I would like to hear, why are you assuming, that this is dangerous…
@radorado,
I have a couple of these (below).
Very nice off-the-shelf integration with Home Assistant.
400v line vs 240v line…
double the voltage, double the danger.
All over Europe we have 230V
first of all thanks all for answers.
All the assumptions were right, yes am from Slovakia and its standard overhere that we have 3 phases. Also somewhere at my house i have 380V (or 400 in current standard? i dont know) plug just for info 
The Shelly 3EM looks fit to my needs right? But the question - will my “old school” electrical guy be able to mount it into the system so it just “start work” ? I already have some shelly devices and they did not work just outside of the box…
and i can integrate it into HA later…
As it seems to be more complex problem than i have originally expected am thinking about solution which will measure ONLY the boiler, which is at the end “eating” most power. If needed, I can set the boiler to consume only 14 kw instead of 21.
What i found on shelly web page is Shelly EM as discussed in previous reply, it is suppsed to be 20A. Woudl it be possible to connect this just to the boiler if it has max 14Kw?
On first glance looks like not considering 230v x 20A = 4,6 Kw (sorry if my assumption is complete nonsense), but what i dont understand also in that link is the “120A clamp”. What does it mean, can it handle the bolier because is “stronger” ?
The mechanical installation is childish easy. If he does not accomplish this, he can return his diplom… 
Software side of it is just not his business, that is yours… 
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well, it’s not that straight. Danger is a ghost. Appears only in unsafe houses. That’s why we have safety rules. And the safety rules on electrical installations are quiet heavy in CZ and SK.
For example, when your home installation is finished and you want to get delivery of power from a distributor, you need a technical safety revision of the whole installation. There will be an inspector, checks your whole house on even that detail level of checking, if the wires in your outlets are not de-isolated for to long distance. (Like: when an outlet has a screw to attach a wire and the needed length of un-isolated wire for the connection is 0.7cm, and you un-isolate 1,8cm, they will request repair.) Without passed revision certificate you will not get connected.
400V~ mostly is used for heating elements and 1 work-outlet, where you can attach for example a welder.
And there the safety goes actually UP! As using a 3 phase welder is much less demand on your installation, than those el-cheapo 1 phase welders, which consume almost all power, that 1 phase 16A outlet provides. No more outages because of over-consumption.
Safety is not so much about Voltage, it is a sum-up of good engineering, clear rules, healthy maintenance and control of a installation.
I live in NL, but born in CZ, got my electrical engineer diplom there. I can tell you, from my own experience, that here in the Western part of Europe there are also straight rules, but no-one controls, if they are maintained. Not with home installations. That’s, why it feels much safer for me on the east side…
@BebeMischa
Agree totally and it applies to the west side of the pond as well.
If 400+V was unsafe then all heavy industry would be unsafe. This is not true. Unsafe comes from bad habits and not following best engineering practice and design (Code in the US). If you don’t know what you are doing then you should stay away from all electrical wiring. Ignorance is not good in this case.
240v can kill you as easily as 400v will.
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This company used to make a nice turnkey solution for measuring 3-phase power consumption. Seems like they are only selling through partners now.
But it looks like there is a nice HA Integration already done.
Hi Rado
Sorry the late answer, but right now a days I started to face the same challenge as you right now.
I have got the same type of the power meter as you (sx5a2 sels 04) and usage of the RS-485 port is for me not the best solution (due to the long distance and aditional wiring from the power-meter to my house). Maybe will be for You usefull the information, that the same task (power metering in grid) can be performed with and additional costs cca. 130 EUR with an external wifi powermeter SHELLY 3EM Shelly 3EM - Shelly Cloud
It seems to be good supported with the HomeAssistant comunity.
You need nothing to solve, just to fit it on the DIN-rail in your switch board, hang 3 clamps on the 3 phase wires, than download the according integration for the HA and it should work.
I just ordered one, I will keep you informed, when I will have some progress.
The port you marked in blue is the one I am using too, we have the same IR ports on the smart meters in Germany. They are specifically made using IR instead of connected wires so they are safe for the owner to attach anything to it without coming in contact with the meter directly.
I have used this: ttl ir lesekopf lese-schreib-Kopf EHZ Volkszähler Hichi Smartmeter | eBay to read the datagrams sent out from the meter, the port consists of an infrared emitter and an infrared photodiode, so duplex communication is possible, parameters are 9600 baud, 7 bit data, parity even, 1 stopbit (9600 7E1). The device from my link has a ring magnet that will attach to an iron ring around the port inside the meter. The datagram sent out by this port contains current energy total and momentary power (among a bunch of other information), updated once every second.
The connections on this thing are GND, +3.3V, RX, TX and you can connect it for example to an ESP8266 UART RX pin. Optionally you can also connect the TX pin but this was not needed with my meter. I used an ESP8266, platform.io with arduino framework, the softwareserial library, the pubsibclient library (mqtt) and wrote a small firmware to parse the incoming datagram for energy and power and sent that to home assistant via MQTT. I receive a new reading every second.
I have also read (but not tried it) there exists ready made firmware for exactly that purpose from Tasmota and I have also seen variants of these that already contain an ESP8266 with firmware directly built into the small housing, so all you will need is a 5V power supply and your WIFI network in range.
Here is some more information (in German) with schematics: hardware:controllers:ir-schreib-lesekopf-ttl-ausgang [wiki.volkszaehler.org]
More information about the Tasmota version (also in German): Ausprobiert: Günstiger IR-Lesekopf für Smart Meter mit Tasmota-Firmware | heise online
hello Jan
just FYI → at the end i have also decided to use SHELLY 3EM and am happy with the device.
Installation into HASSIO worked like a charm and the device immediatelly started to report the power consumption. However to make it work as needed - calculating cumulative consumption considering the electrical tariff based on time, that was a bit tricky for newbie At least i have learned something new about template sensors and also about helper attributes
hope you are also happy with your device
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Hi. We installed monitoring energy usage and temperature in retail shop. We used few Shelly 3EM, Shelly 4PM and Shelly 1PM with temperature sensors connected into Home Assistant. We had to combine different phases from different 3EM into final Power Monitoring sectors (cooling, heating, lights). We installed this into more shops and implement into one Home Assistant.
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