Solar for Beginners [ask your questions here]

Dozz · 12-06-2026 03:09PM

Hi all. I have a solar setup at home. Standard Solis inverter and approx 6.6 Kwp. Panels all south facing.

I have a good bit of West facing roof that I was thinking of putting panels on but unfortunately I have no spare strings on the inverter.

I have access to a commercial grade inverter (see attached photos). Is it possible to use this in a domestic setup?

Cheers

PXL_20260612_105236712.jpg

PXL_20260612_105255145.MP.jpg

deezell · 12-06-2026 07:45PM

https://www.boards.ie/discussion/comment/124546043#Comment_124546043

Off grid only, and its a three phase inverter. It may not be possible to energise individual phases without a reference 3 phase grid connection at the input, i.e, fully off grid. More tech reading required, but Cananda v Bosnia about to kick off, and I have a duty of care to watch the World Cup. All of it.

893bet · 14-06-2026 01:25PM

only installed Friday.

9.2kw perfect south pretty much.

Assume I am being clipped below at 5.5. But why?

When there is a load of 2-3 on the house I thought I could use the excel solar for the load and still send back 5.5?

Only time I was above 5.5 was when the battery was charging and I was had a house load on that exceeded the 5.5 I think.

KAGY · 14-06-2026 02:58PM

Unfortunately that's the way inverter works. The max it can convert from DC to AC is 5 kilowatts. When you're charging the battery it's not converting so it can supply more power in total.

893bet · 14-06-2026 03:25PM

yeah figured that out. Need to dump battery early in the morning if the weather is to be good

deezell · 14-06-2026 04:28PM

It can charge the battery with excess, but the max it can place on your grid is 5.5kw. it has no way of knowing if there's self consumption or if its all going to FIT. If your hybrid inverter has dynamic Export Power Management (EPM), and a CT clamp on the live cable from the meter, to measure reverse current back into the grid, then it will know how much is going to local load, and should be able to allocate the available solar output to fulfill the local load and send the max 5 5 to the grid.

graememk · 14-06-2026 05:12PM

https://www.boards.ie/discussion/comment/124550457#Comment_124550457

It's max that can leave the inverter, not export.

(And all hybrids have a CT/meter otherwise it can't monitor the grid so it can charge and discharge the battery.)

white_westie · 15-06-2026 10:49PM

Could you connect South-North panels in parallel to 1 MPPT?

So basically question arises from option of connecting East-West panels in parallel to a single MPPT - could the same logic apply to a South-North orientation?
ie: same number and type of panels installed on each aspect, connected in series to form a string on each aspect, then the 2 connected in parallel at the inverter.

In a South-North situation, the south panels would have sun for most of the year, so they would set the voltage to start the MPPT up all of the time. During the winter months the North panels would not be generating much, but in the summer months they would.
The parallel connection would mean the voltage would be fairly constant, but the current would fluctuate - would that upset the MPPT logic? Would it work?

Am only talking about low number of panels (4) on each aspect.

Am I understanding the theory correctly?
If so, anyone ever seen anything like this being attempted? Cannot find anything myself.

TIA
WW

whosedaddy? · 15-06-2026 11:44PM

Connecting panels in parallel means the current is additive. Based on data sheets Imp of most panels is between 10-14 Amp depending on make. And 5kw inverters have max Imp of 16A or less per string.

But when one aspect hits Imp max, there is little headroom for the other aspect before you hit inverter max Imp.
I presume inverter switch off when you hit Imp max - so it could end up toggling instead of producing anything.

deezell · 15-06-2026 11:49PM

https://www.boards.ie/discussion/comment/124553787#Comment_124553787

Yes it will work. North facing will contribute little in winter, its potential output may not even reach the mppt voltage determined by the mppt string, i.e, the south panels will supply current to the inverter, but effectively reverse bias the north panels if their Open Circuit voltage does not reach the mppt setting when loading the panels. In most cases though they will contribute, and in summer, early morning and later in the evening, they will be on par, and north will briefly be dominant towards sunset or from sunrise.

There is debate about reverse current through the weaker lit panels, but this will be very low and will only occur when their OC voltage can't make mppt voltage. In large parallel arrays some might fit reverse blocking diodes on the end of each parallel set, to avoid reverse currents, but this is generally only considered when paralleling uneven number sets of panels, or paralleling more than two sets. There is some debate on this in Reddit, also AI Google answers are substantially correct. It's probably not popular as users tend to just use two strings, but there was a query here a while back from a user who inquired about three string inverters, as he had a large south facing set, and wished to add equal E and W facing sets. Paralleling the latter offered a solution.

jams100 · 16-06-2026 11:20AM

Hi,

My neighbour recently got solar panels installed which included running wires across a flat roof to a battery and this is how they left it. Is this standard / ok or what should they have done here? (To me it looks very tacky and that duck tape is going to fail when an Irish winter hits).

bullit_dodger · 18-06-2026 01:37AM

It doesn't look great does it? That said, it does appear to be affixed by clamps every 18 inches or so, no? (It's kinda hard to see from the photo)

Problem with those flat roofs is that any mounting is going to have to break the waterproof seal to affix the cable(s). I'd personally perfer if it was in a black/grey conduit, but yeah, that tape is probably going <somewhere> once it gets wet in a windy storm

CatInABox · 18-06-2026 10:10AM

https://www.boards.ie/discussion/comment/124559454#Comment_124559454

Looks to me that those are cable ties, to hold together the two cables, so not clamps.

Hard to see how you could clamp these down on a flat roof, as you pointed out, it'll pierce the waterproof seal.

It's definitely something to monitor. Perhaps you could check that where the cable leaves the flat roof, the next clamp is as close as possible, and is heavy duty. A plastic clamp nailed into the wall will come loose as soon as the wind overcomes the tape.

ECO_Mental · 18-06-2026 10:54AM

https://www.boards.ie/discussion/comment/124554616#Comment_124554616

Looking at this closely I don't think that is regular old duct tape, but more a flat roof repair tape that is more substantial. You can see its a bit thicker and designed for outdoors. I would hope they didn't clamp it down to the roof, most equipment on flat roofs is held down using ballast, running cable I woudl assume be in maybe a metal duct to give it a bit of weight and protection. You can then also place some ballast on these metal ducts

deezell · 18-06-2026 11:24AM

The 'clamps' appear to be zip ties possibly threaded through small retainers. If these are attached to the roof by a screw through the felt into the ply, it's a leak risk. Otherwise there might be self adhesive retainers, but tiny, maybe 25mm, as you cant see them. These will have little purchase on the mineral felt, the mineral grit is not that well stuck to it.

Note there is another smaller cable attached to the outside of this larger tubing, you can see it over the tape. The zip ties in my opinion are doing no more than holding this cable to the thicker one, and only the gaffer/felt repair tape is keeping the lot on the roof. A small form cable tray adhered to the roof might sound like a more secure job, the existing arrangements are creating a flat roof water trap,especially as dirt and debris seal the cable to the roof. Nothing like a pool of water to accelerate flat roof felt integrity. Any cable carrier needs to be raised, and its mounts just glued down. The image is pure amateur hour installation, but I doubt they would shell out on a few metres of this type of tray.

Solar for Beginners [ask your questions here]

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