svalvasori avatar image

AC2 Output Current Rating - Multiplus 12/3000/120 and/or Multiplus II 2x120

Reading either datasheets or the manual, the auxiliary output (AC2) shows a current limit of 25A with a fuse rating of 32A. This is the output I should put my non-inverted loads on, like Air Conditioners, ovens and water heaters - which combined, easily exceed 25A. I'm suspecting this is a documentation error, where it was not changed from the 230V value. Can anyone confirm this? Can AC2 have loads up to 50A (if not 75A w/boost) connected?

ac out 2
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4 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·


You could also wire all loads on AC out 1: the 50 Amp one.

And then add a contactor, coil powered from mains and/or AC out2.

Then I think you have what you want for the expense of a contactor. Or perhaps two: one for each leg.

Note that its quite likely we’ll be upgrading AC out 2 to be 50Amps, but that will take a while; easily 6 months, possibly 12. So.. thanks for raising the issue!

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Now that's an interesting idea, create my own AC2, but maintain al the cool features of the Multiplus. Now we are getting somewhere! Thank you for sticking with me :-)

How integrated is the contactor that drives AC2 in the Multiplus? Is is realistic for me to change the one in the case and possibly the wire size? Or is it soldered onto a board or otherwise impossible to change?

Dont go into changing contactors in a Multi; thats really not a good idea.

you dont need to change it for this idea, just add one externally

svalvasori avatar image svalvasori mvader (Victron Energy) ♦♦ ·

Just thought I'd ask :-)

Lyndsay Cotton avatar image
Lyndsay Cotton answered ·

I posed a similar question yesterday. Keep an eye on the responses to my question and I will similarly keep an eye on yours.

Although it might be self explanatory to the writer of the Manuals, being highly skilled technically, I often have to read the Manuals repeatedly to understand the content.

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This issue is the only thing stopping me from ordering a Mutliplus - if AC2 can support a full 50A @ 120V, then it will work nicely in my boat, otherwise it would cripple my electrical system. This should be a simple answer.

If you look at the diagram in the appendix of the manual - then we must make the conclusion that it can carry the full rated pass through (Depending on the model) However I await a more qualified answer from the Pro's

svalvasori avatar image
svalvasori answered ·

I've got my answer from some Victron folks in the US. It seems the Multiplus is only designed to be used in boats with 30A shore inlet, or boats with 50A inlet that never intend to actually use the full 50A.

AC2 is limited to 25A (32A breaker), not a typo. Supposedly this is where you put your big loads that you don't want to invert. Which means more or less everything electrical except outlets - how can that be expected to be less than 25A on a boat with 50A inlets? It's not. They want you buy a Quattro. Rather disappointing. I guess I'll have to hang onto my Magnum.

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cory cantrell avatar image
cory cantrell answered ·

Just curious why you would not just go shore power (assume 50a split phase?) to the AC 1 (on the 120x2 Multiplus-ii), then out of AC 1 back to the distribution panel that has every circuit on it (even large load items)? Then when on battery power and invert mode, don't use the AC, water heater, ect? I guess I don't understand why it cripples you as the AC out 2 wouldn't function when on inverter mode anyway right?

So when you are on shore power you can use them, when on battery you couldn't with your solution (connecting those loads to AC2), but could you not just not use them when on battery? I guess I see the scenario where if you were running those high power appliances on shore power and the shore power went out you might not notice and then drain your batteries, is that the concern? If so would a work around be just setup a notification that you lost shore power and then go shut off the appliances or something similar? I guess you could have "most" (up to 25a) heavy load stuff on AC2, then just do as above for the remaining? I get what you are saying, just thinking of ways you could have a work around and still enjoy the benefits of the victron over the magnum...

If you went with the multiplus-ii 12/3000/120-50 2x120 I believe that is 35A aux output (each leg), surely 70A would be enough? (again assuming you are on split phase 50a service, which could be a bad assumption). Microsoft Word - Datasheet - MultiPlus-II inverter charger 2x 120V - rev 0 - EN.docx ( - This is where I saw the 35a (each leg), but I could have swore I also read it was only as you stated 25a with 32a fuse rating...

I guess the other scenario would be if you lost shore power while away, but I wouldn't think you would want those heavy draw items running while you are not there anyway would you?

This is interesting though, I see the dilemma, just thinking of ways you can get around it. I am sure there is a fancy way to have your cake and eat it too :)? Someone more experienced might be able to help with that.

1 comment
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Hi Cory,

Thank you for taking the time to respond.

I could run it the way you suggest, all on AC1. The boat is currently twin 30A, I'm upgrading it to split phase 240V 50A this spring. Twin 30's is not close to enough power with two water heaters, 3 air conditioners, 2 chargers, stove top and oven. It's exactly the reason I'm moving up to 50A. I spend too much time hearing my over current alarm going off and re-adjusting what's on. It can be done, but boating is supposed to be relaxing.

We leave the dock every weekend and are on anchor. We have solar and a 960Ah house bank, but will run the generator for hot water when a shower is required. There is too much possibility that some large load might get missed and left on, drain the house bank and start the weekend poorly. The beauty of AC2, if it supported the full load is that it would avoid this issue. Even just on L1 I have the oven, one air conditioner and one water heater - that alone is 41.8A, and it's a real situation - come back from a weekend on anchor, cook dinner while the water is heating back up (cold from the weekend) the air conditioning is on because we are now stuck in the marina. Not to mention the batteries wanting to re-charge. We will also have the house bank charger and a separate 32V charger for the starting banks.

I don't have any reason to get rid of the Magnum - it's been a great unit. But I can sell if for reasonably close to what I can buy the Victron for, and I like some of the Victron features, but not enough to make work arounds. From what I can tell, the answer is to buy a Quattro as they have a full 50A on AC2, but I'm not willing to spend that much money on a problem I don't have. As it is designed, I don't consider the Multiplus a valid option for a boat with 50A split phase - what boat like that only has 25-35A per line? If it did, it would probably have twin 30A inlets. I do think the Multiplus is perfect for a boat with twin 30A inlets and will be recommending it to a boating friend who has that setup.

Just to give you a more concrete example (and because I have the spreadsheet open, here are my big loads). I'll do the math, below is 115.4A and doesn't include any of my inverted loads. (Ignore the red, those will be red breakers on the new panel so anyone leaving the boat for the week knows what to turn off.)

32V Charger 16.0
12V Charger 16.0
Sink Heater 6.3
Shower Heater 12.5

Fwd AC 11.0
Salon AC 12.7
Aft AC 11.0
AC Pump 9.6
Stove / Oven 18.3
Main Fridge 2.0