Is this a ground problem?

wingshadow

This might be simple but not for me. Sorry if it is long.

I have Sunpower +grd 215w panels in 3 sets of nine. A 5200 inverter (gridtie). I have no manuals on this except the bits online.

They emphsize a single point ground. I've hooked this up and it works except that it gives limited power. In the morning I have all three series hooked up and it's good until the amps reach about eleven, then the inverter cycles on and off without an error message.

If I take any one of the three out, thus producing less than eleven amps it works fine all day. Then I can plug the third one back in as soon as the sun is lower.

Because they asked for a 'single point ground' I ran one heavy bare ground wire in 'lay in lugs' across all 27 panels and to the inverter. from the inverter a/c side it leaves as L1 L2 and common/grd, and travels two hundred feet through new #8 wires to the power pole. (thus one grd)

It seems I could put a 8ft rod in the earth near the panels and get a much closer grnd... but since the d/c and a/c share a common connection in the inverter case wouldn't I then be using two ground points? Or maybe this has nothing to do with why it won't give me more than 11 amps? (Actually it will give me more... It goes up to 15 or so but then cycles off and resets.)
Thanks..

mike95490

Re: Is this a ground problem?

1) when was this installed ?

2) have you gone to the inverter mfg website, and run the "string" or "array" calculator to see if you are overpowering the inverter ?

Is the inverter getting real hot ?

wingshadow

Re: Is this a ground problem?

!.)It is being installed now, I'm working on it.

2) The inverter says it will handle 500dcv. The most I have seen it produce is about 410. Was in operation for five years at another site.

3)No heat, outside, totally shade, and a good breeze.

I'm thinking it has to do with the ground... I was wondering if there is a better way to ground it. It's not on a roof, more of an open field.

wingshadow

Re: Is this a ground problem?

One more thing Mike.

I checked a manual on this and it says 500 volt dc (max)... I was going on that... but that it operates at around 240-380vdc . Maybe it was designed with 27 panels because of the way the former roof site was aimed in relation to the sun?

Do you think it will hurt anything to remove one panel on each string and lower the total vdc?
Thanks

mike95490

Re: Is this a ground problem?

You HAVE to go to the inverter site, and run the caculator.

icarus

Re: Is this a ground problem?

Are these the Sun Power panels that require a positive ground?

Tony

wingshadow

Re: Is this a ground problem?

Yes Icarus, positive ground.

Mike if you have a website where I can do that, please list it. Sunpower shows nothing that I can find... all I can do is calculate by what the manual says.
( 40v panels x 9)
On that subject I should add that the 405-410 dcv I get is not correct because it is without a load... just testing the series direct. It stay below 380 when running.

BB.

Re: Is this a ground problem?

In general, does not Sunpower only sell to distributors and have Sunpower branded equipment (like Xantrex and other GT inverters?).

Basically, you have to either get Sunpower's design software/website or you need to figure out which brand/model of GT inverter that they are using for your installation (does not sound like a Xantrex unit).

The problem is that the Vinput of the GT inverter needs to match up against the Vpanel (typically Vmp-hot and Voc-cold) to make sure that the minimum/maximum input voltage range is respected. And depending on your local Summer peak and Winter minimum temperatures.

So, we need:

• Vmp/Voc of the solar panels
• Temperature Coefficient for Vmp/Voc of the panels (usually one number)
• Vinput range of the GT inverter (some include Start UP voltage and MPPT range)
• Minimum temperature (at sun up at coldest winter day) Voc-cold
• Maximum temperature (middle of summer day) Vmp-hot

Then we can work out the supportable number of panels per string.

The grounding (single point, positive ground, etc.) should have nothing to do with your problems.

And, remember that Voc-cold and Vmp-hot really do not have much to do with angles of panels to sun... These voltages are reached pretty much as soon as there is direct sunlight on the panels (with or without a lot of current flow).

-Bill

Cariboocoot

Re: Is this a ground problem?

These Sunpower panels have a Vmp of 39.8. Nine in series would be 358.2, which is within the given input range of the inverter.

The manual shows the inverter having positive panel ground connections (page 8). Therefor the panels and inverter are compatible.

It is perhaps a wiring problem; some connection with high resistance that is failing under high output but allows Voc to pass.

Or maybe the unit is defective, which is why they sold it.

niel

Re: Is this a ground problem?

i can't say that i'll have an answer for your problem, but maybe you should be more specific with a make and model number for the inverter just so everybody doesn't overlook something there.

Solar Guppy

Re: Is this a ground problem?

The ground has nothing to do with this. Postive ground might running standard ground might have a 5-10% hit over time, your system has a functional fault.

If the inverter is tripping offline, you need to figure out why. Start by finding out the inverter manufacture and see if there is software available to get status information or explanation of the status LEDs.

If it really worked at the old site, the only difference is your AC connections. Put a DVM on the inverters AC connection and see what the voltage is when the inverter trips.

I'll bet you find your AC line is rising in voltage as the inverter power output increases and then trips out with a UL1741 AC over-voltage fault ( ~264 volts ). This indicates you have too much resistance on the AC side. Should be where you tied the inverter into, could be your on a rural connection, bad main panel ect.

The other possibility is the inverter is defective and wasn't performing at the old site and that's why the guy put it on craigs list in the first place.

Cariboocoot

Re: Is this a ground problem?

Folks if you read the OP's first post carefully you'll see the inverter is a Sunpower 5200:
http://us.sunpowercorp.com/cs/BlobServer?blobkey=id&blobwhere=1300257327287&blobheadername2=Content-Disposition&blobheadername1=Content-Type&blobheadervalue2=inline%3B+filename%3DSunPower%2BSPR%2BInverter%2BManual%2B%2528SPR-4600-5200%2529.pdf&blobheadervalue1=application%2Fpdf&blobcol=urldata&blobtable=MungoBlobs

Since this inverter/panel combination should work but doesn't, there's something wrong. Apparently it's not producing any fault codes, which is highly suspicious. Although I think Solar Guppy has a very good possibility with the AC side resistance.

wingshadow

Re: Is this a ground problem?

OK, I will get the info on the inverter, all I know at this point is that the label says sunpower 5200.

It never gives a fault code. A check of the positive side reads zero volts, as referenced to ground, as I understand it should.

I have the 5200 manual which says what the fault codes mean, but as I am currently receiving none so it doesn't tell me much.

I will first do what solar guppy has advised on the ac side. I'll get back with what the readings are before and after it trips. I don't really know the condition of the main panel in detail, but it did have a burn out of a 50 amp breaker some years ago. If necessary I'll get a new panel.

Today I have sweet potatoes to plant and they won't wait so I might be late getting the info.
Thanks to all.

Solar Guppy

Re: Is this a ground problem?

You need to watch the voltage as it trips, not after. If you see the AC voltage rising as the power output increases, then that's your problem.

The 5200 is probably a PV-power units

http://renewables.advanced-energy.com/upload/File/PVP/97-600100-02-A01_Online_051010.pdf

wingshadow

Re: Is this a ground problem?

OK, Solar Guppy, your bet is safe. There were some odd readings though. I hooked two dvm up just in case it was the meter.

I used a good Fluke23 and a Klien3200 with a good amp clamp on ampmeter. The morning voltage was 256v incoming with the unit off then it rose about 3volts when it came online and slowly progressed up to 261.4 when it kicked off. I ran it about five times to be sure.

After planting I checked it again and for some reason the pole was giving it 253v... but when it came online, it again climbed to about 261 and kicked off.

Just to be sure it wasn't something easily fixable I went to the pole and cleaned all the contacts in the a/c panel with emery cloth and put a new 30 amp breaker on the line. When I went back to check it, it started at about 257 and then climbed to 262 and kicked off.

So... here I am.

Is this saying that my next step is to put the inverter at the pole and run (6) 200ft #8 d/c lines down to the inverter?... plus a ground? Or will I be OK to ground the dc side at the panels and the inverter at the pole? I'm still confused about that single point ground thing. If there is a way to avoid the 6 lines that would be good.

At this point the extra money for a seventh line won't make that much difference, but it makes for one really large conduit.

Please advise and Thanks again

wingshadow

Re: Is this a ground problem?

Hey thanks for that PDF. I've got dial up out here so it took awhile, but I'm going to study it now...

mike95490

Re: Is this a ground problem?

wingshadow wrote: »

...

Is this saying that my next step is to put the inverter at the pole and run (6) 200ft #8 d/c lines down to the inverter?... plus a ground? Or will I be OK to ground the dc side at the panels and the inverter at the pole? I'm still confused about that single point ground thing. If there is a way to avoid the 6 lines that would be good.

At this point the extra money for a seventh line won't make that much difference, but it makes for one really large conduit.

Please advise and Thanks again

Were you measuring the line voltage at the
inverter
your breaker panel
power meter

You may be able to have the power co pull a new line to your meter, it may help the problem, or maybe have them re-set the tap at the transformer, 256V seems a bit high to start from. Or maybe throwing 3 panels away is easier

Solar Guppy

Re: Is this a ground problem?

256V is way high, nominal should be about 240v, check at you main breaker, if its high without the solar, call the power company and complain, I had an issue like that, turns out the power company had a bad regulator and didn't even know about it. Tell the power company your losing appliances due to the high voltage, they will be out within an hour!

For your system, the inverter should be placed at the main panel, then run 3 pairs of wires for the DC side, pair for each string, and a ground conductor for the panel frames.

Quit thinking about the positive ground, its not anything you configure. The Frame ground has nothing to do with the fact that the inverter has the plus from the string of solar panels bonded to ground, from a user prospective, the solar panel strings of +/- can be any potential to ground, its completely isolated from the panel frames.

All positive ground means is the +/- of the solar panels will measure 0v/-300v to ground instead of 300v/0v with negative ground bonding. New system have no bonding and can float anyway in between! ( UL1741 2010 )

One other note, your going to need this inspected, you can't just gridtie a 5kw system and expect no one, especially the power company which best case will wonder why your meter goes backwards OR the meter will increment in both directions so you get billed for the power you export.

wingshadow

Re: Is this a ground problem?

Solar Guppy, Thanks for the news on the 256v, I will check it at the meter without the solar in the mix... and for the grounding info. The PDF you gave me is almost identical to my unit, I'm not so much in the dark now, but that translation from the French is awfully slow...

Will it make a big difference if I'm starting at 240v instead of 256? I guess I would have 16 more volts to separate the cut out point.

I have had to work on a/c electrical stuff around here before and it has always been something over 250v. I do blow lights on a fairly regular basis, so began buying 130v bulbs and that seemed to help some. and... yeah, I know I have to run this by code and through the power company, but if I couldn't get it working first, there would be no point. I'm not rich.

I did once blow a fridge... they called it a power surge... but it was under warrantee, so the power people weren't involved in the fix...

I'll find a certified installer to help when I know I've got the bugs out. I didn't want to pay for him to come out and spend time doing what I needed to learn anyway. I hear they won't take potatoes in trade.

Mike, I measured it just outside the inverter, at the a/c disconnect... I have checked it at the pole before and It is always over 250v. I don't have what they call the 'integrated a/c d/c disconnect' just two boxes a/c and a d/c with throw switches... It's five years old.

Anything you guys can add will be appreciated.
Thanks to everyone

wingshadow

Re: Is this a ground problem?

Let it be known, that Solar Guppy is a pretty smart guy. I'm ready to shut down and make the necessary work to set this system up.

I got hold of the power people, and Solar Guppy was right... they came running. They went to the transformer and found it was an older Tap Transformer... They set it high years ago because I was 14 miles from the substation (the last on the line) and thats how they made up for voltage drop.

In the years since they have improved on the transformers down the line and my voltage kept rising as a result. The fix was quick... Now my solar works as it should.
Thanks to everyone..