Do I need Single or 3-Phase Grid Tie Inverter To Run 240V

[FoxMeister88]

Hi everyone!

I am in the process of planning out a grid-tie solar system for my parent's house and while looking around at which inverters are commonly available I came across mainly two types, single and 3-phase. I am planning on running 240V appliances like AC and Washer/Dryer etc, but I am not sure if I can do so with a single-phase. My understanding is that you need a 3-phase to be able to run 240V... Is this correct? The setup will be simple, solar panels > inverter > grid. No battery storage - not sure if that matters. Thanks in advance

 

[Mars]

No you don't need a 3 phase inverter. If it is a residence then almost certainly it is single phase. If you had a house the size of Bill Gate's house, it might be three phase.

Sometimes town houses, condos and apartments are fed with a three phase service but even then, the feeders to the individual units are single phase.

 

[offgriddle]

Mars is right, USA residential power consists of homes being fed by single phase 240 volt. Then 240 is split at the main panel into two 120 volt circuits, which feed wall outlets and lights. The high draw appliances like clothes dryers, water pumps, hot water heaters, hot tubs and such are typically fed at the full 240 volts via a two pole breaker.

 

[gnubie]

You have to be careful there Mars, the USA has dual 110VAC to most premises as two phase + neutral. Notional 240 is obtained by going across the phases, 110v is phase to neutral.

See how confusing it can be? offgriddle and I just posted the same information, but from a differentperspective.

 

[offgriddle]

You have to be careful there Mars, the USA has dual 110VAC to most premises as two phase + neutral. Notional 240 is obtained by going across the phases, 110v is phase to neutral.

See how confusing it can be? offgriddle and I just posted the same information, but from a differentperspective.

Gnuuuuuu yep two phases 180 degrees out of phase from each other, but we just call it single phase.

 

[Supervstech]

Gnuuuuuu yep two phases 180 degrees out of phase from each other, but we just call it single phase.

Yes, and for some reason, inverter companies call it “split phase”...

 

[Supervstech]

Hi everyone!

I am in the process of planning out a grid-tie solar system for my parent's house and while looking around at which inverters are commonly available I came across mainly two types, single and 3-phase. I am planning on running 240V appliances like AC and Washer/Dryer etc, but I am not sure if I can do so with a single-phase. My understanding is that you need a 3-phase to be able to run 240V... Is this correct? The setup will be simple, solar panels > inverter > grid. No battery storage - not sure if that matters. Thanks in advance

Grid tie inverters should specify what systems they are rated for.

Most will sync with the utility parameters and provide feedback to your solar production.

Don’t get a cheapo China grid tie 230v model for USA appliances... check with your utilities co. To get recommendations and the proper net metering setup... ya don’t want to be charged for the power you produce!

 

[Jcain]

Gnuuuuuu yep two phases 180 degrees out of phase from each other, but we just call it single phase.

It's a single phasor angle with two legs 180° opposing because of the center tapped neutral.

 

[offgriddle]

Interesting thank you.

 

[erik.calco]

It's a single phasor angle with two legs 180° opposing because of the center tapped neutral.

I was wondering how the 180° is created. Are you saying that it's a natural phenomena that will occur whenever I combine two 110Vs with a single neutral, then connect their lives? I'll always get 180°? I just assumed that the 180° was generated by the power company, or the inverter if it supported it with something to synchronize it.

 

[gnubie]

My understanding of the arrangement is that your split phase is supplied by a single phase input HV transformer where the secondary is '220' end to end with a centre tap the forms the neutral point for the two 110v phases so by the nature of the secondary the 2 hots / actives are 180° apart when using the centre tap as the neutral.

This is a fundamental difference from the closest thing to that arrangement in Australia where if you have a 2 phase supply the phases are simply two phases from the street 3 phase 415 and the neutral. Giving 2 x '230v' 120° apart. 2 phase isn't all that common here, its normally single or 3.

 

[offgriddle]

To equal a true 240 volts potential, the two, 120 volt AC sinusoidal waves must be exactly 180 degrees out of phase with one another. When one wave reaches the maximum positive peak and the other wave reaches the maxium negative peak simultaneously, the difference of potential measured between the two out of phase waves is a full 240 volts. This maximum of peak to peak voltage potential happens sixty times in one second in the USA electricial generation standard. Two, seperate, 120 volt invertors would have to somehow be coordinated to be at 180 phase angles from each other.

 

[Jcain]

Any clarification needed ? They explained it pretty well.

 

[FoxMeister88]

Yessir.. Thanks everyone for all the help. I was really overcomplicating in my head and you guys explained it pretty well. Earlier this week I was able to buy all the equipment myself including the correct inverter (thanks again) and will have an electrician come in and do the rest soon

 

[DThames]

To equal a true 240 volts potential, the two, 120 volt AC sinusoidal waves must be exactly 180 degrees out of phase with one another. When one wave reaches the maximum positive peak and the other wave reaches the maxium negative peak simultaneously, the difference of potential measured between the two out of phase waves is a full 240 volts. This maximum of peak to peak voltage potential happens sixty times in one second in the USA electricial generation standard. Two, seperate, 120 volt invertors would have to somehow be coordinated to be at 180 phase angles from each other.

Trying to think about the phase angle just makes one's head hurt and can be confusing. If you looked at the two ends of a transformer secondary winding, you would never start talking about the phase angle difference of those two ends. It is just the two ends and you have a voltage across those leads. On your house, pretend for a moment that the transformer output from the pole outside (I have a pole still) is not grounded. If you ground either end of the secondary output, you will have 240v to ground. If you ground the center (center trap), you will have 120v to ground, on both ends of the secondary, but still 240v across the ends of the secondary. That is what comes into my house, with the center of the secondary winding being grounded at the transformer pole, and brought into the house as the neutral.

The name brand UL approved micro inverters that I am familiar with are 230-240volt. You just connect them up like they are a 240v heater, AC unit, air compressor, oven, etc. If the power you connect them to meets their connection rules, they turn on and start loading the solar panels and driving back into the line they are connected to. I have a 50amp 240v line running out to my panels. Near the panels is a breaker box with 2, 30amp 240volt breakers. Each of those circuits have 4800watts (20amps 240v) of micro inverters connected to them. It is like magic. They just do their thing.

 

[offgriddle]

Trying to think about the phase angle just makes one's head hurt and can be confusing. If you looked at the two ends of a transformer secondary winding, you would never start talking about the phase angle difference of those two ends. It is just the two ends and you have a voltage across those leads. On your house, pretend for a moment that the transformer output from the pole outside (I have a pole still) is not grounded. If you ground either end of the secondary output, you will have 240v to ground. If you ground the center (center trap), you will have 120v to ground, on both ends of the secondary, but still 240v across the ends of the secondary. That is what comes into my house, with the center of the secondary winding being grounded at the transformer pole, and brought into the house as the neutral.

The name brand UL approved micro inverters that I am familiar with are 230-240volt. You just connect them up like they are a 240v heater, AC unit, air compressor, oven, etc. If the power you connect them to meets their connection rules, they turn on and start loading the solar panels and driving back into the line they are connected to. I have a 50amp 240v line running out to my panels. Near the panels is a breaker box with 2, 30amp 240volt breakers. Each of those circuits have 4800watts (20amps 240v) of micro inverters connected to them. It is like magic. They just do their thing.

Yes, annnnnnnd the only way to achieve 240 vac between the two, 120 vac lines is when both lines reach maximum, opposite, peak voltage at precisely the same time, thus, achieving the peak to peak voltage of 240vac. It's all about that phase, that phase, that phase ...

 

[Supervstech]

Yes, annnnnnnd the only way to achieve 240 vac between the two, 120 vac lines is when both lines reach maximum, opposite, peak voltage at precisely the same time, thus, achieving the peak to peak voltage of 240vac. It's all about that phase, that phase, that phase ...

Dang it, now you have that song bouncing in my head...

 

[erik.calco]

Dang it, now you have that song bouncing in my head...

The Dolly Parton twin song?

 

[DThames]

Yes, annnnnnnd the only way to achieve 240 vac between the two, 120 vac lines is when both lines reach maximum, opposite, peak voltage at precisely the same time, thus, achieving the peak to peak voltage of 240vac. It's all about that phase, that phase, that phase ...

I apologize to the thread author for hijacking the thread and my goal is not to argue. My goal is to try to show a better understanding of split phase. There are many images of center tap transformer circuits in public view that show the two outputs being out of phase. BUT that is because the ground reference is on the center and what you are seeing is a flipped polarity on the scope. Consider where you put your meter black lead and explore the circuits in the image below. If you put your black lead on the center point of the two series batteries, you will say that one battery has reverse polarity than the other one does. No, you just flipped your measuring system's polarity. The same is true with the transformers circuit.
A single phase transformer output is always in phase with itself. Half of it can't be out of phase, as it is all one thing. You do have full voltage end to end just like the series batteries do.

 

[offgriddle]

Hello BThames, as a fellow postee, I do not mind your contributions one bit, in fact I find the contributions of others invaluable in developing my own understanding of the concepts discussed in this forum. I'm having a hard time using the DC model in understanding phase relationship, as DC does not alternate, therefore, cannot demonstrate phase. Your thoughts please?