Using 2 inverters for reliability

[schuh8]

I am a beginner at DIY solar and am planning my first installation. All is going well but having trouble finding out one aspect of the installation. I was using an inverter 30 years ago on a live aboard boat and found it to be very unreliable. I know inverters have improved vastly since then but I still want increased reliability. So with that background ... here's the question.

Can I parallel the output of 2 inverters if inverter one is connected to half the panels and inverter two is connected to the other half. Panels will all be identical and neither of the two strings subject to shading? Right now the inverters I'm considering are the Growatt 6kw grid tie inverters (MIN 6000TL-X).

I realize in the event one inverter go's out I will only have half my rated capacity (but half is better than nothing ... right ?) Are there any serious cons to doing it this way ?

Thanks in advance

 

[timselectric]

All grid-tied inverters are paralleled on the outputs.
So the answer, is yes.
But they require a grid connection. Hopefully, this is not going on your boat.

 

[ScrotusGobbleBottom]

Can I parallel the output of 2 inverters if inverter one is connected to half the panels and inverter two is connected to the other half.

I think its worth mentioning that you can only parallel the same brand, and model of inverters and most importantly they need to communicate with each other to mach phasing of the AC output. To put it more clearly, If you took a renogy inverter and paralleled the out put with an amazon special inverter, I would think that it would probably result in at the very least an unhappy inverter, but probably you would let the magic smoke out of both of them.

I am new at this and I hope I am wrong... But I currently dont think so.

 

[timselectric]

I think its worth mentioning that you can only parallel the same brand, and model of inverters and most importantly they need to communicate with each other to mach phasing of the AC output. To put it more clearly, If you took a renogy inverter and paralleled the out put with an amazon special inverter, I would think that it would probably result in at the very least an unhappy inverter, but probably you would let the magic smoke out of both of them.

I am new at this and I hope I am wrong... But I currently dont think so.

That only applies to off grid inverters.

Edit for clarity:
Also applies to hybrids, because of their off grid capability.

 

[schuh8]

Sorry, should have mentioned this will be a grid tied system. But given that info ... If one of my two matching inverters goes out in 10 years and the Growatts are no longer available, I am assuming I could replace it with a similar 6KW grid tied inverter by another manufacturer ?

 

[Hedges]

You can have any brand grid tied inverters, mix-n-match. Because they all interact through the bottomless grid.
If one fails, just need another that accepts the voltage, current, and number of PV strings in some manner. (preferable not to have to rewire panels.)

But you will likely want battery backup for some loads, so consider hybrid inverters, or grid-tie inverters that integrate nicely with battery inverters. Know what is available and at what cost before buying.

Having a battery can also let you deal with time of use rates more cost effectively.

 

[timselectric]

Sorry, should have mentioned this will be a grid tied system. But given that info ... If one of my two matching inverters goes out in 10 years and the Growatts are no longer available, I am assuming I could replace it with a similar 6KW grid tied inverter by another manufacturer ?

Correct
Any size, any manufacturer.

 

[OffGridInTheCity]

I run multiple (redundant capable) inverters but not in the way you're thinking. Each inverter must power separate circuits - the 2 x inverters cannot be synchronized or AC output hooked to each other.

Each 12,000w 240v/120v inverter goes to it's own distribution panel. However, the distribution panels can power each other with an interlock set of breakers/wiring. If an inverter dies, I can power both distribution panels from the other inverter.


Of course I no longer have 24,000w but only 12,000w... but this can be managed by serializing use of household items (i.e. don't run the dryer at the same time as the cooktop) until the situation can be corrected.

And in fact, one of my AIMS died at 5yrs / 25,000hrs of operation and I used the top AIMS to cover the gap (power both distirbution boxes) till I got the new 12,000w SGP to replace it. I was able to get the AIMs repaired after a few months - so now I have 3 x inverters with one as a backup.

 

[marionw]

There are some things to consider:
When paralleling two inverters they must communicate with each other via a communications cable between inverters. One acts as the master and the other a slave. This ensures the proper phase relationship in the AC output of both. It is true that for some inverters they sync with the grid and if two are syncing with the grid they more than likely will be in phase. But what happens when the grid is down. The clock in the Master is used by the slave for phase syncing since both are now running solely on PV/Battery.
Equally important if you have two 120VAC inverters paralleled to create 240 VAC, the "slave" must phase shift it's output 180 degrees from the Master, thus the communications between inverters. You can't be certain that inverters from different manufactures will communicate that same data across the communications link.

 

[MajicDiver]

Right now the inverters I'm considering are the Growatt 6kw grid tie inverters (MIN 6000TL-X).

You appear to be in the US, I don’t think you will be able to grid tie the Growatt MIN 6000TL-X inverter because it’s not intended for US split phase.
If I’m understanding you properly, the MIN 6000TL-XH-US would be the version to use in US. These inverters do not have grid pass thru, in some cases it’s best to select a brand that does. To grid tie two of them at the same time you would need connect them electrically to separate panels and have a power meter for each ( or use what Growatt call a SYN200) such as to a sub panel and main panel or in some cases people have two main panels in a large home as we do and some others on this forum. Alternatively, if you want spare, buy two bigger identical ones and install in a manner that they are easy to swap. Test both and put one back in box or leave both side by side with one disconnected. If you are wanting consider other Growatt equipment types look close at what timselectric is doing. It’s not for me but would do well for lots of folks.

 

[timselectric]

Don't look at anything I'm doing for information on grid-tied. I'm strictly off grid. I don't want any part of the grid-tied nonsense.

 

[Hedges]

Since you have reliable power generation and storage, have you considered providing it to neighbors, for a fee?
Run wires, tie them into it ...

You could call it Tim's Gas and Electric

 

[MajicDiver]

Don't look at anything I'm doing for information on grid-tied. I'm strictly off grid. I don't want any part of the grid-tied nonsense.

I was referring to what I think/thought you were doing, part off grid with some loads still fed from grid separately?

 

[timselectric]

I was referring to what I think/thought you were doing, part off grid with some loads still fed from grid separately?

That is currently the case, because my system isn't complete yet.
But, there is not and will never be any grid-tied equipment.

(At least not connected to the actual grid) lol

 

[james1]

I run multiple (redundant capable) inverters but not in the way you're thinking. Each inverter must power separate circuits - the 2 x inverters cannot be synchronized or AC output hooked to each other.

Each 12,000w 240v/120v inverter goes to it's own distribution panel. However, the distribution panels can power each other with an interlock set of breakers/wiring. If an inverter dies, I can power both distribution panels from the other inverter.
View attachment 198929

Of course I no longer have 24,000w but only 12,000w... but this can be managed by serializing use of household items (i.e. don't run the dryer at the same time as the cooktop) until the situation can be corrected.

And in fact, one of my AIMS died at 5yrs / 25,000hrs of operation and I used the top AIMS to cover the gap (power both distirbution boxes) till I got the new 12,000w SGP to replace it. I was able to get the AIMs repaired after a few months - so now I have 3 x inverters with one as a backup.

So to be clear, you can have 2 inverters(not all in ones) connected to the 1 battery if they each power their own circuit? For instance a 1500 watt aims inverter to run large loads with a dedicated circuit and a small Victron 375 watt inverter to run small things like lights, etc ?

 

[OffGridInTheCity]

So to be clear, you can have 2 inverters(not all in ones) connected to the 1 battery if they each power their own circuit? For instance a 1500 watt aims inverter to run large loads with a dedicated circuit and a small Victron 375 watt inverter to run small things like lights, etc ?

Yes. Each inverter powers it's own distribution panel (with regular breakers) out to circuits. So each inverter powers a different set of circuits. However, the panels are cross connected so that by flipping breakers either panel can power the other. So a single inverter can power both distribution panels - and all the circuits - if need be. Of course if all loads are on at the same time it will overload a single inverter (that's why I have 2 inverters) but that can be managed by serializing use or disabling some of the circuits (turning breakers off) during the emergency period.

 

[james1]

Yes. Each inverter powers it's own distribution panel (with regular breakers) out to circuits. So each inverter powers a different set of circuits. However, the panels are cross connected so that by flipping breakers either panel can power the other. So a single inverter can power both distribution panels - and all the circuits - if need be. Of course if all loads are on at the same time it will overload a single inverter (that's why I have 2 inverters) but that can be managed by serializing use or disabling some of the circuits (turning breakers off) during the emergency period.
View attachment 204309

Thanks. Sounds good.

 

[hwy17]

Redundancy is overrated. I'd rather have one good system and make it less likely to fail.

Hypocritically though, I built my entire system in parallel to standard grid feeders, so my backup is always just switch back to grid.

 

[timselectric]

2 is 1 and 1 is none.

 

[james1]

2 is 1 and 1 is none.

I love redundancy but in my case with my current single inverter of 1500 watt I have to keep draw slightly below 1500. By having a second small inverter in the system I can continuously run the large load and keep the lights and demand water pump and TV etc running simultaneously. In other words I will get the equivalent of a 1900 watt inverter by just adding a small 400 watt inverter to the system.