I’m ashamed. Shelly Pro 4 PM had been on my shelf for months now, waiting for my time and attention. I really wanted to cover it sooner rather than later, but Shelly had other things that caught my eye including no-neutral Shelly L and pretty awesome changes in Shelly Plus series. As ITEAD released Sonoff POW Elite, it gave me the reason to revisit this DIN-rail-mountable relay with a display.
Shelly Pro 4 PM
Shelly’s Pro line refers to bigger, DIN rail mountable switches that offer a more robust industrial design. It’s not to say that your average DIYer can’t take advantage of it, but the price tag may seem hard to swallow at first. Shelly Pro 4 PM costs €89.00 (VAT ex) which isn’t the most pocket-friendly option. As usual, in these cases is more about the value you are getting than the price tag.
It’s a WiFi (2.4GHz) enabled 4-channel relay with a power meter (for each channel). It also offers 100Mbit Ethernet, a colour display and support for traditional switches. Each channel is capable of controlling up to 16A with the device total reaching 40A for all channels. That’s enough to keep a decent heating system operational.
All this is enclosed in a fire-retardant box barely bigger than your usual DIN-rail slice. That’s certainly impressive, as to my knowledge I’m not aware of any other device that would offer all of these features in one box.
I have plans for building a 3D printer enclosure supporting up to 4 printers – as I would like each printer to be equipped with a power monitor and a relay for safety, Shelly Pro 4 PM is excellently equipped to handle that.
Very Shelly problems
I’m aware that actual DIN-rail circuits can accommodate, but on the off chance that you are not using this as a part of a bigger installation, Shelly Pro 4 PM comes with very Shelly problems. To wire up everything correctly (even with a single channel in use) expect to use WAGO style connectors as Shelly Pro 4 PM doesn’t have enough terminals to support required splits.
It’s not the first time I complained about it. For once, I’d like to put the device where it supposes to be and enjoy the ability to pluck all the wires into a sufficient number of terminals. If this means that Shelly Pro 4 PM will get slightly bigger, so be it.
Another glaring problem is the display. Sadly not a touch screen, but the display is very dim. If you happen to look at it when the Sun is shining outside, you will barely make out what’s on it. Keep Shelly Pro 4 PM in shaded areas if you like the screen.
Bluetooth pairing is always a dead giveaway, so I already expected ESP32-based brains of operations. What’s pretty funky is the layout of essentially 3 PCBs stacked on top of each other and connected via pin headers.
The relay board is separated from everything else, the ESP32 is located in the middle of that sandwich topped by a tiny PCB which holds the 3 interface buttons. There are no extra pins or dev pads, so as far as hacking goes, it’s not as easy as on Sonoff devices, but considering all options in the Shelly Cloud app, that won’t be needed to integrate the relay with your DIY automation.
Where Shelly always shines
The physical shortcomings mentioned above are small compared to the huge benefits of using the Shelly ecosystem. I don’t know any other brand that goes out of its way to accommodate its customers with options.
Shelly Pro 4 PM pairs quickly and shows up in the Shelly Cloud app as 4 devices. It’s a good decision, as it allows you to see all the metrics at glance without cluttering the interface. Quick Cards offers access to a toggle, name cloud status and the current power draw. Similar information is available on Shelly’s Pro 4 PM display.
Heading further, introduced the consumption data including a graph with access to historical data. Everything is well structured and presented. Basically, the interface for each channel of the Shelly Pro 4 PM is the same as for other devices from the PM series and offers the same perks as Shelly 1 PM or 2.5 PM. One of my favourites is the power consumption data displayed by the room. While the individual channels of Shelly Pro 4 PM can be monitored, it’s interesting to see aggregated data of all power meters in a single room. It gives instant feedback on how much electricity your automation is using altogether without needing napkin math.
There is a limitation to all this fun, as the data stored in the cloud reflects the consumption in Wh in hourly instalments. If you are looking for a more granular breakdown of your power consumption, you will have to use the device’s DIY options to send that data to your server. By far the easiest way is to harvest this data via NodeRED, Grafana and InfluxDB integrations. It’s easier than you think and I already have a write-up about it.
In case you ever wondered how much you save by running smart lights and switches, I did all the maths for you in this article about the yearly cost of automation.
Made for DIYers
If this is not your first Shelly rodeo, you know what to expect. If you never used Shelly Cloud, you will be happy to learn, that their firmware is optimised for DIY home automation and cloudless use. All that without flashing.
You can useShelly Pro 4 PM in a local mode, force it to create AP or take advantage of Bluetooth and MQTT for connectivity. Built-in REST web requests are compatible with pretty much every DIY automation system out there. Each time I have a Shelly device in my hands, I know, I’ll be able to integrate it without problems.
Cloud services (and web interface too) also offer special web requests triggered by switching lights (or motor) on/off. Multiple requests can be made based on a single trigger. It’s a useful feature if you want to ping your Home Automation server when lights got turned on or command another integration outside of Shelly Cloud.
What’s impressive, is the list of modes your switch can be set to work at. Shelly Cloud has every option covered! From toggles, through edge pulses to completely decoupled operation. Regardless of the switch on your wall, you will find a perfect way to operate Shelly 2.5. Lastly, the app comes with the usual options: timers and schedules and an automation panel to link other Shelly devices together.
Check out other devices from the Shelly series to build your ultimate DIY automation:
Shelly Pro 4 PM is expensive if you are not going to take advantage of all 4 channels. If you split the cost of the relay between all channels, then Shelly Pro 4 PM offers an affordable way not just to control your devices, but to get the power data the way you want! That’s sometimes worth spending a little extra. I’m curious to hear about your use cases, so if you already have Shelly Pro 4 PM in your automation, let me know in this Reddit thread.
🆓📈 – See the transparency note for details.