Connecting more then one ET112 Carlo Gavazzi

Ok, question for the guys that know there way around the ET112. I’m getting my second inverter today. MLT Powerstar 10.0H. We move in to a bigger house begin of this month and my plans is to split my DB in to two parts. The MLT H10.0 will run the main loads in the house like plugs and lights, and my MLT 8.0H will be running the geyser “plans to go heat pump” and garage side and pump for outside garden and the Aircon.

My plans is to get Victron mppts and Smart shunt and Cerbo and then two ET112. I want to use the ET112 on the MLT’s ac output that I can send that info to VRM. So it will be one Et112 per inverter ac output.

The question is, can I connect the the two ET112 in parallel via the RJ45 modbus connectors on front of the Et112 and then send the info via one RS485 cable to the Cerbo. Or must the ET112 run there own RS485 cable to the Cerbo?

I will use 2 cables. That way it remains 2 different devices all together.

You can put two meters on a single cable. The software supports the first meter on address 1, and the second one on address 2 (you will need the UCS software, universal configuration software, from Carlo Gavazzi’s website to change the address for the ET112).

Generally we advise people to put each meter on its own cable, mostly because people make bad splices and then it causes all sorts of issues. But people also extend the cable and make bad splices in that… so yeah, just don’t do that.

By the way, to get the UCS software is somewhat of a treasure hunt. Go to https://www.gavazzionline.com/, then Information and Manuals (takes a few tries, cause the hover-thing is jittery), then click “Energy management”, then look for “Universal Configuraton software” (sic), and download it. First time it will ask for an email address.

Thanks @JacoDeJongh and @plonkster . Ok, so the options is there. So now to decide , two RS485 cables that will cost me just over R1000 for both , or one rs485 and do the configuration. @plonkster is it a tricky one to do the configuration?

If I remember you just need to connect the ET112 to your PC using the RS485 USB connector and run the app.

Why not an ET340?

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Very easy, almost self-explanatory.

OK, that suggestion gave me a mixed reaction.

My first reaction was… on no! Not that meter. The ET340 has a few quirks, the smaller one that it is just really slow (which doesn’t matter if you only care about energy measurement), and the larger one that it counts energy incorrectly on three phase systems (which again, doesn’t matter in some applications).

My second reaction was: Hang on, he has a point!

In a single phase installation, you can use L2 on the meter to measure something else. Usually we put the grid on L1, and a PV-inverter on L2. The software correctly splits the meter into two virtual devices, one that registers as a PV-inverter, and you’re set.

But there is more good news. Once this lands in Venus, you can configure L2 as an “acload”, which is a generic measurement service that simply reports to VRM. So then you can use a single ET340 (or an EM24, but they cost more) to measure both of these.

I have no idea how long it is going to take though…

Thanks for that one. :+1:

@plonkster Would L3 be available as well?

Smappee and EM24-ethernet support now verified as working too. Hopefully soon.

I see that the price of an ET340 is pretty much the same as two ET112 meters… so really not much point. The ET112 is a better meter (refresh rate is 750ms compared to the 2 seconds for the ET340). I’d still opt for 2 x ET112.

Thanks for that one @plonkster . Then it’s a good option to look at. Other question. The two inverters is going feed a DB that I will split, so one side will run with 10.0H with it’s own N and L and then the 8.0H will run a other side with it’s own N and L. So I can run the 10.0H L on L1 and the 8.0H on L2 via the ET340 and it will pick up the power reading with out N because both inverters is running there own DB setup and not connected to each other.

No. And I doubt that will happen. Not a common enough use case to spend time on implementing the feature :slight_smile:

I think the option you mention with the 2 x ET112 will work the best. Less headaches at the the end of the day.

Are these going to be completely separate circuits, ie they are not going to be in synchronisation with each other or the grid?

In that case it is not going to work.

The meter powers itself from one of the phases (L1 I think), so that is where it gets the voltage signal from. It then takes current measurements from the individual phases, but these are isolated (internal CT), so you can run the live through the L2 side without the neutral necessarily having anything to do with the neutral on L1… BUT… that only works if the voltage waveform is properly in sync, otherwise your measured power factor is going to be all over the place as the two sources drift relative to each other, and it’s not going to measure the power or the energy correctly.

So no… Definitely go with 2 x ET112.

ok, thanks .

Yes, they going to be completely separate circuits because they deferent size inverters. If it was the same units size, then I can run them parallel connected by removing the one top part and added it to master unit.

On the grid part, will like to run them grid connected but you know the lovely Coct story. And the inverters was on the NRS list a few years ago. Here is the test info https://mltinverters.com/wp-content/uploads/2015/03/NRS097-2-1-declaration-Powerstar-6kVA-range.pdf

My explanation above is a bit hastily done, about the voltage reference being taken from L1, that is not true. Of course this is a three phase meter so each phase has to do its own voltage measurement from the phase to neutral… but if the neutral is not shared or at least at the same potential (like it is in a grid-connected or parallel setup), that measurement is not going to be accurate, and the numbers are going to be wild.

A question on the ET112 if I may jump in here, or actually on the RS485 to USB cable for it.
I see the price difference between the 1.8m and 5m cable isn’t much so my thinking is that it will be better to buy the longer one. Will that cable do fine being rolled up if it eventually works out that my cable run will be shorter than 5m or will it result in data errors?

Mine is rolled up as I did the same thing. Bought the 5m in case I want to move things at a later stage. No issues so far!

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RS485 has a very high interference tolerance. In a high interference area you can go up to 250m, else normally it can go up to 1000m length. Your 5m in a coil (even if coils can have high magnetic interference) is no issue at all.

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Hi guys, a bit off topic, but I wanted to say something quickly. Us admins (mostly me, cause I’m a little OCD that way) will occasionally edit posts for spelling. It’s not a reflection on any particular person, it’s just to improve readability, especially on high value posts :slight_smile:

Now I’m about to head out and see if I can find some snow…

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