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 Post subject: Panel Problem
PostPosted: Fri Dec 07, 2007 1:06 pm GMT EthGMT 
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Guppy
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Joined: Thu Dec 06, 2007 11:34 am GMT EthGMT
Posts: 105
Location: Maine
For starters let me start by saying that I am a 25 Yr old Cadd Technician and former Computer Repair Technician. I work for a Utility Power Engineering firm out of Augusta Maine. 2 or 3 months ago I agreed to help my parents Upgrade thier existing solar power system. Thier current system is only 10 75watt siemens solar panels and Trace Power Panel with a C40 charge controller and a DR3624 inverter (POS) :? . I was planning on upgrading thier system to an Outback PS2 system with a GVFX3524 inverter.
Now here is the problem, My parents got ansy and found a deal on the internet. 14 215watt solar panels for a really great price, almost 1/2 off. They asked for an explanation and he said he works with a solar company out of Southern California and these were left over from a project with the Utility, he got a great deal and was going to mount them on the roof of his new house but then decided to sell the house and the panels were still sitting in storage in open, but original boxes. The guy also said he was comming to Maine for thanksgiving and could bring them up for us to check out. If we wanted them, we could buy them right there, if not we could tell him to take a hike. So they agreed. They met with him and the panels looked great, not a scratch on them. They bought the panels and brought them home. Then I looked at them, found out that they were SUNPOWER brand panels and when I researched them I found that they are supposed to only be used in a POSITIVE GROUND system. By my understanding, Due to this fact it seems that we cannot connect them to Outback MX60 controllers, unless we want to deal with up to a 30% loss in efficiency due to surface polarization. When I looked at the market for Positive ground inverters I find that in the USA only SunPower makes Positive Ground inverters that are designed for these panels. Sun Power only sells packaged systems with all the hardware (inverter especially) included. Im beginning to wonder were he may have got them as well, as this is sounding more and more like we got screwed. :oops: :cry:

-Anyway, they haven't decided what we are going to do yet. If we hook them up in the standard fashion it's my understanding that they will work, just that they could experience surface polarization which could reduce output up to 30%. I saw that thier smaller panels, SPR-90 are labeled "Do Not Wire In Series" but they are rated for battery charging and utilize the same back-contact construction method, this would seem to suggest that if you wire them all in parrallel that it would reduce or resolve the Polarity problem by keeping the voltage below 50 volts DC. Would I be right to assume this? If not what do you recommend they do about their situation. They don't have the money to buy new panels due to this, but they may have insurance against fraud so.... what should they do? :?: :?: :?:


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 Post subject:
PostPosted: Fri Dec 07, 2007 1:17 pm GMT EthGMT 
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Red Cobra Delta Guppy
Red Cobra Delta Guppy
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Joined: Sun Jun 02, 2002 1:01 am GMT EndGMT
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Location: Lakeland Florida
Not sure what your thinking saying fraud, they got panels half price and doesn't sound like there is anything wrong with them except they aren't ideal for YOUR application.

Xantrex GT ( gridtie ) inverters do postive ground, that what sunpower resells under there own label .. Sunpower doesn't manufacture any electronics

As for off-grid, I'd say run it as you would any panel ( yes you put sunpower in series ) and live with the reduced performance, even at 30% loss, its 20% better than full price panels


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 Post subject: Re: Panel Problem
PostPosted: Fri Dec 07, 2007 1:18 pm GMT EthGMT 
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Guppy
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Joined: Fri Aug 04, 2006 10:24 am GMT EthGMT
Posts: 284
Location: Los Angeles
Well, from what I know, sunpower does not manufacture any grid tie inverters, they get branded ones from Xantrex, the GT series, which can be configured for positive ground. You can use their Sizing Tool, http://www.xantrex.com/support/gtsizing/index.asp to see if you can come up with a combo of panels that works with one of their smaller GT inverters.
( it looks like a GT 3.3 would work well with 2 strings of 7) price compare here: http://store.solar-electric.com/xagt33grties.html

So, it looks like it is solvable, for another $5K for inverter and mounts

_________________
"Since the dawn of time it has been mankind's dream to blot out the sun"
Montgomery Burns


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 Post subject:
PostPosted: Fri Dec 07, 2007 1:41 pm GMT EthGMT 
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Guppy
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Joined: Thu Dec 06, 2007 11:34 am GMT EthGMT
Posts: 105
Location: Maine
The reason I say fraud is because it sounds like he could not have recieved them through any Legitimate means, Sun Power sounded a little miffed when I called them on the phone and told them what I had. They said "We only sell our panels with packaged systems". :roll:


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 Post subject:
PostPosted: Fri Dec 07, 2007 1:55 pm GMT EthGMT 
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Guppy
Guppy

Joined: Thu Dec 06, 2007 11:34 am GMT EthGMT
Posts: 105
Location: Maine
Ok, well that sounds about right then. I just wanted to see if anyone would say "YOU CAN'T DO THAT BECAUSE.....!" but if you all agree same as I do that it should work, and there was nothing typically illegal or wrong about the way they got the panels (I thought they sould have checked in to whether or not they could have been stolen) then we are good to go. I think maybe I will test them on an MX60 to see what happens, I will still need an outback inverter for the current 750watt array to make its power usable and saleable without needing to be either only On grid or only Off Grid. Currently they are used as nothing more than backup power whenever the grid goes down (Twice a Month or so) I can always hook them up to a Xantrex GT later and keep the Outback and MX60s for backup in case we ever have some major disaster and grid power is out for a long period (weeks or months). This isn't thier only source of power anyway, they have a Skystream 3.7 going up today and 2 old Air 403 Windmills. I will check back here to see if anyone else had anything to add but I think we are probably all set now. Thanks Everyone! :lol:


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 Post subject:
PostPosted: Sat Dec 08, 2007 2:44 am GMT EthGMT 
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Guppy
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Joined: Mon Mar 20, 2006 7:58 pm GMT EthGMT
Posts: 214
Location: pittsburgh
they are good pvs if they are intact and you can accomodate the positive grounding. check the pvs for their open circuit voltage and short circuit current if you know of somebody with a good digital multimeter and if he knows how to use it.


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 Post subject:
PostPosted: Mon Dec 10, 2007 12:49 pm GMT EthGMT 
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Guppy
Guppy

Joined: Thu Dec 06, 2007 11:34 am GMT EthGMT
Posts: 105
Location: Maine
They are all in perfect shape except one has a very fine hair-line scratch about 3 inches long that you can only see if you shine a flashlight on it at an angle. They work well too. Open circuit on a fairly clear day yielded a VOC of 47 volts or 48 volts and the Short Circuit current was pushing 5 amps or higher on each panel, right where they should be. Even the scratched one. We have a several good Multimeters of our own by the way. We are pretty far from most Knowlegeable solar people. Not too many good electricians around either. We need to be self sufficient and be able to take care of the system without any help. There are after all only 1600 people in my home town most of the year. :?


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