Afci for

kevin
kevin Registered Users Posts: 9 ✭
in PV Installers Forum - NEC, Wiring, Installation #1
the AFIC"Arc-Fault Circuit Protection" is require in NEC 2011.690. is there any body know this is require for system or it require for pv inverter?

thanks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #2
    Re: Afci for

    It appears that the code is getting ahead of what is actually available at this time... Some Google Search Results.

    Code     Breaker
    There is currently no product offering on the market for DC AFCI to meet 690.11 of the 2011 NEC.
    Eaton Corporation is working hard to bring a product

    The folks at Midnite are working on Arc Fault breakers for DC systems.

    They have a new breaker product line that they have recently announced (although, this looks like a multi-point remote DC disconnect system--probably will be very nice for a battery system--pull any remote disconnect to kill power to everything in the off grid system).

    Further reading seems to indicate the above may not the Arc Fault breaker setup...

    The existing NEC solution for Arc Fault protection is really a DC Ground Fault protection setup. Personally, I believe that setup is actually quite dangerous and supplies only a minimal protection for some forms of ground faults--But the issues the DC GFI raises is worse than the original problem it was intended "to fix".

    Ground Fault Protection
    http://forum.solar-electric.com/showthread.php?t=10650

    -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 ✭✭✭
    #3
    Re: Afci for

    Another over-rated (pun intended) safety device.

    Arc-fault AC breakers are required for bedroom circuits in Canada now. They cost a lot of money (3-4 times standard breakers) and serve mostly to make it impossible to vacuum the carpet. :p

    Almost as bad as the DC ground-fault requirement.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #4
    Re: Afci for
    BB. wrote: »
    The folks at Midnite are working on Arc Fault breakers for DC systems.

    Their arc fault protection is already built into their Classic charge controllers. It should be noted that the built in arc fault protection in the Classic will only protect against series arc faults. Arc fault protection at the combiner box will also protect against parallel arc faults.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • jaggedben
    jaggedben Solar Expert Posts: 230 ✭✭
    #5
    Re: Afci for

    Hopefully we can expect that this will be built into new inverters, just as the GFDI now is.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #6
    Re: Afci for
    vtmaps wrote: »
    Their arc fault protection is already built into their Classic charge controllers. It should be noted that the built in arc fault protection in the Classic will only protect against series arc faults. Arc fault protection at the combiner box will also protect against parallel arc faults.

    But, I don't believe there are any combiner boxes available at this time with Arc Fault detection/protection.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #7
    Re: Afci for
    vtmaps wrote: »
    Their arc fault protection is already built into their Classic charge controllers. It should be noted that the built in arc fault protection in the Classic will only protect against series arc faults. Arc fault protection at the combiner box will also protect against parallel arc faults.

    --vtMaps

    What's the diff between series and parallel arc faults?
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #8
    Re: Afci for
    ggunn wrote: »
    What's the diff between series and parallel arc faults?

    Series arc faults are essentially intermittent open circuits, caused by bad connections or broken wires. They generate heat by resistance (I**2)R when the load is drawing current.
    Parallel arc faults are essentially intermittent short circuits caused by insulation failure or mechanical contact of uninsulated wires. The generate heat by resistance (V**2)/R whether the load is connected or not.

    A conventional breaker or GFCI cannot detect a series arc fault at all.
    A conventional breaker may not disconnect on a parallel arc fault before a fire starts and a GFCI cannot detect a parallel arc fault between the hot and the neutral, since no ground current is associated with it.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Afci for
    ggunn wrote: »
    What's the diff between series and parallel arc faults?

    Parallel: arcing between one side and the other (as in positive to negative intermittent short).
    Serial: arcing within one side of the circuit (as in intermittent connection to power source).

    The serial fault happens more often in panel arrays which is why the guys at MidNite thought it a good idea to protect against. If the (+) arcs to (-) on panels it either does nothing but lose power or pops the fuse/breaker (if so equipped). Not to be confused with the DC GFI which looks for current finding an alternate path rather than the designated one.

    Arc fault AC breakers trip on what they think is a sudden short to prevent arcs from igniting flammable materials nearby. This is as opposed to current over-load provided by standard breakers which requires the Amperage rating to be exceeded by 'so much for so long'. This doesn't happen when a circuit is arcing of course. Seems to happen when you turn on the Hoover, though. :p
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #10
    Re: Afci for

    As I understand the terms being used here:

    Series arc faults would be a, for example, failed/arcing connection/connector in a single wire/bus bar connection (in series with the load). "Turning off the load" would stop current flow through a series arc fault.

    A parallel arc fault would be from hot to ground or hot to return/neutral. Turning off a load will not stop a parallel arc fault.

    The DC GFI "arc fault" can stop a +/Hot to Earth Ground fault (arc or simple hard fault) because there is a a small ~1 amp fuse/breaker between Return (typically negative) and earth ground.

    As I understand, an Arc Fault Breaker monitors the energy spectrum on the wiring and if it "hears" a frequency spectrum similar to that of an "arc", then it turns off (opens/trips the breaker).

    Or, in the case the Marc/Cariboocoot typed about--Brushed (universal) motors can appear very similar to an "arc fault" spectrum and cause false trips.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #11
    Re: Afci for

    Almost a photo finish..... :-)
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #12
    Re: Afci for

    Close only counts in horse shoes and hand grenades (and solar forums). ;)

    -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 ✭✭✭
    #13
    Re: Afci for

    Great minds think alike; fools seldom differ. :p
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #14
    Re: Afci for
    Cariboocoot wrote: »
    Great minds think alike; fools seldom differ. :p

    Or, as I am fond of saying, "Great minds run in the same gutter...."
    SMA SB 3000, old BP panels.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #15
    Re: Afci for
    Cariboocoot wrote: »
    Great minds think alike; fools seldom differ. :p

    "The "Fools seldom differ" part is found in British English only." --Wiktionary.
    Another of my personal favorite turns of phrase: "That is a subject about which even reasonable men may differ, so I am not all surprised that you disagree...."
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: Afci for
    inetdog wrote: »
    "The "Fools seldom differ" part is found in British English only." --Wiktionary.

    That shouldn't surprise anyone who's been around here very long. ;)
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #17
    Re: Afci for

    The 2011 NEC required series arc fault protection. The 2014 NEC will require series and parallel arc fault protection.

    A charge controller or inverter (like the SMA) with built in DC AF protection can only turn itself off to protect against
    a series arc fault all by itself.

    For both series and parallel arc faults, more hardware is required.

    boB
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  • kevin
    kevin Registered Users Posts: 9 ✭
    #18
    Re: Afci for

    Hi，
    i get a figure about the AFCI，it's very similar with GFCI，but i think there is a MCU in it. does it difficult to realize？I think it will required for all the device which higher than 80V.
    Attachment not found.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #19
    Re: Afci for

    The question I have (and it really is a question, not an agenda push) is whether arc fault protection is a requirement that will actually save lives and property, or is it a solution searching for a problem?
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #20
    Re: Afci for
    ggunn wrote: »
    The question I have (and it really is a question, not an agenda push) is whether arc fault protection is a requirement that will actually save lives and property, or is it a solution searching for a problem?

    If I had a large array of high voltage panels on my roof, I would feel better with an arc fault combiner box on the roof. Presumably I would be less likely to have a roof fire.

    I have no idea how many roof fires (caused by DC arc faults) actually occur each year.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #21
    Re: Afci for

    I suspect that like so many safety requirements these days it's a case of "we do it because we can*" rather than something based on actual statistics of incidents.

    Seems strange to me that in all the years over-loaded extension cords have been burning houses down there has been no effort to force circuit protection in to them. Any type of multi-tap outlet device is a greater danger than the arc-fault potential in my opinion.

    *Ironically, as Bill mentioned, we can't yet with the DC side; there is a surprising lack of equipment in the marketplace that meets the new series/parallel DC arc fault regulations.
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