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Setting up Parallel Multiplus for a 50Amp RV all documents are very imprecise...

So a 50amp RV shore outlet is actually two 50amp connections for a total of 100amps right? So when I program my multiplus inverters, is my input current limit 100amps meaning I program 50amp or is it 50amp and I program 25amp? Or am I totally misthinking this because it mentions "per phase" and a parallel system is single phase so I should just set it to 100amp... or is that 50amp...

I'm following the following information from the Parallel and three phase VE.Bus systems document

The following settings need to be made in the master of each phase:

  • Inverter output voltage

  • Input current limits
    (the effective input current limit is the setted limit multiplied by the number of units per phase. For example, setting a 10A limit with VEConfigure in a system with two units per phase results on a 20A limit for that phase. Being able to set a different limit per phase allows for maximum configurability.

Also when I'm looking at the maximum charge current, if my total charge limit is 70amp I would set it to 35amp?

input currentshorepowermultiplus in parallel
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2 Answers
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Woody answered ·

I'm setting the system up in parallel. I have no need of 240v split phase as I have no 240v appliances. I'm trying to get the most AC bang for my buck specifically when on batteries, if there is a better way to do it I'm open to redoing the system. I've attached my schematic below.

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I don’t think it will work as drawn. You Basically have a split phase schematic. The shore neutral can’t be used for 2 different inverters unless you wire it in split phase, or they are truly paralleled and use only 1 hot and the neutral.

I would set up in split phase. This way the neutral only carries what imbalance exists between L1 and L2.

Stacked (or parallel) system can only utilize one hot and a neutral and won’t allow full use of the shore input.

An even better solution would be to get one larger 230V inverter and an autotransformer. It will utilize full shore power and will balance the loads between L1 and L2.

Well it's too late for a new inverter, so this is what I have to work with. I've been getting a lot of contradictory information on parallel vs split phase. I can't find and nobody can tell me which one is better for my situation or even make arguments for one over another. Right now it's wired as two stand alone systems each powering one half of the breaker box. While on shore power this works without issue. When I switch to run on batteries I get overloads when I run A/C with another high draw device like toaster, hair dryer etc. on the same side of the breaker. I was told that parallel would allow the two inverters to work together to overcome those sorts of issues. I don't see how split phase can as it seems the two inverters are still basically just stand alone devices unless you have a 240v appliance. Am I right in this?

The input to your RV is split phase with 50 amps per leg for a total of 12,000 watts. Each leg is 6000 watts max but are 180 degrees out of phase and can't be combined. So you really have no choice but to run the two Multis in a split phase configuration.

It is true that one inverter feeds half of the loads so if you draw more than what the inverter can supply on that half, an overload will exist even if the other half is lightly loaded.

As solardude says, you could use HALF of the incoming 120/240 split-phase service. ONE incoming leg would feed both inverters and both halves of the breaker panel. But that means the entire system is now limited to 6000 watts including when running from generator. The other shore and generator legs would be unused.

You may be able to rearrange branch circuits so that your most common loads are balanced between the two legs.

Installing soft starters on your air conditioners will also go a long way to allowing more things to run simultaneously. But it will still require some balancing.

You could install chargers powered by the incoming 120/240v and NOT connect the AC ins to the inverters. The inverter outputs could then be connected in parallel and supply the RV's AC loads 24/7. But there would never be any passthru or assist possible.

This is all very good and valuable information, but it doesn't address my question of what Amperage do I program? I think I've settled on running it split phase. parallel has too many draw backs and running the two units independently has issues with overloading the shared neutral. So split phase is the best compromise.

So since each inverter gets one leg of the split phase service I assume they each get programmed for 50A for a total of 100A? What about charge limit? Is that 35A or 70A if I want my max to be 70A?

Hi @Woody

the input current you set, is for each phase, so if you have split phase, 50A setting means 50A per inverter (each has a phase)

if you have parallel inverters, a 50A setting means 25A per inverter, as they share a phase.

Charge current is set per inverter, so 2x 50A = 100A

The input limit should be based on your breaker size and transfer relay size on the inverter. You could also reduce it down to accommodate a smaller genset if needed. But 50A input limit is the standard.

For charge limit, setting to 35A will yield 70A total. If you have a CCGX or Venus, you could also set up DVCC with max 70A. But this is only necessary if you have other charging inputs such as MPPT. If inverters are the sole charge source then 35A is correct

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solardude answered ·

A diagram of how you are setting up the system would be helpful. Are you only inverting one leg of your 125/250 system? Or are you trying to invert both legs (split phase system)? If you are stacking 2 inverters (parallel) then you can only connect it to one leg and get 120V.

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One thing maybe I did not make clear, is that I only want 120v. I don't need 240v. I really just want to be able to produce the most amps possible while on batteries. Is this going to happen with a split phase or a parallel system or something different entirely?

Split phase will give you the most available power. You don’t have to use 240V just because it is configured as split phase. Using either leg of 120V plus neutral will give you 50A AC per leg @120V.

I guess it also depends on how many watts your inverter is. What models are they?

But wouldn’t just leaving the two multiplus 24v 3000/70 in stand alone mode running half of the electrical panel produce the same result? They would each get 50A from one of the two split phase legs and pass that as split phase to the panel (this is how I currently have it set up) but when you switched to battery they would just provide power to whatever is drawing?