New inverter for old 2.6 KW system

[FresnoFlats]

Greetings from very, very smokey California. Fresno is quite a ways from any of the present fires, but we are in the huge San Joaquin Valley and the smoke that drifts here from the fires can't escape over the mountains. Good news is that the smoke lowered our daily high to only 96 degrees. We had been hitting 108 and 109 a few days ago. But on to my story.

We bought a house 3 years ago with a 15 year old system of 20 Kyocera 130 watt panels and a Xantrex STXR2500 grid tied inverter. A couple months ago, the inverter went, "Bang!" and has not worked since. I can't get anybody to show any interest in replacing the inverter for me, so I am trying to figure out how I can do it. I have no previous experience with solar, so I am reading up. I am comfortable with electricity and wiring. I am about 3/4 through rewiring the whole house. It is old and still had a fair bit of knob and tube wiring, with a lot of weird and poorly done "upgrades". I am replacing a lot, upgrading a bunch and adding circuits.

When the system first went down I looked at our electric bill and saw that the system had been under performing for some time. I figured the whole system was feeble, but later I started testing the modules and they seem to be performing close to specifications. The panels are presently wired in 5 parallel banks of 4 panels in series. Mid day the open circuit voltage of each bank was right at 76 Volts. Today I removed one panel, cleaned it up and got 20 V, open circuit, which is very close to what it was supposed to be when new.


The first couple of people I asked about replacing the inverter, discouraged me and thought that I would not be able to find an inverter to work with such old panels. But, from my reading it seems that I should just wire enough panels in series to match the voltage range of the new inverter. Some inverters are designed for higher watts than my panels and I wonder if wiring banks in parallel is an option? It would be nice to find an inverter that didn't require rewiring, but so far I am not seeing anything.

When our old system went out we started looking into getting a larger system that would match our total electrical use. We are looking at an 8 to 10KW system, but the house roof is too broken up to hold that many panels, so the old system can remain. We will probably build a shade structure big enough to hold the new system. Need all the shade we can get around here!

Until I stumbled on this group a few days ago, I was pretty discouraged about finding any useful information. It has been very interesting reading some of the topics already. Thank you!

Paul

 

[Archetype-IS]

Just did some quick specs on your existing system on the KC 130 -- VoC 21.9 and Isc 8.02a. You definitely would need to rewiring it meet the newer DC input higher voltage grid tie inverters by taking 10 panels in series to make it 200 VDC and do the same for the other 10 panels. Parallel them into the new GTI. If you want, you can even series them together and do 400VDC. Little more in the danger zone there.

Example of the SMA Sunny Boy 3.0 specs. It needs the min of 100VDC and 125VDC for the MPPT to track.

Just saw that SMA GTI is in the same price range as a Schneider Hybrid SW4024/4048 range. You might want to look into that and get battery backup with it since your near a fire zone.

 

[EricBarbour]

The first couple of people I asked about replacing the inverter, discouraged me and thought that I would not be able to find an inverter to work with such old panels.

Bullshit. Who told you this? Some solar contractors are absolutely NOT to be trusted and will say anything to extract tens of thousands of dollars from you. DO NOT throw the old panels away. As long as they are delivering useful power and are solidly mounted, use them.

76 volts open-circuit would be okay for the vast majority of inverter/controllers on the market. Better efficiency would be had with an inverter/controller rated for 200v and the panels reconnected to put out 152 volts instead.

The Schneider Conext SW4024 would be a good choice for your system, although it is off-grid only and can't export power. It will need a 24v battery. A grid-tied inverter will be more expensive. SMA and Enphase are the most popular brands. This one has THREE inputs for three separate panel arrays.

Sunny Boy 5.0-US-41

SMA Sunny Boy 5.0-US-41 Inverter w/ Integrated DC Disconnect, Triple MPPT, 208/240 VAC

www.wholesalesolar.com

A grid-tied inverter really probably should be installed by a licensed electrician with experience in solar.

 

[FresnoFlats]

Archetype-IS - Thanks for the suggestions. They are very reassuring. I was gradually coming around to those ideas, but having little experience with solar panels, I wondered if I was missing anything. The Sunnyboy is the inverter that I had been looking most closely at.

Eric - Yes, naturally a couple solar salespeople told me that. Though a few days ago, one said that the inverter was not a problem, but that it would cost $4 or $5000 with installation. Seems I could install a new bigger system for that. I have electricians that I can call in when needed, but the existing system has all the cuttoffs and breakers that are required. At this point, I am just trying to get a sense of the feasibility of continuing to use these panels. Before I order anything I will clean all the panels and test them individually. Since I didn't see any variation between the banks, I suspect they will all test good. Before I started testing the old panels, my wife was worried about how we were going to dispose of them.

I was wondering about getting an oversize inverter with additional inputs, so I could add another array at a later date. Is there any drop in efficiency with an oversize inverter?

 

[Archetype-IS]

Archetype-IS - Thanks for the suggestions. They are very reassuring. I was gradually coming around to those ideas, but having little experience with solar panels, I wondered if I was missing anything. The Sunnyboy is the inverter that I had been looking most closely at.

Eric - Yes, naturally a couple solar salespeople told me that. Though a few days ago, one said that the inverter was not a problem, but that it would cost $4 or $5000 with installation. Seems I could install a new bigger system for that. I have electricians that I can call in when needed, but the existing system has all the cuttoffs and breakers that are required. At this point, I am just trying to get a sense of the feasibility of continuing to use these panels. Before I order anything I will clean all the panels and test them individually. Since I didn't see any variation between the banks, I suspect they will all test good. Before I started testing the old panels, my wife was worried about how we were going to dispose of them.

I was wondering about getting an oversize inverter with additional inputs, so I could add another array at a later date. Is there any drop in efficiency with an oversize inverter?

Oversize should be okay as long you plan out the voltage range per string or mppt inputs. Also check the existing wires if it could meet the requirements. Check the feed panel breaker on the main panel to see if the high wattage exports will be okay with the local code. Currently 2000W export is fine, but if you plan to do 5K export to the main breaker require an upgrade. Best to ask installer or electrician.

 

[FresnoFlats]

The present system connection from the inverter is 10 awg wires connected to two 30 A breakers on the main panel. Theoretically that should cover 7200 watts. (30A x 240 V)

 

[FresnoFlats]

Encouraged by the comments here and my other research, I ordered the SMA SunnyBoy 5.0 today from AltE
https://www.altestore.com/store/inv...s-41-sunspec-inverters-p41385/#SMASB5_0-US-41
It is quite a bit larger than the present system needs, but offers expansion options for minimal price difference. The fellow I talked to explained some of the changes required by new codes if I did add more panels at some point. Mainly that voltage cut offs would have to be installed in all panels to bring it up to code. Made sense.

The new inverter should arrive next week, so I will pull the old one off, to get ready. Today, I disconnected the panels from the wires leading to the inverter, so I can remove the old inverter without any live wires. I'll probably double check open circuit voltage and amps on each panel while I have them disconnected, but it is so hazy with smoke right now that readings are likely to be low. Could be quite a while before the smoke goes away.

 

[FresnoFlats]

The SunnyBoy 5.0 installation was finished yesterday, Saturday. All the old panels are wired in series now, providing a voltage around 360 VDC open circuit voltage. Garrett with AltE was very helpful in figuring out the options. Unfortunately, when it started up, it gave an error code of 102, which is "Grid Voltage or Impedance Too High". I figured PG&E hadn't changed their voltage so maybe there was a loose connection. No, the connections were all fine. Settings??

The SunnyBoy connects to a computer either through ethernet or wifi. The WiFi signal is pretty strong and I had no problem connecting to it. The monitoring interface is pretty nice, especially compared to my previous experience walking out and peering at a dim lcd screen with two readings on the old inverter. Figuring out the configuration process was pretty "Greek" to me I will call AltE on Monday to have them step me through the process. I did take a few guesses on a few items that seemed either obvious or not too dangerous. I did find a setting that seemed to match the PGE voltage of 240VAC.

Nothing changed the error code. That was disappointing. Considering the system has been down for three months, and it took me a week to install the new inverter, waiting another day or two shouldn't be a big deal. But......I sure wanted it to work right then. Oh, well.
----------------------

Walking around the yard this morning, I hear a buzzing noise coming from the inverter. Oh, Oh! Not super loud, but obnoxious and its mounted outside a bedroom. Then it stopped and I noticed the green light glowing in the way it is supposed to glow when generating power! It works!

Logged in with the Wifi connection and have been watching the generation all morning. Well, I did a few other things as well, but it has been very interesting to watch the power curve as the sun rises higher. Couldn't do that with the old system.



This time of year PG&E charges $0.299 per KWH, so the system will save several dollars a day.

I am pretty happy.

 

[FresnoFlats]

Specs on the output:
Voltage under load: 300 VDC
Peak wattage at noon: 1770 Watts
KWH on first day 12.4 KWH

I was hoping to see a bit higher peak wattage, but when I look back at old PG&E records since we moved in, the output looks about 3 times the best i saw on the old electric bills. None of my old bills show output higher than 100 KWH per month and most months were much lower. Appearantly the old inverter had been greatly underperforming for a long time. If the output keeps up near 12 KWH per day, we should see 360 KWH for the month.
Very glad that we invested in this new inverter.

 

[road glide]

Following your story....we also have PG&E. Have the same SMA SUNNY BOY 5.0-us-41 GTI coming next week but will not be installed right away. Did your code 102 resolve itself on it's own? Did the inverter reconfigure the setting on it's own?

I have a Samsung Android AT&T and am looking forward to be able to monitor the system from afar or from my desktop...
We have 20 Jinko 72 cells at 320 watts, so a potential of 6400 watts.....
2 strings of 10 wired in series calculates correctly for summer, winter temps, start up (125V) and sweet spot 220-480 volts...my voc per panel 46.4V times 20 panels plus adding for lowest winter temps on record is approx 50-54 volts per panel which is under the 600 volt max per dc input on the inverter.

Reading everything I can find, I cannot find if this new Inverter #41 has a built in feature after being commissioned in it's programming to LIMIT export to the grid. Found an older YouTube video from SMA Australia but didn't seem applicable...
We are still smoky as well here in 95222

 

[FresnoFlats]

I am not sure if the inverter somehow found the correct configuration on its own or if configuration changes I made fixed it, but sometime after I made the changes. Here are few things I struggled with or discovered that may be helpful.

The user manual is available from the SMA website. Download and give a look ahead of time.

The initial Wifi connection from my computer directly to the inverter was easy and it has a strong signal. Using the installation "Assistant", the first thing it does is set up the connection to the local area network of your choice. Then it logs you out and you have to reconnect through your local network. It is a different url once you are using the wlan. In my case it then refused to let me reconnect through the local network and I went back to the direct connection and manual configuration. Today, we finally figured out that my laptop was connected through a wifi extender rather than the main router. Once I connected through the same router as the inverter, I was able to access it on my local wifi network.

In manual configuration there is a setting for country and the entry was some long number that meant nothing to me. I also saw a setting under "Grid Monitoring" for

Country standard

CA Rule 21 / 240 L-L

which sound right and I took a chance. However, after saving the setting, nothing changed that I could tell. The error code was still displayed. Then the next morning it worked properly. Maybe my configuration change needed time or a reset take affect? Maybe the inverter was able to tell the correct setting after a day, or after being connected to the internet?

The time display was incorrect on the inverter display for the first two days, then it was correct. Pretty sure I didn't change anything between when it was incorrect and when it corrected itself. The default setting is for it to automatically check and set the correct time. Just took a couple days.

I am already plotting where to add another 10 or 12 panels to get the full 5 KW. My impression was that the inverter will clip any output over its capacity, but I can't find that in the manuals. The rep at AltE that I worked with was pretty helpful in answering those kinds of questions.

My immediate next step is to install a few of the SMA module cut off devices at critical points to eliminate voltage in the wires coming into the attic, during shutdown. However, I will have to find or make connection adapters from the old connectors to the new mc4 connectors. I am not positive what the old connectors are, but they may be mc3. I took some photos of the old connectors which I need to post, so people can identify them for me.

 

[road glide]

Looking at "grid monitoring" on a YouTube video last nite that might be where you can set "authorization" from 100% to zero...Not sure that's it but this is a work in progress....
Are you setting your parameters on your Sunny boy 5k to NOT export or zero export? If possible. Another words no back feeding any excess production....So, if you are producing 2000 watts and only using 700 watts , the overage does not go to the grid...

 

[FresnoFlats]

I want any excess production to go to the grid. And happily for the last few days production has exceeded use for a few hours around noon. That provides some credit for all the other hours where our use greatly exceeds solar capacity and we are using grid energy.

I thought you were wondering whether you could install 6400 watts worth of panels on a 5,000 watt inverter without any problems.

 

[road glide]

Most people install 25% more wattage in their panel's than the inverter. So a my case that would be 6250. What will happen Morning Sun & late afternoon sun I will still pick up more energy because I have more panels. At noon if the production goes over 5000 W the inverter will top off at 5000.
You realize with a smart meter from PG&E you're charged for energy going to the grid and energy coming from the grid unless you have a net meter agreement

 

[FresnoFlats]

I had not realized that you could get charged for electricity going out as well as in. However, we do have an existing net metering agreement with PG&E. We just have not had any energy generation for the last three month since the old inverter gave up.
That is interesting about the 25% more panels than inverter capacity. I had not seen that number, though I had sort of gotten the idea that some excess panel capacity is good. I would like to read more about that.

 

[road glide]

Back on 8-21-2020 on this forum - different topic
Solar Queen wrote:
Oversizing the array by about 25% or more is very common. It will not harm the inverter (as long as you don't wire too many in series and have too high of a voltage. Remember that it will be very rare for you to get full rated output from the array. That's at 77F (25C), noon sun, perfect angle, no bird poop, the list goes on. So on the rare occasion that you do get almost full rating, the output of the inverter will just clip to output 3800W. But during the rest of the day, you'll have increased your output having a bigger array that is putting out less than its rating, so even with occasional clipping, your daily output is higher.

Since we both have smart meters they read both ways whether you take or give. You have a net meter in force so that is fine. I do not.
If you search around on the net (google) many residential/rural solar installations across the country are upset when the old dial meter was replaced
because they previously could spin it backwards. Supposedly cannot with the smart. Landis or GE brands. We have Landis.
May I ask what PG&E pays you for a Kwh? We both pay around 24-29 cents for usage.

 

[FresnoFlats]

Thanks for the info from Solar Queen. Makes sense.

We have never generated enough for PG&E to pay us, and I don't see anything stated in the monthly bill. The calculation shown on the monthly bill, simply subtracts the Net Generation from our Consumption to show a Total Usage number. Mathematically it is similar to running the meter backwards.

Our latest bill has Peak pricing at $0.402 per KWH (4pm to 9 pm). Off Peak pricing is $0.299 per KWH. The bill only shows the Net Generation being subtracted from our gross total usage, but they certainly only subtract it from the Off Peak usage, or rather (I assume) from the same rate period that the energy is generated. I have read that battery systems can store up during off peak times and provide back to the grid during Peak times. My system is not likely to ever have any net generation during Peak time, but if it did, our bill would not show me.

The above prices are during the 4 summer months. During the rest of the year the prices have been $0.24 Off Peak and $0.26 Peak times.

Thinking about your idea to maximize your solar generation while still staying below your PG&E usage at all times. Sounds difficult since your usage could be jumping around moment to moment, while your mid day generation will be pretty steady. Maybe some of the battery systems could manage that. Or you have to manage your energy usage to somewhat mirror your energy production during the middle of the day.

Interesting, but I don't think there is any financial penalty for being on Net Metering. The once a year True Up bill is a pain, but they do tell you the monthly usage cost with every bill, so we could easily pay that money into a savings account and have it ready when the True Up bill is due. My cousins say they got money back this year. I will have to ask them how much they earned per KWH.

 

[Ampster]

You realize with a smart meter from PG&E you're charged for energy going to the grid and energy coming from the grid unless you have a net meter agreement

I have never heard that with PG&E. I know of a friend who waited for a year to get his PTO and someone left the breaker on and he never got charged. We checked his PG&E meter and it was recording his net solar production.

 

[road glide]

Thinking about your idea to maximize your solar generation while still staying below your PG&E usage at all times.

We generate KW's but pay for KWh (hour)
2 different things..

This would be seasonal IMO, maybe monthly but not hour by hour or even daily.
No one wants to monitor the inverter that frequently. Kinda like taking your blood pressure hourly....LOL
Once I get my SMA sunny boy in hand, I'll study the OM, I've already downloaded it but is vague about what happens after commissining.
I have a feeling I wiil be talking to SMA techs anyway..

 

[Ampster]

The concept is zero export and some inverters can be programmed that way. It takes a set of CT clamps to monitor the main panel and of course firmware or a user setting.