Neutral/Ground bonding on 3000EHV-48 inverters

[elizabethii]

With the recent video from Signature Solar regarding neutral/ground bonding recommendations and my permanent install of 4 3000EHV-48 inverters in process, I'm thinking about how my neutral/ground bond should be configured. It looks like SS's video is specifically in regards to their 6kw units, and they solved the neutral/ground bonding problem through a software change and removing the chassis grounding screw from inside the inverters. At least so far, it doesn't look like an updated firmware has been provided for the 3kw units, and I have 2 v1 units and 2 v2 units. I haven't looked in any of them yet for the presence of the chassis bonding screw.

My incoming power feed is from a main panel that I don't control. In that panel, neutral and ground and bonded together. I get a 4/3 feed with ground. I'm planning on using SBU mode in the inverters, so grid is a last resort or if I overload the inverters. My tentative plan is to bring the incoming feed into a sub-panel where I break out the feed to 4 30-amp 1-pole breakers to feed grid into each inverter. The output of the 4 inverters would feed my main panel with all of my loads. Since I'm getting an already-bonded feed, I would think I want to stay unbonded, but in the event of a grid failure, I'm theoretically unbonded if I were to remove the internal bonding screws.

So, I don't know what methodology I should use to ensure a correct N/G condition. Suggestions are greatly appreciated.

 

[eleceng1979]

You cannot be bonded anywhere else in the system except the first means of disconnect (first breaker in first panel, more than likely). Downstream, you must be UNBONDED everywhere else in the system. The previous statement is always true, due to 1. you are not using a transfer switch that breaks the neutral. 2. Because EG4 inverter closes an internal relay to pass the neutral from grid AC input to AC output. 3. Because you have chosen an inverter that takes grid AC in and passes grid AC out. 4. The inverter mode of operation has nothing to do with these requirements, ever.

Signature solar says this statement below, take note of the bold print. Since you have a 3000EHV-48, the NEC requirements still apply to you, but Signature Solar hasn't fixed the inverter you have that is in clear violation. You should contact the manufacture on how to make their equipment compliant to such bonding requirements that have existed since being written into code in 1897, formally recognized by NFPA in 1911.

"EG4 has removed this bond screw and configured the inverter’s relay using software to always pass through the neutral to match US industry standards for stationary systems. This way, you will always have the grid’s neutral bond passed through and have the bond on the output panel as well. This applies to units shipped after February of ‘23 and beyond as well as any firmware update with version 61.13 or later on the 6000w unit or 79.63 on the 6500w unit.

If you have inverters installed with grid connection, we recommend ensuring that you have the latest firmware and that there are no ground bonds on the output side of the inverter."

I will also inform you that this particular inverter DOES NOT have a UL listing. The National Electrical Code REQUIRES LISTING by a NRTL (National Reliability Testing Laboratory) as approved by U.S. O.S.H.A. (Occupational Safety and Hazards Agency) to U.L. 1741. Your inverter is not even listed, let alone tested. Any reputable inspector will fail you automatically. If you have insurance policies on your home/belongings, they can and probably will be void if this inverter was to start a fire. This problem about UL listing is why you have a bonding problem. There are reasons why a outback/schneider inverter cost 2-5X more. It is not due to corporate greed, it is proper operation, testing, certifications, and approvals to be sold safely here in the USA. None of which Signature Solar has done for your particular inverter model, which is still sold/marketed as of today on their website. Notice how it is classified as off-grid on their website? But states in their manual about using the grid on the AC input? The word "Grid" is mentioned 11 times in their manual in the context of the utility grid. This inverter should not be operated in North America, neither off-grid nor on-grid per the NEC. The reason signature solar fixed the 6500 inverters is because they are UL listed. Your unit will probaly never be fixed due to no UL listing.

Interesting reading...
https://diysolarforum.com/threads/e...added-the-battery-rack-and-3rd-battery.42356/

https://diysolarforum.com/threads/ul-1741-must-see-for-all.55312/