thanks for that. That forces me, to go my way with 1 emonTX. 1% is the accuracy of a calibrated device.

I now plan to buy this stuff:

  • One emonTX with 4 CTs for 3 phases House consumption and 1 Phase PV generation.
  • One emonBase with SD card enclosure and power supply. It will be conneted by LAN to my FritzBox.
  • One Additional LED Pulse sensor for my Gas meter, will be connected by “long” wire

Is there any comment on this? I dont wanna buy things that I have to send back to GB :wink:

Thx in advance

However, the result should still be treated with caution, since the measurement period is too short to be able to make a good statement. In addition, I measured worse values on a single-phase connection with the same setup: 185 kWh (measured by emontx) and 190 from the official meter. This results in a deviation of 3%. That’s why I’m a little surprised myself that the result was so good. However, the meter from the network operator only has to have an accuracy of 2%, so this is not the absolute reference.

I will also try to make some comparison measurements with the IoTaWatt.

As you are from germany, too, I can tell you that voltage varies between the different phases. In my street, we have 5 (5 of 12) of PV installations and they may be on 1 ore more phases. This may shift the voltage of some phases related to sun intensity and used phases. On my phase I see a global variation from 225 - 235V.
±5V bring a variation of about 2%. At the moment(very cloudy) I measure 232V on my PV phase.

So (if there is no other bug in my plan) I will be satisfied with my plan, mentioned above.

That looks good to me. Do you have a UART-USB adapter? You can also leave a comment with your order and ask the shop to kindly flash the three-phase firmware for you. Note that only 4.5 kW can be measured at the fourth CT input of the emontx.

I ordered and kindly asked them, to flash the three-phase firmware on the emonTX.
They shipped today but did not comment regarding my request.
If they didn’t do that, I need your kind help :smirk:

Hi again, now I got the goods. emonbase is working, i cant contact it by the web interface.
But the emonTX seems not to boot.
When I power it with the 9V AC, red LED lights 4 times, then goes to solid red. 12 secs later, it goes dark for 2sec, than goes solid red again.
Sometimes there is a little flicker, sometimes LED goes dark for 2 secs agein but there is no flash like described.
Further, I do not see it in Inputs of emonbase.
Pushing reset does not help. Plug or unplug the CTs does not help

edit: now, powering it with external 5V DC, it works…

The emonTx is starting. The LED flashes 3 times to signify this is the 3-phase sketch - so it would appear that you do have the correct sketch loaded.
It then lights steadily for 10 s while it waits for a possible configuration input via a serial programmer.
It should then light steadily, with a very short dark period every 10 s indicating a radio transmission.
If the LED goes off at any other time, it indicates that the PLL has lost lock. If you have a programmer, you would see something like this printed on the monitor:
emonTx V3.4 CT1234 Voltage 3 Phase PLL example - Firmware version 1.00
Loaded EEPROM config
vCal = 268.97
i1Cal = 90.91
i1Lead = 2.00
i2Cal = 90.91
i2Lead = 2.00
i3Cal = 90.91
i3Lead = 2.00
i4Cal = 16.67
i4Lead = 0.20
Network: 210
Node: 11 Freq: 433MHz
POST.....wait 10s
'+++' then [Enter] for config mode
0.00 0.000 0.000 0.000 0.000 0.00 0.00 0.00 0.00 0.000 0.0000 0.0000 0.0000 0.0000 302.00 Pulses=0  PLL is unlocked 
238.49 0.081 0.000 0.000 0.000 1.65 -47.47 -50.42 0.00 50.075 0.0848 0.0000 0.0000 0.0000 302.00 Pulses=0  PLL is locked 
238.50 0.087 0.000 0.000 0.000 1.53 -0.20 0.07 0.00 50.114 0.0736 0.0000 0.0000 0.0000 302.00 Pulses=0  PLL is locked 
238.51 0.086 0.000 0.000 0.000 1.78 -0.04 -0.14 0.00 50.103 0.0869 0.0000 0.0000 0.0000 302.00 Pulses=0  PLL is locked 

(I have no c.t’s &, no temperature sensor.)

I think your PLL might not be acquiring lock. Why is a difficult question to answer. I wrote the sketch for @Simsala, and as far as I know, you have exactly the same version that he has installed successfully many times, and in Germany too.

In emonhub config, do you have an entry for Node 11, like the example in the sketch?

Do you see anything in emonhub log - a line like NEW FRAME : OK 11 199 0 230 0 44 93 160 145 0 0 0 0 (-65) (but everything after “OK 11” will be different)?

I see you have added "it works". Are you getting input in emoncms now?

I think you might not have enough voltage from your a.c. adapter to supply enough power for the emonTx to work. The power supply was designed for the lower power requirements of the RFM12B radio module.

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Hi Robert, thanks again.
Going to Inputs, I see the data fpr L1-L2 and power4 now.
I will go on getting familar with this things.
It is something new for me :slight_smile:

Now as the data aquisition is running, I see, that the measured voltage is 250V instead of 230V and the Power is to low by a factor of 2. I see it on my PV which has a very exact data measurement and with my 2kW water boiler or similar devices. Is this normal?

The voltage should not be wrong by that amount, but I cannot give you a reason, because I don’t know the exact combination of hardware that you have, and I don’t know which version of the sketch you have and what options are set inside it. You can use DIP switch 2 to change the voltage calibration from the UK adapter to the EU one - but that does not explain all of the 8.8% over reading. The a.c. adapter itself could be wrong by 5%, and the DIP switch setting gives you a further 3.5%, so together, those alone could explain the error. (There are other things that can contribute to an error in the readings - see ‘Learn’ for an article explaining all the possible sources of error.)

The power being wrong by a factor of two makes me suspect that you have the phase sequence wrong. The installation instructions (in emonTx 3-phase PLL User Doc.pdf which you should have as part of the zip file) give detailed instructions on how to use the sketch.

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