service upgrade required?

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xiphias
xiphias Solar Expert Posts: 52 ✭✭✭✭
in Grid Tie and Grid Interactive Systems #1
One potential installer has said I need to upgrade my existing electrical service from 100Amp to 200Amp in order to add a ~3kW grid-tie system (Evergreen panels, SunnyBoy inverter).

Another potential installer has not.

Thoughts as to why or why not, and whether/why an upgrade would be needed?

Thanks.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
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    Re: service upgrade required?

    i'm not seeing the need for a service upgrade based on just the service ratings as a 3kw solar can work on it. at best if it is a battery backed grid-tie then an added sub panel can be put in. the solar will not add to that which is passing into the house, but would rather subtract from it seeing as how it would cancel out that same amount of power would be needed going inward bound. if the installer is adding the solar current to the overall passing through the main breaker he is wrong and do not go with that installer as he doesn't seem to have enough of a grasp of the basic concepts of what solar is doing imho. 3000w/240v=12.5amps outbound from solar at max output. i think a 100a panel will take it just fine.
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #3
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    Re: service upgrade required?

    Thanks. No battery backup. Just straight grid tie. This particular installer has done most of the installs in this region, including some pretty complex commercial stuff, wind/solar combos, thermal, PV, etc. He's been around for 20 years. I've seen several of his residential installs and they are quality pieces of work. Never did notice whether they all had 200Amp service, though. Might have to go back to him on this.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: service upgrade required?

    yes, do ask him why that upgrade is needed as i'd like to know the reasoning he is using.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #5
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    Re: service upgrade required?

    Either installer could be correct. The answer lies in two areas:

    (1) Is this a commercial or residential installation, and
    (2) What size breaker(s) is/are planned between for the inverter feed(s) to the service panel?

    Check this Code Corner article by John Wiles for the explanation: http://www.nmsu.edu/~tdi/pdf-resources/CC111.pdf

    HTH,
    Jim/crewzer
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #6
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    Re: service upgrade required?

    I would trust installer that has the local experiance, its most likey true due to local inspectors will requiring the upgrade to 200 amp service and what ever they want you have no choice but to comply.

    When renovations are done to a structure, its common that services are required to be brought up to the current code standards. I've seen some commerical jobs where the costs to bring a structure to current code was 4X the cost of the actual addition/renovation.
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #7
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    Re: service upgrade required?

    Thanks for the article. Will give it a read. Both installers are trusted, long-time locals with many installs under their belts. If anything, I think it's likely that the one who did not specify the service upgrade missed noting that we have 100Amp service, not 200Amp, if in fact 200Amp is required.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #8
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    Re: service upgrade required?

    it may be a case that you would need the 200amp service anyway be it from inspectors or that your service was too low in amps for your residence anyway. in actuality, as i had said before, solar does not increase the current flowing through the main breaker so it is not a valid reason for a higher rated service panel imho. however, if inspectors tell you to pick your nose to pass, you pick your nose no matter how unfair or assinine it is to do so. failure to do so may result in not only a failure, but he may require you to pick your seat too!:cry:
    this is premature imo as this is coming from an installer so please ask him why the need.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #9
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    Re: service upgrade required?
    xiphias wrote: »
    Thoughts as to why or why not, and whether/why an upgrade would be needed?

    Profit, or code may require an upgrade when any electrical permit is pulled. Grid-Tie inverter would not matter till you get to about 50A output ( @ 240VAC ) THEN, a 100A panel may need to be upgraded.


    Or

    Your panel uses old breakers that can't be found anywhere, or has no more empty slots for 2 new breakers.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #10
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    Re: service upgrade required?
    solar does not increase the current flowing through the main breaker
    niel,

    Right. But, adding the output from an inverter can increase the total current flow in the bass bar(s), and that may cause its/their rating to be exceeded. Therein lies the potential problem.

    HTH,
    Jim / crewzer
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
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    Re: service upgrade required?

    ok so add about 12.5amps to the 100amps and i still see no need to go to a 200amp panel let alone a 150amp panel. a 100amp panel can easilly go 125amps and 112.5amps is still below that. let's put the speculation aside and wait to hear what the explanation is.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #12
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    Re: service upgrade required?
    a 100amp panel can easilly go 125amps
    Not according to NEC 690.64(B)(2). Here is what the section says for commercial applications:
    The sum of the ampere ratings of overcurrent devices in circuits supplying power to a busbar or conductor shall not exceed the rating of the busbar or conductor.
    If a commercial installation panel / busbar rated at 100 A, and it’s supplied from the grid via a 100 A breaker, then no other power sources (i.e., PV and inverter) can be connected to the panel as a power source.

    The reference NEC article includes a 120% exception for residential applications. For example, if a 100 A panel / busbar is supplied from the grid via a 100 A breaker, then another power source can be connected via a 20 A breaker.

    So, the NEC limit would be 120 A on a 100 A panel / busbar for residential applications.

    HTH,
    Jim / crewzer
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #13
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    Re: service upgrade required?

    This is a residential application. There is plenty of room on a new (2005) subpanel. Or some of the existing load can be moved from the main panel to the subpanel if that matters.

    Will inquire tomorrow.
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #14
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    Re: service upgrade required?

    After further review, it seems the upgrade is neither necessary nor required by code. Thanks for the insights.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #15
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    Re: service upgrade required?

    could you elaborate on who said what?
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #16
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    Re: service upgrade required?

    The installer who said that an upgrade would be required misspoke. An upgrade is not necessary. (Technically, I think he was looking at the job site pics and/or notes of someone else's house, but was writing my proposal. He went back to the pics/notes of my job and saw that all was indeed well.)
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #17
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    Re: service upgrade required?

    or, in speculation, maybe he was trying to get away with something. good news for you and i thought as much.:cool::D
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #18
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    Re: service upgrade required?

    This guy is totally above board. Excellent reputation, earned the old-fashioned way, and assiduously maintained. I'm a skeptic in general, and can say this was an honest mistake. Ever have two or three Word documents open at once? Save one file over another? Paste a bit of semi-custom boilerplate into a cover letter and forget to modify? That's what this was.

    (He would also not have profited from this, as he doesn't do underground service work, nor does his regular electric sub, so he would have to have found a suitable sub.)

    Some people are actually still honest.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #19
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    Re: service upgrade required?

    honesty in this day and age now that's a rarity. you going to have him do the work?
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  • xiphias
    xiphias Solar Expert Posts: 52 ✭✭✭✭
    #20
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    Re: service upgrade required?

    still looking at the household economics. might start with SDHW and add PV later as resources permit.

    This has been a useful and informative thread, and site. Thanks.
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