solar panel AC main disconnect

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hhsting

Senior Member
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Glen bunie, md, us
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Junior plan reviewer
Since they have no neutral conductor, I would say no. :D

Not the inverter I guess but They have something called Enphase Envoy 2 which needs to be powered from AC solar sub panels which require neutral. Not sure how much neutral current it draws.


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synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Not the inverter I guess but They have something called Enphase Envoy 2 which needs to be powered from AC solar sub panels which require neutral. Not sure how much neutral current it draws.
With only a quick look I didn't see info on an Envoy 2, but the power draw of the IQ Envoy is spec'd at 3 watts typical. Seems negligible to me in the context of this discussion.
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
What IQ7 and Envoy 2 bring to this discussion beyond earlier Enphase inverters and the standard Envoy is a little beyond me. But their standard inverters supply power at 240; the transformer CT (center tap) is used to verify line voltages, as it was explained to me. They put a signal on both 120V APPARENTLY referenced to the CT.

The Envoy "reads" the modulated, imposed, signal and makes it available on "my" network. I understand the Envoy 2 is not compatible with older inverters, and the older Envoy is not compatible with newer inverters, the IQ7 in particular. Thus if one of my inverters fails, it is questionable if it can be replaced with the newer design ... I've not asked if it will work but not communicate; will when the need arises.

I do know that with my home's meter-main and feeder to my panel, and with the inverters connected to a breaker in the meter-main, my installer had a difficult time finding a receptacle with a good signal; he could not use one near (perhaps 2 feet) but maybe 60 feet from the panel. One 3 feet from the panel was marginal, but I did have wired internet available there via a 10BaseT powerline bridge, and now via a mesh node with 1000BaseT ports.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Whether or not the inverters or any other equipment utilizes a neutral is an irrelevant detail that is a distraction from the original question. You need an effective ground-fault current path at the disconnect, and to do this you need an adequately sized wire bonding the disconnect enclosure to the service neutral. One way to do this is, as advocated above by shortcircuit2, is to call the the new PV disconnect a service disconnect and to then comply with 250.24(C) and other sections that require bringing a neutral to the disconnect and installing a main bonding jumper. Another way is to bring a supply-side bonding jumper sized to 250.102. It is not really valid to use table 250.122 for sizing since there is no OCPD ahead of the disconnect, hence I strongly suggest using 250.102, especially the minimum size. However, as long as the wire is adequately sized and ultimately connects to the service neutral, it really does not matter if it is white or green. The code ultimately only requires one wire, not two. (This is leaving aside grounding electrode conductor stuff, which depends on other details not essential to the main question).

In the past I've posted a list of code sections that can be used to argue 'for' and 'against' considering a supply-side disconnect to be a service disconnect. (But I don't have that list on the device I'm typing this on and I'm having trouble finding it with searches.) It is notable, as shortcircuit mentioned above, that the 2020 NEC changes the definition of a service. Thus the strongest argument that it is 'not a service disconnect' is no longer supported by the code. On the other hand, there was proposed language for the 2020 NEC that would have told us exactly how we could ground the disconnect in the new 705.11, but it got deleted from the final version. I don't have the inside scoop on how and why it got left out, but I do know there were negative comments filed against the first draft. I hypothesize that the CMP couldn't come to enough of an agreement on the matter, so they just punted the issue as they always have in the past. So really, not all that much has changed. It's still up to the AHJ.

hhisting as a contractor to the AHJ I think you are free to make your own recommendation as to whether to consider the disconnect a service disconnect, if they do not already have a clear policy in place.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Whether or not the inverters or any other equipment utilizes a neutral is an irrelevant detail that is a distraction from the original question. You need an effective ground-fault current path at the disconnect, and to do this you need an adequately sized wire bonding the disconnect enclosure to the service neutral. One way to do this is, as advocated above by shortcircuit2, is to call the the new PV disconnect a service disconnect and to then comply with 250.24(C) and other sections that require bringing a neutral to the disconnect and installing a main bonding jumper.
When I mentioned a neutral not being utilized in the PV disconnect it was to eliminate any concerns (and which in the OP's case would be distractions) about objectionable current that a bonding jumper in the PV disconnect could introduce. Such objectionable current from paralleled ECG and grounded conductors was cited as one of the possible code issues by shortcircuit2 in his reply to the OP's question #1 below. Obviously without any equipment connected to the grounded conductor it will be conducting no current and so there would also be no current in a parallel ECG. Therefore in the OP's case not having any utilization equipment connected to neutral means that a full sized neutral can be brought to the PV disconnect and a bonding jumper installed without any technical basis for concerns about objectionable current.

OP posted question:
Spoke with the engineer and he replaced and modified post #1 sketch with attached sketch this post. He provides main bonding jumper in main PV AC disconnect ......
Was wondering few questions and people who encountered how different AHJ handle or what are their opinion:
1. Is their anything wrong per code attached sketch?
shortcircuit2 responded:
1. The EGC may carry objectionable current in violation of 250.6(A) and it could be considered an installation of the grounded conductor in parallel in violation of 310.10(H) 2014/2017 NEC or 310.10(G) 2020 NEC
 

shortcircuit2

Senior Member
Location
South of Bawstin
Of interest here and something I want to point out, posts 21-24 discuss how much power consumption the PV system uses. As with most systems that are Utility Interactive, there is some electric energy consumed. Although minimal, power is consumed. (Nighttime & Standby Mode for example)

IMO, and something that has long been my counter argument against the advocates argument that the PV system is not a Service as in post #14...the Serving Utility does deliver Electric Energy to the Interconnected Electric Power Production Source wiring system. This is essential for the operation of the associated equipment.

2014-2017 Service: The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
When I mentioned a neutral not being utilized in the PV disconnect it was to eliminate any concerns (and which in the OP's case would be distractions) about objectionable current that a bonding jumper in the PV disconnect could introduce. Such objectionable current from paralleled ECG and grounded conductors was cited as one of the possible code issues by shortcircuit2 in his reply to the OP's question #1 below. Obviously without any equipment connected to the grounded conductor it will be conducting no current and so there would also be no current in a parallel ECG. Therefore in the OP's case not having any utilization equipment connected to neutral means that a full sized neutral can be brought to the PV disconnect and a bonding jumper installed without any technical basis for concerns about objectionable current.

OP posted question:

shortcircuit2 responded:

Thanks for the clarification and I understand the point you were making in that context. But I would just expand my comment to say that the whole kaboodle - including shortcircuit's point about objectionable current - is ultimately still irrelevant to the original question. Nobody is arguing for a parallel neutral and EGC/SSBJ with neutral bonded at both ends. Or at least no one should be. (And again, let's leave aside grounding electrode system, which the code allows to create a parallel path for service disconnects.)

Once one decides whether the PV disconnect is a service disconnect or some other kind of disconnect not included in that category, the code becomes fairly clear what to do with it and how to make it both code compliant and safe. (I mean, there's still lot's of relevant sections to become familiar with, but their application becomes relatively clear.) The problem is that the code doesn't offer solid guidance on making that decision.
 
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