A potential code violation that seems to be too elusive and difficult to understand. Please help!

[jaggedben]

My PV inverters puts about neutral current. Good bit! about 500 mA or so.

What inverters are they using?

 

[jaggedben]

Some corrections, That ground wire is pulled through, it is connected on the main panel and it feeds into my PV disconnect also and bonds with the disconnect. Not sure what you were looking at.

There is neutral current on the exposed parts of the PV system. When the PV system is energized, that neutral current grows further and it dumps that on the conduit shell which then dumps it into the EGC of my home systems. See picture. I've seen that neutral current go up as much as .5Amps when the PV system is engaged and now considering that the EMC conduits are directly bonded to the panel, the "outer shell" of the conduit is carrying that neutral current and looping it with my home EMC. Which code can I site for violation? Common guys!

If you are getting as much as 1A on the neutral when the PV system is off then I think you most likely have accidental connection between an EGC for the PV system and the neutral for another circuit, as I described above. This would not be due to the neutral and ground being bonded in the PV disconnect. It would be showing up on the PV EGC regardless.

 

[winnie]

Well I tske thst bsck. If you have a separate service entrsnce panel for solar with a separate utility connection in probably a dual- metering system then neutral would be bonded to ground in that second panel BUT there must then be no electrical connections at all between the L1,L2,N or ground or the solar system and the house wiring. Effectivley you have to treat it as if they were sepatate houses!

IMHO this is one of those situations where code and physics don't align well.

In general code requires that there be one (and only one) connection between the 'grounded circuit conductor' (the 'neutral') and 'non-current carrying exposed metal' (everything connected to or used as the EGC, including metallic piping and conduit, metal equipment frames, etc). But this requirement is 'per service', and code doesn't do a good job dealing with multiple services.

This is a known problem in residential situations with a shared underground metallic water pipe system, where you have a ground-neutral bond in each residence, and each residence has a GEC connection to the water pipe. Significant neutral current can flow on the water pipes, and in addition to stray magnetic fields caused by this, plumbers have been electrocuted when working on underground water pipes.

This is also a possible problem when you have multiple services on one building, or in the very common situation of a 400A residential service built with a pair of 200A panels; you have a ground-neutral bond in _each_ service disconnect. Usually, however, the parallel path issue when you have multiple services on one building is confined to the local region of the service equipment. Yes, you have a parallel path for neutral currents, but with a shared neutral conductor in the service drop, the voltage difference between the two neutral bond points is very small, and since both are physically in the same location any parallel neutral currents driven by this small voltage difference are confined to the shared GEC between the two bond points.

The calculation in post #45 points to the relative magnitude of any 'parallel path' current induced between the service equipment at the service equipment vs 'parallel path' current going down one EGC and returning on another EGC for the other service. Obviously that example was pulling numbers out of the air, but the general feel is correct: if any current is flowing on this parallel path, far more is flowing on the fat GEC conductors near the service(s) than down branch circuit EGCs.

To the OP:

1) If I found high current flowing on an EGC, I would not spend time chasing parallel paths caused by ground/neutral bonding at the service. I would be looking for any ground-neutral connections at a distance from the service equipment. The multiple ground/neutral bonds in a single service entrance are IMHO slightly problematic but are code legal and not likely to be the source of hundreds of ma of current on a branch circuit EGC.

2) One possible source of currents on an EGC are ground referenced filters and surge protective devices. These are often connected between line and 'ground' (EGC), and can inject current into the EGC system.

3) Another possible source of currents on an EGC are connections to external ground electrodes. This is not code prohibited, but if there is any current flowing through the soil from external sources (say utility MGN design or a line-earth fault at an adjacent customer), then ground electrodes can act to carry current in from the soil at one electrode, pass it through the EGC system, and have it exit another ground electrode. Code permits 'supplemental' grounding electrodes to be connected to the EGC, rather than requiring a solid connection via the GEC. Is it possible that the solar installation included its own ground rod? Could the solar ground be connected to a non-bonded unintentional connection such as a cast iron sewer waste stack?

4) I cannot condone a non-electrician making measurements inside the electrical equipment. This is not a DIY forum. However if you are chasing currents injected into the EGC system to try to eliminate stray magnetic fields, keep in mind that you are looking for _net current_ on each circuit path. You really should be putting your clamp around the _entire_ circuit, conduit and all. Any current that is balanced by nearby current in the opposite direction nets to zero and doesn't result in a widely spreading magnetic field. You will see high fields between the conductors of a circuit, but not any significant distance from the circuit. So take your current clamp around the entire MC cable from the PV system. Is there larger _net_ current on that cable?

5) I have a close friend who has electromagnetic sensitivity, and have seen enough to believe that there is something there. My personal _hunch_ is that it is psychosomatically mediated. To be very clear, I am _not_ trying to dismiss you by saying 'it is all in your head', rather my hunch is that someone _perceives_ AC E or B fields, and that sensation triggers further responses that are called electromagnetic sensitivity. The reason I believe that this is important is because if the issue is mediated perception, then any other sensation which triggers the same mediation will be 'felt' as an electromagnetic problem.

I am personally very sensitive to the high frequency _audio_ hiss that some switching power supplies create. If my phone is plugged into the wrong sort of charger near my bed, then it interferes with my sleep. This is nearly white noise that is very difficult to discern and disambiguate unless you put your ear right up to the power supply, but I find that it _really_ bugs me.

I bring this point up because in my hunch you are feeling _something_, but it right at the edge of perception, and hard to pin down. It is very easy to keep chasing one possible source of this annoying sensation, and ignore chasing other more fixable sources. You might be responding to the acoustic noise of the PV inverter, not to the electromagnetic fields of the system.

Good luck
Jon

 

[GuruLal]

My county inspector says the following.

"
I wanted to address the code book related to your solar panel installation. It appears that you have been referring to the 2014 NEC book for your grounding requirements. I'd like to point out that the 2017 NEC has revised the grounding equipment electrode stipulation for solar panel frames in section 690.47 (D), removing the necessity for direct grounding to the solar panel frame. Instead, you can consider adding an auxiliary electrode as outlined in 690.47 (B), although it's not typically recommended.

During our previous conversation, we discussed the importance of lightning protection for your solar panels, as the NEC does not specifically address this issue. NFPA 780, specifically related to Lightning Rods, is an excellent resource to safeguard your panels from potential lightning strikes.

To help clarify the grounding and bonding of solar panels further, I've attached a short video that explains the concept in detail. Additionally, I've included a copy of the DOI (Department of Insurance) guidelines for grounding and bonding relevant to your system. Please take note that it emphasizes the need for bonding at two separate points, not just one.

Regarding concerns about cable arrangements, it's important to note that there is no code reference indicating any negative issues associated with cables touching each other unless there's a galvanic reaction, which I assume is not applicable in your case. Metal conduits are routinely connected together for separate circuits in various scenarios such as troughs, strapping, and termination in metal boxes. In these cases, there can be both insulated equipment grounds and insulated neutrals coexisting within the same conduit or cable.

Upon reviewing the information provided, I couldn't identify any code issues you've raised. Any additional installation requests or concerns should be discussed directly with your contractor, as they can provide guidance based on your specific project needs.

I hope this information proves helpful in addressing your queries.

"

 

[tom baker]

That last post wraps this up