E-panel wiring questions

khotton
khotton Solar Expert Posts: 38 ✭
in Advanced Solar Electric Technical Forum #1
Solar Experts,

I will be getting a stretched Outback e-panel (MNE125-STS Left). I already have the FX3048 inverter, C40 charge-controller, and MNPV6 combiner box and 15A breakers. I also have lightning protection devices: (1) Delta DC surge arrestor, (1) Delta AC surge arrestor, (1) Delta AC surge capacitor.

I have been studying the e-panel wiring diagram drawn by Robin Gudgel 10-10-05. It shows (4) "Lightning Arrestors"

I will have my PV array on the roof with the combiner box next to the e-panel (with aprox. 25-ft 10-AWG MC cable runs from the panel-strings to the combiner box. Array is 3 strings of KC130GT (four panels per string. i.e. 48V nom. array).

My questions are the following:

1) do I need a separate DC surge arrestor at both the combiner box and the charge-controller?

2) I don't believe the e-panel comes with the 60A DC output disconnect or the 60A PV+ input disconnect shown on the wiring diagram. I was planning on buying (2) 50A Square-D QOU breakers for these disconnects. Are these the correct breakers that I need?

3) What do I need to purchase for the Ground Fault Protector "GFP" circuit shown? I will be off-grid with a 48V battery bank, is this circuit still recommended?

4) Will the AC surge capacitor mount on (or in) the e-panel, or on (or in) the separate AC-power panel (with all my home's AC branch circuit breakers)?

5) What other components (lightning protection, safety devices, etc. am I still lacking)?

Thank you,
Kevin Hotton
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Comments

  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
    #2
    Re: E-panel wiring questions

    You wire a LA302DC arrestor direct to your C40 charge controller,no point IMHO in wiring one in your combiner box no electronics to protect. One LA302DC for each DC rated electronic device .HTH

    I have a AC LA in my mains board and a sub board and one on my Generator input.

    Some may scoff at Delta LA but Ive read 2 many articles in Home Power Magazine in the last 4 years about failures with no Lightning protection and problems solved when fitted. The cost is minimal.......part of belt and braces mentality....an English Phrase, if the belt fails the braces are there for additional support ;) I assume its tavelled to your continent.:p:p
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #3
    Re: E-panel wiring questions
    2) I don't believe the e-panel comes with the 60A DC output disconnect or the 60A PV+ input disconnect shown on the wiring diagram. I was planning on buying (2) 50A Square-D QOU breakers for these disconnects. Are these the correct breakers that I need?
    Probably not. The QO and QOU breakers are rated for 48 VDC max. You're likely to see higher voltages in your “48 V” system. They also won’t mount to the DIN rails inside the E-Panel.

    Figure out the right size (current) breakers you need and buy the CBI brand DIN mount DC breakers from Midnite Solar or OutBack via NAWS. They’re rated for 125 VDC to 150 VDC depending on model and application. You can order these at the same times as you order the DIN breakers for your MNPV.
    3) What do I need to purchase for the Ground Fault Protector "GFP" circuit shown? I will be off-grid with a 48V battery bank, is this circuit still recommended?
    This is an NEC requirement if you’re mounting a PV array on an inhabited building. A compact GFI “combo” breaker assembly is also available from MidNite; here are the specs from the MidNite price list:
    MNDC-GFP $69 63 amp 150VDC DC ground fault protector (UL listed breaker assy) 3 Lb. 150VDC ETL listed in the US and Canada
    HTH,
    Jim / crewzer
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #4
    Re: E-panel wiring questions

    Also with with the most recent NEC 2008, ANY solar array must now have GFP protection, not only roof mount arrays ...

    FYI, there is usally delays from rules being published to inspectors/city/county/states implement the newest rules, check with your local inspectors to see what verision of the NEC they are following
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #5
    Re: E-panel wiring questions

    Right you are, SG, on both points!

    Regards,
    Jim / crewzer
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #6
    Re: E-panel wiring questions

    you can also shoot Robin an email he can plug the breakers in and install the wiring as well for an additional cost and it will be all ready to go. and as SG stated you need the gfci protection period now it is in the 08 NEC
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: E-panel wiring questions

    i'm guessing that wiles now knows that voltages could crop up with seperate grounds and he decided to cover his butt on it by requiring the gfis.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #8
    Re: E-panel wiring questions

    I still think that the GFI requirement is just a way of trying to copy how GFI protects people from shocks around sinks, tubs, outdoors, and pools.

    Since the solar system is just part of the facility wiring and not an outlet next to a swimming pool, and the fault current is 1 amp or greater, it does not even approach the safety offered by GFI in AC branch circuits. And it only "protects" against a specific type of ground fault (positive to earth) on the solar panel side at the controller--and once tripped, the panels are still "hot" or "faulted" so it does not protect anyone. All it does is turn of the inverter. And it does not protect against ground faults on the battery side where there is sufficient voltage and amperage available to cause fire, injury, or death...

    And since NEC still does not protect against ground faults in the neutral/ground legs of normal branch circuits anyway (I have seen more than a few places with messed up neutral/safety ground screw-ups)--why does solar get this "help".

    If the DC GFI was intended as an active safety circuit--it fails miserably and takes what was an isolated wiring system (all leads float with respect to ground--impossible to get a +/- to earth short/shock) to now where a shock/short is guaranteed with a "+" to earth short with no method of disconnecting the short anyway (blowing the 1 amp fuse in a Grid Tied Array may interrupt some failures--not sure in DC installations). At best, the system will identify a "+" lead insulation failure that needs to be found/repaired--but that is about it.

    End of rant...
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: E-panel wiring questions

    well said rant none the less.
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #10
    Re: E-panel wiring questions

    The point of array GFI as I understand it is

    1) to prevent structures/conduit from becoming current carrying that was not designed for it

    2) to prevent structures that are suppose to be grounded to be otherwise a potentional higher than ground ( you know we don't want to have people on the roof getting shocked if the frames are not truely grounded )


    Like other discussions on the NEC, a very specific person is behind this and its maybe at most half a dozen people that make and approve these rules. This GFI is total BS ...

    In the EU, everything is allowed to be floated, they realize for example there is no physically connection anywhere in a solar panel with the frame and live parts. There is no possible faulire of a solar panel to have any voltage or potenional effect the frame.

    My array's , in the two installations I built, the arrays are intentionally unground FOR SAFETY reasons. I live in litterally the lighting capital of the world. To ground the frames and racks is increasing the chances of direct lightning to the stuctures ... lunacy. Forunatley, the NEC is nothing more than a guide for the local inspectors and MY inspectors are 110% in complete agreement to leave them ungrounded, allowing the panel frames and structure to float is much safer.

    By the way, the story was there was an installation in CA that was ground mounted, where a nicked wire burned a hole thru some conduit. Our favorite NEC sponsors then deemed that ALL solar installations should have GFI's to be safe to protect from improperly pulled wire.

    Mind you commerical building are required to have conduit for everything, can have the exact same fault ( nicked wires ) but they don't have gfi on every circuit and thats OK ... oh crap, they will read this and NEC2011 will have ... oh never mind
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  • khotton
    khotton Solar Expert Posts: 38 ✭
    #11
    Re: E-panel wiring questions

    Thanks for all your answers and personal opinions. I now have even more questions to ponder. My installation is off-grid (outside city limits; no building permit or inspections required) in Mexico. Hence, I want to use the best "common sense" installation. I was ignorantly assuming that grounding all the PV panels frames to a ground-rod was the best way to go, but now I have my doubts. What is the general consensus about PV panel grounding.

    Further, after reading Solar Guppy and BB, I think I will skip the GFI circuit (and save the +60$).

    However, I am still abit confused as to the proper wiring of the AC surge capasitor. Can you help me with this?

    Thanks,
    Kevin
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: E-panel wiring questions

    Grounding all of your aluminum panel frames and making sure your metal structures are all bonded to a ground rod is a very good idea... Prevents something becoming energized with respect to ground and shocking somebody...

    If you have lighting in the area, grounding becomes another issue that borders on religion... If you don't have lighting in the area, just following good practices for normal electrical is probably good enough...

    If you have lightning and strikes in your area--Niel, Jim, and Solar Guppy can give you the details... Usually the big issue is ground referencing issues... Say you have panels 200' away from the home... If you stick one ground rod in a the panels and another at the home, any nearby strike will create a voltage gradient across the 200'--causing one side of your system (say the panels) to have a much higher voltage than your home--and you got nice heavy copper wires (solar +/- leads) running between the too--an ideal way to cause arcing somewhere in your system.

    Tying all of the metal parts through nice heavy copper wire and taking it to one central point and you may have a better chance at preventing the high voltage differential among the various points in your system (may take multiple ground rods spread around your "ground window" if the soil is dry or rocky).

    If you can keep all of the parts close together, and avoid running wires from the panels through your home (and taking lightning energy into/through your home), it is a good idea (and probably NEC code--if I understand correctly).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
    Re: E-panel wiring questions

    guppy and i have differing approaches to the issue and we both understand each other's points of view. guppy views it as just metal in the sky much like a plane would be. that plane is not really attractive to lightning until there is a path to the ground involved. i don't view pvs like a plane and wires imho don't need to go to ground to cause a path as the leads from the pvs are going down and into the home making it a better target than the tree next to the house with the rest of the path being air arcthrough. i haven't been hit and guppy hasn't been hit.
    grounding is the more traditional route and i believe it to be the better route due to my experiences in radio and seeing that charges can build on an ungrounded metalic object in the air or just higher up than the ground is. these charges can attract a lightning strike and i saw it first hand many years ago on an antenna i had in another location that the ground wire broken off through human error. it was hit on the first storm that came. after reconnecting the ground all was fine with no more hits though the antenna suffered some damage and didn't last too much longer.
    i guess it's all in what you might feel is more comforting as you could say would it be better to stand in an open field with a flag pole that doesn't eneter the ground during an electrical storm or would it be better to stand next to a flag pole that goes into the ground during an electrical storm? there are no guarantees either way. i'd prefer the inground flag pole.
    oh, and what bill sad as most will go with a ground, but you don't have to follow wiles' ruling and needlessly bring that grounded wire into the house. from your pv frames send it straight down into the ground with an 8ft copper ground rod with at least a #6 copper wire for a staright path with no sharp bends to the wire.:roll:
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