3 Years with Grid Tie

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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 3 Years with Grid Tie

    Scott;

    A lot of "code stuff" is subject to the interpretation of the local AHJ too. Sometimes they don't "understand" the rules the same way we might "understand" the rules. There's one or two bits of the NEC that everyone has disagreement with at times. :roll:

    Personally in an AC install such as micro-inverter output I see no reason why the grounds can not be connected in the same manner as any other AC install, complete with joining where necessary. The panel/mount ground, on the other hand, is usually one wire fed continuously through each unit's ground lug and run on down to the Earth ground. At least that is SOP for off-grid installs.

    What your local inspector requires is, ultimately, what you have to do.
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: 3 Years with Grid Tie
    CAOkie wrote: »
    but the same power coming from my roof must have a single unspliced ground wire? Am i missing something here? The logic just does not hold for me. What i have noticed is that this "continuous" designation is used often but its real definition is vague. Continuous does not necessarily mean unspliced to me. Strictly speaking continuous means uninterupted or stopped.
    You are right - continuous means that you can splice it together with an irreversible splice (usually a special crimp/crimp-tool). You'll often have to do this when you bring your ground indoors and switch to stranded ground wire in conduit from solid ground on roof.

    Your typical cheap crimping tool/crimps that you'll find at your local hardware store isn't sufficient. Your local electrical supply house should be able to help. Perhaps someone can post a link to an acceptable crimper/crimp.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 Years with Grid Tie

    Yea--the National Electric Code does have a requirement for unspliced ground wires.

    For installing a large solar array, that is pretty stupid and actually will be worse in terms of lighting protection (straight runs to earth with large diameter curves where needed). There are ways of bonding ground wires (welding, thermite) for "unbroken" runs.

    Your installer and your local inspector should be able to work this out. An unbroken run from the ground rod to the beginning of the array should meet the "spirit" of the NEC--but only your inspector can approve (or not).

    Regarding your power usage--It sounds like you are in the 1,000-1,500 kWH per month type range--For an area with hot summers, that is not bad (as I understand--we only would like to use A/C a few weeks a decade here).

    (More) Attic insulation (~R40 or more?) and a high SEER A/C system would be a great way to continue. Adding solar panels to the roof (on my home) really reduced attic temperatures.

    Looking at the rest of your appliances that run 24x7 (fridge, entertainment systems, desktop computers, servers, irrigation pumps, etc.) are a great place to look for conservation opportunities. They are frequenty bigger energy hogs than microwaves and cook tops.

    If you have electric hot water (or expensive propane), the new standalone heat pump water heaters can easily cut 1/2 off of your water heating bill.

    Also, look at various options for monitoring your home's electric loads. Either a whole house system, or even one that can monitor branch circuits.

    If you have Time of Use electric billing (now or in the future)--look at timers that can push the automatic energy usage outside of the peak power periods.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: 3 Years with Grid Tie
    Personally in an AC install such as micro-inverter output I see no reason why the grounds can not be connected in the same manner as any other AC install, complete with joining where necessary. The panel/mount ground, on the other hand, is usually one wire fed continuously through each unit's ground lug and run on down to the Earth ground. At least that is SOP for off-grid installs.
    While I don't necessarily disagree, I believe that best practices currently dictate running 2 parallel grounds for micro systems - one for the DC and one for the AC side.

    1 ground for the DC side - this includes panel frames, racking and inverter chassis (your typical uninterruptible 6-8-ga ground)
    1 ground for the AC side - this will be a conductor from the micro-inverter AC cable.
  • CAOkie
    CAOkie Registered Users Posts: 8
    Re: 3 Years with Grid Tie

    Yes the AC ground coming out of the microinverter goes to the mainpanel ground.

    Drees, Do you mean i should not take the DC (equipment) ground to the mainpanel via the subpanel and disconnect? That it should go to a dedicated rod?

    Cariboocoot, well said. The local AHJ guy is King.

    Bill, great conservation tips, thanks.

    Scott
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 Years with Grid Tie

    It should go to the same ground rod that your AC Panel Earth Ground is connected too. If you have two ground rods (front and real of home)--I would still run a ground wire between the two ground rods for safety.

    If there are any short circuits (AC or DC), you want the energy to safely close the loop (pop the breaker, short out the panel, etc.) so that your metal framework does not become energized and a shock/fire hazard.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 3 Years with Grid Tie
    drees wrote: »
    While I don't necessarily disagree, I believe that best practices currently dictate running 2 parallel grounds for micro systems - one for the DC and one for the AC side.

    1 ground for the DC side - this includes panel frames, racking and inverter chassis (your typical uninterruptible 6-8-ga ground)
    1 ground for the AC side - this will be a conductor from the micro-inverter AC cable.

    See that's another 'interpretation' thing. I think the NEC considers the micros to not have a DC side because they're directly attached to the panel: no DC GFD is required for these, for instance, and this is why we get that horrible misnomer of "AC solar panel" used in some places. Not sure if the micros have an AC ground out, since I've never installed one. Mainly the necessary ground here is the one on the panel frames/mounts/inverter cases.

    Or maybe cows are purple and pigs do fly. It's hard to to with regulations. :p
  • CAOkie
    CAOkie Registered Users Posts: 8
    Re: 3 Years with Grid Tie

    The Enphase inverters do have a gound out of the AC side. I asked Enphase if i can combine all the nuetrals and grounds at the roof and make single nuetral and ground homes runs. Have not heard back from them yet.

    I mean combine the 3 strings i have.

    Scott
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: 3 Years with Grid Tie
    CAOkie wrote: »
    Drees, Do you mean i should not take the DC (equipment) ground to the mainpanel via the subpanel and disconnect? That it should go to a dedicated rod?
    Bill covered it...
    See that's another 'interpretation' thing. I think the NEC considers the micros to not have a DC side because they're directly attached to the panel: no DC GFD is required for these, for instance, and this is why we get that horrible misnomer of "AC solar panel" used in some places. Not sure if the micros have an AC ground out, since I've never installed one. Mainly the necessary ground here is the one on the panel frames/mounts/inverter cases.
    When you're dealing with a micro integrated into the panel as one unit, yes, I think you're right. But the majority of micro systems these days are separate from the panel.

    Anyway, if you have a look at Enphase's field wiring diagram, they clearly list 2 separate grounds back down to the grounding rod. The DC ground does not go back in to the main service panel, just straight to your grounding rod.

    All that said - I've seen it done both says (separate and combined grounds).
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 3 Years with Grid Tie

    Do not combine the neutrals/grounds. Neutrals should be wired just like the hot wires all the way back to the main panel.

    There is only one connection between Neutral and Earth ground in the power system (typically bus bar inside the main panel).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CAOkie
    CAOkie Registered Users Posts: 8
    Re: 3 Years with Grid Tie

    Sorry, my choice of words is confusing.

    What i mean is that i have 3 strings. Can i combine the 3 neutrals together at a jbox say on the roof or underneath in the attic, then run one neutral to the subpanel neutral bus? Same for the AC grounds of the 3 strings, seperate from the neutral. Hots are all independant for the strings.
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: 3 Years with Grid Tie
    CAOkie wrote: »
    Sorry, my choice of words is confusing.

    What i mean is that i have 3 strings. Can i combine the 3 neutrals together at a jbox say on the roof or underneath in the attic, then run one neutral to the subpanel neutral bus? Same for the AC grounds of the 3 strings, seperate from the neutral. Hots are all independant for the strings.
    No, run a separate neutral per circuit.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: 3 Years with Grid Tie

    I may have to buy one of these micro-inverters just to see what they're like.
    And see how long it takes me to fry one with experiments. :p
  • CAOkie
    CAOkie Registered Users Posts: 8
    Re: 3 Years with Grid Tie

    Gotcha, thanks drees

    Scott
  • TheBackRoads
    TheBackRoads Solar Expert Posts: 274 ✭✭
    Re: 3 Years with Grid Tie
    I may have to buy one of these micro-inverters just to see what they're like.
    And see how long it takes me to fry one with experiments. :p

    Please do! :D:-);)
  • autoxsteve
    autoxsteve Solar Expert Posts: 114 ✭✭✭✭
    Re: 3 Years with Grid Tie

    By the way, I did end up picking up a retrofit heat pump kit for my electric water heater and it's saving me $. I can't really tell yet but will know soon enough when my annual bill comes in April. I've had it installed for 3-1/2 months.

    Look for my thread on this heatpump kit here.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: 3 Years with Grid Tie
    CAOkie wrote: »
    Sorry, my choice of words is confusing.

    What i mean is that i have 3 strings. Can i combine the 3 neutrals together at a jbox say on the roof or underneath in the attic, then run one neutral to the subpanel neutral bus? Same for the AC grounds of the 3 strings, seperate from the neutral. Hots are all independant for the strings.

    Actually, with an Enphase system you don't have strings at all. Whether you connect all the inverters daisy chained together or divide them into groups, it's still a completely parallel arrangement. If you split your inverters into three groups then you are going to have to combine them somehow, and if you do it with an AC combiner, then the neutrals will be combined in that box just as are the "hot" conductors. I wouldn't think that you'd want to combine only the neutrals and run the energized conductors separately back to the panel, though. I would think that would be a code violation.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: 3 Years with Grid Tie

    I don't know why you couldn't do a sub panel and add a breaker in for each group and then run it back as one set of wires with no loads being added. I have that for my dual big inverters where the AC is combined. Wouldn't that meet NEC?
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: 3 Years with Grid Tie
    solar_dave wrote: »
    I don't know why you couldn't do a sub panel and add a breaker in for each group and then run it back as one set of wires with no loads being added. I have that for my dual big inverters where the AC is combined. Wouldn't that meet NEC?
    Yes, you can do that. That's how my 2 Enphase strings are combined before going into the main panel. Just size your home-run feed appropriately.