Just an FYI post for anyone looking to use the Shelly EM in the US as it was pretty hard to find install instructions for US panels. I am not an electrician and of course you should not mess with your panel if you are not comfortable, you could die etc…
If you want to monitor the whole house in the US you will need to get 2 clamps as US Panels have 2 separate lines which come into your house. I chose to go with 120A clamps though not sure if that was entirely necessary, someone with more knowledge could probably chime in on that.
You will need to connect both clamps to the shelly as per the diagram which points you where the red/black wires each go.
Then you will need to wire the shelly itself to power so it can read the voltage as follows:
L should be connected to one of the breakers
N should be connected to the Neutral Bus which is where all the white wires are connected on the side of your panel. It may be easier to just connect the shelly to a regular plug and plug it into an outlet if you have one free nearby.
There is a caveat here: You will be measuring the Voltage on only one of the lines. If there is a significant difference in voltage between your 2 lines this will affect your reading and they will be less accurate.
One last note, your clamps have a direction. One of the clamps will need to be reversed. The direction will need to be opposite between the 2 clamps. The easiest way to figure this out is to just fire up the shelly em and configure it. If you see any of the channels reporting negative, reverse the corresponding clamp.
That is pretty much it, you can add the shelly to homeassistant using the integration or mqtt if you prefer. Then you will need to set both channels up separately under the Energy configuration as “Consumption”. You will see each line reported separately but you will get the total of the 2 as well in the graph. You can also set a template sensor to add both wattages up and show you the total wattage used. Hope this helps anyone else looking to set this up.
Look at the main CB rating for each phase. You want a clamp at least that big. Not much bigger as this will reduce your resolution.
Unless… you know the CB is oversized for your loads. Then pick a lower rated CT for better resolution.
e.g. I have a 100A main circuit breaker, however I know I never get close to drawing that. So a 50A CT is ok. I’m not in the US but the same applies everywhere. How do you know this without measuring first? Look at the compliance plates for the major loads in your house (electric stove, Aircon etc…) and add them up.
Unless you have residual current CBs. Then the N must go to the same breaker as L (not the neutral bus), or you will get an unbalanced current that trips the breaker.
I’ve recently switched over from using mqtt to the Home Assistant integration. It works very well and is much easier to set up. There’s no need to use mqtt (or flash alternate firmware) for Shelly devices any more. The integration has come a long way. Very impressed.
Much appreciated extra info! The Shelly comes with either 50A or 120A clamps, my main breaker is rated at 200A so chose to stick to the safe side…my readings appear pretty close to what my utility is reporting and they make sense from what I have seen when turning on various appliances.
I don’t expect to get exact but am pretty close…
Not sure what “residual current CB’s” are and pretty sure I don’t have them as there is no connection except the hot on the breaker I connected to.
Residual current CBs are very common in the rest of the world. They monitor for any difference in line and neutral current in a circuit. Indicating a possible fault to earth.
Have a read of this topic:
https://community.home-assistant.io/t/shelly-em-trips-circuit-breaker-australia/328329
Aha, yep I assumed that was the case and I did see those instructions…I wrote it up for US panels as there seems to be little info out there about wiring this to our panels.
Does anyone know what the max wire size on the CT clamps? I’ve been thinking about buying one of these, but my house runs on a 200A service that has 4/0 wires feeding the 200A main breaker.
I’ve been looking for specs and reached out to shelly tech support, but they failed to answer the question
The wire size on the CT clamps is not really relevant. The voltage and current seen in the CT clamp wires is very very very small, mili-Volts and mili-Amps. The clamps sense the magnectic field generated by the current flow throu the main wires and produces a proportional voltage to the current.
I doubt the wire range on the clamp is entirely irrelevant. The opening looks small and in the US, people like to run thick wires. Will this still work if the wire is too thick to wrap the clamp around it?
The AWG of the wire is adequate for safely carrying the current that would be produced. Whether or not it fits in the panel is a case by case bases. CT clamps work by ratios like 100:1 for every 100 amps 1 volt is induced in the CT clamp.
I guess what I need to ask is… Are these clamps big enough to clamp around a 4/0 COPPER conductor?
The specs on the wire say it is 0.624 thick (outside diameter)
The internal diameter of the 120A clamp is 17mm. The 50A is 11mm. https://shop.shelly.cloud/current-transformer-120a-wifi-smart-home-automation#65
And no they won’t work if not fully closed around the cable.
I couldn’t measure but I have a 200A main breaker and the 120A clamps fit snugly on each line coming into my panel.
Is that four size zero or is that quad-ought
If indeed 4/0 (four ought) then the diameter is 11.68mm (on average)
if you need to go around two size zero then 8.251mm x 2 so at a minimum of 16.5mm
Thank you guys. This clears it up for me
I just wired mine up like this but can anyone help me explain the data that I’m getting? I labelled them right side of the box and left side of the box because each one should just measure the power going through the breakers on their respective side?
Why is the power sometimes mirrored on the other side? Like that first comb-like area at 5pm was the oven running but it seems to be affecting both channels? Then some items only seem to affect one side or the other.
Im no expert but if you are on US power, you usually have 2 phases at 110 volts, so when appliances are on a 220v circuit, you will see power being used on both phases in an identical manner. Your 110v circuits will still draw from the separate phases and affect them separately.
I think that’s it! It’s the 220V stuff that’s affecting both sides.
Thanks for the info in here, most helpful. I have solar and a 200A panel. I guess I’m going to need 2 of the EMs, one to support the 2 120A clamps I’ll need on the cables from the grid, and one to support the single cable from the solar system. Does this sound right?
Or one E3.