bardel33 avatar image
bardel33 asked

two phoenix 48/5000 inverters using one autotransformer

I acquired two surplus phoenix 48/5000 inverters and am planning on using one or both in a tiny home here in the US. I need at least one to be split phase for 110-120v. So the first question is if these are hooked up in parallel, would I only need the one bigger 100a autotransformer ? or it just doesnt work that way and I need one per inverter ..... Second very minor question is will the autotransformer work best splitting 240v down to 120 ? vs say 230 to 115 ? or does it really matter. thanks in advance for any input .

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1 Answer
Jason Bolduc avatar image
Jason Bolduc answered ·


We run 2 x MultiPlus 230v 48/5000 in parallel mode into the 100amp autotransformer. We then use the autotransformer to produce the split-phase 120/240 for general use.

This configuration was chosen vs. the more common design of using 2 x MultiPlus 120v 48/5000, one for each phase.

You can of course still use the autotransformer for managing unbalanced loads in both configurations.

A few things:
1) You can set the 230v Multiplus's way up to 245v in the control panel, so setting this to 240v is easily done if desired (VeConfig).

2) The frequency of course can be switched from 50 to 60hz as well via VeConfig.

3) The regular requirements for proper parallel setup for the inverters of course must be followed. (I have no idea if the Phoenix inverters have this ability)

4) Splitting 240v vs 230v would mostly depend on:

- Potentially modest energy savings using 220v or 230v vs. 240v.

- How far you're running your cables and what size of cable are you running? 230v split to 115v x 2 might have your end-use equipment running below 110v depending on cable/distance/resistance.

- Depending on design, such as the one described here, there are also benefits of running 240v on our main "service line" from the inverters to the autotransformer which is almost 300feet away. Double the voltage = half the amperage and therefore cables run cooler and more efficiently.

Our thinking was to design an off-grid split phase system that will survive any single component death (other than the autotransformer).

We will hopefully maintain the "microgrid" even in the event of one of the MultiPlus's having a breakdown (hopefully a graceful one.....). Or at worst, require simply removing the faulty unit from service and STILL have 5000va of power for both 120v legs. (therefore heating/cooling still works, all 240v appliances work etc)

The system has been running since March, going into it's first winter here in Canada. Zero equipment failures from any Victron equipment.

If you'd like any details on how we set this up, send us a message. I don't work for Victron nor do I know if this configuration is officially supported.

Jason Bolduc

CanWest Renewable

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bardel33 avatar image bardel33 commented ·

Thank you very much for your informative answer. Yes what you indicated was pretty much what I figured on my 230-240 question, just wanted to hear someone else's thoughts on it. Very good to hear someone is already running similar to what I was considering. I would very much like to know more details on your system. thanks Mark

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Jason Bolduc avatar image Jason Bolduc bardel33 commented ·

Sure, glad to share what info I have.

If it's your personal setup or detailed information, you can e-mail me at

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ben avatar image ben ♦ commented ·

Great answer above, I'll just add: definitely set it to 240V or a little higher for drop. USA standard is 120V, and motors are happier at that level.

(We use a single inverter through an A-T for the same result.)

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