[RE-wrenches] N-G bond for supply side connection Midnite Power

Sat Oct 25 06:46:17 PDT 2025

It shouldn't be too hard in a partial backup situation to check for
inadvertent N-G bonds on the load side of your new protected load panel. I
would just shut the power off and remove all of the load neutrals from the
neutral bar and check for continuity to ground.

I would not remove the N-G bond in your solar combiner panel, which
contains what is effectively a second service disconnect. I would remove
the GEC from that circuit, as it creates a parallel return path. The GEC
only needs to come from one location on the supply side of the service
disconnecting means. By keeping the N-G bond in the solar combiner panel,
the neutral wire will carry any fault current to the GEC, which is
acceptable in this case. It's effectively the same as having the GEC
originating from a wiring trough ahead of the service disconnecting means,
or as we do in Florida, the GEC comes from the meter enclosure, and all
downstream service disconnects are bonded.

In other words, no GEC or EGC is required to the solar combiner panel. Just
L1, L2, and N in non-metallic conduit.

I haven't seen this issue with the AIO, but I have seen it with the Sol-Ark
inverters, which seem particularly picky about bonding issues (perhaps
rightfully so).

On another note, why the supply side interconnection? It's my understanding
that the AIO is listed as a Power Control System. I haven't used it that
way, and the details in the manual are weak, but I believe it can be done.
I would have considered a 125A load side feeder from the main service panel
(if you are moving loads out to a protected load panel anyway, there would
be physical space for a breaker). You could even run a 200A feeder to the
AIOs to get a full 200A passthrough with dual inverters and move over even
more loads and use the smart load capabilities.

With that said, I rarely do partial home backup in these situations. I know
you said it's a small subset of loads, which is reasonable given the
battery capacity, so that might make perfect sense. Depending on the
circumstances, sometimes it's just easier to put a new service disconnect
ahead of the inverters and make the existing main service panel a subpanel,
and then remove non-backup loads and put them on smart load circuits or
otherwise do load shedding. It increases the owner's flexibility to back up
anything they want in the house selectively.

One more thing. It looks like you have all PV circuits running through
J-Box "B." There was some talk recently about cross-talk between multiple
RSD transmitters that can make things go south if you have circuits from
different transmitters in close proximity. I have not seen that problem in
practice, but I have started to isolate my raceways and enclosures in
multiple inverter setups.

Enough unsolicited advice... I would start with removing that GEC and see
if it fixes the problem, and if not, investigate for inadvertent load side
bonds.

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208

On Fri, Oct 24, 2025 at 8:50 PM Dave Tedeyan via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Thanks all for your thoughts here. It seems that the general consensus so
> far is that the N-G should be bonded in the solar main disconnecting means
> when doing a supply side connection (even if it is not technically a
> separate service). When talking with Midnite Power, we made it very clear
> that we were talking about a N-G bond in the inverter combiner / solar main
> disconnect, and not the backed up loads panel. And being that NY is still
> on 2017 code (only going to 2020 next year), with the ambiguity in the code
> I am probably okay to undo the N-G connection in the main solar disconnect.
>
> In this case specifically, we are backing up only a small subset of loads
> in the house. The reason for the two inverters is because there is about
> 24kw of solar. There is also a manual transfer switch to normally be able
> to power the loads off the inverters, but to be able to switch to powering
> the loads off the main panel in case of service needed on the inverters.
> The neutrals in this system are all connected together, and I am not sure
> if that could cause issues. It is probably difficult to explain all the
> details in words, so I am copying part of the three line diagram here. The
> second picture is the conductor and conduit schedule.
>
> Tom, I get it that the error sounds like it is on the DC side based on the
> words, but when I talked to Midnite about it they were pretty clear about
> it being due to multiple N-G bonds and they did not mention that it could
> have anything to do with the DC side.
>
> Jason, that is a good idea as well to check the loads that got moved over
> to see if there are any other inadvertent N-G bonds on the premises. This
> also similar to what Midnite suggested, which was to lift the N-G bond in
> the main panel and then see if they are still bonded somewhere else. It
> seems like it can be a slow process to track that down with power cut to
> the house, but that might be what I have to try if removing the N-G bond in
> the solar main disconnect does not help.
>
> So, my main questions to anyone who has an opinion here are two fold:
> 1. Do you bond the N-G in general in the main solar disconnect for a
> supply side connection?
> 2. Specifically with the Midnite AIO inverters, has anyone else had issues
> with this "CA-DC link Overvoltage error" due to having a second N-G bond in
> the house? (one in the main service panel, and one in the solar main
> disconnect if it is a supply side connection). Or have you seen this error
> and found that it was caused by something else?
>
> Cheers,
> Dave
>
>
>
> On Thu, Oct 23, 2025 at 5:25 PM Jason Szumlanski via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> I agree. It is not a separate service. It is a "tap" of the existing
>> service (I use that term loosely here). The additional service disconnect
>> for the supply side interconnection should have L1, L2, and N
>> connected ahead of the premises main disconnect with no EGC. There should
>> be a N-G bonding jumper in the PV service disconnect. Then there should be
>> no N-G bonds downstream of both the premises main disconnect and the PV
>> service disconnect.
>>
>> Basically, it's the same as two main disconnects running from a meter
>> enclosure. Each of the service disconnects has a N-G bond required.
>>
>> Some AHJs (the crazy ones) require an EGC between the enclosure where the
>> supply side connection is made and the PV service disconnect. This creates
>> a parallel fault path, and should not be allowed, in my humble opinion.
>>
>> Now it sounds like you might be doing a partial home backup. The issue
>> there is that sometimes the loads or enclosures you moved over the backup
>> load panel have inadvertent N-G bonds. Sometimes it's as simple as someone
>> who got creative and used a ground as a neutral in a switch box. I say
>> simple, but that can be hard to track down.
>>
>> When Midnite said to remove it from the inverter distribution panel,
>> they were probably talking about the protected loads panel.
>>
>> I think more information is needed.
>>
>>
>>
>> Jason Szumlanski
>> Principal Solar Designer | Florida Solar Design Group
>> NABCEP Certified Solar Professional (PVIP)
>> Florida State Certified Solar Contractor CVC56956
>> Florida Certified Electrical Contractor EC13013208
>>
>>
>> On Thu, Oct 23, 2025 at 11:03 AM Tyrone Houck via RE-wrenches <
>> re-wrenches at lists.re-wrenches.org> wrote:
>>
>>> My interpretation, and the way it was explained to me by both Ryan
>>> Mayfield and Kyle Bolger(several years ago at this point, popular opinion
>>> may have changed since). Is that it is not a seperate service.
>>>  It is however required to have a ground-neutral bond( though in my
>>> opinion pointless and redundant as there is a bond in the enclosure where
>>> the tap is made). If it gives you any issue, ensure as close to equal
>>> potential to the grounding electrode as possible(and make sure your neutral
>>> is appropriately sized). I personally don't see the point but it is an NEC
>>> requirement
>>>
>>>
>>>
>>>
>>> On Thu, Oct 23, 2025, 6:08 AM Dave Tedeyan via RE-wrenches <
>>> re-wrenches at lists.re-wrenches.org> wrote:
>>>
>>>> Hi All,
>>>>
>>>> For years I have understood that when doing a supply side connection,
>>>> you are supposed to bond the neutral to ground in the solar service
>>>> disconnect. I have a Midnite AIO system with two inverters (set up as a
>>>> supply side connection) that recently was getting a CA-DC link Overvoltage
>>>> error. When talking to Midnite, their first response was to make sure that
>>>> there was only one N-G bond in the whole system. When I mentioned that the
>>>> solar is a separate service and thus there is a N-G bond in both the main
>>>> panel and the inverter distribution panel, they said to remove it from the
>>>> inverter distribution panel. I want to make the system work right, but I
>>>> also am hesitant to do something against how I have understood the NEC to
>>>> be for a long time. I am curious if you all have thoughts on this or run
>>>> into a similar situation.
>>>>
>>>> Cheers,
>>>> Dave
>>>>
>>>> --
>>>>
>>>> [image: Logo] <https://www.sungineersolar.com/>
>>>> Dave Tedeyan, P.E.
>>>> Owner | Sungineer Solar
>>>> p: he | him | his
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