Daisy-chain equipment grounding conductors (EGC)

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alej27

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Location
Venezuela
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Electrical Engineer
Many devices in a PV system are wall-mounted, like inverters, solar charge controllers (SCC), disconnects, busbars, etc.

Is it allowed by the NEC to connect the ground terminal of inverters and SCC in daisy-chain, and then connect the first (or last) device to the ground busbar? As shown in the following figure.

1717609650716.jpg

Or must I run a separate GEC for each device? As shown below. Is there a section requiring it?

1717609660650.jpg

I suppose the best practice is the second one, kind of similar to how it's usually recommended to pig-tail the hot and neutral of receptacles instead of daisy-chaining.
 
alej27 said:
Many devices in a PV system are wall-mounted, like inverters, solar charge controllers (SCC), disconnects, busbars, etc.

Is it allowed by the NEC to connect the ground terminal of inverters and SCC in daisy-chain, and then connect the first (or last) device to the ground busbar? As shown in the following figure.

View attachment 2571956

Or must I run a separate GEC for each device? As shown below. Is there a section requiring it?

View attachment 2571957

I suppose the best practice is the second one, kind of similar to how it's usually recommended to pig-tail the hot and neutral of receptacles instead of daisy-chaining.
Click to expand...
I don't believe that most modern inverters require a GEC.
 
ggunn said:
I don't believe that most modern inverters require a GEC.
Click to expand...
Many do have a ground terminal on the AC input. For example, look at the schematic from Victron Energy for a three-phase system using 3 Quattro inverter-chargers and SCCs:

1717624880411.jpg

Or look at the connection of the AC input of the MPP Solar LVX 6048 hybrid inverter with grid injection:

1717624994740.jpg

Or the connection of the AC input of the Growatt SPF series hybrid inverters without grid injection:

1717625160933.jpg

They all require a ground wire at the ground terminal of the AC input. Other brands like Sol-Ark and Must too.
 
alej27 said:
Many devices in a PV system are wall-mounted, like inverters, solar charge controllers (SCC), disconnects, busbars, etc.

Is it allowed by the NEC to connect the ground terminal of inverters and SCC in daisy-chain, and then connect the first (or last) device to the ground busbar? As shown in the following figure.



Or must I run a separate GEC for each device? As shown below. Is there a section requiring it?



I suppose the best practice is the second one, kind of similar to how it's usually recommended to pig-tail the hot and neutral of receptacles instead of daisy-chaining.
Click to expand...
Op needs to decide if they are asking about EGCs or GECs. Installation requirements are different. EGCs can be daisy-chained.
 
pv_n00b said:
Op needs to decide if they are asking about EGCs or GECs. Installation requirements are different. EGCs can be daisy-chained.
Click to expand...
Yes, but I usually don't if each inverter has its own conduit to an AC combiner. I don't have any experience with the inverters he mentioned, but for normal grid tied inverters we stopped wiring them with GEC conductors when they stopped being transformer coupled.
 
electrofelon said:
I would avoid running separate "ground wires" to equipment. It is confusing and unnecessary. Just run an EGC with the conductors serving the equipment.
Click to expand...
As we discussed in another thread, it's a belt and suspenders approach but I run an EGC in every conduit.
 
alej27 said:
Many do have a ground terminal on the AC input. For example, look at the schematic from Victron Energy for a three-phase system using 3 Quattro inverter-chargers and SCCs:


Or look at the connection of the AC input of the MPP Solar LVX 6048 hybrid inverter with grid injection:


Or the connection of the AC input of the Growatt SPF series hybrid inverters without grid injection:
They all require a ground wire at the ground terminal of the AC input. Other brands like Sol-Ark and Must too.
Click to expand...

As pv_n00b said, you need to understand the difference between an EGC, which bonds non-current-carrying parts, and a GEC, which usually connects a circuit conductor to earth. For the EGC you can daisy-chain. For a GEC, under the NEC you are not supposed to do that. Whether the ground terminal is for an EGC or GEC depends on the equipment, and you need to review the documentation. (Often a GEC terminal also has the earth symbol inside a circle, but I don't know that this convention can be counted upon. Read the equipment documentation too.)

Grid tied inverters in the US nowadays mostly don't need their own GEC. Obsolete equipment, off-grid systems, or equipment sold outside the US might be different.

That Victron diagram also complicates the question. Is that the equipment you are actually using? If not I would ignore that diagram because it's not likely comparable to other equipment and systems. That diagram shows an off-grid system, and doesn't show any earthing. My understanding is that Victron mostly sells equipment used on boats, where that diagram might make some sense. That would not be covered by the NEC, and also wouldn't have any GECs because there is no earth. That diagram also shows the inverter grounds being connected to the negative battery bus. That is unusual, and would not be done for a grid-tied system under the NEC, or for Sol-Ark and most other brands. But it might be done on boats.
 
ggunn said:
As we discussed in another thread, it's a belt and suspenders approach but I run an EGC in every conduit.
Click to expand...
That's what I was saying to do, just run a wire EGC in the conduit with the conductors. What I was saying to avoid, and what I was under the impression was being proposed, is running a separate "grounding system" not run with the supply conductors.
 
electrofelon said:
That's what I was saying to do, just run a wire EGC in the conduit with the conductors. What I was saying to avoid, and what I was under the impression was being proposed, is running a separate "grounding system" not run with the supply conductors.
Click to expand...
Nope, I wasn't asking whether to have a separate grounding electrode system for the devices 😅. I was asking if it is allowed by the NEC to daisy-chain the EGC, or if I have to run a separate EGC for each device.
 
jaggedben said:
That Victron diagram also complicates the question. Is that the equipment you are actually using? If not I would ignore that diagram because it's not likely comparable to other equipment and systems.
Click to expand...
Yes, Victron is the brand I'm using for the inverter-chargers and solar charge controllers. Their diagram shows running a separate EGC for each inverter-chargers and each SCC. My question was if I can daisy-chain the EGC of the three inverter-chargers, and then run just one EGC to the ground bar; and the same for the SCCs.
jaggedben said:
That diagram shows an off-grid system, and doesn't show any earthing.
Click to expand...
The system has two AC input connections per inverter-charger, so I wouldn't consider it off-grid:
1717700486313.jpg

It does show an earth ground, with the ground rod and the GEC, on the ground bar:
1717700137470.jpg
jaggedben said:
My understanding is that Victron mostly sells equipment used on boats, where that diagram might make some sense.
Click to expand...
Their equipment can be used on boats, but also for off-grid systems on earth ground, or even hybrid systems.
 
alej27 said:
Yes, Victron is the brand I'm using for the inverter-chargers and solar charge controllers. Their diagram shows running a separate EGC for each inverter-chargers and each SCC. My question was if I can daisy-chain the EGC of the three inverter-chargers, and then run just one EGC to the ground bar; and the same for the SCCs.
Click to expand...
 
alej27 said:
Nope, I wasn't asking whether to have a separate grounding electrode system for the devices 😅. I was asking if it is allowed by the NEC to daisy-chain the EGC, or if I have to run a separate EGC for each device.
Click to expand...
Yes, you can daisy chain EGC conductors but not GEC conductors.
 
alej27 said:
Nope, I wasn't asking whether to have a separate grounding electrode system for the devices 😅.
Click to expand...
Nor was I talking about a GES. I am just trying to say that considering 300.3(B) and common methods, daisy chaining an EGC is often not doable. For DC you do have 250.134(B) exception #2, but I would generally still run a single conduit to each device with an EGC contained within it.
 
alej27 said:
Yes, Victron is the brand I'm using for the inverter-chargers and solar charge controllers. Their diagram shows running a separate EGC for each inverter-chargers and each SCC. My question was if I can daisy-chain the EGC of the three inverter-chargers, and then run just one EGC to the ground bar; and the same for the SCCs.

The system has two AC input connections per inverter-charger, so I wouldn't consider it off-grid:

It does show an earth ground, with the ground rod and the GEC, on the ground bar:

Their equipment can be used on boats, but also for off-grid systems on earth ground, or even hybrid systems.
Click to expand...

I see. Actually they show both a generator and a grid/shore power connection.

It seems that the ground symbol by the battery negative could represent either earth or the hull of a boat.

For what it's worth, the diagram appears not to be NEC compliant because the PV arrays do not have GFDI. Although the manual says a GFDI device could be added. This may not matter where you are.

The NEC requires EGCs to be run with circuit conductors, so to be able to daisy chain EGCs unless you would have to tee multiple circuits off one conduit.
 
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