question

Herve RV Nizard avatar image
Herve RV Nizard asked

Multiplus II AC OUT 2 only when grid is connected? Or just available.

Good day. I read a lot of Q&A on the subject, but still have 1 question:

I understand AC OUT 2 works if grid is available .

But does this mean that it only works if AC OUT 2 "feels" grid is available (whether using grid or not), , or does it mean that AC OUT 2 loads must be powered by the grid ?

Thanks.

Details are as follows:

system Is 3x Multi II 48/5000 in parrallel , with ESS

2 SMA PV inv SB 5000 on AC OUT side

1x SMA PV inv SB5000 on AC IN side

For a specific system, i would need to use AC OUT 2 for large loads when there is enough sun or when grid is available (even if not used) , but would NOT want these to be powered when grid is not available .

AC Out 1 would have essential loads connected , and should be the only one operating if from batteries. (Simply because the battery bank cannot handle such large loads as those on AC OUT 2).

SO : 1- in normal times, with grid available, :

- during daytime , loads connected to both AC 1 and 2 are powered from the PV inverters when there is sun ,

If not enough sun, AC OUT 1 is taking from batteries, and AC OUT 2 is taking from the grid ,

- at night, AC Out 1 is taking from the batteries , but AC Out 2 is taking from the grid

2 - If the grid fails , all AC OUT 1 loads are powered from the batteries, and all AC OUT 2 loads are off .

Thanks .

Multiplus-IIESSac out 2
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4 Answers
waninae39 avatar image
waninae39 answered ·

ac2 only works only with the grid on

it does not use the convert/invert path like ac1

ac1 is for loads that must stay

ac2 is for loads like an air conditioner etc

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fanda avatar image fanda commented ·

I have an off-grid system with MP-II 5 kVA and AC Out 2 DOES work. As "nickdb" says below: "AC2 behaviour can be overidden with an assistant." Therefore the statement "ac2 only works only with the grid on" is misleading at the least, I think.

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celts88 avatar image celts88 fanda commented ·

Would you be able to show me how you did this please, what are the settings as I would like to do the same with my AC2.

Thanks.

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fanda avatar image fanda celts88 commented ·

Well, I am using AC Out 2 to direct "superfluous" solar energy into a 400 W bathroom radiator. The logic is as follows:

1) Switch on if (load < 180 W) AND (DC voltage > 52,15 V) AND (SOC > 99%)

2) Switch off if (load > 650 W) OR (DC voltage < 49,55 V) OR (SOC < 98%)

3) After switching off, keep switched off for at least 333 s (to prevent constant switching on/off)

I am using Pylontechs US3000C (---> DC voltage thresholds). Of course, the various threshold values can be tuned to suit specific requirements. The specific values above fit mine quite well. Also, the logic works fine for me, which is not to say that there can not be better solutions. This one is simple and does work (for me) though.

It is implemented using 4 "programmable relay" assistants & 1 "relay locker" assistant:


assistants.jpg

assistant-1.jpg

assistant-2.jpg

assistant-3.jpg

assistant-4.jpg

assistant-5.jpg

Also, I am thinking about inserting a timer switch to the AC Out 2 line going to the radiator to prevent switching on 1 or 2 hours before sunset, which may play a role during winter months.

Cheers,

F.

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assistants.jpg (77.7 KiB)
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lifeingalicia avatar image
lifeingalicia answered ·

Think about it as AC1 AC2 is one line just split from grid AC Both are controlled by the Multi.

When grid fails grid is isolated upstream (grid) to safeguard any linesmen. AC2 is shed. AC1 is powered by the inverter / battery.

Normal operations AC1 AC2 are powered by the Multi. Grid setpoint - SoC - max discharge of inverter - controls AC and grid demand.

If required power is drawn from batteries to top up PV up to max inverter setting rest from grid.

https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems

Also note: If you use external meters grid is used first then balanced to grid setpoint (if possible) using bat.

If you use the internal ones, its the other way round first bat then balanced out by grid.



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nickdb avatar image
nickdb answered ·

AC2 behaviour can be overidden with an assistant.

It is a regularly discussed topic. Look for iirc general relay assistant.

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celts88 avatar image celts88 commented ·

I would like to set AC2 the same as AC1 but configuration can only be done with VE.Config on a Windows computer, not a Mac like I have :(

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Kevin Windrem avatar image Kevin Windrem celts88 commented ·
I run veconfig via Parallels on my Mac. There are other virtual machine environments and also Apple's BootCamp.
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celts88 avatar image celts88 Kevin Windrem commented ·
I just wish Victron had built assistants into Victron Connect, I don't understand why not?
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sharpener avatar image sharpener commented ·
See e.g. this recent post.
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Kevin Windrem avatar image
Kevin Windrem answered ·

The measurement of output power is made before AC 1 and AC 2 outputs are split. So there is no way for the Multi to know what AC consumption is from the AC 1 output and which is from the AC 2 output, and no way to specify that AC 1 power comes from the battery and AC 2 comes from the grid.

Grid power when available will be used over battery power unless you have an ESS system configured. Then the logic shifts to prioritizing consumption from battery over grid but a low state of charge will trigger grid power usage.

If you want to insure that some loads only draw power from the grid, then you need to place them on the input side of the Multi/Quattro.

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Herve RV Nizard avatar image Herve RV Nizard commented ·
That's interesting . " put loads on the input side of the multi". Could you elaborate ? Thank you anyway.
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Kevin Windrem avatar image Kevin Windrem Herve RV Nizard commented ·
You simply put branch circuits in a box ahead of the Multi. The grid would feed this breaker box. There would also be a breaker for the Multi in this box.
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