2x Inverters Help / Advice

Deagol · 28-03-2026 11:55AM #1

Hi all, hoping someone with expert understanding can help me with this.

I currently have a Solis Hybrid 5kw inverter with 5Kw battery and 6.1Kw panels installed and working (2 strings).

I've now installed another 2Kw of panels and I want to utilise an older Trannergy non-Hybrid inverter to boost the output in low light (winter mostly) conditions.

I'm getting conflicting advise on how / if it's possible to do this safely etc.

My tentative plan was to split the current AC feed from the CU to the existing inverter (6mm2 cable) and add the second inverter to that line (putting in a new AC isolator and a small sub panel with 25A RCD before the second inverter).

Is this a viable setup?

My understanding was that the non-hybrid doesn't need any comms / CT clamp etc, it will just sync with the grid and the Hybrid will not know or care about this second inverter?

Anyone help with some advise?

10-10-20 · 28-03-2026 01:35PM

The simplistic view on this is that the Trannergy will push all available solar capacity into the house and grid (as it has no monitoring facility), but the Solis will follow and only manage the power which it pushes onto the grid. In effect the Trannergy will be the lead supplier for the house, and the Solis will follow.

The critical points to watch out for:

The supply cabling and fusing needs to be within spec for the new capacity of 5kW PLUS the design capacity of the Trannergy.
You need to double-check that the Trannergy is EN 50549 compliant so that it does anti-islanding in a similar way to the Solis.
You should ideally also have panel isolation to match the Solis (fireman's switch or similar automated power isolation).

In terms of how the two inverters will work together, I've said before on another thread that not all parings such as this work out well as some older inverters use a poorer quality sine-wave and have poorer response times to grid changes, and may have worse harmonics; hence there's always a risk of issues around pF and significant harmonic issues, but as others pointed out - that's not commonly an issue in residential environments. It's a suck-it-and-see really.

Deagol · 28-03-2026 02:22PM

Thanks for the information.

The wiring is going to be 2.5mm2 from the Trannergy inverter to a small 3 way CU, that will have a 20A RCD fitted. This will be connected back to a JB with split from the Solis Hybrid which is using at least 4mm but I think it's 6mm cabling (because of the 40A RCD) and that goes back to the main CU with 40A RCD etc.

My understanding is 4mm2 will happily handle total load from both inverters anyway in free air (the cabling runs through a crawl space to the main CU so not enclosed anywhere). I am going to get a family sparks to check everything before I turn it on though! He's not a solar guy though so he wasn't at all sure about the inverter setup hence asking here about that element of it.

The Trannergy SGN2300TL I'm using, I think it has the EN50438 standard so has anti-islanding but not the latest grid stability updates for 50549. It was previously used so my understanding is because it was installed prior to 2022 it can still be used?

On the DC side, I have installed a seperate firemans switch and a new DC isolator. The AC side will have it's own new AC isolator also.

I'm assuming if the modified sine wave etc are a problem, it won't damage anything - just cause faults and the inverters to suspend etc? If it is an issue, I'll buy a new inverter as the non-hybrid ones are cheap enough. I was trying to be environmentally friendly by not chucking a perfectly good inverter in the bin!

10-10-20 · 28-03-2026 04:09PM

https://www.boards.ie/discussion/comment/124347326#Comment_124347326

Grid stability updates are just min/max voltages, frequencies and durations, IIRC. It might be better to be shy of the values anyway for some level of isolation during a power event.

The main benefit here (as you know) is that all of your solar on the Solis can be redirected to the batteries, leaving the Trannergy to do the daylight duration grunt-work. Time for a new 14kWh battery, I'd say! 😉

bunderoon · 29-03-2026 03:05PM

I'm kind of in the same boat.
I currently have a 4kw non-hybrid managing 5kw (5 x 550w at 17 degrees on roof of shed and 4 x 500w at 90 degrees vertically on shed wall). They are on separate arrays - MPPT 1 and 2. Working well. However I have bought a new Solis 5kw hybrid and will buy a 16kw battery. Have EV and 2-5am EV rate with BGE.
Shed has it's own subboard and is connected to house via 10mm sq SWA to 40A MCB at house CU.

My options are 1) to remove the 4 at 90 degrees and put them down in from of the shed and ground mount them at 17 degrees and add them in series with the other 5. So 9 in series on MPPT1. Panel IMP and Voltages etc are fine for 9 of them on the MPPT1 of the new 5kw (S5-EH1P-5K-L).
I can then use MPPT2 for a 3kw eastern array. But absolute pain to bring those 4 down as there are services under the ground where they'd be placed.

Option 2) Done touch the two arrays. Attach battery to 5kw hybrid as RBCO etc already in place and rated for it.
Reuse the 4 kw non-hybrid for the new eastern array. It will have its own fireman switch, rcbo, DC and AC switches. Technically will have to get electrician back to wire it in.

And this is where I'm in the same boat. Do I simply set 4kw inverter (with 3kw panel eastern array) to export to the grid and set the hybrid to monitor via the metered clamp at the ESB box to dynamically reduce its AC output to ensure that no more than 5kw total ever gets exported? Can also set it to charge the battery it has.

BGE - 2am to 5am. Already have immersion 3kw, EV 6.6Kw and I'm not too comfortable in another 5kw going into battery at that time of the morning. All goes back to House CU which is managed by a 63A MCB in ESB box.

First world problems. And not exactly inline with NC6 if total inverters amount to 9kw.

All advice welcome.

Deagol · 31-03-2026 10:23AM

NC6 is export limit as far as I understand it. So you can have as much solar as you want provided you don't export more than 5kw.

To keep within that, you could tell the hybrid to limit the export to 5kw. I think if you do that, it will simply watch the CT for export and limit itself once you hit the 5kw limit. The fact that the hybrid won't be supplying all the 5kw because the other inverter is doing some won't matter…I think! Hopefully more expert / experienced people can answer.

For me, I'm going to be a naughty boy and see if anyone notices my export is potentially 7kw…. I don't think they check it? And if anyone does and I get scolded, I'll plead ignorance and say my Hybrid setting went astray or something. As long as there's no safety issues around doing this I'm happy to chance it.

As always, expert advice welcome.

graememk · 31-03-2026 10:58AM

https://www.boards.ie/discussion/comment/124352640#Comment_124352640

NC6 is the inverter limit, export limiting is not a part of the NC6. Just to clarify the rules.

ELM327 · 31-03-2026 11:05AM

https://www.boards.ie/discussion/comment/124352640#Comment_124352640

NC6 is inverter limited not export limited. NC7 is export limited. Adding the extra inverters makes you non compliant. Now they won't be noticing this unless you exceed your stated NC6 MEC which is likely 6kW (check your specific MEC and MIC with networks if you don't know).

So if you are going "out of spec" I absolutely would under no circumstances exceed 6kW of export. If you have a smart meter they WILL be able to see this at a moments notice.

https://www.boards.ie/discussion/comment/124352725#Comment_124352725

Yes, an important clarification.

bunderoon · 31-03-2026 03:31PM

I bought a 5kw hybrid, soon to be swapped in for the 4kw non-hybrid I have at the moment. The max rated AC for the Solis 4kw is 4.4kw. So the electrician put 4.4kw on the NC6 and that is what shows on my Bord Gais Energy account.

I'm curious, when I swap to the 5kw hybrid and where I can be exporting the max 5kw, would BGE notice anything as they would be giving me the FIT for what I export.

Deagol · 31-03-2026 07:24PM

https://www.boards.ie/discussion/comment/124352750#Comment_124352750

Thanks for the advice. I'm hoping that due to orientation, angles, base load etc, that I shouldn't be exceeding the limit but I'll look at limiting the Hybrid to control it.

...Ghost... · 02-04-2026 09:46PM

https://www.boards.ie/discussion/comment/124353534#Comment_124353534

BGE won't care, but your NC6 paperwork says 4.4kW and ESB can see if you export more. You can either ask for the NC6 to be updated to reflect the additional 0.6kW, or software limit the new inverter.

bunderoon · 03-04-2026 12:19AM

Would ESB do anything over an additional 600w?

...Ghost... · 04-04-2026 10:47PM

https://www.boards.ie/discussion/comment/124359766#Comment_124359766

Let us know if you find out

bunderoon · 05-04-2026 03:51PM

Will do.

2x Inverters Help / Advice

Comments