EGC back to service on PV system

jlemaster

Member
Location
Tampa
Occupation
Electrician
Why is it required to bring the PV system GEC to the homes GEC. I know why just disputing with someone and can’t find the resources to justify why I am right.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Do you mean EGC (title) or GEC (question)? It obviously makes a difference.

With the 2017 NEC, which Florida moved to at the beginning of the year, I believe it is no longer required to provide a GEC to a PV array. An EGC is still required.

Cheers, Wayne
 

jlemaster

Member
Location
Tampa
Occupation
Electrician
Do you mean EGC (title) or GEC (question)? It obviously makes a difference.

With the 2017 NEC, which Florida moved to at the beginning of the year, I believe it is no longer required to provide a GEC to a PV array. An EGC is still required.

Cheers, Wayne
Do you mean EGC (title) or GEC (question)? It obviously makes a difference.

With the 2017 NEC, which Florida moved to at the beginning of the year, I believe it is no longer required to provide a GEC to a PV array. An EGC is still required.

Cheers, Wayne
Can you give a reference to that change please.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I think the info notes gives some explanation

690.47 Grounding Electrode System.
(A) Buildings or Structures Supporting a PV Array. A building
or structure supporting a PV array shall have a grounding electrode
system installed in accordance with Part III of Article 250.
PV array equipment grounding conductors shall be connected
to the grounding electrode system of the building or structure
supporting the PV array in accordance with Part VII of
Article 250. This connection shall be in addition to any other
equipment grounding conductor requirements in 690.43(C).
The PV array equipment grounding conductors shall be sized
in accordance with 690.45.
For PV systems that are not solidly grounded, the equipment
grounding conductor for the output of the PV system, connected
to associated distribution equipment, shall be permitted to
be the connection to ground for ground-fault protection and
equipment grounding of the PV array.
For solidly grounded PV systems, as permitted in 690.41(A)
(5), the grounded conductor shall be connected to a grounding
electrode system by means of a grounding electrode
conductor sized in accordance with 250.166.
Informational Note: Most PV systems installed in the past
decade are actually functional grounded systems rather than
solidly grounded systems as defined in this Code. For functional
grounded PV systems with an interactive inverter output, the ac
equipment grounding conductor is connected to associated
grounded ac distribution equipment. This connection is often
the connection to ground for ground-fault protection and
equipment grounding of the PV array.
 

romex jockey

Senior Member
Location
Vermont
functional grounded systems rather than
solidly grounded systems


oh, that's just too good to pass up Denny

i'd love to read the definitions behind those two..... :cool: ~RJ~
 

Carultch

Senior Member
Location
Massachusetts
functional grounded systems rather than
solidly grounded systems


oh, that's just too good to pass up Denny

i'd love to read the definitions behind those two..... :cool: ~RJ~
Solidly grounded means that you have a direct connection between the grounded polarity, and the EGC. For separately-derived systems in general, you also connect the GEC at the location where you bond the grounded conductor and EGC. The word "solidly" means the continuity is intended to be permanent between the groundED conductor and groundING conductor, and that there is no reason for the continuity to ever be removed.

Functionally grounded means that the system has a reference to ground in some form or another, but with an indirect connection. Like a connection through power electronics, or a connection through a protective device. The NEC has an informational note that indicates examples of what kinds of systems this would be. The short answer, is that it is most systems you'd build today would count as functionally grounded.

One example is what we used to just call a grounded system, which bonded one of the polarities to ground via a GFCI fuse or breaker. During normal circumstances, the grounded polarity would have continuity to the EGC, exclusively through this GFCI device. When there is a ground fault, this device would trip, and temporarily make both polarities ungrounded, until the ground fault is fixed. Such systems had an isolation transformer as part of the inverter, because the waveform produced by the power electronics would have a DC offset that needed to be eliminated to in order to be connected to a grounded AC grid. The indirect grounding of this kind of system was necessary with the way the required GFCI technology worked at the time.

Another example of what is now called a functionally-grounded system, is what non-isolated inverters typically use. We used to call this an ungrounded system. Instead of using a GFCI fuse or breaker, this kind of system uses a residual current sensor that looks for discrepancies between the positive and negative current, in order to identify a ground fault. These inverters have both polarities ungrounded, but by the nature of being connected to a grounded AC grid without isolation, the two polarities are at equal and opposite voltages when measured to ground. Suppose there is 500V between the polarities, this would mean that the positive is at +250V, and the negative is at -250V. This DC setup could therefore generate both the positive half, and the negative half of the AC waveform, and have it be symmetric about ground, as it needs to be in order to feed in to the AC grid. This kind of inverter will make a functionally-grounded DC system, when connected to a grounded AC grid.

A truly ungrounded system would be created, if you connect a non-isolated inverter to an ungrounded AC grid.
 

romex jockey

Senior Member
Location
Vermont
Solidly grounded means that you have a direct connection between the grounded polarity, and the EGC. For separately-derived systems in general, you also connect the GEC at the location where you bond the grounded conductor and EGC. The word "solidly" means the continuity is intended to be permanent between the groundED conductor and groundING conductor, and that there is no reason for the continuity to ever be removed.

Functionally grounded means that the system has a reference to ground in some form or another, but with an indirect connection. Like a connection through power electronics, or a connection through a protective device. The NEC has an informational note that indicates examples of what kinds of systems this would be. The short answer, is that it is most systems you'd build today would count as functionally grounded.

One example is what we used to just call a grounded system, which bonded one of the polarities to ground via a GFCI fuse or breaker. During normal circumstances, the grounded polarity would have continuity to the EGC, exclusively through this GFCI device. When there is a ground fault, this device would trip, and temporarily make both polarities ungrounded, until the ground fault is fixed. Such systems had an isolation transformer as part of the inverter, because the waveform produced by the power electronics would have a DC offset that needed to be eliminated to in order to be connected to a grounded AC grid. The indirect grounding of this kind of system was necessary with the way the required GFCI technology worked at the time.

Another example of what is now called a functionally-grounded system, is what non-isolated inverters typically use. We used to call this an ungrounded system. Instead of using a GFCI fuse or breaker, this kind of system uses a residual current sensor that looks for discrepancies between the positive and negative current, in order to identify a ground fault. These inverters have both polarities ungrounded, but by the nature of being connected to a grounded AC grid without isolation, the two polarities are at equal and opposite voltages when measured to ground. Suppose there is 500V between the polarities, this would mean that the positive is at +250V, and the negative is at -250V. This DC setup could therefore generate both the positive half, and the negative half of the AC waveform, and have it be symmetric about ground, as it needs to be in order to feed in to the AC grid. This kind of inverter will make a functionally-grounded DC system, when connected to a grounded AC grid.

A truly ungrounded system would be created, if you connect a non-isolated inverter to an ungrounded AC grid.
Well, it would appear at first sniff, 690.47 and multiple art 250 ref's are dancing all around an SDS , and subsequent GEC Carultch

~RJ~
 
Top