Multiplus-II 48V 3000VA 120V, AC-out-1 Powerassist does not supplement above 50A (edit)?

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cklio asked Sep 14, '23

Multiplus-II 48V 3000VA 120V, AC-out-1 Powerassist does not supplement above 50A (edit)?

Such is the title. Why has Victron made this specific inverter incapable to perform power assist to exceed the AC output limit? They explain how other inverters are 3kVA = 25A (@ 120V) and can be used to supplement the 50Amp Max AC input to get 75Amps total for a brief period on the AC output for their other models, but then simply note in the documentation that 50Amps is a hard limit for this exact model (Multiplus II 48V 3000VA) only - why?

Was this a certification requirement or a design flaw? Am I misinterpreting somehow?

https://shop.frankensolar.ca/content/documentation/Victron%20Energy/Manual_Victron_Energy_Manual-MultiPlus-II-120V-EN_(frankensolar).pdf Source. See table on page 14, and subsequent explanation of this table on page 15 Titled "AC-Out-1" , Victron states exactly "On the 48/3000/35-50 unit, AC-out-1 is limited to 50A." Which is the same as the AC input (50A). So... No Powerassist capability above 50Amps AC input??

Thanks All.

Multiplus-II powerassist

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Answer 1 · 2023-09-14T16:58:21Z

Alexandra answered · Sep 14, 2023 at 04:58 PM

@Cklio

You could have the load on the second AC and power assist is still since that is a 32A output as well.

50A on 120v is already 6kva so you want to add another 3 to the 6 - so 9kva load?

At that point maybe a re evaluation of inverter size is needed in that case.

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cklio commented · Sep 14, 2023 at 05:48 PM

Hi @Alexandra ,

That still doesn't address the question, though. "Powerassist" is to supplement the AC source fed to the AC input. If 50A is fed to the input of the multiplus, the Multiplus is able to pass it through to the AC ouput; and on most inverters - Assist the AC source with the 3kVA from the batteries (75A total) to the output to power a load. This appears to be true for all other inverters except this one.

If I recall correctly by the way; AC out 2 does not do power assist, and it's only function is to serve as an AC pass through. So that still won't work.

A customer of mine is asking to use the feature and specifically wants a UL listed victron inverter (48V). But victron offers no explanation why this inverter can't do powerassist on AC out 1. Just says it cant.

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derrick thomas cklio commented · Sep 14, 2023 at 08:20 PM

ACout2 DOES provide power assist function, so this could provide a way to utilize the full 50 amp input and 75 amp output, by placing some non-critical loads on ACout2. The only difference between ACout1 and ACout2 (besides the amp rating) is that ACout2 disconnects it's relay in the event of a AC input failure.

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cklio derrick thomas commented · Sep 15, 2023 at 02:03 PM

Hey Derrick, thanks for the reply. Do you have a source where I can confirm? I think you may be right based on what I'm reading; it seems as long as L1 is active on the AC input, then it should be able to perform power assist. However! The issue still remains that this feature is inconsistent across different models.

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derrick thomas cklio commented · Sep 15, 2023 at 02:36 PM

Usually when there are feature differences like this between similar platform devices it would be a hardware limitation. I imagine that is the case with the 48 volts model. It would not make sense for Victron to impose a software limit like this if the hardware is not the limiting factor.

If you look at the schematic for the victron inverters, you will see that the ACout1 and ACout2 are only separated by the ACout2 relay, essentially becoming a single output (with 2 connection points) when the AC input is available and qualified.

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cklio derrick thomas commented · Sep 15, 2023 at 03:00 PM

Hi Derrick, Which Schematic? Be specific please, or provide one from Victron or authorized source confirming your statement.

Also yes, there is a reason behind the software limitation; the fact that this is the only unit with UL1741. It could have likely been a stipulation with the ESA that the inverter have this feature removed. Whether you can use the auxiliary AC output to supplement this missing feature still doesn't explain why it's missing. The limitation imposed by UL1731 is complete speculation from my part; I'd like confirmation as to why it's a requirement/limitation for this model only, and I can't find anywhere that confirms this reason.

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Alexandra ♦ cklio commented · Sep 15, 2023 at 03:05 PM

@Cklio

It is in the manual, under block diagram

https://www.victronenergy.com/media/pg/MultiPlus-II_3kVA_5kVA120V/en/UUID-48d2edaf-21c1-5a2c-51fe-32532f2562ee.html

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cklio Alexandra ♦ commented · Sep 15, 2023 at 03:15 PM

Perfect, thank you.

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Answer 2 · 2023-09-14T19:44:43Z

Alexandra answered · Sep 14, 2023 at 07:44 PM

Possibly the thing is to verify the information

https://www.victronenergy.com/media/pg/MultiPlus-II_3kVA_5kVA120V/en/technical-specifications-120v.html#UUID-20e62c26-0cb9-9b4d-128b-0b871f5bbf02

I wonder about the 75A in that document linked in your origional post on the other models. It doesn't make sense from a manufacturer point of view to have so much change between what is essentially only a battery voltage change on the other models.

Usually the input or transfer switch allows the battery to be charged at full chat and the full inverter (inverting ability) load to be supported. Seems to be the MO on all Victron inverters even in the 230v ranges.

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cklio commented · Sep 15, 2023 at 03:07 PM

Hi @Alexandra, I agree. I don't understand why this model specifically differentiates in it's ratings surrounding power assist. Even if you're able to compensate using AC-out-2 (which I've yet to see in writing that you can do this, if you have any input there let me know - appreciate your time).

I don't really comprehend "verifying the information". The link I gave is written by victron - are you saying that's not the case? But yeah the ratings seem uniform with 75A being the max "surge" on the AC-out-1 having the inverter supplement a 50A source for all inverters except this model. That's why I'm wondering why. Hopefully someone from Victron can clarify?

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Alexandra ♦ cklio commented · Sep 15, 2023 at 03:11 PM

No the information that was linked in the origional post is not the victron website. Best to get information from there.

Their documents are always being updated.

The power assist works. Just check out the block diagram.

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cklio Alexandra ♦ commented · Sep 15, 2023 at 03:42 PM

Oh I getcha. Yea that makes sense.

In short wanted to say I know powerassist works, just does not work in excess of 50A. I checked through Victron's website for the inverter for an answer and still the same. "With its PowerAssist feature the MultiPlus-II can add up to 3 kVA (that is 3000 / 120 = 25 A) to the output during periods of peak power requirement. Together with a maximum input current of 50 A this means that the output can supply up to 50 + 25 = 75 A. On the 48/3000/35-50 unit, AC-out-1 is limited to 50A." Verbatim from your link still. Their line about the breaker further points to my theory that it has to do with a certification requirement. A breaker sized to 50A would pop if it was fed with 25% more current than expected, so that's probably the reason for limitation. You can't safely size a breaker if you want to use the inverter for power spikes above the normal limits of the AC in.

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