Benefits of Parallel Inverters

[Latimer1776]

I cannot seem to be able to find a straight answer, so I'll bite the bullet and ask what is probably obvious: What are the benefits of paralleling inverters? Specifically, how does it affect amps available?
I know that parallel inverters allows greater PV array size, and I know how parallel vs series works with PV and batteries. But if I have 2 inverters that can handle 50 amps, can they now handle 100 combined in parallel?

Reason: At some point, I'll need to replace my house AC unit (and buy a soft start), at which point I was planning to add off-grid solar. This would allow me to separate out my biggest energy expense. But even with a soft start, AC units have a high surge and that could change how I would have to plan the set-up if I want to expand the system so that I can slowly migrate other circuits over to solar.

 

[wdwtx2.0]

If both inverters are the same, and allow paralleling, they will provide double the power output.
If you have 2 ea. 6000 watt inverters, you will have one 12000 watt output system.
If each inverter is capable of 25 amps of 240VAC output, your paralleled system would output 50 amps of 240VAC.
The inverters need to be identical.

 

[Latimer1776]

If both inverters are the same, and allow paralleling, they will provide double the power output.
If you have 2 ea. 6000 watt inverters, you will have one 12000 watt output system.
If each inverter is capable of 25 amps of 240VAC output, your paralleled system would output 50 amps of 240VAC.
The inverters need to be identical.

Thank you, that makes sense. I was seeing a lot of results (google and whatnot) saying that power output would increase, but they weren't specifying if amps would increase in addition to the KW and didn't want to make assumptions.

I'm looking at the EG4 18k with the 50 Amp output, so a pair should cover a soft start heat pump/AC with room to spare.

 

[wdwtx2.0]

Yes it should.

 

[Mattb4]

It is not all that different for AC than it is for DC. The only problem comes in that some in the PV world refer to being in parallel when they really should use the term "stacked" for a series type AC hookup. To parallel AC you must match not only voltage like you do in DC but you must match frequency and phase angle. Once 2 units are in parallel each one can pick up a portion of the total load up to their capability. The AC voltage and frequency are in synch. So just like DC in parallel the currents can add.

Now comes in those setups where people want to get double the voltage. Taking 2 inverter outputs and causing them to be 180 degrees out of phase from each other allows this to happen When 1 inverter is outputting (+120vAC) and the other is outputting (-120vAC). The voltage between them is 240vAC. Like DC in series the voltages add.

 

[Quattrohead]

When you are looking at HVAC system replacement, go with the fully variable speed inverter type pumps, they ramp up slowly so there is no need for an easy start it's basically built in.
I personally have installed an ACIQ 3 ton unit.

 

[DIYrich]

I'm looking at the EG4 18k with the 50 Amp output, so a pair should cover a soft start heat pump/AC with room to spare.

I have a 3 ton AC, and the ONE 15k can handle it without a soft-start. It can deliver 50 amps continuous off battery, 62.5 amps with solar, 75 amps for 10 seconds, and 93 amps for 100ms.

 

[Videotec2000]

My EG4 18k runs my new 4 ton on the roof AC unit with a SS soft start with no problems. The lights are on and small things , phone chargers, lots of things in standby mode running as well. Just about to reach my first Meg watt hour.
Started running home first of April. Love it

 

[CaliSunHarvester]

in parallel when they really should use the term "stacked" for a series type AC hookup

I understand that inverters need to cooperate to be in sync if you want them both to feed one single electric service panel.

But what if I already have an AIO that cannot be linked to a parallel unit? I would think that I could have a 2nd inverter that is just straight on the battery bank and feeds a second independent electric service panel. The only issue that I see is that the AIO will be surprised that the battery keeps draining when the AIO is putting in more pv than load on the AIO. The reporting by the AIO about energy consumed would be incomplete as well, it would need to be merged with the data (Wh discharged) from the 2nd inverter.

Am I correct?

 

[Mattb4]

I understand that inverters need to cooperate to be in sync if you want them both to feed one single electric service panel.

But what if I already have an AIO that cannot be linked to a parallel unit? I would think that I could have a 2nd inverter that is just straight on the battery bank and feeds a second independent electric service panel. The only issue that I see is that the AIO will be surprised that the battery keeps draining when the AIO is putting in more pv than load on the AIO. The reporting by the AIO about energy consumed would be incomplete as well, it would need to be merged with the data (Wh discharged) from the 2nd inverter.

Am I correct?

I run this way presently. 2 AIO's linked to a common battery but supplying their own distribution box (transfer control boxes). They can not parallel or be stacked as they lack communication and the programing. It works out without problems other than having to monitor each as a individual unit.

 

[CaliSunHarvester]

I run this way presently. 2 AIO's linked to a common battery but supplying their own distribution box (transfer control boxes). They can not parallel or be stacked as they lack communication and the programing. It works out without problems other than having to monitor each as a individual unit.

I was talking about a second inverter. You have a second AIO with additional pv-in, I assume?
How does that work with the charge controlling where 2 chargers charge parallel, unaware of each other?
Or are you charging from one of the AIOs only?

I guess both AIOs could have their own grid-in as well?

I could imagine a setup where AIO 1 switches to grid pass-through when the battery drops to 20% SOC and the 2nd AIO switches to pass-through at 10% SOC.

 

[Mattb4]

I was talking about a second inverter. You have a second AIO with additional pv-in, I assume?
How does that work with the charge controlling where 2 chargers charge parallel, unaware of each other?
Or are you charging from one of the AIOs only?

I guess both AIOs could have their own grid-in as well?

I could imagine a setup where AIO 1 switches to grid pass-through when the battery drops to 20% SOC and the 2nd AIO switches to pass-through at 10% SOC.

You can have multiple SCC. In fact I run 3 solar arrays. 1 to each AIO's SCC and one to a stand alone SCC. In terms of AC in to the AIO's they do have their own circuit from my Main and sub panel.

Yes each AIO can be set to go to grid and back at different set points. I do not run battery communications so it is not a complication who is in charge which it might be if that was desired to have. Battery voltage is the setting used for back and forth. You can even set this up so that one goes back to the grid and begins charging the battery and thus the other never needs to transfer.