Combiner Box

With54
With54 Registered Users Posts: 21 ✭
in Solar Beginners Corner #1
I came across this article on the web about building your own combiner box from an AC Breaker Panel (http://www.freesunpower.com/project1.php) using 15 amp AC breakers. Is this safe? Will any 15 amp AC Breaker do the job?

Thank you for any information.
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  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #2
    Re: Combiner Box

    Some Ac breakers are rated for DC ... most are not! Unless you have the parts lying around; it would be cheaper and safer to buy a UL listed combiner box.
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #3
    Re: Combiner Box

    Just a few comments on that use of AC rated panel. He shows several bad examples of poor workman-ship.
    As a minimum if you are going to do this and you need a outdoor rated box get one, they are available in the stores, don't use silicone to try and make it raintight.
    Don't run wires thru box knockouts with a raintight box connector if outside or at least a proper box clamp if used indoors.
    Don't mix color codes on the wires, NEC say's black would be "Hot" or positive and white would be neutral or negative. If you are off grid and will never be inspected can do what you want but at least mark them for what they are.
    Be sure and correctly size the wire's for the current they will carry. Jumper from buss #2 to #1 buss will carry the combined current of breakers that use it.
    Getting DC rated breakers is questionable at best.

    Best advice has been given and that is to get a Rated Combiner-box and appropiate DC rated breakers or fuses and be safe.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #4
    Re: Combiner Box
    SkiDoo55 wrote: »
    Just a few comments on that use of AC rated panel. He shows several bad examples of poor workman-ship.

    Yea he does. Horrible.

    Don't mix color codes on the wires, NEC say's black would be "Hot" or positive and white would be neutral or negative.

    That's for AC. For DC common usage would be black for negative and {some other color - usually red or white} for positive.

    NEC doesn't really specify colors for hot (other than phase labeling black/red/blue) - it specifies colors for neutral and ground, but pretty much any color that isn't neutral or ground is fine for hot.
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #5
    Re: Combiner Box

    So by what you just said that White or gray is for neutral or grounded conductor and not positive.

    So the earliest NEC dealt with DC, including
    color coding for conductors that still holds today. If the
    conductor is a grounded circuit conductor, the insulation or
    marking on larger conductors must be white or gray. If the
    conductor is an equipment-grounding conductor, it must
    have green or green with yellow-striped insulation—or be
    bare. Ungrounded conductors may be any color other than
    the ones listed above, with black and red being the most
    common in the field.

    so red could be OK for positive but not with a White Input from the solar panels switching to Red. If nothing else stay consistant is what I meant by my statement. He is using White for and ungrounded conductor! HOT from the panels.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #6
    Re: Combiner Box

    Wow this guy should be in jail. I love his way of sizing wire and his blatant disregard for safety let alone the NEC I absolutely despise people that reverse white and black like he did that is a death waiting to happen when someone uses the right color code down stream and gets electrocuted from the white supposed grounded conductor that they made hot.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #7
    Re: Combiner Box
    SkiDoo55 wrote: »
    So by what you just said that White or gray is for neutral or grounded conductor and not positive.

    Again, that's for AC. There is no neutral in DC.

    So the earliest NEC dealt with DC, including
    color coding for conductors that still holds today. If the
    conductor is a grounded circuit conductor, the insulation or
    marking on larger conductors must be white or gray. If the
    conductor is an equipment-grounding conductor, it must
    have green or green with yellow-striped insulation—or be
    bare. Ungrounded conductors may be any color other than
    the ones listed above, with black and red being the most
    common in the field.

    so red could be OK for positive but not with a White Input from the solar panels switching to Red. If nothing else stay consistant is what I meant by my statement. He is using White for and ungrounded conductor! HOT from the panels.

    That's what I'm saying - for DC it's black that is normally used for negative (even if it is a "grounded conductor") - not white or gray.

    So white for positive is okay in DC wiring, and that is how it's often done. For a DC circuit, using a cable with say a black, white and green - green is ground, black is negative. What's that leave for the positive?

    As far as I know the NEC doesn't specify. Wiles has recommendations, but it's not consistent - on one he uses white for negative, on another black.

    Consistency would be great, and they'll probably get around to fixing it in the NEC.


    EDIT: Also, there are lots of low-voltage cables out there. They are commonly black (for -) and black w/white stripe (for +). Take a look at 12/2 Malibu lighting wire - it's all black, but one strand has a raised stripe (a ridge all the way down). That ridge is the same as the white stripe - it's to signify positive (or hot).
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  • SkiDoo55
    SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    #8
    Re: Combiner Box

    NEC by definitions in Article 100 definitions of Grounded and ungrounded conductors and Section 200.6 of NEC, 310.10 (a) grounded conductor, 310.10 (c) ungrounded conductor. These cover both AC and DC systems.

    Grounded conductor does not necessarly mean one going to earth/ground. In case of a (-neg) ground system the negative would be colored white or gray. Could be a black wire marked with white tape etc.
    Ungrounded conductor (+Pos) could be red or any other color other than white or gray.

    This would be reversed if you were using a Positive ground system such as some panels are. (+pos / White or Gray), (-neg black/red etc)

    Automotive and other equipment can use what colors they want as they are not covered by the NEC as PV systems are, Stand-alone or on grid are no different.

    Correctly colored tape at the ends of the wires and/or tape labels identifying them as either + or - DC would help someone from getting hurt or killed from incorrect contact.

    Back to my orginal concerns was that this web site shows very poor workmanship, multiple code violations and the improper use for location and type of equipment, and people are using it to make installations at there own sites. I have seen post here were people have purchased equipment, installed it and can't read a Digital Volt Meter. If they would ask for help first as many do, it would save lots of injuries and burnt-up equipment.

    We should all strive to keep this as safe as possible!!
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #9
    Re: Combiner Box

    The NEC specifically addresses ac or dc conductors. Any one installing a PV system should have a grasp on simple color coding or hire an electrician in my opinion. I have seen crap like the linked combiner on grid tied systems running at 500vdc and it really burns my you know what. Someone could get killed or seriously injured if they assume the white is a grounded conductor as NEC says it is.
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  • vcallaway
    vcallaway Solar Expert Posts: 157 ✭✭✭✭✭
    #10
    Re: Combiner Box

    I think the problem is most peoples experience with DC is automotive or computers. Cars typically have black and brown as ground and other colors as positive.

    It gets really confusing in my motorhome where the chassis electrical system has black ground wires and the coach side has white with black as positive.

    I do agree with most of you. It is better to use the parts designed for the application. I've been down that road before. Call it a noob tax.
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  • nsaspook
    nsaspook Solar Expert Posts: 396 ✭✭✭
    #11
    Re: Combiner Box

    The nice thing about standards is that there's so many of them. From my 30+ years of industrial electronics and electrical work, I've learned colors on wires don't mean a lot even on the AC power side. Always check an unfamiliar circuit with a good meter and label it.

    The NEC codes are great but still allow for totally ungrounded power circuits without even a neutral to exist. So be careful, a hack job can get you killed.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #12
    Re: Combiner Box

    Well, I don't see anything in 310.10 about DC, and I can't seem to find Article 100 on the net. My local library doesn't have the NEC so I'd have to have it sent over from another branch (and only one has 2005, all the rest are older) which would take days at least.

    However, I do find that the NEC color code applies to grounded systems, but not to ungrounded systems.

    I also find that there is some debate on whether or not the PV system falls under the definition of "premises wiring" - if it does, then NEC applies, if it doesn't then NEC does not apply.


    In any case, I'll refer to Wiles:

    "If the PV system were an ungrounded 12 volt PV
    system, the NEC has nothing to say about the color of the
    insulation on the two ungrounded conductors."

    http://www.nmsu.edu/~tdi/pdf-resources/cc99.pdf


    But not just 12v:

    "Twelve and twenty four volt PV systems have open circuit voltages
    less than 50 volts and therefore are not required to have one
    conductor grounded."


    "The local inspector will be looking for that green or bare grounding
    conductor in all PV systems and a white grounded conductor in
    those over 50 volts or those which are grounded below 50 volts."

    http://www.nmsu.edu/~tdi/pdf-resources/cc18.pdf
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