EGC required in each conduit from a PV Array?

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PaulHartley

Member
Location
United States
For a PV Array where multiple source circuits feed into a Transition Box, and then from there multiple conduits feed these source circuits directly to multiple inverters...

PER NEC '11, Does each conduit (EMT) have to have it's own EGC, or can a single EGC wire run from the equipment grounding point in the Transition Box through one of the conduits to one of the Inverters (and on to the AC combiner)?

Each inverter output would have its own EGC that connects the inverter to the ground in the AC combiner. All the conduits would have grounding bushings at both ends. But each conduit from rooftop Transition Box to Inverter would not have its own separate EGC (this is the main question...whether this is allowed per the NEC?)

Section 250.134 (B), Exception No. 2, allows the DC EGC to not run with the circuit conductors, which seems to speak to this question, but I'm not sure of this is the correct interpretation.

Thank you for any insights.

Paul Hartley
 

Smart $

Esteemed Member
Location
Ohio
Technically speaking, EMT qualifies as an EGC... so you aren't required to run any wire-type EGC.

(Didn't look it up, but if Article 690 requires a wire-type EGC, yes you can put it in any one of the EMT runs.)
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
For a PV Array where multiple source circuits feed into a Transition Box, and then from there multiple conduits feed these source circuits directly to multiple inverters...

PER NEC '11, Does each conduit (EMT) have to have it's own EGC, or can a single EGC wire run from the equipment grounding point in the Transition Box through one of the conduits to one of the Inverters (and on to the AC combiner)?

First of all, forget specific NEC requirements for a minute and remember that the primary purpose of the DC EGC in a PV system is ensure the functioning of the ground-fault detection and interruption. Does your proposal provide an effective ground fault current path to the other inverter(s) for DC ground-faults? Maybe, or maybe not depending on the details. But if not, it violates both 110.3(B) and 690.5 and arguably 250.4. Keep in mind also that for fuse-type GFDIs on PV systems, greater resistance on the DC EGC means a fault is less likely to be detected.

Also, take a look at 690.48 and consider whether you are potentially creating a danger in the future when that one inverter gets serviced.

If nothing else, I have to say I think it's a bad practice not to run a dedicated wire EGC to each inverter from the DC side.

Section 250.134 (B), Exception No. 2, allows the DC EGC to not run with the circuit conductors, which seems to speak to this question, but I'm not sure of this is the correct interpretation.

690.43(F) could be read to overide that. Sort open to interpretation.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Technically speaking, EMT qualifies as an EGC... so you aren't required to run any wire-type EGC.

(Didn't look it up, but if Article 690 requires a wire-type EGC, yes you can put it in any one of the EMT runs.)

While true, 250.97 effectively negates this in many situations for PV systems.

690 does not require a wire type EGC, AFAIK.
 

Smart $

Esteemed Member
Location
Ohio
While true, 250.97 effectively negates this in many situations for PV systems.

...
Doesn't negate EMT as EGC... just requires more-assured bonding at raceway terminations... and that can be as simple as using a bonding locknut on the connector.
 

Carultch

Senior Member
Location
Massachusetts
For a PV Array where multiple source circuits feed into a Transition Box, and then from there multiple conduits feed these source circuits directly to multiple inverters...

PER NEC '11, Does each conduit (EMT) have to have it's own EGC, or can a single EGC wire run from the equipment grounding point in the Transition Box through one of the conduits to one of the Inverters (and on to the AC combiner)?

Each inverter output would have its own EGC that connects the inverter to the ground in the AC combiner. All the conduits would have grounding bushings at both ends. But each conduit from rooftop Transition Box to Inverter would not have its own separate EGC (this is the main question...whether this is allowed per the NEC?)

Section 250.134 (B), Exception No. 2, allows the DC EGC to not run with the circuit conductors, which seems to speak to this question, but I'm not sure of this is the correct interpretation.

Thank you for any insights.

Paul Hartley


If you have multiple conduits, and you are using an EGC wire, all CONDUITS need to have a full size EGC.


If you are sharing a single conduit among multiple inverter circuits, you can use a common ground wire for both, sized for the larger of the two circuits. And then you can splice it and route a short segment of wire to each.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If you have multiple conduits, and you are using an EGC wire, all CONDUITS need to have a full size EGC.


If you are sharing a single conduit among multiple inverter circuits, you can use a common ground wire for both, sized for the larger of the two circuits. And then you can splice it and route a short segment of wire to each.
IMHO, the requirement to put a wire EGC in all canduits or none applies only when the conduits contain parallel wire sets. That is not the case here.
You can add a wire EGC to any, several, or all conduits to serve the array connected to those conduits.
I do agree that specifically connecting one wire EGC to service all arrays can be a violation.
But supplying a wire EGC to only one array and then binding all of the arrays together (such as through a GES) might be technically OK.
I have not looked as hard at the same situation for GECs if that should come up. I suspect that a conduit EGC cannot serve as a combined EGC/GEC because of the sizing rules.
 

PaulHartley

Member
Location
United States
Multiple EGC's....my Takeaway

Multiple EGC's....my Takeaway

Thank you all for the valuable insights. What I'm hearing is that the Code does not specifically require each conduit to have its own EGC (as long as all equip. is bonded when, say, an inverter is removed for service) BUT,
some are recommending a wire EGC in each conduit as good practice, primarily to ensure the easy path to the ground fault protection.

In this case, all conduits are EMT, and both ends of each conduit have a bonding bushing (bonded to a wire EGC or ground bar, etc.). If this is true, is there really any advantage to having a wire EGC (say a green-insulated wire, which is typical) running through the conduit? I may be wrong, but I'm thinking that any fault current inside the conduit will not find its way into the wire EGC until it travels (through the conduit) to the bonding bushing whether there was a wire EGC inside the conduit or not, because of the insulation. So what is the advantage of having the wire in there?

If the EMT (as EGC) meets the code, and provides the path to the closest wire EGC (at either end of the conduit) then are there any advantages to a wire inside each conduit?

To qualify as an EGC, does the EMT have to have special fittings/couplings along its length or do standard fittings comply?

thank you all! :)
 

Carultch

Senior Member
Location
Massachusetts
Thank you all for the valuable insights. What I'm hearing is that the Code does not specifically require each conduit to have its own EGC (as long as all equip. is bonded when, say, an inverter is removed for service) BUT,
some are recommending a wire EGC in each conduit as good practice, primarily to ensure the easy path to the ground fault protection.

In this case, all conduits are EMT, and both ends of each conduit have a bonding bushing (bonded to a wire EGC or ground bar, etc.). If this is true, is there really any advantage to having a wire EGC (say a green-insulated wire, which is typical) running through the conduit? I may be wrong, but I'm thinking that any fault current inside the conduit will not find its way into the wire EGC until it travels (through the conduit) to the bonding bushing whether there was a wire EGC inside the conduit or not, because of the insulation. So what is the advantage of having the wire in there?

If the EMT (as EGC) meets the code, and provides the path to the closest wire EGC (at either end of the conduit) then are there any advantages to a wire inside each conduit?

To qualify as an EGC, does the EMT have to have special fittings/couplings along its length or do standard fittings comply?

thank you all! :)


Reliability. If you run a wire EGC, you definitely have your array bonded to the inverter.

If you rely upon all the intricate fittings in the conduit run, then any improper connection means you loose your ground. A lot more chance of error.

Most standard fittings for metal conduit comply as electrically continuous, and in fact you have to have your metal conduit electrically continuous even with a wire EGC. The main issue occurs when you terminate at an enclosure that is either nonmetallic, or has ring knockouts remaining. Then you may need bonding fittings.
 

mwm1752

Senior Member
Location
Aspen, Colo
Then it appears without something not defined in this conversation- your AC EGC would aslo serve as a DC GEC per 690 electrode system requirements & be a min 8# for circuits below 50A. Not knowing the location of each array I could not tell you if the GEC would need to be in each conduit.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Then it appears without something not defined in this conversation- your AC EGC would aslo serve as a DC GEC per 690 electrode system requirements & be a min 8# for circuits below 50A. Not knowing the location of each array I could not tell you if the GEC would need to be in each conduit.

Since he said 2011 code, there is no 690.47(D), and thus no requirement to run a GEC from the array. In any case, there would never be a requirement to run more than one GEC from one array. (From his description I gather it is one array.) And the GEC is not required to be run with the circuits, it can take an entirely different route if he wants (not that I recommend it).
 

mwm1752

Senior Member
Location
Aspen, Colo
Since he said 2011 code, there is no 690.47(D), and thus no requirement to run a GEC from the array. In any case, there would never be a requirement to run more than one GEC from one array. (From his description I gather it is one array.) And the GEC is not required to be run with the circuits, it can take an entirely different route if he wants (not that I recommend it).


I was referring to 690.47( C )(3) which is in both the 2011 & 2014. I always refered to the installation of the electrode system as installing the GEC towards the power scource but thats just the way I look at it. I do not know if this is a pole mount or roof mounted arrays, his transition box? I concluded as a J box due to conduit bends. Gennerally, individual inverters are fed from separate arrays though one could call a complete system of panels an array. How you install the electrode system is up to the individual and not really clear how the GEC is supplied to the array. He has only mentioned a conduit system that connects the array(s) to the inverters for my assumptions. Maybe you have seen this install which gives you better insight, as I said "Then it appears without something not defined in this conversation"
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I was referring to 690.47( C )(3) which is in both the 2011 & 2014. I always refered to the installation of the electrode system as installing the GEC towards the power scource but thats just the way I look at it.

Most people look at it as being the inverter, which is where the grounded conductor is bonded if there is one, and where there's a marked GEC terminal. Since there is no AC wiring between array and inverter, 690.47(C)(3) does not apply to any grounding conductor there.

I do not know if this is a pole mount or roof mounted arrays, his transition box?

Presumably he means the box where he transitions from PV wire to THHN inside conduit, or similar.

Gennerally, individual inverters are fed from separate arrays though one could call a complete system of panels an array.

Note that the NEC definition stresses 'mechanically integrated', not electrically. To me, if the racking system and panels are all contiguous then it's one array, regardless of whether it feeds more than one inverter or is connected to other arrays on the same inverter.
 

mwm1752

Senior Member
Location
Aspen, Colo
Most people look at it as being the inverter, which is where the grounded conductor is bonded if there is one, and where there's a marked GEC terminal. Since there is no AC wiring between array and inverter, 690.47(C)(3) does not apply to any grounding conductor there.

you have certainly missed the point I was making -- I moved on from EGC to GEC a long time ago for the sake of whether an additonal green type wire may be needed for some reason overlooked in this installation. Sorry to confuse.
 

Carultch

Senior Member
Location
Massachusetts
Since he said 2011 code, there is no 690.47(D), and thus no requirement to run a GEC from the array. In any case, there would never be a requirement to run more than one GEC from one array. (From his description I gather it is one array.) And the GEC is not required to be run with the circuits, it can take an entirely different route if he wants (not that I recommend it).

690.47(D)anger does not belong in the NEC. It makes your installation less safe, in the event of a ground potential difference.

Sure, I'll drive an auxiliary electrode. It will be 3 ft long, and I'll run CAT5 wire to it. I'll even bond it with homemade unlisted lugs.

Bond your grounded inverters via the GEC to the premises wiring electrode.
Bond your ungrounded inverters via the AC side EGC alone, which ultimately goes to the premises wiring electrode.

Everything above ground bonded together. Everything below ground bonded together. Exclusively one connection between the two.
 
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