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jbartee7 avatar image
jbartee7 asked

Multiplus Powerassist Limit question

I was wondering if there is a way to limit how much power the powerassist feature adds to the shore power coming in? I've seen that there is a setting that allows you to limit at what shore power input the powerassist kicks on but not how much power will be added.

I have the 24/3000/70 and have not setup my solar system on my rv yet so haven't been able to look for the setting itself.

The reason why I need to know is that I have to run triplex wire 30 feet from shore power to multiplus and 30 feet from multiplus to my ac distribution panel. If I can limit the powerassist+shorepower to never go above 30A then I can run 10awg triplex for both wire runs. If not I have to get 6awg triplex to run from multiplus to ac distribution and it is considerably more expensive wire.

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4 Answers
hjohnson avatar image
hjohnson answered ·

What I did in your situation was to put a 32A breaker immediately adjacent to the multiplus. It also serves as a whole-boat RCD. That way, it’s safe to run 10awg triplex (hot/neutral/PE) to my (small) distribution panel. This also lets brief overloads through, by design.

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jbartee7 avatar image jbartee7 commented ·
So is there not a setting to limit how much power is assisted? when you say it allows brief overloads through, does that mean like I can go over 32A briefly for something like my air conditioners surge wattage?
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jbartee7 avatar image jbartee7 commented ·
would I just run the hot wire through the breaker or are there breakers specifically made for triplex wire?
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jbartee7 avatar image jbartee7 commented ·
@hjohnson Just wanted to get these couple questions answered since I am doing my install today and tomorrow. Also I am having trouble finding a 32A breaker, mostly 30A out there, would a 30A be sufficient and still allow brief overloads through? and do you just use a standard breaker for triplex and run the hot wire through it only?
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hjohnson avatar image hjohnson jbartee7 commented ·

@jbartee7 I bought a couple of ASI 32A DIN mount breakers from Amazon. They’re ELCI type (basically a GFCI, but with a 30mA trip rather than 5mA. They also protect and lift both poles, which they have to do in this situation.

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jbartee7 avatar image jbartee7 hjohnson commented ·

@hjohnson would this be the right kind?

https://www.amazon.com/dp/B08H1Q3V4Y?psc=1&ref_=cm_sw_r_cp_ud_dp_Y82M64B4KXVG35BJ4729

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hjohnson avatar image hjohnson jbartee7 commented ·

The ones I purchased have a part number of NDB1L-32C-32-120V . They’re UL listed and seem to be pretty solid. (they’re a ground fault breaker)

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jbartee7 avatar image jbartee7 hjohnson commented ·
@hjohnson sorry for all the questions but just wanna make sure I get it right. Can you explain how you used the two breakers and how to wire them properly with triplex cable? I'm not super familiar with all this stuff, first time doing a big electrical install like this
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hjohnson avatar image hjohnson jbartee7 commented ·
So I have two small DIN breaker boxes, one for each of the two breakers I linked. The first is in my Lazarette, and is used as the main disconnect for my shorepower. Shorepower comes in, line and neutral (black and white) go to the breaker, Green earth goes to my galvanic isolator. I have also rigged in a couple of indicator LEDs to show when power is present, and reverse polarity. (green 120V indicator between neutral and hot, and a red one between neutral and earth).


The second breaker is directly connected to the output of the multiplus, line and neutral going through the breaker and the ground link passing it by. This effectively prevents more than 32A from coming out of the Multiplus, even though it's theoretically now capable of 50A.


As far as straight wiring directions, if this is something you're not sure about doing, I strongly advise hiring someone who is comfortable with it. We're talking about significant power here, both on the DC side and the AC side. If you're not 100% confident in doing it yourself, please don't. There's too much risk of creating an electrical fire if you get it wrong, or don't make the connections correctly.

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Kevin Windrem avatar image
Kevin Windrem answered ·

There is really no way to limit AC output power/current. Doing so while the shore power is present (assisting) would simply mean drawing more power from the shore power and less from the inverter. At some point, a breaker will trip.

The only way output power could be limited while inverting would be to reduce output voltage which isn't a very good idea.

A breaker in the output path will limit the current to what is save for the wiring. Breakers will allow a brief overload for surges but that depends on type and the amount of overload. I highly recommend soft-starts for air conditioners when a generator or inverter is involved in their startup.

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jbartee7 avatar image jbartee7 commented ·
I do plan to get the softstart for the AC unit before using it with the inverter. That's kinda my last step with all my solar install. So considering the AC unit being the largest power draw I will ever use on the inverter, would it be ok to use say a 32A breaker on 10awg triplex wire? or would it be better to just bite the bullet and run 6 awg triplex across the camper? I'd rather not end up tripping the breaker often or making things more complicated so I'd be willing to spend the extra for bigger wires if it means ease of use.
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Trevor Bird avatar image
Trevor Bird answered ·

ad8ce4f2-d60c-43a6-8806-e875fe5a8f81.pngIn the inverter section of the multiplus adjust the power assist factor down to what you would like it to be. Factory default is 2 but you could turn power assist off or reduce the factor down to say, 1.2.



ad8ce4f2-d60c-43a6-8806-e875fe5a8f81.png (268.3 KiB)
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jbartee7 avatar image jbartee7 commented ·
Awesome! that's what I was looking for! so If I limit the powerassist to kick on when shore power is 15A or less, then with boost factor of 1.2 it would only assist with 15A*1.2 correct?
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Kevin Windrem avatar image
Kevin Windrem answered ·

Unfortunately VictronConnect does not define Assist current boost factor and the various manuals do not provide any insight either. VEConfig provides an explanation however. It does NOT control the amount of power assist, at least in the steady state so isn't going to give you what you want.

Here's the info from VEConfig's help:

This setting is a special setting for PowerAssist. When the Multi is charging and, due to a sudden load, the mains current exceeds the AC input current limit the Multi will switch to assist mode (when enabled, see PowerAssist).

At that moment the current needed is unknown. The Multi makes an assumption of the magnitude of this current. This assumption is equal to the AC input current limit multiplied by this "Assist current boost factor" setting. The default factor is two. This will prevent the circuit breaker from tripping because current provided by the inverter minus the current drawn by the load is always lower than the rating of the circuit breaker. This, of course, when the AC input current limit is correctly adjusted to the circuit breaker.

If, for instance in a generator application, the circuit breaker has a higher value than the AC input current limit. (Nominal capacity of the generator is lower than the maximum peak load) and one knows that the load which is switched on always draws a certain current one can consider to increase this factor to achieve better results with sudden load changes.

So assist mode boost factor appears to only apply when the load current changes and ends when the load current has stabilized.

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