grreener steve
Member
- Location
- schenectady,ny
For a line side tap, should the neutral and EGC be connected at the fused AC disconnect, or remain separated (unconnected) until the main service panel?
connecting EGC and neutral for a line side tap (supply side connection)
- Thread starter grreener steve
- Start date
- Status
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Yes. :angel:
This is an area where the code is ambiguous, pubic discussion by experts varies in conclusion, and, most important, AHJs differing what they require. The best answer at this time is to ask your inspector.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Please elaborate on why combining egc and neutral would be allowed at an ac disco. A code section (up to interpretation) would suffice. :angel:
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The line (supply) side disconnect of a PV system is in exactly the location that a clustered service disconnect would be installed if the PV system were a load.
This supports the argument that there should be an EGC to neutral bond on the PV side of the disconnect.
But the code also says that the PV AC disconnect hardware does not have to be rated as a service disconnect, supporting the argument that there should not be an EGC to neutral bond there either.
I do not find either argument totally persuasive and sufficient to settle the issue.
NYSolar
Member
- Location
- Rensselaer, NY. Rensselaer County
I think you will find in upstate NY working through NYSERDA on a supply side connection they want neutral to ground bond on the AC disco. Thus, making your former main panel a sub.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Exactamundo. In San Antonio we are required to bond neutral to ground in the disco (and all that comes with that) but in Austin we are required NOT to bond N to G in the disco.
Carultch
Senior Member
- Location
- Massachusetts
So electrons flow differently in different parts of the state of Texas? Or we just have an ambiguous situation that requires an arbitrary judgement call.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Bonding a new disconnect to the neutral does not turn your existing main panel into a sub. You simply would have multiple disconnect enclosures bonded to the neutral. If all were loads this would be uncontroversial.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Articles 230 and 250. Bonding the EGC system to the neutral at the service disconnect is what is normal. What is controversial is whether a PV disconnect on a supply side tap is considered a service disconnect.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
The latter, of course.
SolarPro
Senior Member
- Location
- Austin, TX
Pretty sure that San Antonio and Austin are both in Texas. So it's more of a micro climate type of deal, whereby electrons flow differently in Bexar County than in Travis County.
There are two opposing camps on the issue of the supply side interconnection being a service entrance. That drives the AHJs to have different interpretations. Most I have talked to or heard from believe that the PV disconnect of a supply side interconnection is a service entrance and needs a service bond, but there are a few who believe otherwise. The NEC could make this more explicit but if you chase thorough a long string of references and exceptions in 230 and 250 it seems to be making a case that it should be treated as a service entrance. But then we have 690.13 that says the PV disconnect does not have to be service equipment rated.
There are a couple of things that work in our favor either way. If the PV disconnect does not have a system bond then there will be an EGC from the disconnect to the ground in the main panel. If it is wired with a service bond then it will have a GEC connecting back to the grounding electrode system and the ground in the main panel. Electrically these two work very much the same. In addition the main source of fault current is from the grid and not the PV system. So a fault in the PV side will mainly be supplied with current from the grid and under either connection the current will have a return path to the grid and trip the OCPD, which will trip the inverters offline. There are technical differences but in operation it all works about the same which is why we don't have things burning down depending on how they are connected.
The 2014 NEC restructured 690.13 and 690.14 to make it more clear. Did it do that? Jury is out. But 690.13 is now specifically talking about the PV disconnect for conductors going from a PV system into a building or structure and not the disconnect at the POCC. The information for the POCC disconnect is in 705.21 and 22 where all the interconnection information was moved. In 705 it does not state one way or the other on the service rating of the disconnect. That's not to say that these disconnects might be one in the same on smaller systems.
Yes, the grounded conductor needs to be bonded.
Yes, the grounded conductor needs to be bonded.
Let's slow down a minute on 690.13. That is for the DC disconnecting means. To say that the disconnect for a supply-side connection doesn't need to be service rated is false. (See 705.16, 705.22(4))
There is a fairly clear string of Code that prescribes a "neutral" bond at this new AC disconnect. Check it out.
705.12(A) > 230.82(6) establishes that we can connect on the supply side.
Now that we're in Article 230, take a look at 230.71(A), specifically "The service disconnecting means for each
service permitted by 230.2, or for each set of service entrance conductors permitted by 230.40, Exception No.1,
3,4, or 5
Exception 5 is where we go next. It reinforces what was just stated, that we are dealing with a new service disconnecting means and set of service-entrance conductors.
It doesn't take much of a leap to see that 230.70 is in play, and there's also one more place that 230.71(A) is mentioned...take a guess where? Correct...250.28(D)(2) tells us we need a main bonding jumper. (Please don't get bogged down in 250.28(D)(3) for now). Finally and most importantly, 250.24(B) and (C) make it crystal clear that we need to bond the neutral in each service disconnecting means.
This topic comes up less frequently, which might be a good sign. I'm happy to speak with any AHJ that is still struggling to understand the logical or safety reasons why we need to bond the neutral at this enclosure. There are some that get too hung up on where the "supply" is; at the end of the day we need to consider the supply that has the greatest fault current and build to mitigate that danger.
*All references 2014
Yes, the grounded conductor needs to be bonded.
Let's slow down a minute on 690.13. That is for the DC disconnecting means. To say that the disconnect for a supply-side connection doesn't need to be service rated is false. (See 705.16, 705.22(4))
There is a fairly clear string of Code that prescribes a "neutral" bond at this new AC disconnect. Check it out.
705.12(A) > 230.82(6) establishes that we can connect on the supply side.
Now that we're in Article 230, take a look at 230.71(A), specifically "The service disconnecting means for each
service permitted by 230.2, or for each set of service entrance conductors permitted by 230.40, Exception No.1,
3,4, or 5
Exception 5 is where we go next. It reinforces what was just stated, that we are dealing with a new service disconnecting means and set of service-entrance conductors.
It doesn't take much of a leap to see that 230.70 is in play, and there's also one more place that 230.71(A) is mentioned...take a guess where? Correct...250.28(D)(2) tells us we need a main bonding jumper. (Please don't get bogged down in 250.28(D)(3) for now). Finally and most importantly, 250.24(B) and (C) make it crystal clear that we need to bond the neutral in each service disconnecting means.
This topic comes up less frequently, which might be a good sign. I'm happy to speak with any AHJ that is still struggling to understand the logical or safety reasons why we need to bond the neutral at this enclosure. There are some that get too hung up on where the "supply" is; at the end of the day we need to consider the supply that has the greatest fault current and build to mitigate that danger.
*All references 2014
NOT. AND ≠ OR
Yes, the service side conductors are Service Entrance Conductors (SEC). There is no Code stipulation that a service disconnecting means must go on the end of an SEC.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Around here my experience is just the opposite. CPS in San Antonio is the only AHJ I know of in Texas who dictates that there be a G-N bond in the PV AC disco. I have no dog in this hunt; we have debated it until we are blue in the face but no argument however emphatically presented carries the day. It would be great if the NEC would explicitly state in 705 which way it should be. Even if it really doesn't make any difference, pick one already.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
It's not that some electrons arbitrarily flow differently, some just interpret the code differently and adjust their flow accordingly.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Um, 230.70, General? Definition of service entrance conductors?
(I'm pretty sure that last time around you ended up arguing that they are not SECs because of the definition of a service. [EDIT: actually it appears you never really responded to my points on this.] )
Last edited:
- Location
- Massachusetts
- Status