Sunpower 3.2kW fail to run

praseto
praseto Registered Users Posts: 22
The system has been in service since Feb 2013. Until 10 days ago it was performing as expected.
The system consists of 10 Sunpower 320W run in two strings of 5. The specs are Voc 64.8; Isc=6.24;Vmp=54.7;Imp=5.86; The inverter is Sunpower SPX-4000x ( re-branded Xantrex 4.0 GT).
The system for the last month is putting 12-18kw/day but 10 days ago is start cycling between 0w to 100-300w and then back to 0w with occasionally. First thing I thought is the inverter. I have a spare 3kw Sunpower that I install to find the same thing.
Voltage When checked at the inverter(or DC disconnect) shows 270-290Vdc,The inverter shows correct voltage(AC and DC ) but Amps is really low-0.5 then may change to 0.9 up to 1.5 then back to 0.5A
I have two strings so I tried only one-same- good voltage, no Amps. I tried the other one-same.Today I checked one of the strings panels for Isc and all of them showed up 4.3-4.6A (it was 3pm with the sun hitting at 30 degrees only) as the array is pointing east. I also checked the USE-2 wire with mega Ohm meter for shorts-nothing. The system is grounded via 4AWG bare copper (each panel and rail) inverter and disconnects.
Any suggestions what to check next will be appreciated.

Comments

  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Sunpower 3.2kW fail to run

    One would assume you checked it's connection to the Grid mains to make sure your getting a reference voltage to activate the Inverter.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Sunpower 3.2kW fail to run

    Any fuses on the DC side?
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run
    One would assume you checked it's connection to the Grid mains to make sure your getting a reference voltage to activate the Inverter.
    Thank you for the fast response.
    The DC and AC voltage as I said is good. AC shows 246V and 60Hz(The hertz value is from the inverter display) Volts is from the Fluke
    There is no fuse in the DC side.
    There was Y connectors on the array where the two strings connect .Then a 10awg USE-2 wire to the DC disconnect on the wall next to inverter.Half of the length of the USE-2 wire runs in metal conduit. I test each string without the Y connector - same thing. Because of the metal conduit I test USE-2 wire for a leaks with Mega Ohm meter.The panel +wire after the disconnect on the inverter side shows grounded, but the inverter is Sunpower and have positive ground internally. I also checked the ground fuse for Amps-shows 0 A
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run

    Interesting thing was that 4-5 days ago all of the sudden the system was working for half a day. When I checked it at 4pm the inverter was showing 9kw made and was making 600w+ at the moment. Next day was back to 0.
    Is it any way to test the whole string-250/290V dc at 5-6A?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Sunpower 3.2kW fail to run
    praseto wrote: »
    Interesting thing was that 4-5 days ago all of the sudden the system was working for half a day. When I checked it at 4pm the inverter was showing 9kw made and was making 600w+ at the moment. Next day was back to 0.
    Is it any way to test the whole string-250/290V dc at 5-6A?

    Clamp-on DC Ammeter to do a short-circuit test of the whole string.

    It sounds like an intermittent connection problem though, which means you'll end up taking everything apart and inspecting every connection from the panels to inverter.

    It's the worst kind of problem to find too.
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run
    Clamp-on DC Ammeter to do a short-circuit test of the whole string.

    It sounds like an intermittent connection problem though, which means you'll end up taking everything apart and inspecting every connection from the panels to inverter.

    It's the worst kind of problem to find too.
    If I use the clamp DC meter can I short circuit the whole String. Negative to positive leads?
    I already check the connections-there is 5 connections between the panels, then there is the connections where the panels connect to USE-2 wire(male and female that I crimp and then solder) and then is the dc disconnect Square D HU361RB. the disconnect is rated for 30A and looks solid. There is another build in disconnect in the inverter(Xantrex GT) that shuts off the AC and DC together, but I try different inverter and the same thing happened.
    I have a friend who is going to help me build a tester device that produce DC current. Will be making ruffly 300DCV with 2-4A. This way I can eliminate the inverter out of the problem.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Sunpower 3.2kW fail to run
    praseto wrote: »
    If I use the clamp DC meter can I short circuit the whole String. Negative to positive leads?

    Yes: the Isc for a string of panels is the same as for one of the panels in the string.
    I already check the connections-there is 5 connections between the panels, then there is the connections where the panels connect to USE-2 wire(male and female that I crimp and then solder) and then is the dc disconnect Square D HU361RB. the disconnect is rated for 30A and looks solid. There is another build in disconnect in the inverter(Xantrex GT) that shuts off the AC and DC together, but I try different inverter and the same thing happened.
    I have a friend who is going to help me build a tester device that produce DC current. Will be making ruffly 300DCV with 2-4A. This way I can eliminate the inverter out of the problem.

    Whoa. Not a good idea to feed the inverter from a rectified AC source or from high Voltage batteries. It may not take kindly to the imperfect DC from AC, and the deadly potential of a HV battery bank is huge.

    Accept that if the array is putting out within specs it is okay. If two inverters will not run from the array the problem may be intermittent on the AC output side such as high resistance in that wiring: you could see proper Voltage and frequency when testing but there would not be the full current flow under load. You can try a 'reverse' test of the AC connection by taking the wires off at the inverter and replacing them with a load near the current rating capacity of the circuit. Then turn the breaker on at the box and check the Voltage at the inverter end to see if it sags too much.
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run

    I never think about the AC side. You right. If a cable connection is loose it will get a lot of resistance. I have a 18000 btu AC window that got from a friend and wanted to test. Now it a perfect opportunity. The AC runs on 230V and I was thinking to plug it at the dryer outlet...
    When I a was building the system I got roll of #6 AWG really cheap so used it to run the L1 and L2 to the breaker box in the garage(60 ft). Because I used bigger gauge wire I stop thinking about AC side. But it can be a bad breaker or AC disconnect. Putting a load on the ac side will show clear if there is a problem. Thanks. great idea. Will update ASAP
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run

    I put a 9A load on the AC side and AC voltage dropped from 247.3 to 245.5 only 1.8 volts. It looks like AC side is good, unless the AC/DC disconnect on the inverter itself is bad.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Sunpower 3.2kW fail to run
    praseto wrote: »
    I put a 9A load on the AC side and AC voltage dropped from 247.3 to 245.5 only 1.8 volts. It looks like AC side is good, unless the AC/DC disconnect on the inverter itself is bad.

    What is the Voltage service there? You're talking about 240 VAC in this post but in the previous one you mention a 230 VAC A/C unit (which wouldn't be the same frequency).
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run
    What is the Voltage service there? You're talking about 240 VAC in this post but in the previous one you mention a 230 VAC A/C unit (which wouldn't be the same frequency).

    Orlando FL voltage is always high 245-251 VAC. All A/C units in the USA are rated 230V but they work from 220 to 260, some even 208V.

    The strange thing I saw was the Apm meter(clamp on the AC side ) was going really high from 0.4 went to 7.4 in less then 15 seconds. Simultaneously the inverter W reading went from 0 to 150/250watt. and the same ting repeat it self every 40 seconds.
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run

    I was able to get my hands on Fieldpiece multimeter and checked the Hz they showed ok -60.1. the inverter shows 60.0Hz
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Sunpower 3.2kW fail to run
    praseto wrote: »
    Orlando FL voltage is always high 245-251 VAC. All A/C units in the USA are rated 230V but they work from 220 to 260, some even 208V.

    The strange thing I saw was the Apm meter(clamp on the AC side ) was going really high from 0.4 went to 7.4 in less then 15 seconds. Simultaneously the inverter W reading went from 0 to 150/250watt. and the same ting repeat it self every 40 seconds.

    At this point you're up against it. Without a lab to check the inverter specifically all you can do is monitor the PV output for fluctuations and the AC line for fluctuations - without the inverter connecting the two. If you see these undulations only when the inverter is connected there is something wrong with the inverter. The cyclical nature of the phenomenon would also point to that.

    The combine DC & AC disconnect was the same for both inverters? Be sure there is no short between the two sides. I don't know if you have DC GFCI on the input or arc-fault detection either; both of those can act up. Usually DC negative is grounded as well as AC neutral.

    It is very frustrating when something was working and then begins to work intermittently. Most of the time that is a failed connection or a failed complex component (inverter as opposed to PV which usually either does or doesn't work).
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run

    I have one more inverter in the storage. It is Aurora PVI-3000. It rating is in the array that I have. I hope that to give some light to the problem.
    One more question. What is exactly the difference in the grounding the Sunpower panels vs regular panels.The way I have mine grounded is the frames+the rails to the 4AWG bare copper that connects to the grounding rod. To the same grounding rod is connected the inverter.That rod is 5inches away from the house main grounding rod. There is no connection between that 5 inches but they are connecting via the ground of the AC side. The only difference is (the way I understand) is the internal ground protection of the inverter.In this case Sunpower inverter the fuse is grounded to the positive side vs negative side for the "normal" inverter.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Sunpower 3.2kW fail to run

    The difference is whether the negative or positive is connected to Earth ground; frame, mounts, and case grounding is the same. The purpose is to reduce static charge build-up in the panels. How effective it is ... not many panel makers do it. Practically none other than SunPower.

    Switching from a positive ground inverter to a negative one with those panels means you'll have to temporarily unground it. This should not matter for brief testing purposes. If you don't and the inverter has an internal negative to case ground connection it will create a dead short across the panels and nothing will work.
  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Sunpower 3.2kW fail to run

    Sounds like it could be diode failure in one of the panels.
    You should see a reduced VOC by 30%, and the amps would be under .9amps.
    I've came across the problem with the spwr425panels.

    Sunpower is required to use positive ground for the "older" model panels. If not it causes reverse polarity to the solar cells, creating both VMP, and IMP inefficiency up to 50% if not properly installed. Thats how sensitive the older panels are. Newer panels and including the maxeon cells are all now negative ground for that reason.


    All GEC postive grounding occurs at the point of the inverter, one of the reasons why sunpower rebadges xantrex, and sunny boy inverters because the grounding archetecture is a request specifically done for sunpower panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Sunpower 3.2kW fail to run
    Newer panels and including the maxeon cells are all now negative ground for that reason.

    Just to be really clear--The panels themselves have "floating" outputs.

    The grounding takes place elsewhere (inside the GT Inverter, somewhere around the Battery Bank negative bus, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Sunpower 3.2kW fail to run
    BB. wrote: »
    Just to be really clear--The panels themselves have "floating" outputs.

    The grounding takes place elsewhere (inside the GT Inverter, somewhere around the Battery Bank negative bus, etc.).

    -Bill

    Just to be clear floating and it's relation to PID are separated of their relations and conditions. PID occurs from the type of use of raw material @ the panel, the wrong material causes static which will either move closer to ground from negative, or positive pole. This event occurs at the panel, not at GT inverter, Battery etc. When it is in a state of floating....... Well then ground doesn't really matter accept according to code for safety ground, but in the case of PID, that safety ground is used to alleviate a static discharge at the point of the panel (or array).


    http://www.solon.com/export/sites/default/solonse.com/_downloads/global/article-pid/Pingel_et_al_PID.pdf
  • praseto
    praseto Registered Users Posts: 22
    Re: Sunpower 3.2kW fail to run

    Update: I tested the panels. I used a heater that is 46 ohms. Each string put around 1400W at 248Vdc/5.8A. I believe that prove that the panels and DC wiring is OK.
    When I was looking at the display at the inverter I saw the AC voltage fluctuated "a lot" 0.3-1.0 volt every 1-3 seconds. So I called the power company. The service tech reassured me that this is normal. He spent 45 min doing load test,re-torquing all the connectors etc. I also tried connecting the inverter to a different breakers in the panel-same problem. The only thing left is the inverter. The inverter works normal early in the morning or late afternoon when the watts are less then 200.
  • SolarPowered
    SolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Sunpower 3.2kW fail to run

    This is exactly why micro inverter is the only way to go. So much less headache, and when one inevrter goes out atleast the rest of the system is still running.