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Yusef Neblett avatar image
Yusef Neblett asked

Multi+ Duplicating Watts readings on a 230v Split Phase with Autotransformer

Hi Victron,


I live in Central America where we use the US Split phase grid system, I have a ESS system with:

- 1ea Multiplus 48/5K/ 230v

- 48v Lifepo4 Bank 450ah

- SmartSolar MPPT 250/100 rev2

- AutoTransformer 32amps

Note: the system does not feed to the grid.

I have setup my system as per Auto-transformer manual advice for Split Phase systems as below:


I have noticed from the beginning of my setup a drastic Watts measure change when Grid goes out and I already read your article here https://www.victronenergy.com/live/ccgx:ccgx_faq including the Q6.

But My case is in my opinion more drastic reading difference.

This is a normal Watts reading with Grid power:

- My home consumption says: 1016W

- Battery charge current: 48.6Amps (2452W)


Right after I open or disconnect the Grid:

- Home Power consumption: 480W (Half reading). I confirm No changes in the Real home Load equipment.

- Battery Charge Current: 58.8A (2971W) Yes the MPPT generation increases in that moment 100W but that does not justify the 500W (10Amps) Battery Charge increment. Looks like the increment in charging is due to the decrease in Loads need by the Multi+


The behavior is telling me that for some reason having a 230V Multi connected to 2 Live power lines (L1=120v + L2=120v), the Multi is duplicating the reading in the ACin/ACout side and direct affecting the battery charge performance. Since this 230v Multi+ is designed to connect L1=230v + Neutral. I think this Multi+ is not properly reading 2 live phases L1 + L2 correctly, instead it is duplicating the reading.

I have done other testing with a 3rd party watts reading and the reading is half lower than Multiplus AC Loads reading and that make me think my suspicious is correct. Can Victron staff please confirm my situation here?

I know that an option here is to get the Carlo Gavazzi meter for better reading, but I will like to ask if Victron can do a Firmware adjustment for customers that use their 230v Multis in US market before expending more money.


@mvader (Victron Energy)


Thanks a lot



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7 Answers
edgardogarcia avatar image
edgardogarcia answered ·

The Issue is the House Neutral. Meaning the Autotransformer creates a new neutral. This New Output neutral should not be connected to the House Neutral. A way to test ,eliminate the Output cables from the transformer and connect a 3 cable L-N-G multi-plug or extension to the transformer output. Therefore isolating the neutral, Connect some load and test. The autotransformer uses less than 50 watts. Hope this works.

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chrisfullpower avatar image chrisfullpower commented ·

I found this thread after having a similar issues with my 230v Multiplus II and autotransformer. Odd current readings when the grid and autotransformer were both connected.


I grabbed my amp clamp and noticed that I had current on my ground between the Multiplus/Autotransformer and the main panel in my house. Temporarily disconnecting that ground solved the problem, all my currents and watt readings were accurate. I had the ground and N bonded on the transformer.


However that brings up the next question... how to ground the system from here? Leave the N and ground unbonded?

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Yusef Neblett avatar image
Yusef Neblett answered ·

Hi Victron,


After further testing during the Day and activating and dis-activating the Grid Breaker multiple times during the day I can conclude that system is not really "Duplicating" the reading. It is actually a differential reading on 600Watts with Grid available vs Grid not available in ESS system.


After fully charging the batteries I continue testing during discharging phase (No enough solar to continue charging) and the same behavior was notice

With Grid present:


right after disconnecting the grid: I can guarantee that the Load has not change. it is not a fridge or appliance kicking in/out the same moment or something like that

I was able to notice in my BMV712 that battery autonomy increases for about 3 hrs and this is where I care of. Charging and Discharging performance seems to be affected by this behavior.

@mvader (Victron Energy) @Guy Stewart (Victron Community Manager) Please advise

thanks


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Johannes Boonstra (Victron Energy Staff) avatar image
Johannes Boonstra (Victron Energy Staff) answered ·

Hello, when having a setup lik yours its essential to have the look at the ground connection. In a 230Vac system one leg (N) is ground and therefor PE/N = 0 Vac and N/L is 230Vac. If an autotransformer is used the centre tab becomes the new N so that needs to be grounded. If thats done (either fixed or with the groundrelay ) there is the risk you have two points grounded and in between there is 120Vac. so there will be a fault current as well!

So make sure that the incoming N is NOT grounded OR the centre tab is NOT grounded.

Ideally, in inverter mode the ground relay in the Multi needs to be disabled and the AT one should be used. then the power readout should be OK and the system has the voltages as expected 120-0-120Vac. In grid mode the voltage depend in the incoming system. If that N is grounded you will see 0-120-240Vac.

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Yusef Neblett avatar image Yusef Neblett commented ·

Hi Johannes,

first Tanks so much for your support!

I will like just to make sure I understand when you said: So make sure that the incoming N is NOT grounded OR the centre tab is NOT grounded. you mean I have to make sure the N coming from the AT is not grounded in 2 points? (Fixed + with the AT ground relay?). I currently have the N from the AT grounded with the AT ground relay (Multi gnd relay disabled and External contact wire connected to the AT) and the Home Distribution Panel.

we are sync that in this configuration I am not using the N from the grid.


Thanks

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Yusef Neblett avatar image Yusef Neblett commented ·

Hello,


I will like to confirm that the N from the grid is not grounded.


I have been doing more troubleshooting and found the following:

1. I found my AT is providing a 6 volts difference between Legs for example 117-0-123

2. I had my Multi and AT connected to the same chassis ground stud and I separate them

3. after that the same behavior in my AT output, then I unbound my Gnd and N bars in my Home distribution Box but Still the AT is delivering this 6v difference.

4. Multi input is perfect balance against the Dedicated gnd bar connected to the Multi Chassis and the Multi ACOut1 is also balanced L1=120 N/L2=120 (also measured against the Dedicated Gnd bar connected to the Multi Chassis Stud.


How come AT is delivering this phase difference? How I can test if the H2 gnd relay is working or not? it is connected to the Multi and configured in the Veconfigure with the option un-checked.

Is this AT failed? is this voltage difference the reason of this 600 Watts consumption difference between grin/on and grig/off?

Note: I noticed inside the AT there are 2 wires comming out from the AT Bracker and they are labeled J7 and J8, but they are connected swapped, meaning J7 is connected to J8 and J8 is connected to J7.

Any support will be appreciated

Thanks

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Yusef Neblett avatar image
Yusef Neblett answered ·

Hi Victron,

I ask a friend to test their AT and looks like it is transforming in the same way: 117-0-123 and this seems to be a AT way to work (unless Victron staff confirm a bad AT).

I finally found the correct way to configure the external Gnd relay with the help of @WKirby. solution here: https://community.victronenergy.com/answers/53219/view.html


I will definitely have to buy the ET340 meter. And I will have to go overseas because it is impossible to find it online in America, besides my local distributor will take months to get this meter.


Will be grate if Victron seriously advice to use external meter for ESS and most in the cases the customer is thinking to use the 230v Multi/Quatro + the AT for SplitPhase in America. since the muti/quatro are not measuring devices like they said.



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Yusef Neblett avatar image
Yusef Neblett answered ·

This is very frustrating!

I finally found an Online website to buy the ET340 and Installed, hoping this Energy meter will fix this reading issues and guess what... It did Not fix anything. It is the same or MP is behaving even more crazy.

I was hopping any update in this treat from Victron Staff but looks like they are very busy with other customers... my support experience with Victron is getting worse and worse...

Issue again: ESS just dont work. The home consumption reading when grid is connected is 600Watts more than when grid is disconnected (pure inverter mode).

Using a 230v Multi with AT for split phase it is just NOT AN OPTION TO CONSIDER! unless again Victron can confirm I have a Bad Multi+ but I haven't received any other update from Victron


ESS + Grid Connected


ESS + No Grid:


above picture shows a 600Watts difference and around 5 dc amps charging increase from Victron mppt (this is s min, this treat with show cases of 10 amps increase). This is a performance issue that Victron shall pay attention; at night the battery bank autonomy is kill due to this Issue.

Using a 230v Multi designed to work with L1=230v + N and connect L1=120 + L2=120 instead and then an AutoTransformer (Also Victron) it is not performing acceptable.

Victron Please take a look a this case and support, I expend a couple of thousand box for this equipment and now I am thinking to Sell them for cents because I cant even know who will accept such low performance equipment

@Johannes Boonstra (Victron Energy Staff)

@mvader (Victron Energy)

@Guy Stewart (Victron Community Manager)



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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @Yus

this system is effectively a single phase system, so you have to wire your grid meter also like a single phase system.


on the output power increase / decrease: I'm suspecting this has something to do with power factor of the loads, causing a misreading somehow.

what is your VRM id?

also: 5A the increase in charge current comes from stopping feed-in. so that's not an issue, as far as I can judge now it's a measuring error.

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Yusef Neblett avatar image Yusef Neblett commented ·

Hello @Daniël Boekel (Victron Energy Staff)

Did you have the chance to see my VRM? I give you the ID above (My ID is: b827ebabe2fe )

Please let me know. I suspecting it is a Multiplus Issue in the ACout, it does not make Any sense the Output reading is a lot higher than the AcIn.

Like I said above, right Now I removed the ESS configuration and I am running in a Ignore AC with the Generator Star Stop Assistant. and this is the ACout reading example.

Now having the ET340 in the AC input as a Grid Meter I can see the huge reading Issue this Multi+ have in the Acout Side

Thanks

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Yus


what is the VRM id or name of your system?

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Yusef Neblett avatar image Yusef Neblett commented ·

Hi Daniel,

My ID is: b827ebabe2fe

But Right Now I removed the ESS configuration and I am running an Ignore AC with the Generator Star Stop Assitant. and Now having the ET340 in the AC imput as a Grid Meter I can see the huge reading Issue this Multi+ have in the Acout Side.


This is an example at night when the SOC reach the min as per Ignore AC assistant configuration and the Multi connects the Grid. It is not right to see an ACout reading that high in Bulk and no PV. The ET340 confirm what is the real consumption and the issue in the Multi ACout.


what are your thoughts?


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pganguet avatar image
pganguet answered ·

I am having the same issue. All readings are wrong when connected to grid. See my diagram as I believe it to be correct. Did you ever find a resolution?schematic.jpg


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Oluwatobiloba Adedeji avatar image Oluwatobiloba Adedeji commented ·

Hi,


@pganguet , did you find a solution to this issue? I am having the same issue and my readings are off by 300W to 400W when charging from the grid.


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pganguet avatar image pganguet Oluwatobiloba Adedeji commented ·

Yes, but its not a great answer. An isolation transformer must be installed between the grid and the input to the multiplus. Because there is minimally a slight unbalance between the two phases and neutral on the input, and the Multiplus only measures current on one input leg, it will both draw and backfeed unbalanced. So isolate the grid and the current on both inputs will always be exactly the same and the reading will be correct. But standby losses of 25-50w should be expected from an isolation transformer, and some designs can't tolerate that much loss 24/7.

This only happens in split phase countries where the neutral is tied to earth ground. (Americas).

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