Failed inverter replacement on orphaned system

[cliftonrhamilton@gmail]

I have two solar power systems; one installed before I purchased the home way back in 2002, and the other immediately after I purchased the home in 2020. I also have a battery backup system installed in December of 2023. The 2020 system is Enphase/LG based system and is working perfectly, maxing out at 7.8 kwh of power. It makes up about 90% of my electrical usage.
The 2002 system I believe maxes out at 1 kwh and it no longer works. Based on the manual and the person that installed by battery backup system in 2023, the problem is a faulty inverter. The 2002 system is a single phase in-line system with a Sunnyboy 1800 inverter. I've attempted to call multiple solar companies to have them come out and troubleshoot and replace my bad inverter, but I can't even get a call back. It doesn't seem like any company actually wants to waste their time working on an orphaned system. Without it up and running, I'm now getting monthly electric bills again, as the Enphase system doesn't quite meet my needs by itself.
Is it possible to just replace the inverter myself? Could I just purchase and install the Growatt 5kW Grid-Tie Inverter system from Signature Solar? I've seen plenty of negative reviews of this company, but I've also seen a few defenses, and I haven't seen many other small inverters that would seem to work. I've included pictures of the system in this post.

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[Hedges]

Check what DC voltage comes in to the Sunny Boy. That will help in selecting a replacement inverter.
You can buy a used or new old stock Sunny Boy or other brand on eBay. Some support wide Vmp range, others require it to be high, so check data sheet. I try to pay $0.10/W, e.g. a couple $hundred for an inverter that size. I'm not seeing any (offered as still working) at a good price right now. I've bought some as "parts/repair" and about half have been function, half broken.

Romex carrying high voltage DC indoors is not to code, at least not current codes. Supposed to be in metal conduit.

You could also consider connecting the individual panels (or maybe 2 or more panels) to Enphase microinverters. That could make it part of your other system; does that work for backup when grid down?

 

[cliftonrhamilton@gmail]

Thanks for the quick reply-

My understanding from the electrician that was here installing the battery backup system is that he couldn't actually measure voltage or current coming into the Sunny Boy because the inverter was broken, and with no load, he could tell there was power coming in, but couldn't measure how much power that would be. Do you have any tips regarding how to measure despite this?

As for the Romex, the power boxes are immediately on the other side of the wall, so assuming the wiring is all external down from the roof, I can upgrade the housing the wires without too much trouble.

As for buying a used Sunny Boy, they were all listed in questionable condition and being sold for over $1500 with no wifi or apps, so no ability to actually troubleshoot it or monitor the energy production in the future. so I was looking at some oversized grid connected systems that had more capabilities for monitoring. The input DC voltage looks fine for most items I'm seeing I think, but the problem I'm seeing is that my system appears to be single phase 120VAC output, and pretty much every unit I'm seeing on the market has a 240VAC output.

The idea of hooking the 4 panels up to mini-inverters and adding them to the other system would sound awesome, though I believe they're all wired in series on the roof, and those specific 4 panels are on an area of the roof where I cannot safely get to, so I was hoping anything that would be done could be done through the wiring at ground level.

I also went to the SMA website and called all the authorized dealers that list an ability to work on orphaned systems, but like I said, all of them said they're backed up with no installs and don't want to work on orphaned systems. Essentially not worth their time.

And yes, my system works quite well for backup. It also has an external plug to hookup a standard generator in case of a prolonged power outage and poor sunlight as a last resort. I'm septic and well water, plus have multiple fish tanks and ponds, so when power goes out, I lose plumbing and heat and start having mass deaths in my tanks, which is why I installed the backup power system. It was during that installation I realized the old panels were down and figured out why I was starting to get electric bills again. So I've been calling companies and looking online at various inverters since December.

Thanks,
Clif

 

[Hedges]

The old system is so small you could just forget about it. The panels - have a picture of the label? are small compared to what is used today.

With switch on, display may or may not report Voc.

Open the safety switch and you can measure voltage there. Although, likely only PV+ goes through the switch, PV- may be joined in a connector.

Take the lid off SB and you can measure PV voltage there, with switch turned on. Unless it is shorted.

The 700W, 1200W, and 1800W Sunny Boy are 120V. Occasionally available but maybe not cheap.

Most inverters are 240V. Most will work without neutral connected. If you mounted a 240V inverter like SB 2500SWR, you would just install a 2-pole breaker and feed L1/L2 through black/white wires.

Some newer ones like SB 5000US which I'm using optionally connect to neutral, so they can auto-recognize 208/240/277V. Without neutral, you move a jumper to select 240V. I'm using some each way, depending on conduit and wire size already installed.

The 5000 to 8000 models are larger, up to 4000 are smaller.

There are also the -22 series, and more recent -40 and -41.

Only 4 panels, 1000W total? You could probably put an Enphase inverter on each (but may have to adapt MC3 to MC4.) Maybe 2s or 2p panels into one microinverter.

Panels are so cheap these days, and can be up to 220W/m^2 compared to 130W/m^2 when I bought my first ones. Better to take everything down except the rack mounts, and buy new panels and microinverters. Assuming mounting rails which accommodate other sizes, not just L feet.

Or get a cheap hybrid, set it up with battery as UPS + PV, feed its AC input from other backup system, use for critical loads?

I'm curious about your backup - you said Enphase microinverters and LG battery. Have a link for that?
Hmm, I knew of Enphase Ensemble, but here's something that also mentions LG, but I think only for comparison:

Enphase Ensemble Solar Battery: The Complete Review

Enphase Energy changed solar power conversion with their microinverter technology, now, they have revolutionized energy storage with their newly released Ensemble Series. Unlike traditional hybrid battery backup systems, which power down your solar array in the event of a blackout, all...

www.solaris-shop.com

Oh, you have a battery now. Do you have time of use rates? Do you store PV production off-peak, maximize exports from battery on-peak? Another forum member had Sunny Boy Storage + LG RESU-10H for a year and it was cycling entirely off-peak, wasn't programmed to earn him higher credits on-peak.