Ground mount/Enecsys microinverter grounding question

I have installed a 6KW ground mount system 400 FT from main panel. The enecsys microinverters do not have a neutal, only a ground. I ran two legs of power to main panel, but only installed a separate ground rod at the array. The inspector wants a ground back to main panel. I thought NEC 250.4 A1 would justify my actions. Any thoughts on how to diffuse the situation?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Ground mount/Enecsys microinverter grounding question

    Welcome to the forum.

    I see two things you can do:

    1). Argue the point with the inspector, possibly ending up in court and needing a team of engineers to back you up.

    2). Install a ground wire between the array and the main panel that satisfies the inspector.

    Frankly I agree that there is no need for this, given the distance involved.
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Ground mount/Enecsys microinverter grounding question

    Assuming you are in North America, we do have "another issue". Modern (less than 5-10 year old GT central inverters) have added a "voltage check" between the two 120 VAC hot leads and Neutral.

    So, it no longer just checks for 240 VAC (~218 to 264 VAC) between the two hot leads, many (some, most, all?) also check for ~120 VAC between Hot and Neutral.

    In most installations, the voltage difference between neutral and ground on a home is a few volts at most. When I and a replacement GT Inverter installed, they just ran a ground jumper to the neutral sense line in my inverter.

    With 400' of distance, if your inverters "qualify" the neutral voltage--You may have some issues with different ground voltage between the home and 400' away at the array. Usually not a problem, but I have seen 60 VAC or more between ground an neutral in commercial locations (large aquarium/theme park--pumping salt water).

    So, there can be an advantage of running a neutral from your main panel out to the remote array (prevent false "broken neutral" shutdowns). The neutral would only need to be the minimum wire gauge allowed (14 AWG?) as it just carries a very small amount of current. But would the inspector "buy" installing a 14 AWG wire? Would you have to to dig up/re-pull wiring between the array and the home?

    But you said there is no neutral connection on yours--And the website/manual seems to support that... I guess I would ask the AHJ where you would connect the neutral too? There is nothing and the neutral would just be floating.

    If you could use 120/240 VAC at the array for lights/tools/etc... It could be nice to install the neutral for future use (put an extra sub panel out at the array).

    In the end, if you show the AHJ that there is no connection for neutral, and there is no place to install it, and he requires the neutral--You may be stuck. The Authority Having Jurisdiction is "god" in many places.

    You might try getting a letter from Enecsys saying that their unit does not need a neutral and that they have been installed and approved in your region/state/utility district... They may have experience with central inverters and not realize that this "two wire+Ground install" is also code compliant.

    Good Luck,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Ground mount/Enecsys microinverter grounding question

    Bill;

    My interpretation is that the AHJ wants him to run the ground for the inverters into the house and connect it at the main panel. Neutral is not involved. This would be an interpretation of the "single point ground" rule, albeit in my opinion an incorrect one.
  • BB.BB. Super Moderators, Administrators Posts: 29,511 admin
    Re: Ground mount/Enecsys microinverter grounding question

    Oopps... My mistake. I got to read the original posts better. :blush::cry:

    Personally, I would like to run a 6 awg cable between the ground points... You can "energize" the remote array mounting (hot to frame short) and not kick off the main breakers.

    I wonder if you can get 240 VAC GFI type breakers?

    http://www.homedepot.com/p/Square-D-by-Schneider-Electric-QO-Qwik-Gard-20-Amp-Two-Pole-GFCI-Breaker-QO220GFICP/100194077

    Attachment not found.

    I am not sure if you should install that in the home panel or in a sub panel at the array (probably fewer false trips if installed at the array).

    I have to go right now--But that would make me feel better about not having a common ground connection between the remote array and the home panel.

    If this breaker needs a "neutral connection"--Then it would have to be mounted in the main panel. for $105 -- It may be worth trying to convince the AHJ to let you use it in place of a continuous ground cable.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DanS26DanS26 Solar Expert Posts: 239 ✭✭✭
    Re: Ground mount/Enecsys microinverter grounding question

    WOW! 400 feet with micro inverters. What size cable are you running? I understand now why your installer did not want to install a ground wire.

    I've got to agree with the inspector, the array needs to be at the same electrical potential as your panel. I know the NEC says otherwise but a lightning strike will seek out that array and all your electrical connections in between if it sees that array as a better path to ground. Think side strikes also. Your inspector is doing you a favor to protect your valuable equipment.
    18.2kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Ground mount/Enecsys microinverter grounding question

    The OP is not proposing the array & inverters not be grounded. He has it grounded at the array. This is fine for system protection.

    Running the ground wire 400 feet until it connects to the main system ground would not be. The resistance in that length of wire would make for a poorer ground connection than the rod at the array.

    Connecting the two ground points together might be considered best, but somehow I doubt this particular AHJ would understand that.
  • DanS26DanS26 Solar Expert Posts: 239 ✭✭✭
    Re: Ground mount/Enecsys microinverter grounding question
    The OP is not proposing the array & inverters not be grounded. He has it grounded at the array. This is fine for system protection.

    Running the ground wire 400 feet until it connects to the main system ground would not be. The resistance in that length of wire would make for a poorer ground connection than the rod at the array.

    Connecting the two ground points together might be considered best, but somehow I doubt this particular AHJ would understand that.

    I know the NEC looks at it this way.... the resistance is too great. But in my personal experience, lightning does not see it this way. Yes, 400 feet of #6 is costly. Its a judgement call. Depends on location and other factors. IMHO bond the rods.
    18.2kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Ground mount/Enecsys microinverter grounding question
    DanS26 wrote: »
    I know the NEC looks at it this way.... the resistance is too great. But in my personal experience, lightning does not see it this way. Yes, 400 feet of #6 is costly. Its a judgement call. Depends on location and other factors. IMHO bond the rods.

    This has nothing to do with lightning protection, it is about the electrical safety ground.

    Bill suggestion of the 240 VAC dual-pole GFI breaker is a good one. It could be located at the main panel, because if a current imbalance causes it to trip the inverters will shut down (anti-islanding circuitry). The AHJ may not understand this either as quite a lot of people don't.

    If you are concerned about lightning protection, ground the array frame and use a MidNite surge protector on the output line.
  • DanS26DanS26 Solar Expert Posts: 239 ✭✭✭
    Re: Ground mount/Enecsys microinverter grounding question
    This has nothing to do with lightning protection, it is about the electrical safety ground.

    Bill suggestion of the 240 VAC dual-pole GFI breaker is a good one. It could be located at the main panel, because if a current imbalance causes it to trip the inverters will shut down (anti-islanding circuitry). The AHJ may not understand this either as quite a lot of people don't.

    If you are concerned about lightning protection, ground the array frame and use a MidNite surge protector on the output line.

    With no disrespect intended, a ground rod at the array has nothing to do with the "electrical safety ground" but everything to do with lightning protection. Sorry I misunderstood the discussion and the issue at hand.
    18.2kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Ground mount/Enecsys microinverter grounding question
    DanS26 wrote: »
    With no disrespect intended, a ground rod at the array has nothing to do with the "electrical safety ground" but everything to do with lightning protection. Sorry I misunderstood the discussion and the issue at hand.

    Um, yes it does.
    Even when there's no neutral involved.
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