GFCI upgrade to older Outback system

NZRR
NZRR Registered Users Posts: 28 ✭✭
in Advanced Solar Electric Technical Forum #1
We recently added PV to an older (2005) Outback system which has the negative and ground tied to the same bus bar. Since this is the case, we could not add in a GFCI as required by the NEC. We would like to suggest upgrading the system by adding a negative bus and separating the negative and ground wires. Otherwise, it is not clear how the GFCI will work if the negative and the ground are bonded together. Any clarification would be appreciated.

Also, we think we should add a separate GFCI for each PV system (the original installed in 2005 and the one we just installed). Does this make sense?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: GFCI upgrade to older Outback system

    If it works as is, don't change it. Just my opinion but this GFCI obsession of Wiles' is getting out of hand. Next the NEC will demand arc-fault breakers on all panels over 0.5 Watts. :roll:

    But if you feel you must comply with this code change then yes you'll have to separate the ground and negative and make sure the two are isolated save the GFCI connections. And you should do all the arrays because inevitably the negatives are shared in common throughout so leaving even one -/G connection could foul the whole system.
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #3
    Re: GFCI upgrade to older Outback system

    Yep my feeling is about the same. If there is not a large gauge bond between Battery - and earth ground then the Battery - actually becomes a current carrying conductor like the Battery + not a Grounded conductor like IT SHOULD BE. So I feel that there at minimum needs to be breakers on + and - conductors when GFP is used.

    BB did a wonderful paper on the hazards of GFP and I completely agree with his statements made and actually verified a few for him here at MidNite. Here is a link to the paper that was submitted to Wiles.

    http://www.midnitesolar.com/pdfs/DC-GFP-Draft3-5.pdf
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  • NZRR
    NZRR Registered Users Posts: 28 ✭✭
    #4
    Re: GFCI upgrade to older Outback system

    What I hear you recommending is to NOT upgrade the existing system unless we have to, but if we have to, make sure there are OPDs on both positive and negative conductors. Is my understanding correct?

    Also, if we do add the GFCI, do I need two (one for each PV array), or should there be a triple pole GFCI (if one exists) so they both open at once if one faults?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,640 admin
    #5
    Re: GFCI upgrade to older Outback system

    If you have solid battery to earth grounds--you only neeld one breaker/fuse on each + connection.

    If you fuse/breaker the battery to earth ground--my opinion is you need dual breakers (sort of like the pair of 240 VAC breakers you see in your home breaker panel) for safety.

    I am not sure if you have two+ solar arrays how you do the GFI. Partially, depends on the charge controller you select...

    If you use the external DC GFI setup--You might have to simply parallel the two 1 amp breakers, one for each 1a/63a Solar Array disconnect.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: GFCI upgrade to older Outback system

    My take (which may not be right): all panels connected to one charge controller is a single array which should be protected by one GFCI system - one which interrupts both (+) and (-) like Bill said.
    If there is a second charge controller its panels would be considered a separate array and would require its own GFCI system.

    And good luck getting the negative and ground separated everywhere. Next thing you know one GFCI per array won't be good enough; they'll want one per string. Meanwhile more houses burn down from over-loaded 18 AWG extension cords that have the ability to connect between a source and a load capable of exceeding their capacity, but have no circuit protection requirements for the cords themselves. Go figure. :roll:
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,917 ✭✭✭✭✭✭
    #7
    Re: GFCI upgrade to older Outback system

    Bill,

    What has been your feedback from John Wiles ? I have not agreed with you in one aspect of GFCI. This is with XWCC's when operated as part of an XW system. Care to guess? It is a reason to want GFCI as implemented by Xantrex in the XW.

    --Dave
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,640 admin
    #8
    Re: GFCI upgrade to older Outback system

    Dave,

    Sorry, I lost the thread and never replied to your question...

    No, I have not heard from anyone about my issues that is connected with the NEC process (that I know of).

    I have had about a 1/2 dozen people that emailed and called--And those that expressed an opinion/discussion back with me all believed that a breaker/fuse between return and frame/earth ground was not acceptable in their fields of engineering/product design.

    I did send an email take discussion of the NEC ground fault code overlaid against the UL requirements for safety grounding in Solar Charger Controllers and Inverters... Basically, one of the major requirements is to pass a 30 amp (I think it is around 30 amps) test current between return and frame ground in order to define it as a safety ground. Obviously, a 1 amp breaker or fuse is not going to meet that requirement.

    Dave, regarding why you like the XW integration of ground fault detection... My guess is that a ground fault will indicate it on the inverter/charge controller so you can take positive action and fix the shorted circuit instead of waiting for other failures to manifest (such as a fire, shock, or failure to charge battery bank which then cost a bunch of $$$ to replace).

    However, I believe the safety and system integration issues are still problems that cannot be fixed/addressed by the current GFP detection breaker scheme--which (as near as I can tell) was intended to reduce the chances of sustained arc faults causing a fire (and which the GFP detection breaker does a fairly poor job at preventing/suppressing).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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