2023-10-07

Shelly Plus PM Mini

Another in the Mini series from Shelly, the PM (Power monitor).

Update: explanation from Shelly: Easy, N is almost double the heat inside of the device. Sorry but in such small size we didn't want it. Double out allow to use single device in double socket which is most useful than second N.

Obviously this wants to be in-line with the device you are monitoring.

What struck me as odd from the pictures, and did confuse others as well, is that it has L/N (in) and O/O (out).

Is that L/N in and L/N out? That would make sense if it is to go in-line to a device being monitored.

No it is not!

As you can see, the O/O are both wired together and are the Live out after the monitor.

There is no second N, so wiring in this in-line either means two neutral in one screw terminal (not ideal) or a wago to join the neutral wires.


Why Shelly? Why?

I appreciate an L/N/gap/L/N may have been messy to track the neutrals, but what they could, very easily, have done have N/N/L/gap/O. This would allow live in and out, and neutral in and out and no wagos, and no two wires in one screw terminal. Way better.

I had to draw diagrams to explain to the people on the Shelly group on facebook!

How you have to wire it now

How it could have been

As explained above, the explanation is N through the device is extra heat, but to be honest I do not buy it.

The two O, meant that if one uses the second O only, all the current has to flow an extra few mm via a nice thick track to the second O terminal and that is extra resistance and heat. But surely that is exactly the same as would happen with N flowing to an adjacent N terminal the other side.

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