Measuring consumption of a 400v 3 phase load

I’m getting started with energy tracking and for most of my loads it’s pretty straight-forward using a combination of Shelly plugs and PM1s. However, I have a sauna that I would like to also track the consumption of, and it is a 3phase 400v system. I have been unable to find equipment which can take that voltage. I was looking into the Shelly EM3, but while it would work in terms of amps, it is also rated 230v.

Does anyone know of hardware that can take a 400v load and measure its energy consumption?


Shelly em3 can monitor all 3 phases, its good for your use case. Its just being powered by one phase 230V, but can monitor the whole house consumption perfectly.

Iammeter should do it too Three Phase Energy Meter Wi-Fi,split phase,residential energy consumption,solar pv monitor,net energy metering, Modbus TCP/RTU I use these

Interesting! I actually asked Shelly but their response was that it was not possible since the device needs a neutral line from the load it tracks, and it does not support neutral from a 400v load.

Have you tried?

Ty! Looks interesting

That’s a bit confusing. Monitoring 3 phase systems is exactly what the 3EM is made for. Since it’s measuring currents through a clamp, I don’t see why it would need N from a load. There is no physical reason for that. Though it should measure the currents of a 3 phase 400 V symmetric load just fine. I guess it is a symmetric load, because otherwise there’d be an N.
Further: If the heater is really symmetric, without an N connection, you could also measure just one phase, both other phases have to have the same load.

Thanks for that!

Did you find a solution for your 3x400v consumption tracking ? I’m in the same situation and would like to know if Shelly 3em can do it.

There may be differents power grids around the world.
However, I can confirm that Shelly 3em will work with the typical European grid which is
3 phase 230/400V + N at 50 Hz

I contacted Shelly, and they told me that the 3em would NOT work with 400v. It will with 3 phase 230V, but not 400V. I did not try it myself but took their word for it.

I ended up using this one instead. It is rated specifically for 400v, and I can confirm it is working very well (incl local control via HA).

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I guess that was some kind of missunderstandig.

When you have 3 phases and N, you can get 230V and 400V at the same time and that will work with the 3em. If you have only the 3 phases without N, you have 400V only and that will not work.

EDIT: Again: thats for the european grid, somewhere else it might work differently.


L1 - L2 -> 400V
L2 - L3 -> 400V
L1 - L3 -> 400V
L1 - N  -> 230V
L2 - N  -> 230V
L3 - N  -> 230V

It’s sad that technical support for energy meter does not understand 3-phase systems and different voltages. That Shelly would have worked just fine.

It seems that op was installing it to a residential electrical cabinet, where he has neutral for sure (even the meter* he got needs neutral). If the sauna stove works like it should, even measuring just one phase and multiplying the result by 3 would get you more data than you ever need. I might have used that shelly for monitoring three different devices or for the whole house consumption.

I’m a bit curious about that sauna though, i’m 99,4% sure there is neutral to it and the heating elements are connected in wye, with that neutral connected. Pretty sure the controlling is happening in 230 vac (or lower, but transformer would be in the sauna equipment) etc. I can’t remember that i have ever seen a sauna stove without neutral and i have seen a couple of saunas in over 20 years as an electrician in Finland :smiley: Even the ones at public swimming pools with 15 heating elements in them have neutral busbar directly on the resistor connections.

/* that eastron meter seems a bit overkill for sauna, it’s even mid certified, so you could use it to bill the electricity usage. I would use something like that for the whole house.

3 x 400V, are you sure about that ? In what country do you live ? I’m not aware of any country with a 400/700V 3P+N residential electrical grid. A 3x400V system would have a P-P voltage of 700V, the insulation requirements for that would be quite a thing for residential. And since you could not get either 120V or 230V out of such a grid, you couldn’t use any electrical appliance manufactured anywhere in the world without massive transformers in every house.

I think you mean 230/400V 3P+N, which is the standard in Europe and probably many other countries. The Shelly 3EM works fine for that.

I think Shelly insist on having N as it is used for reference for voltage measuring by 3EM. Also device itself is designed to be powered by 230V (one of phases to N) not the 400V. So technically it should be able to measure current throug the clamp, but a) would not function without N to power it on and b) reading of power from 400V would be innacurate, as clamps reading are calibrated to 230V.

Can you share how you have added the Eastron SDM630-Wifi to Home Assistant?
Thinking about getting it myself as well.

Via Homewizard. They sell a branded version that works seamlessly with their platform.
This one: Wi-Fi kWh meter 3-phase MID - HomeWizard

Ah thanks. Following the guide on the integration page?

You still happy with the product and would recommend it? Any Issues?

Very happy. It is rock solid. The integration also works well: everything was auto detected and working in HA without any hassle.

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