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

[PaulWDent]

a You are dead wrong

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!

 

[GuruLal]

That is incorrect for a PV "line-side" interconnection. Which is effectively a second set of Service Entrance Conductors for the PV, and the PV disconnect becomes a second service disconnect. Any service with multiple service disconnects in separate enclosures will have multiple neutral-EGC bonds, one per service disconnect enclosure.

Ideally those different EGC systems from the different service disconnect enclosures will be kept separate from each other everywhere. In practice that is difficult, and the EGC systems from two different service disconnects will often be interconnected downstream. That will lead to neutral current on the EGC systems, since it creates a loop Service Neutral - MBJ 1 - EGC 1 - EGC 2 - MJB 2 - Service Neutral.

Cheers, Wayne

County officials sided with you on this point also. What would happen if that grounding screw from the panel was removed? What's the risk?

 

[wwhitney]

exactly! this loop is killing me

Well, since you are under the 2017 NEC, IIRC there is some leeway in how a PV line side interconnection is done. The 2020 NEC and especially 2023 NEC require the PV line side interconnection to be done like a second service disconnect as I indicated.

But I believe that the 2017 NEC would allow (but not require) that in the PV line side disconnect, the neutral is kept insulated from the case, there is no main bonding jumper in that disconnect, and a separate supply side bonding jumper is run from the primary service disconnect to the PV line side disconnect's EGC bar. This would avoid multiple N-G bonds and the resulting loop if the different EGC systems end up interconnected.

However, since the 2017 NEC is not 100% clear on the topic, different AHJs have had different interpretations of the requirements, and some do require it to wired like a second service disconnect.

Cheers, Wayne

 

[jim dungar]

All metallic surfaces must be bonded together, effectively creating a single common reference. These surfaces are connected to the system neutral through a system bonding jumper only at the source/service entrance. The common reference is also connected to 'dirt' through the grounding electrode conductor.

The NEC does not worry about ground loops, as it expects the grounding system to carry minimal current, except during fault conditions. The NEC acknowledges that its requirements may not be ideal and should be considered as a minimum design.

It is possible that current from a neighbor or other utility customer, is flowing through your grounding conductors on the way back to the utility even though their transformer is working correctly. Look at multi-grounded neutrals (MGN) and stray voltage issues.

 

[jim dungar]

County officials sided with you on this point also. What would happen if that grounding screw from the panel was removed? What's the risk?

Faults may not be cleared properly.

 

[wwhitney]

County officials sided with you on this point also. What would happen if that grounding screw from the panel was removed? What's the risk?

As Jim just mentioned, if you remove that Main Bonding Jumper in the PV line side disconnect and make no other changes, then the EGC system originating there will have no intentional fault clearing path. I.e. if you don't have an inadvertent interconnection of the two EGC systems, then on the PV wiring, a line to EGC fault would not clear but simply energize all the bonded metal parts. If you subsequently touch those bonded metal parts and the earth, or the EGC system of the primary service disconnect, you would get shocked or electrocuted.

Cheers, Wayne

 

[GuruLal]

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!

The system is designed for net metering. How do you actually go about keeping these systems separate as if they are on a totally different house then?

 

[wwhitney]

If you have a separate service entrance panel for solar with a separate utility connection . . . then neutral would be bonded to ground in that second panel

Yes, that is how the 2020 NEC and especially the 2023 NEC require that a PV line side interconnection be done, where "separate utility connection" can just be a splice to the existing service conductors upstream of the existing service disconnect.

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.

Except that there is no prohibition in the NEC on interconnecting the EGCs from the two systems, and at times it would be required to do so. Creating the loop I mentioned.

In particular, if GEC(s) for the service are landed in the service disconnects, rather that at a single upstream location (which is allowed by the NEC), the Grounding Electrode System will itself create a connection between the two EGC systems and both GECs will carry some neutral current.

If the NEC allowed a single N-G bonding jumper upstream of the service disconnects, basically creating a single EGC system rather than one per service disconnect, then this neutral loop could be avoided. But it doesn't have any allowance for that.

Cheers, Wayne

 

[GuruLal]

As Jim just mentioned, if you remove that Main Bonding Jumper in the PV line side disconnect and make no other changes, then the EGC system originating there will have no intentional fault clearing path. I.e. if you don't have an inadvertent interconnection of the two EGC systems, then on the PV wiring, a line to EGC fault would not clear but simply energize all the bonded metal parts. If you subsequently touch those bonded metal parts and the earth, or the EGC system of the primary service disconnect, you would get shocked or electrocuted.

Cheers, Wayne

Why would it not clear? The EGC from solar can be directly connected to the EGC of the line side and let Neutral+Ground bond occur on the main panel. This would keep bonding at only 1 place in the entire home. The main line side panel.

 

[wwhitney]

Why would it not clear? The EGC from solar can be directly connected to the EGC of the line side and let Neutral+Ground bond occur on the main panel. This would keep bonding at only 1 place in the entire home. The main line side panel.

Yes, that arrangement is what I described in post #23.

But Jim and I were referring to what would happen if you just remove the PV main bonding jumper without also running that supply side jumper.

Cheers, Wayne

 

[GuruLal]

What I know is that the EGC from solar" which includes the MC conduit" since it is bonded on PV disconnect is
carrying current from "N" and looping it with the other home EGC wiring. If the MC conduit is bonded, it would effectively be a neutral wire and if that Neutral wire( conduit) is then touching EGC-home (with less than 1ohm of resistance) then why isn't that viewed as double bonding. Which would be a clear code violation? Bonding just means to bring diverse voltage of two different surfaces into equilibrium with one another. So in this case, so long as that MC conduit remains connected to the PV disconnected with the bonding screw then it acts as a neutral wire. Now we ask the question? If that neutral wire touches a ground wires ( as evidenced by <1ohm) or resistance, whether you wrap around a metal or screw them in doesn't matter very much ( resistance is resistance). You would effectively be creating a second bond no matter how you do it. Why is this not a "clear" code violation?

 

[PaulWDent]

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!

Further to the above, I can see that this can be a big issue for dual-metered systems opening the door to msny pooh traps. I seems you would have to have separate service entrance panels for dual metering. It's time States mandated 4-quadrant metering if not plain net mezering.
First pooh trap: If 10 xears on the homeowmer needs to add new circuits, the electrician needs to understand that he can't use any spare slots in the solar panel.
Second problem: You can't easily use solar for back up if it's on a separate service entrance panel as if a circuit is sometimes going to be powered by a solar+battery back-up inverter and sometimes by utility, then neutral routing becomes interesting. Since I pretty much only work on such back up systems I have worked on that issue a lot and in my house I had to resort to a big ugly 10kva isolation transformer, not because of having two service entrance panels, but because the utility neutral feeding the inverter- charger had to come from a different place than the utility neutral feeding the transfer switch.
Dual metering is such an obsolete idea.

 

[PaulWDent]

What I know is that the EGC from solar" which includes the MC conduit" since it is bonded on PV disconnect is
carrying current from "N" and looping it with the other home EGC wiring. If the MC conduit is bonded, it would effectively be a neutral wire and if that Neutral wire( conduit) is then touching EGC-home (with less than 1ohm of resistance) then why isn't that viewed as double bonding. Which would be a clear code violation? Bonding just means to bring diverse voltage of two different surfaces into equilibrium with one another. So in this case, so long as that MC conduit remains connected to the PV disconnected with the bonding screw then it acts as a neutral wire. Now we ask the question? If that neutral wire touches a ground wires ( as evidenced by <1ohm) or resistance, whether you wrap around a metal or screw them in doesn't matter very much ( resistance is resistance). You would effectively be creating a second bond no matter how you do it. Why is this not a "clear" code violation?

It wouldn't be double neutrsl grounding, but it would be a very undesirable ground loop.

 

[GuruLal]

Further to the above, I can see that this can be a big issue for dual-metered systems opening the door to msny pooh traps. I seems you would have to have separate service entrance panels for dual metering. It's time States mandated 4-quadrant metering if not plain net mezering.
First pooh trap: If 10 xears on the homeowmer needs to add new circuits, the electrician needs to understand that he can't use any spare slots in the solar panel.
Second problem: You can't easily use solar for back up if it's on a separate service entrance panel as if a circuit is sometimes going to be powered by a solar+battery back-up inverter and sometimes by utility, then neutral routing becomes interesting. Since I pretty much only work on such back up systems I have worked on that issue a lot and in my house I had to resort to a big ugly 10kva isolation transformer, not because of having two service entrance panels, but because the utility neutral feeding the inverter- charger had to come from a different place than the utility neutral feeding the transfer switch.
Dual metering is such an obsolete idea.

It wouldn't be double neutrsl grounding, but it would be a very undesirable ground loop.

Extremely undesirable. I think you understand exactly the heart of the matter. Now I need to get this fixed.

 

[PaulWDent]

It wouldn't be double neutrsl grounding, but it would be a very undesirable ground loop.

Providing they are not being very naughty and using the conduit shell to carry neutral current. That would be a nono

It wouldn't be double neutrsl grounding, but it would be a very undesirable ground loop.

I think I have read some regulation regarding ligjtning protection that requies the grounding of the solar panel frsme and rails to go directly to main system ground. It can even have its own ground rod but you have to run a buried grounding wire from that ground rod the the house ground rod. The solar grounding conductors must contact other house grounding conductors as a lightning strike on tje panels vould then damage other household equipment

 

[PaulWDent]

Extremely undesirable. I think you understand exactly the heart of the matter. Now I need to get this fixed.

Have the MC conduit replaced by liquitite

 

[PaulWDent]

Providing they are not being very naughty and using the conduit shell to carry neutral current. That would be a nono

I think I have read some regulation regarding ligjtning protection that requies the grounding of the solar panel frsme and rails to go directly to main system ground. It can even have its own ground rod but you have to run a buried grounding wire from that ground rod the the house ground rod. The solar grounding conductors must contact other house grounding conductors as a lightning strike on tje panels vould then damage other household equipment

...must not contact....

 

[jaggedben]

a You are dead wrong

No, you are. And you're muddying the waters which is not helpful to the OP.

 

[jaggedben]

This is how the line side panel was tapped into and this is what's fed into the PV disconnect. This image here is what you see inside the main line side panel. Notice they tab the supply side wires and not the load side. Is it supposed to be this way? This system has to completely turn off if there is a power outages situation. I don't have a battery backup either.

They tapped on the supply side which is an allowed way to connect a PV system. It looks like they pulled a ground wire but did not connect it, instead using the neutral as the fault current return path from the disconnect (since you said they bonded neutral to ground in the PV disconnect). This does not result in anything meaningfully different from what is allowed for multiple service disconnect enclosures under the NEC.

Arguably under the 2017 code they should land the green wire in the main panel where your picture is taken and not have the neutral-ground bond in the PV disconnect. HOWEVER your solar system almost certainly does not put any current on the neutral in any case (The neutral is only used as a voltage reference.) So that change would make no real difference to what is happening.

Again, if there is neutral current on the exposed parts of the PV system - (and you haven't shown us exactly why we should be believe that) - then it's due to something else. Some other accident or mistake somewhere else.

 

[jaggedben]

County officials sided with you on this point also. What would happen if that grounding screw from the panel was removed? What's the risk?

In this case the neutral wire is providing the ground fault return path that trips the breaker or fuse in the PV disconnect in the case that the 'hot' AC conductors going to the inverter become accidentally faulted to the metal conduit or other equipment. So if you remove that grounding screw then potentially the overcurrent device doesn't trip, and the conduit or equipment becomes energized and a shock hazard to anyone who touches it while effectively grounded.

Under the 2017 code it's open to bond the conduit and equipment back to neutral in the main panel with a green wire or suitable conduit instead. But you have to bond that stuff to the service neutral somehow.