There are a couple of ways to set up a split phase 120/240 volt system using an inverter.  The drawing below shows the conventional way where two inverters are paired together in a back to back configuration to work in sync and produce 120/240 volts.  This works fine as long as you have inverters that can be ganged together like this to work in sync.  The main disadvantage of this arrangement is   1) You need two inverters and   2) You can only draw from inverter one to power leg A and inverter two to power Leg B.   If leg B has a lot of load and leg A has none there is no way to get the other inverter to help out, it just sits there.

Twin inverters

There is an alternative way of doing this that is more versatile.  It uses a 240 volt inverter in combination with an Autotransformer.  This is what it looks like.  

Autotransformer with 240V inverter

In this arrangement the Autotransformer can split the 240 volt output of the inverter into two legs and balance the loads between the legs in such a way that you can have all the load on one leg if you want.  Its a much better setup with greater functionality and it allows you to use the inverter to its full potential.

All Victron VE Bus Inverters, Multi Plus Inverter Chargers and Quattros are available in 230 volt 50 Hz and with a simple software tweak can be converted over to 240 Volt 60 Hz.  They are available for 12,24 or 48 volts DC and in outputs up to 15 KVA.  Take a look at our Inverter Charger page for more details.  If you dont see a 230 volt version just ask, we dont have them all listed on the site.  The Autotransformer is relatively inexpensive and comes in two sizes, 32 Amps and 100 Amps

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9 Comments

Andrew Addison

Date 4/27/2019

Hi Peter, Does this give me a way to provide the same 50A supply that I get from the shore power and generator? I currently have an inverter that can provide 30A on each leg but it drives me nuts that I have to be careful what I run before popping the breakers, whereas on shore power I can run the lot - stove, AC, microwave, etc - without worrying. It would be great to be able to run the stove to boil the kettle without having to switch on the generator. Clearly the battery bank needs to be fairly large - we currently have 880ah of lead acid batteries but it is looking like when they need replacing lithiums are going to be a sensible price. I've been told that getting a separate charger to the inverter makes more sense especially if we take the boat from the US to the UK/Europe - is that still the case or can the inverter chargers cope with different input voltage/freq? Cheers, Andrew

Peter Kennedy

Date 6/17/2019

This Autotransformer is for a special purpose only as described above. If you read the manual there are a few other specialized applications. It isnt intended for use to change the voltage of shore power for international voyages and it certainly isnt an isolation transformer.. In some applications it doesnt really behave as a transformer at all because the two input wires go straight through to two of the three output wires. Victron have two transformers that can be used for international voltage conversion, 120 to 230 volts and vice versa. They are both limited to 32 Amps at 120 volts, 16 Amps at 230 volts. Neither convert the frequency. One version has automatic voltage detect for the input and a predermined user adjusted output voltage. The other version has to be set up manually. You will find both of these in our SHORE POWER > TRANSFORMERS section.

MICHAEL SHORE

Date 8/8/2019

I have been thinking of using my camper system as emergency power at home. .Sadly my domestic water well pump needs 240VAC and the van system produces only 120VAC. I have read that I can add one more multiplus in parallel to create the needed 240VAC . Will I then go nuts as the poster above describes and wish I had chosen and tweaked a single 230v viltron inverter?

Mark

Date 9/16/2019

This is all well and good but what do we do with the neutrals? If I'm looking at a not so typical scenario where I have an RV with 240V loads mixed with 120V loads on either phase, how do we handle the neutral ground bond with a Quattro in the middle? It's not really clear from the datasheet and manuals how that works. To further complicate matters, how would we change things if we had a second set of inputs from, say, a single phase 120V source (such as a 30A/120V connection or a single phase 120V genset). Stepping that up to 240V seems straightforward enough but I'm pulling hair out trying to keep the neutral/ground bonds straight. Thanks!

Peter Kennedy

Date 9/17/2019

I didn't go into the details of grounding and neutrals in the article because it is quite complicated for boats, easy for RV's. I can answer questions from prospective customers on an individual basis.

Alan

Date 9/21/2020

Am I correct in assuming that the inverter/charger combined with auto transfer would require a 240v input to the inverter charger, or does victron make a unit that can accept 110v shore power and output 240?

Bob Nob

Date 10/4/2020

I have a 5500 emerald gold RV generator it only puts out 120v but it has 2 legs of 120v going to the panel in the RV. I would like to use the RV generator to power my ductless 240v AC heat unit in my home, that pulls about 12amps maybe 18amps for a few seconds starting current. Everything else, including the lights in the house never go over 3 to 4 additional amps. Is my situation what this post talking about? If so then I'm in the right place. Thanks for any help you can offer.

Marshall Eberling

Date 12/8/2020

Hello Peter. My home is prone to power outages, so for years I've used the Onan generator on my motor home to back feed my 200amp panel to the house. The generator is a 5.5 HGJAB-1038D which provides two120v's on each leg of the motor homes panel. I know its weird how they wired the generator to not provide 230v split phase power but in all fairness the motor home does not have any 240v circuits. Please note I installed a main breaker lockout device which cannot physically open with the power from the gen set back feeding into the main house panel, so I don't back feed the utility lines. Anyway this has been working fine but I didn't have any heat, only refrigerator micro and lights. A few months ago in my home I installed a 18k btu mini split heat pump Ductless Aire model DA1821-H2-0, its nameplate says compressor 10 amps, outside fan motor .6 amp , inside fan motor .4 amp. Minimum circuit 15 amp. 1.5 hp. My question is do you sell some type of device that I can connect the gen set power to and feed the circuit that feeds the 230v split phase mini split unit. Hopefully a device that would be less expensive or comparably priced with the alternative of having to buying a separate inverter generator for the mini split unit? I was hoping to find a way to avoid running two generators.

Ronald Monical

Date 2/5/2021

I have a 50amp rv in the us. the ac distribution box goes from 2 50 separate legs in the first box and half of the second leg goes to a 2nd . I have wired the 2 Victron multiplus to go from original transfer switch to box with 2 separate 50 amp breakers to feed each multiplus with 1 leg of the rv 50. then out to each side of the original house boxes . How do I program the multiplus to function in this configuration. I'm setting them up to be standalone and to just provide the power to there respective leg. but do I tether them together with a r45 cable from 1 to the other then from the other 1 to cerbo gx. I know this will only provide me with information from the 1 but may add another cerbo in future. will this give me any problems I know I only have 3k of wattage per side but if on shore it would give me the full 50 per side correct. I thank you Ron

Alan Howell

Date 3/10/2021

Hi Peter The 240v and auto transformer looks like an interesting alternative. I have a 110v 50 amp input to a Beneteau Sense 51. This splits upon entry to the boat to two 30 arms. There is a 110 to 230v up converter on the boat to run air conditioning and water maker. There are times that we have to plug into two 30 amp outlets and use a marinco plug converter with safely circuit to get a 50 output. Am I correct that if we ever ended up at a dock with only a single 30 amp dock plug or two 30 amp on he same phase that the Victron 230v inverter charger would not work at all? Is this a case where using two Victron Multiplus might be better? Thanks for your thoughts.

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