Some questions regarding 3EM (FAQ)

There is too much outdated information or not completely coherent answers regarding these questions.

I've selected (bottom) some of the topics and their answers, as well as some of the official documentation to try to answer the following questions, but some remain unanswered (??) or with an incomplete answer.

I would like clarify some FAQ of this product not yet "answered" as of 2023/06 (Firmware 20230510-083155/v1.13.1-gda6f9f2)

What is the minimun polling time of 3EM?

??

How does the 3EM handle non-linear loads i.e: inverter, pc-power supplies etc?

??

What is the accuracy/precision of the measurements? Do they comply with any standard?

Some topics state 1% accuracy (other people describe it as precision...) but do not clarify if in voltage, current or phase and if its related to nominal values or any other reference value.

EN 50470-1 for reference.

After all most people, IMHO, would be satisfied to know the expected deviation/error in energy mettering per month f.e. in +-kWh, to compare with their bill.

Can 3M handle a 4th current clamp for the neutral conductor and show its data as a normal channel?

It can handle the 4th clamp for sure if its 120A model.

Regarding data collection N is not considered as a fourth channel in the interface.

??

Which is the correct accessory for 3EM the 120A, the 50A or both clamps?

Some topics state that the 50A is not compatible with the 3EM, but the box of the 50A clamp states its an accesory for 3EM.

The following link states that "other transfoerms may destroy the device" but some topics describe other transformers as compatible and secure.

3EM calibration of the N-clamp

If the 50A clamp is compatible, which is the reference, part number, specifications for the 4 pin connector? (50A comes with bare wire)

??

How can the neutral current clamp work ("uncalibrated") as an accessory but the provided current clamps are "factory calibrated" and are not interchangable? Does the accesory come with a calibration file?

3EM provides a current calibration system in its webserver. Instructions are in the LEXICON of this site.

Is the energy (power*time) data logging (In/out) corrected or you still need a third party software to compute it?

??

Related topics with no "clear answers":

Thema

How to connect to a 3 phase network without neutral

Dear,

i hope somebody knows...
In belgium we have some electrical networks that don't supply a Neutral to the home.

So the network is 3x230V i.s.o 3x400+N ....

The shelly 3EM requires a N to be supplied ... probably to measure the voltage per phase.

Is it possible to power the 3EM without neutral ?
Worst case i need to wire it up as 1 phase... but then the information of voltage per phase will be lost so the wattage will be slightly of.
Or does the 3EM measure the phase between voltage and current…

barry2002

19. September 2020 um 05:41

Thema

Transformer factory calibration

Hi,

I tried to do a factory calibration for the transformers. The option is under transformer calibration but when I press it I have only an error message.

What is the right way of doing factory calibration?

Cs4b4k

25. September 2022 um 09:27

Thema

Wrong prefix for consumption and returned

I just installed the first EM3 last weekend and the manual stated to put the amp clamps from K -> L which states K as the power delivery and L as your home consuming power.

I did exactly that an installed the clamps between the first fuses and the grid power meter.

The values itself are correct or at least seem to be correct but the prefix is wrong - the shelly app shows a 25kwh consumption and 4.5 kwh returned. But it's simply the other way round. The PV delivered about 30 to 35kwh and in the…

fitmompjpzdfrujvfy

13. Juni 2023 um 19:44

Thema

How accurate is 3 EM

I wonder how accurate is shelly really?
I'm comparing the values I get from electricity company and shelly.

Import

1 October: 22.78 kWh (real) 24 (shelly)

2 October: 30.59 kWh (real) 32.1 (shelly)

3 October: 25.69 kWh (real) 27.3 (shelly)

4 October: 30.19 kWh (real) 31.4 (shelly)

5 October: 37.33 kWh (real) 37.5 (shelly) almost correct...

And export(returned) is even worse

1 October: 8.29 kWh (real) 9.51 (shelly)

2 October: 0.15 kWh (real) 1.6 (shelly)

3 October: 0.79 kWh (real) 2.3 (shelly)

4 October:…

mattfro

8. Oktober 2022 um 20:03

Thema

Are the 50A clamps smaller than the 120 A?

Hi

I don't have much room in my fuse box -- I would like to install a second 3em to monitor a few circuits when the currents will not likely exceed 15A. Are the 50A clamps physically smaller than the 120A ones and therefore worth getting to facilitate the installation?

wigster

14. März 2023 um 14:32

Thema

What is the accuracy of Shelly EM and 3EM for small wattages (5-50W)?

I know, the handbook states the accuracy of the EM is 1%. Whatever that means.

Given the maximum current is 50A or 120A, the maximum wattage is 220V x 50A = 11.0kW, or x 120A = 26.4kW.

But what does this mean for small wattages?

Do I always have an absolute precision of 11kW x 1% = 110W, for the 50A solution?

What about measuring small values like 10-50W? How precise is the Shelly EM then?

Did somebody compare Shelly EM with Shelly 1 or 1PM, for such small values?

Thank you!

ploneric

25. November 2021 um 09:54