Best solution for a 3-phase home - General Discussions - Energy Talk

Hi All

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I am looking for the best solution for a 3-phase home.

My first idea was 2 single phase inverters on a phase each (see attached pic)

But I have been advised that a 3-Phase inverter might be a better solution.

My first choice would be Victron equipment (hence the 2 single phase inverters) with Pylontech batteries, but I am open to other brands. For the 3-Phase solution, SolarEdge seemed to be a good pick, but apparently the battery integration is much more complex??

Cheers
Fritz

It seems that you drink a lot of coffee if that machine shares half the inverter with the kitchen ! I like your priorities.

Could you give us more detail (if you have it) on how much power you need/use on each phase/db. What is your total consumtion, as well as peaks?
Some equipment like the welding and borehole might need the 3 phase, but it could be that all the rest could run on just one phase and then you only need one inverter for it’s back up. That would save you much and be less complicated, but it would depend on your usage and needs.

Ja thanks coffee IS important…

The 3-Phase thing is maybe a mental-block on my side. If you give it up with our municipality it is difficult and hugely expensive (R100k +) to get back. But to be honest I probably don’t need it. If I keep it I need to try and do phase-balancing to get my COC or so I’ve been told.

Usage wise it will be a biggish household (still renovating) and my medium to long term plan is to be off grid, but Eskom is still there if you really need it. We had a Studer XTH -48 in the previous house and we’ve only ever tripped it once when the dishwasher, washing machine and tumble dryer were running during load shedding (weekend kids in hostel). But our geysers and stoves were not on the inverter. So, I assume one is not enough even with a solar/heatpump geyser setup.

The billing is prepaid and is the sum of the 3 phases. Feeding back to Eskom sounds like a complicated idea!?

Bear with me! Electricity novice!

Fritz

I’m not sure about the phase balancing to get your COC. Someone else will need to comment on that.

If you can put everything on one inverter it will be a very large cost saving. And so much simpler which would meen less things that can go wrong. That would be my suggestion.
If you want to go blue, then the 5kVA Multiplus II is a good option and it has all the certifications to be grid-tied and get a COC. (4kW continuous power with a 9kW peak)

It sounds like you are making things more complicated than they need to be, from what I can see you have no 3-phase devices.

Just convert your house to single phase and get one single phase Sunsynk 8kw (they have a 12kw as well now) inverter. I did it and it works like a charm. I even have a 3-phase pump running of a VSD so 3-phase devices can be accommodated if necessary.

Is really easy for an electrician to do and takes about 5 minutes, does not involve rewiring your DB-Board. They just need to bridge the phases on the supply so you are only running of one phase.

Contact us to discuss your requirements of three phase hybrid inverter. Our experienced sales team can help you identify the options that best suit your needs.

As long as you are not going to be pulling more than 60A (13.8kw) of the phase you will be fine.

My hamster goes to the pub when it comes to 3 phase, however from my understanding you have options.

A 3 phase AC PV inverter like a Fronius on the house and then you put a Victron inverter on only one of the phases for your night time / battery consumption. You split your phases and put all essentials on the Victron phase. The non essentials, borehole, pool pump, oven, aircons etc. doesn’t have to be on the Victron phase.

Like I said my hamster goes to the pub, come in @JacoDeJongh
But if I understand correctly the essentials and non essentials will still be able to run off the AC PV by day.
The essentials will run off the Victron / battery by night.
And if you want to use non essentials at night they will run off Escom

Makes sense! I missed the Fronius part (a little under the weather and in bed).

And in getting a single inverter, might even be able to go for one of the bigger Multis.

@plonkster And during loadshedding he will have to rely solely on batteries? Could it be possible to put in a change over to move the Fronius to the critical output of the Multi? And can such a changeover be automated with the relay on a GX?

If it is a 3-phase Fronius and a single-Phase Multi, then no. If three single-phase Froniuses, then yes, you could put one on the output (but the cost of that would be prohibitive, compared to a single 3-phase unit).

The Multi will also feed energy into L1 to compensate for loads on L2 and L3, given that the billing arrangement bills on the total.

Side note: Don’t worry if the phase where you want the Multi isn’t L1. Simply rotate the phases (physically, or relabel for the sake of the installation) so that the Multi ends up on L1. As long as the rotation is correct, the system doesn’t care if it is L1-L2-L3, L2-L3-L1, or L3-L1-L2.

You should also bear in mind that most of the 3-phase inverters are in essence three smaller inverters linked together.

So, 12kw3-phase = ±3 x 4kw inverters

Fronius 12.5kw for example, max current is 19.9A = 4.5kw

So, if you go over 4.5kw on one of your phases you will overload the inverter.
This makes the balancing of your phases much more important.

Would be better in my opinion to convert to a single phase. You can run your 3-phase borehole pump of a VSD without any issues and you could then also run it off the solar with a soft start.

Would speak to them to find out if they have a suitable one for running your 3-phase welding machine of one as well

Yes. But in this scenario they are grid-coupled, so if you go over 4kW on any phase, the rest simply comes from the grid, and because the billing arrangement is that the total power over all the phases is accumulated into a total, the balancing isn’t as big an issue.

In an off-grid situation with a Hybrid inverter (eg Voltronic used to have 10 kW infini that was 3.3kW per phase, and Fronius has a hybrid too), you are absolutely correct though. Just because you have 10kW doesn’t mean it’s available on every and any phase

Want more information on single phase solar inverter? Feel free to contact us.

Blurb time!

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round ) and help figure out which parts and pieces you're going to want to get.

Well that's the thing about solar systems, there is no 1-Size-Fits-All answer. Your system will need to be designed to fit YOUR needs. When you design and built the system, it's not going to be the perfect system for me, or Will or 12vInstall or anyone else, but it Will be the right system for You and that's the goal.

As for where to get started, let me throw my standard blurb in here to help point you in the right direction. There's going to be a lot of math and research involved, but that's going to be a LOT cheaper than just buying parts off of someone's list and finding out that it doesn't do what you need.

Don't panic on the Power Audit, you'll actually be doing that a few times. When you do the first pass put in ALL the Things that you might want. AirCon? Sure. Jacuzzi? Why not. MargaritaMaster-? Go for it.

The second pass will be the "I Absolutely Need This To Survive" list that isn't going to have much on there.

The third pass will be the "This is what is realistic" audit that you'll use to design the rest of the system.

The Power Audit is going to tell you 3 primary things: 1: How big does your inverter need to be to power your loads? 2: How much battery bank do you need to last $N number of days with krappy weather? and 3: How much solar panel will I need to install to refill those batteries in a 4 hour day (the average usable sun hours rule-of-thumb).

Once you know what you Want and what you Need and what your budget can Afford there will be somewhere in that Venn diagram where those three things meet.

After that, THEN you can start looking at parts.

Yes, it's a long drawn out process, but it's worth it in the end. Not every house has the exact same floorplan, not every vehicle is the same make & model, and not every solar system is designed the same.