[RE-wrenches] Getting "GFDI Open" Message When It's Not

Sun Sep 21 12:38:22 PDT 2008

Hi Kirk,

Aha!  I suspected it might be as much.   Thanks for the quick reply! 
Looks like the SB3000 is also part of it.

So on that SMA "fix".  Is that a one time boot up reset of ROM and 
then it's fine for life or is it liable to recur on any given 
morning's startup?

And I assume I don't change the polarity on the cables themselves - 
just the jumper and fuse positions?

Thanks!

Jeff

>Yes. It happened to me on a recent SB 4000US installation. SMA knows of the
>problem but doesn't know the cause. It's shown up in about 20 of 4000
>(that's quanty of 4000) inverters sold. SMA did not tell if its unique to
>the 4000US or other models as well.
>
>But you can get the inverter to boot up properly by changing the jumper to
>pos gnd, and move the gfi fuse to the positive gnd fuseholder. Then power up
>the inverter and let it run for 1/2 hour. Then shut it off and change the
>jumper and fuse back to a neg gnd. Then power up and it will boot properly.
>This is the recommended work around by SMA and it worked for me. BTW, I
>tried the pos gnd thing for only 15 minutes the first time and it did not
>work, so do 30 minutes as recommended.
>
>Kirk Herander
>Vermont Solar Engineering
>802.863.1202
>fax 802.863-7908
>NABCEP(tm) Certified Solar PV Installer
>Xantrex Certified Dealer Charter Member
>NYSERDA-eligible installer
>VT Solar Incentive Program Partner
>
>
>-----Original Message-----
>From: re-wrenches-bounces at lists.re-wrenches.org
>[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jeff
>Clearwater
>Sent: Sunday, September 21, 2008 2:42 PM
>To: RE-wrenches
>Subject: [RE-wrenches] Getting "GFDI Open" Message When It's Not
>
>Good Day All,
>
>I'm getting a "GFDI Fuse Open" message on a SB3000 and the fuse is good.
>
>What I've checked:
>
>1) I've checked POS to GND and NEG to GND both floating and when
>connected to the integral DC Disco both for continuity and voltage .
>I show expected Voc on both strings and no continuity to GND nor
>voltage to GND when the fuse is pulled.  There appears to be no
>ground faults or miswiring.
>
>2)  I've visually inspected all array wires - no pinching can be
>seen.  I've checked for Voltage and Continuity to GND from both the
>array side and the inverter side to isolate the wires in the conduit
>- no problems there either.
>
>3)  I've replaced the fuse even though it shows good with a good fuse
>with no change.
>
>4)  I've cycled the SB several times - no change.
>
>5)  I've run through John B's method below twice - no change.
>
>6)  I've confirmed that the GFDI fuse is in the top position of the
>two possible GFDI position - the one for negative ground.
>
>About the only thing I forgot to do was check if the Jumper for
>Negative or Positive GND was in the correct position - it dawned on
>me after coming home that if somehow that got set wrong at the
>factory that it would perhaps show a fault but not blow a fuse?
>Could this be it?  (I hope!)
>
>Anyone experience this condition before?
>
>Next step is to just swap out the inverter but as it's Sunday SMA
>tech support is probably not open so I hesitate to do that without
>their go ahead.
>
>Thoughts?
>
>Thanks!
>
>Jeff C.
>
>
>
>
>At 12:18 PM -0800 11/21/07, John Berdner wrote:
>Subject: RE: SMA Ground Fault troubleshooting advice. [RE-wrenches]
>
>>
>>Dave/Wrenches:
>>
>>Locating ground faults in the array is fairly straight forward albeit a
>>little dangerous.
>>A DVM and some spare fuses (just in case) is all you really need.
>  >Be very careful when you are doing all of this because you will be
>>working with live wires hanging in space and PV negative is no longer
>>necessarily at ground potential.  If the equipment grounding on the
>>array is not up to snuff it is also possible to see hazardous voltages
>>on the module frames or structure so measure everything and be really
>>careful.  Treat everything as hot and potentially lethal until your
>>meter says otherwise. Remember each time you disconnect something the
>  >whole situation can change so measure again to be sure.  Also, depending
>>where the ground fault is and the order in which you pull the wires out
>>of the inverter (or disconnect) it is possible to see double the array
>>Voc.  This can be a very bad thing since the spacing on all components
>>was designed for 600 Vdc max and you could be at double that.  A 960 Vdc
>>arc at  5 to 8 Amps is pretty ugly.
>>
>>Start by opening the DC disconnect and removing the GFDI fuse in the
>>inverter.
>>Measure the array open circuit voltage form the PV plus in the dc
>>disconnect to the PV negative in the inverter.
>>Lets say it is 480 Vdc.
>>Now measure PV positive to ground and then the PV negative to ground.
>>An array without a ground fault should give you roughly equal values of
>>around 240 Vdc but the measurement should decay down towards zero.  What
>>you are seeing is a discharge of the capacitive coupling between the
>>array and ground.
>>
>>In an array with a ground fault you will measure a fixed voltage to
>>ground on both the PV positive and PV negative.
>>The sum of the PV positive to ground and PV negative to ground
>>measurements should equal the open circuit voltage.
>>The difference in this case is that the voltage will be fixed and will
>>not decay towards zero.
>>The voltages you measure actually tell you where to start looking for
>>the ground fault.
>>
>>For example: with 12 modules in series and an open circuit voltage of
>>480, each module is equal to 40 Vdc.
>>If you measure PV positive to ground and get 0 volts then you should
>>see a PV negative to ground voltage of - 480 Vdc.  This tell you the
>>ground fault is in the PV positive output conductor.
>>Alternatively, if you were to see PV positive to ground at 400 Vdc and
>>PV negative to ground at -80 Vdc this tells you the ground fault is
>>between the 2nd and 3rd modules "up" from the PV negative.
>>
>>To figure out which string the ground fault is in, isolate each string
>>(remove the wires from the disconnect/inverter) and repeat the PV
>>positive to ground and PV negative to ground measurements.  On one
>>string the measurement will float around and the other will give you a
>>fixed measurement to ground.  The fault is in the string that has the
>>fixed measurement to ground.  My suggestion is to pull both positive and
>>negative wires for string 1 and measure.  If you are lucky you picked
>>the right string the first time out and you don't need to pull the
>>second string at all.
>>It is unlikely but also possible to see a ground fault in the "middle"
>>of a module.  In this case you might see 380 Vdc from PV positive to
>>ground and -100 Vdc from negative to ground.  This would indicate a
>>fault in the middle of the third module "up" from the PV negative.
>>Normally this means the module itself has a ground fault due to a nick
>>in the backskin, fault in the edge seal, etc. You can verify this by
>>isolating (unplugging) the suspect module then measuring PV positive to
>>ground and PV negative to ground for that isolated module.
>>
>>
>>Lastly, In some very rare case the ground fault will actually be in the
>>string combiner, dc disconnect, or (heaven forbid) in the inverter
>>itself. You can verify this if the array voltage measurements show a
>>ground fault when connected to the combiner/disconnect/inverter and then
>>both strings float when measured in hanging in free space.  While
>>unlikely, if you find this situation reconnect the PV back up then
>>disconnect one thing at a time and measuring relative to PV positive and
>>PV negative to ground until you find where the fault is.
>>
>>Best Regards,
>>
>>John Berdner
>>
>>
>>
>>>>>   ipl at sover.net 11/21/2007 07:40:51 AM >>>
>  >
>>Wrenches,
>>
>>I have a grid tied system with a SB3800U inverter being fed by 2
>>strings of
>>(12) Evergreen 180's (4.32kW). UniRack rail mounted on garage roof.
>>Good
>>installation all wiring neat and well supported. Only DC bond to ground
>>is
>>in the inverter etc. And no external monitoring equipment.
>>
>>The system has been operating very well (over 5,000 kWh over 2 months
>>in
>>Northern Vermont), this is the first problem.
>>
>>We are in the middle of a snowy spell and the array is covered in snow,
>  >but
>>I should be able to check out the array within a few days. According to
>>the
>>error message on the Sunny Boy the GFDI 1 amp fuse is open. The array
>>has
>>made it through lots of rain, ice and snow over the past year.
>>
>>My suspicion is in the MC connector(s) themselves. We had a bad batch
>>of MC
>>cables purchased from a large distributor 12 to 18 months ago. The MC
>>connector would pull off the wire when tested. Of course not all of
>>them
>>where tested before they got into the field, so one could be on this
>>roof.
>>
>>Obviously I will check connections in the combiner, the dc disconnect
>>etc,
>>could be a moisture issue. Of course it could be a squirel I guess.
>>
>>Any advice on troubleshooting this ground fault would be appreciated.
>>Safety
>>wise do we need to cover the array with a dark tarp?
>>
>>Dave
>>
>>
>>
>>
>>--
>>[Non-text portions of this message have been removed]
>>
>>
>>- - - -
>>Hosted by Home Power magazine
>>
>>To send a message: RE-wrenches at topica.com
>>
>>Archive of previous messages:
>http://lists.topica.com/lists/RE-wrenches/read
>>
>>List rules & how to change your email address:
>>www.mrsharkey.com/wrenches/etiquette.php
>>
>>Check out participant bios: www.mrsharkey.com/wrenches/
>>
>>Moderator: michael.welch at homepower.com
>>--^----------------------------------------------------------------
>>This email was sent to: jeffc at villagepower.com
>>
>>EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.a9hBZi.amVmZmNA
>>Or send an email to: RE-wrenches-unsubscribe at topica.com
>>
>>For Topica's complete suite of email marketing solutions visit:
>>http://www.topica.com/?p=TEXFOOTER
>>--^----------------------------------------------------------------
>
>--
>~~~~~~~~~~~~~
>Jeff Clearwater
>Senior Design Engineer
>NABCEP (tm) Certified Solar PV Installer
>http://www.nabcep.org/
>Village Power Design
>Turnkey Solar Design & Installation for the Commercial Sector
>http://www.villagepower.com
>gosolar at villagepower.com
>
>Voice: 413-259-3750
>Fax: 413-825-0703
>65 Schoolhouse Rd
>Amherst, MA 01002
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>_______________________________________________
>List sponsored by Home Power magazine
>
>List Address: RE-wrenches at lists.re-wrenches.org
>
>Options & settings:
>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
>List-Archive:
>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
>List rules & etiquette:
>www.re-wrenches.org/etiquette.htm
>
>Check out participant bios:
>www.members.re-wrenches.org
>
>
>_______________________________________________
>List sponsored by Home Power magazine
>
>List Address: RE-wrenches at lists.re-wrenches.org
>
>Options & settings:
>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
>List-Archive: 
>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
>List rules & etiquette:
>www.re-wrenches.org/etiquette.htm
>
>Check out participant bios:
>www.members.re-wrenches.org

-- 
~~~~~~~~~~~~~
Jeff Clearwater
Senior Design Engineer
NABCEP (tm) Certified Solar PV Installer
http://www.nabcep.org/
NorthEast Solar Design
Turnkey Solar Design & Installation for the Commercial Sector
http://www.villagepower.com
gosolar at villagepower.com

Voice: 413-259-3776
Fax: 413-825-0703
65 Schoolhouse Rd
Amherst, MA 01002
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~