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Inexpensive grid-tie inverter suggestions

chicagoted

New Member
Joined
Jul 6, 2020
Messages
26
Location
Chicago IL USA
Hi all -
I bought ten refurbished poly 210 watt panels from a local solar manufacturer (Hitec Solar in Michigan City IN) for an astoundingly low $40/ea and I'd like to put a couple of them on my garage roof to load offset my usage. I bought an ebay Grid Tie Inverter but it stopped working after a couple days, and it complained about DC voltage being too low with a single panel and too high with two in series despite being rated for this class of panels.

The panels I bought are Suntech STP210-18/Ub-1 with the following specs:
Imp 7.95A
Isc 8.33A
Vmp 26.4V
Voc 33.6V

Can anyone recommend an inexpensive grid-tie inverter in the 600 - 800 watt range that will work with these panels?

I have two on my RV roof that are working great with an Amazon MPPT controller to keep the batteries charged and going to put another 3 up for an off-grid chicken coop monitoring & control system.

Thanks!
 
With only two panels, microinverters may be a better way for you to go. One for each, can add more later if you want. They don't need to match.
 
I guess I should have been clearer.

I'd prefer a single grid tie inverter, to keep cost down. My test was only using two panels, but I'd like to use four or five. The eBay inverter was about $80, and worked fine for a couple days.
 
Grid tied inverters have a voltage window that has a minimum and max. The smallest grid tied inverter we currently have is a SMA 3000W SunnyBoy. It doesn't start working until its solar input is 100V. But it needs 155V for its rated output. That's one of the lowest voltage windows I know of. With a Vmp of 26.4V, I wouldn't even think about using fewer than 5 panels to get it to even turn on, 6 or 7 to get it to work properly. You will be hard pressed to find a UL listed (required for grid tied) inverter much smaller than that. Which is why a few microinverters would be a code compliant, flexible way to go.
 
Thanks - I appreciate the info. Looking into microinverters now, and there certainly seems to be quite a variety of them. Some need a controller, some are standalone, some need to talk to each other...
 
Ten panels wired in series would be 330 Voc, 264 Vmp, 2100W (STC)

A small string inverter would be one way to go. I use SMA Sunny Boy, which mostly range from about 3kW to 7.7kW
Various new and old models would work, but you have to pay attention to minimum MPPT voltage. On a hot day your panels will drop below 26.4V, and some inverter models require at least 250V. Some models require more.

Many of the inverters have a DC disconnect switch built in, so all you need to do is wire a pair of MC4 pigtails into the switch and connect to the panels. On the AC side, a circuit breaker in your panel connects it.

Not saying that will meet all the latest codes and utility company requirements, but it should function until you hear a knock on the door.
I hooked mine up 17 years ago and had the mechanical meter spinning backwards until PG&E said, "You'd better ask for our permission."
 
I;m not sure about the safety aspects of buying grid tied / micro inverters off Amazon.
I'm all for diy when it comes to myself but dyi grid tie puts others at risk.
 
For grid-tied operation in the U.S., the inverter should support "UL 1741"

There are a bunch of new features for fire safety, fireman safety, promoting grid stability and all that is good. But UL-1741 ensures you won't electrocute an unsuspecting utility worker.

"Arc fault" is one of those semi-new features that is very nice to have if the panels are mounted on your roof (no needed for ground mounts). Just look at what happened to Walmart.
 
I am a DIY homeowner and have a 980 W parallel 12V system. I used a Y&H 1000W Grid Tie Inverter and made about 2.0 kW per day in Arizona in November. The inverter costs about $130. I think of buying some used cheap solar panels ($42.50) at SanTan Solar (solar outlet) and offset my usage. Did you try to contact the manufacturer and ask what kind of inverter fits in your setting? I asked Y&H several times in an Amazon open forum and got my answer in less than 24 hours. If the inverter doesn’t work, I will return it before the refund window expires.
 
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