Greetings from cloudy Frederick, MD

[Mike90250]

If it failed, why is it still on line ? You are only allowed to power it for testing till it's approved.

[Naptown]

The array failed electric inspection today. I've asked AtisSun folks for advice. Great guys, and I'm sure there's an explanation. Still, a major bummer. Thanks again for feedback.

After three weeks online, all seems well with the inverters. The array hit 1MWh total today (data at http://tinyurl.com/7ess5fp). Free juice for the power company, I guess. No net meter until it passes electric. More to come.

What did the inspector fail you for?
70% of the time it is lack of knowledge on the inspectors part.
The other 30% is usually for dumb things.
Did the inspector ask for string calculations?

[websterize]

The array failed electric inspection today. I've asked AtisSun folks for advice. Great guys, and I'm sure there's an explanation. Still, a major bummer. Thanks again for feedback.

After three weeks online, all seems well with the inverters. The array hit 1MWh total today (data at http://tinyurl.com/7ess5fp). Free juice for the power company, I guess. No net meter until it passes electric. More to come.

[Naptown]

Not on those inverters. If it were the sb3000HFUS that are rated at 600V yes 13 is OK but the sb3000us if there are 13 on a string should have fried already.

[websterize]

Your house looks like it was made to fit that array. Looks really nice and tidy. Hopefully you can get confirmation on the concerns raised by Naptown.

Thanks much, Patafil. That's basically how I got my wife on board -- had to look nice and tidy. (That and she was sick of me droning about solar.) Site quality -- azimuth, pitch, no shade -- was too good to pass. Because the array had to go out front, aesthetics were a concern. We worked to get the modules as close to the edges as possible. What we got matched plan drawings. Placed on a corner lot, near a road with commuter volume, the array gets seen, and I'm glad it's not hidden out back. Many friends and neighbors seem intrigued by the notion of PV on their homes.

Rich, the electrician who was part of the installation team stopped by today to attach signs around the inverters and to make grounding tweaks. This was in advance of an electrical code inspection tomorrow. Although he couldn't confirm, the electrician said it was possible that the installation manager (on vacation this week and out of reach), who was actually on the roof plugging in the modules, left one of them unplugged. So we'd have a 10.1 kW system instead of a 10.4. I could be misreading the kW data coming off the inverters on the SMA site (They're the bottom three links at http://tinyurl.com/7ess5fp). Maybe one *isn't* running higher. There's a lot of surface up there, and I suspect not all modules are getting equal light. Again, shade isn't an issue.

If 39 panels, not 40, were plugged in, does the cold-weather problem with the 14-module inverter go away? (13 13 13 instead of 13 13 14.) Max voltage on each of the three 3000US inverters is 500 V. Each module is 260W.

[Patafil]

Your house looks like it was made to fit that array. Looks really nice and tidy. Hopefully you can get confirmation on the concerns raised by Naptown.

[Naptown]

Thanks, Rich. Have not seen specs on how the array was strung, but one of the inverters does seem to be running higher than the other two, so I suspect it's 13 +13 + 14 for the 40-panel array. (All 40 panels are hot ) You can see real-time data on the array at http://tinyurl.com/7ess5fp. We've had a few 60+ kW harvests. The three inverters are in fact the SMA 3000US, with a max DC voltage of 500 V.

The electrician is scheduled to revisit the house tomorrow to add code signage around the inverters, and the electrical inspector will be out Friday. I'll be sure to raise your concerns. If all passes, we'll then submit our application to the local utility for a net meter and hope to receive by end of April.

All the best.

In that case they could have strung 2 inverters with one string of 11 Right in the sweet spot of the inverter Max input is 2.86KW inverter is rated for 3KW no problem with cold weather.
Now the third inverter is probably strung with 18 modules in two strings of 9 This fits within the parameters for the most part In other words there is no possibility of frying the inverter on a cold morning. However the max wattage input for this inverter with 18 modules is 4.86KW. This is an input of almost a third more. It won't harm the inverter but will clip, meaning it will reduce output power to save the inverter. It will only put out 3000 watts at max power. The excess power the modules are producing are wasted. You did see a higher output on one inverter. Was it a third more than the other two. According to SMA you are losing on average 4% of harvest on this inverter. This will happen more in cooler weather than in the summer.
If anyone else has anything to say or check please feel free.

[websterize]

Thanks, Rich. Have not seen specs on how the array was strung, but one of the inverters does seem to be running higher than the other two, so I suspect it's 13 +13 + 14 for the 40-panel array. (All 40 panels are hot ) You can see real-time data on the array at http://tinyurl.com/7ess5fp. We've had a few 60+ kW harvests. The three inverters are in fact the SMA 3000US, with a max DC voltage of 500 V.

The electrician is scheduled to revisit the house tomorrow to add code signage around the inverters, and the electrical inspector will be out Friday. I'll be sure to raise your concerns. If all passes, we'll then submit our application to the local utility for a net meter and hope to receive by end of April.

All the best.

[Naptown]

I had a bit of time today to run some numbers on your inverters and panels.
The inverter you specified in your post was a SB3000US If this is the correct inverter than the max input voltage is 500V
If by chance it is a SB300HFUS-30 the input voltage is 600V
I would hope it is the latter as the former is worse.
The sweet spot as far as configuration on the SB3000HFUS is 13 modules on 1 string. This falls within the voltage and input maximums.
You can add one more module to the string and still be within the sweet spot array to inverter size (+/- 20%)
However and this is the kicker and the reason I have been on this. When the 14th module is added to the string the voltage open circuit on the coldest record day in Frederick is -13C(8.4F) the voltage is over 600. It isn't till we get to -10C (14F) that the voltage drops below 600 (598 according to the SMA calculator). Now if by chance they did two strings of 7 modules on that inverter it would work and the inverter would not fry but the voltage will not be high enough to start when things get warm out due to low voltage.
So here is what can happen. During the winter if the temperature is below 14F you run the risk of frying the one inverter with the 14 modules. And here's why It doesn't take much light for the modules to start producing voltage. They will produce full voltage in dim light not much in the way of watts but full voltage. In the morning your inverters are sleeping and disconnected from the array. So the modules are in Once they wake up the voltage will drop but it is during the period that they are waking up that the problem occurs.
So as long as the temperature never falls below 14 degrees no problem.
If by chance it goes down below that then you have a problem.

If they are using the SB3000US inverter the situation is worse If the temperature falls below Well never mind they would have fried already

[Naptown]

Have they provided any of the information to you regarding string and inverter layout?
It is something I would insist on if I were the purchaser and these type of questions came up.
If the system is up and running is there any variance between inverter outputs on a daily basis. In other words is one inverter putting out more or less than the other 2 by more than say 1 or 2%

[Naptown]

AtisSun stands behind the array configuration: "Every system we install is not only highly scrutinized by us for proper design, but also by our manufacturer's team of engineers who are responsible for accurately designing thousands of PV systems worldwide."

At each step of the process so far, they have exceeded my expectations. We'll see how it goes.

Thanks again for the feedback.

that's what they told you. Have they provided any documentation from Schuco or SMA on the equipment?
Ask them to give you the string calculations, The array configuration how many modules on each inverter and how is each set up. You are the customer you have a right to the information.

[websterize]

AtisSun stands behind the array configuration: "Every system we install is not only highly scrutinized by us for proper design, but also by our manufacturer's team of engineers who are responsible for accurately designing thousands of PV systems worldwide."

At each step of the process so far, they have exceeded my expectations. We'll see how it goes.

Thanks again for the feedback.

[websterize]

Yes, more to come. Thanks again.

[Naptown]

Websterize
Have you asked your installer for more information about what he is installing?

[Naptown]

Good to hear the installer didn't add the extra cost. Hard to say whether a standalone 10 kW or 3 separate array system better because each will have their pros and cons. I like the isolation affect with 3 separate solar systems especially when the cost similar. Excellent setup

In his instance there is no way to configure 40 of those modules on those three inverters.
Either one module is diconnected or he runs the risk of overvoltage on one of the inverters.
I ran that every which way I could think of and could not come up with a solution that worked.
Try for yourself The sunny design tool is free and online. you will need version 2.2 as those modules don't show up in Ver2.1

So not so excellent a set up IMHO