Wiring Two SolarEdge Home Wave Inverters Together

Elroy · November 2023

Hello, I've currently got a single 3800 watt SolarEdge inverter, along with 16 ground-mounted solar panels (two strings).

Basically, a one-line is:

Solar Panels ---(two strings, 4 wires)---> Inverter ---> Fused (60a) Cutoff Switch ---> Backfed 30a breaker.

I'm wanting to double what I've got. I've already got a second SolarEdge inverter (identical to the one I've got), and my solar panels. I'll be putting pipe in the ground this Saturday.

But, I just want to verify that I can just wire the AC output of those inverters together in my gutter box. Basically, I'm wanting this:

Solar Panels ---(two strings)--> Inverter#1 \
>----- AC Lines (L1,L2,N) ---> Fused (60a) Cutoff Switch ---> Backfed 60a breaker.
Solar Panels ---(two strings)--> Inverter#2 /

I'll upgrade all the AC wires to #6AWG. And I'll use three-way lugs in the gutter to put those together.

DOES THAT LOOK RIGHT?

TIA, Elroy

ps: All grid-tied.

SumPower · November 2023

Wire size, 16 amps x 2 = 32 Amps. Continuous load is multiplied by 1.25.

So 32A x 1.25 = 40 Amp rated wire minimum.

If you have voltage drop to consider a #6 cu is good like you have.

Depending on the code cycle your jurisdiction is on the breaker size at the main panel may need to be adjusted lower.

If you have a 200 amp main, then a maximum of a 40 amp breaker would be allowed for your grid tie feeder at the main panel.

If you have a 175 amp main breaker, then you could use a 65 Amp breaker at the main panel for your grid tie.

Divide breaker size by 1.25 to find max. allowable continuous inverter current. With a 40 amp breaker the max allowable amps to feed to the grid would be 32 amps.

All this is dependant on the code cycle you are on.

Elroy · November 2023

All I'm really wanting to know is if it's correct to tie the AC side of the two inverters together as they're getting to a single back-fed breaker.

Elroy · November 2023

@SumPower: Thanks for bringing my attention to the 120% rule! I've done more calculations, and a 40 amp breaker will get done what I need to do. I didn't realize there was that limit, but 40 amps seems to squeak by.

SumPower · November 2023

Elroy said:

All I'm really wanting to know is if it's correct to tie the AC side of the two inverters together as they're getting to a single back-fed breaker.

Yes, it will work. Just as long as you use 75° C rated conductors and lugs, Before I retired I used a lot of Polaris lugs.

https://www.platt.com/p/0286638/nsi-tork/multi-tap-connector-3-port-black-insulated-14-4-awg-1-sided/662381910011/nsiipl43

BB. · November 2023

Need to look at the installation requirements... (Actual manual, your country, local codes, etc.).

The typical requirement would be for 2x 20 amp breakers installed at the opposite end of the main panel inlet breaker (opposite end of internal panel but bars).

Generally, a single 40 amp breaker would exceed the branch circuit wiring requirements for a typical {not large) gt inverter.

Note, if this is North America, then you would have a 2 pole breaker for 240 VAC circuit (120/240 VAC split phase power).

And 2x 20 amp 2 pole breakers.

Details matter here.

Bill

SumPower · November 2023

As always, very good comment BB!

My post above only works if the (2) griid tied string inverters are run to a a sub panel first. Then to a main panel.

BB. · November 2023

Yep--A sub panel with (at least) 40 amp feed and 2x20 amp breakers should do it... You may have labeling requirements (caution solar power, etc.)...

-Bill

Quanta · January 23

This thread got my attention due to the fact, it appears the poster is trying to determine if it is possible to connect the inverters in parallel.

OP Diagram:

But, I just want to verify that I can just wire the AC output of those inverters together in my gutter box. Basically, I'm wanting this:

Solar Panels ---(two strings)--> Inverter#1 \
>----- AC Lines (L1,L2,N) ---> Fused (60a) Cutoff Switch ---> Backfed 60a breaker.
Solar Panels ---(two strings)--> Inverter#2 /

I'm a newbie to the solar industry, yet have significant EE back ground. My question: Will the output of the two inverters sync in phase automatically? I would think this would be a routine feature for the medium to high end systems on the market now.

Quanta.

BB. · January 23

Quanta,

In solar (and electrical, electronics, etc.) it is the details that matter.

Always (or at least most of the time), Grid Tied/Utility Interactive Inverters can have their AC outputs (L1/L2/N in North America) tied together (generally through some sort of circuit breakers, possibly sub panel).

Off Grid Inverters, PSW/TSW (pure/true sine wave inverters) cannot have their outputs tied together--Unless they have have a sync cable of some sort (note there is tying the outputs together in parallel to increase AC amperage output, and tying the outputs in series to convert two 120 VAC inverters into 120/240 VAC split phase power).

And Off Grid MSW inverters are a special case--The parallel/series issues for off grid inverters still applies, and another "gotcha"... The standard inverters have isolation between the battery bus and AC output. So you can have grounded DC negative and grounded AC Neutral. MSW inverters will "short circuit" if you do this because there is NO ISOLATION between DC input and AC output.

On the solar side, there are many GT/UI inverters that cannot support a large solar array. These (called transformerless?) GT inverters do not have isolation between Solar DC input and AC output... For those, each GT Inverter requires its own personal Solar panel/solar array.

Just as an FYI, more or less a GT inverter outputs current following the AC sign wave form. So, paralleling standard GT inverters to the same AC mains is not an issue.

And today there are lots of Hybrid Inverter units that have GT/Offgrid/Genset/etc. capabilities... You need to look very carefully at the specifications/installation manuals before you make any assumptions about what any particular hardware requires for power connections.

-Bill

Quanta · January 26

Bill: "You need to look very carefully at the specifications/installation manuals"

I'm finding this engineering field to be: Not grandpa's off grid solar. Very complicated. Enjoying the dive.

Thanks,

Quanta.

Wiring Two SolarEdge Home Wave Inverters Together

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