Grounding Code 690.47(C)(3) implementation with SMA SunnyBoy TL-US-22

[samotlietuvis]

Guys, trying to understand how to implement 690.47(C)(3) with SMA SunnyBoy TL-US-22 String inverter on my permit.

690.47(C)(3) - Combined Direct-Current Grounding-Electrode Conductor and Alternating- Current Equipment Grounding Conductor. An unspliced, or irreversibly spliced, combined grounding conductor shall be run from the marked dc grounding electrode conductor connection point along with the ac circuit conductors to the grounding busbar in the associated ac equipment. This combined grounding conductor shall be the larger of the size specified by 250.122 or 250.166 and shall be installed in accordance with 250.64(E).

The way I interpret the 690.47(C)(3) on SMA SunnyBoy TL-US-22:
1) Connect PV EGC to SunnyBoy grounding terminal in the DC Disconnect
2) Connect L1, L2 and N (White) to the SMA AC terminals and run them to AC Disconnect followed to Solar Breaker on Bus bar. N(White) goes to Neutral bus bar.
3) Connect #8 AWG Green CU on the Ground Connection of SMA inverter (not in DC disconnect) and run it to the to the service panel Ground busbar. This is continuous combined AC EGC and DC GEC per 690.47(C)(3).
4) Irreversibly Splice from combined AC EGC and DC GEC cable (above) a #8 AWG Green CU and run it to the AC disconnect.

Is the above correct? Can I run separate #8 AWG Green CU from AC disconnect to the service panel ground busbar so that I avoid splicing in step #4?

If I do the above steps, then I do not need a separate Grounding Electrode for DC side, correct?

Thanks,
Tomas

[CA_Tom]

Guys, trying to understand how to implement 690.47(C)(3) with SMA SunnyBoy TL-US-22 String inverter on my permit.

690.47(C)(3) - Combined Direct-Current Grounding-Electrode Conductor and Alternating- Current Equipment Grounding Conductor. An unspliced, or irreversibly spliced, combined grounding conductor shall be run from the marked dc grounding electrode conductor connection point along with the ac circuit conductors to the grounding busbar in the associated ac equipment. This combined grounding conductor shall be the larger of the size specified by 250.122 or 250.166 and shall be installed in accordance with 250.64(E).

The way I interpret the 690.47(C)(3) on SMA SunnyBoy TL-US-22:
1) Connect PV EGC to SunnyBoy grounding terminal in the DC Disconnect
2) Connect L1, L2 and N (White) to the SMA AC terminals and run them to AC Disconnect followed to Solar Breaker on Bus bar. N(White) goes to Neutral bus bar.
3) Connect #8 AWG Green CU on the Ground Connection of SMA inverter (not in DC disconnect) and run it to the to the service panel Ground busbar. This is continuous combined AC EGC and DC GEC per 690.47(C)(3).
4) Irreversibly Splice from combined AC EGC and DC GEC cable (above) a #8 AWG Green CU and run it to the AC disconnect.

Is the above correct? Can I run separate #8 AWG Green CU from AC disconnect to the service panel ground busbar so that I avoid splicing in step #4?

If I do the above steps, then I do not need a separate Grounding Electrode for DC side, correct?

Thanks,
Tomas

Are you doing a grounded or "ungrounded" array?
I thought from another post you were doing "ungrounded".
In which case I believe you don't have a GEC involved, just an EGC.
And EGC dont' require an irreversible splice.

[samotlietuvis]

Are you doing a grounded or "ungrounded" array?
I thought from another post you were doing "ungrounded".
In which case I believe you don't have a GEC involved, just an EGC.
And EGC dont' require an irreversible splice.

Yes, I am doing ungrounded array that has no System Ground, but I am grounding the Equipment to the existing Main Ground Electrode (PV’s, Rails, DC disconnect, Inverter, AC Disconnect).

Quoting an article I read: “If it’s metal, it needs to be grounded. That means the racking-and-mounting, junctions, frames — everything. If the steel bonding to your conduit is a metal pole, connect a copper conductor to it and conduct it to the ground. On PV systems, you always have to do equipment grounding — no one wants to be electrocuted.”
.
The above refers to GEC.

690.47(C)(3) says combined DC GEC and AC EGC. I do believe I need EGC and GEC that can be combined into one conductor per 690.47(C)(3).

Drawing permit next Friday - the permit guy should clarify if I am doing something wrong. I intend to walk him through all my reasoning and how I will install the system.

What confused me is inspecting my neighbors solar system that was done with SMA Sunny Boy 6000 TL-US that has a dedicated Grounding Electrode installed. The installers did upgrade his Main Busbar because 100A one he had originally was not big enough. Maybe the reason for the dedicated Grounding Electrode is because the Main Busbar was upgraded, not because the installers were grounding the DC System.

[sensij]

On step 2, make sure you are connecting Grid AC -> DC Disconnect AC -> Inverter AC (6.3.2 and 6.3.3 of the inverter installation manual).

On steps 1 and 3, as a sanity check, verify internal continuity between the DC equipment ground terminal and the AC equipment ground terminal.

On step 3, the service panel ground busbar may not be sufficient. For example, the following note could appear on a permit due to local requirements:

2. IF THE EXISTING MAIN SERVICE PANEL DOES NOT
HAVE A GROUND ROD OR UFER, IT IS THE PV
CONTRACTOR'S RESPONSIBILITY TO INSTALL ONE.

Another good reference, page 17 in particular discussing electrodes for ungrounded systems.

And again, based on the questions you are asking, seek professional help.

I sent a PM, let me know if it will help.

[CA_Tom]

Yes, I am doing ungrounded array that has no System Ground, but I am grounding the Equipment to the existing Main Ground Electrode (PV’s, Rails, DC disconnect, Inverter, AC Disconnect).

Quoting an article I read: “If it’s metal, it needs to be grounded. That means the racking-and-mounting, junctions, frames — everything. If the steel bonding to your conduit is a metal pole, connect a copper conductor to it and conduct it to the ground. On PV systems, you always have to do equipment grounding — no one wants to be electrocuted.”
.
The above refers to GEC.

"you always have to do equipment grounding" - that's correct and is EGC, not GEC
EGC = equipment grounding conductor.

690.47(C)(3) says combined DC GEC and AC EGC. I do believe I need EGC and GEC that can be combined into one conductor per 690.47(C)(3).

Drawing permit next Friday - the permit guy should clarify if I am doing something wrong. I intend to walk him through all my reasoning and how I will install the system.

What confused me is inspecting my neighbors solar system that was done with SMA Sunny Boy 6000 TL-US that has a dedicated Grounding Electrode installed. The installers did upgrade his Main Busbar because 100A one he had originally was not big enough. Maybe the reason for the dedicated Grounding Electrode is because the Main Busbar was upgraded, not because the installers were grounding the DC System.

From what I see in the instructions I think SMA Sunny Boy can be either grounded (with GEC and EGC) or ungrounded (EGC only)
So - do you know if your neighbor's was ungrounded array?
If you don't know, then it's quite possible it does have a GEC connecting to either the DC + or the DC -.

Also - what do you mean by "a dedicated Grounding Electrode installed"?
Do you mean a dedicated ground wire connected to the DC?
Or when you say "Grounding electrode" are you really talking about a ground rod that they drove in the earth to connect the new subpanel's ground to?
Or the new wire they ran from the new main panel to the ground rod and/or to a clamp connecting to the metal water supply line coming into his house?


I agree with sensij.
Based on the questions you have, you really should hire an electrician to at least supervise your work if not do it for you.
Yes it's probably a few hundred $.
But it'll be well worth it.


IMO the permit guy isn't going to spend a lot of time on your permit. If there's obvious glaring mistakes he'll probably point them out if he notices. But most likely he won't know that much about solar PV. He might know some, having seen other permits come across his desk - but his assumption is that *you* know what you're doing. Same with the inspector - his assumption is that *you* know what you're doing. He's there to do a double check - not to help you with your design. When they question something you should be able to say "Yes, I looked at that and I believe my design does meet code. I believe I can find the correct section of the code that applies for my situation if you have your code book handy."

Possibly the permit guy or the inspector will be helpful (beyond saying "this doesn't meet section xx.xx"). After all they are human, and people are generally helpful when approached the right way.

[samotlietuvis]

On step 2, make sure you are connecting Grid AC -> DC Disconnect AC -> Inverter AC (6.3.2 and 6.3.3 of the inverter installation manual).

On steps 1 and 3, as a sanity check, verify internal continuity between the DC equipment ground terminal and the AC equipment ground terminal.

On step 3, the service panel ground busbar may not be sufficient. For example, the following note could appear on a permit due to local requirements:


Another good reference, page 17 in particular discussing electrodes for ungrounded systems.

And again, based on the questions you are asking, seek professional help.

I sent a PM, let me know if it will help.

Thanks, receiving the inverter this Friday. Now looking at the installation manual only. I already looked at "Photovoltaic System Grounding" document. Good read.

Is installation manual 6.3 steps 11 and 12 refer to the EGC that I will use per 690.47(C)(3).

I was under impression that all Main Service panels have a grounding rod. Now since you mention it, there is nothing but concrete around my main. I will open my Busbar this evening with my electrical contractor friend to see if ground rod is there.

"you always have to do equipment grounding" - that's correct and is EGC, not GEC
EGC = equipment grounding conductor.



From what I see in the instructions I think SMA Sunny Boy can be either grounded (with GEC and EGC) or ungrounded (EGC only)
So - do you know if your neighbor's was ungrounded array?
If you don't know, then it's quite possible it does have a GEC connecting to either the DC + or the DC -.

Also - what do you mean by "a dedicated Grounding Electrode installed"?
Do you mean a dedicated ground wire connected to the DC?
Or when you say "Grounding electrode" are you really talking about a ground rod that they drove in the earth to connect the new subpanel's ground to?
Or the new wire they ran from the new main panel to the ground rod and/or to a clamp connecting to the metal water supply line coming into his house?


I agree with sensij.
Based on the questions you have, you really should hire an electrician to at least supervise your work if not do it for you.
Yes it's probably a few hundred $.
But it'll be well worth it.


IMO the permit guy isn't going to spend a lot of time on your permit. If there's obvious glaring mistakes he'll probably point them out if he notices. But most likely he won't know that much about solar PV. He might know some, having seen other permits come across his desk - but his assumption is that *you* know what you're doing. Same with the inspector - his assumption is that *you* know what you're doing. He's there to do a double check - not to help you with your design. When they question something you should be able to say "Yes, I looked at that and I believe my design does meet code. I believe I can find the correct section of the code that applies for my situation if you have your code book handy."

Possibly the permit guy or the inspector will be helpful (beyond saying "this doesn't meet section xx.xx"). After all they are human, and people are generally helpful when approached the right way.

I understand definitions of EGC and GEC. This is what I have for GEC:
Grounding Electrode Conductor (GEC) - a conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system.
Equipment Grounding Conductor (EGC). The conductive path installed to connect normally non–current carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor, or both.

Let me see if I understand it right. GEC is a conductor that connects to a rod that’s in the earth, and EGC connects to all the equipment together. An EGC shall not be used as a GEC per 250.121. Ultimately, where does EGC connect to? A separate ground rod?


I do not know for a fact if the neighbors array is ungrounded, but he’s system has exactly the same Panels, Inverter, AC disconnect, and even racking equipment (all coincidence). Yes I am aware that grounding can be connected to DC+ or DC-, but since I am doing ungrounded system, it does not apply to me. I will research this topic more.

By "a dedicated Grounding Electrode installed" I mean a rebar rod that is installed in the ground right below the inverter.

I will engage the permit guy into conversation, and I will engage inspector into conversation as well.

Drawing permit and learning code is good learning experience. There will be a licensed electrical contractor when I do the installation. My licensed contractor friend looked at my HVAC electrical work (I replaced entire system), upgrading all the lights in the home, and installing bathroom fans, and everything was per code.

I am mechanical engineer by schooling, and there was a time I worked as a controls engineer. I designed simple electrical systems before. My experience did not have me dealing with NEC code before. Few gaps left to fill in. I like the line in Prometheus movie: "Big Things have Small Beginnings". Thanks for replies.

[samotlietuvis]

Talked to EE's at work, and did some reading / answered my grounding questions. These two are excellent links that explains grounding:

http://www.doityourself.com/forum/electrical-ac-dc/170812-ground-questions.html

http://www.homepower.com/articles/solar-electricity/design-installation/ask-experts-pv-grounding

[CA_Tom]

I was under impression that all Main Service panels have a grounding rod. Now since you mention it, there is nothing but concrete around my main. I will open my Busbar this evening with my electrical contractor friend to see if ground rod is there.

All main panels have a grounding bar - someplace to connect ground wires to.
A ground rod is a piece of steel ~8' long 5/8" diameter, with a copper coating. (and is labeled and sold as "ground rod")

Many panels have a wire that leaves the panel and connects to a grounding rod.
Not all.
For my house the main grounding is the water pipe coming into the house. The only reason I have a grounding rod at my house is that I put one into the soil myself - before that it didn't have one - just had the copper pipes.

Let me see if I understand it right. GEC is a conductor that connects to a rod that’s in the earth, and EGC connects to all the equipment together. An EGC shall not be used as a GEC per 250.121. Ultimately, where does EGC connect to? A separate ground rod?

By "a dedicated Grounding Electrode installed" I mean a rebar rod that is installed in the ground right below the inverter.

EGC connects to the ground bar in the main panel.
EGC includes bare copper wires in your 12-3 romex, ground bar in subpanel, etc.

GEC connects to the ground bar in the main panel.
GEC is the wire to your grounding mechanism (ground rod, plumbing clamp, or ufer ground)

The "rebar rod" should actually be a 5/8" copper covered steel rod (maybe 1/2" copper covered if your AHJ lets you)
If it's actually rebar, just buried in soil that's not up to code. (If it's rebar that's part of an ufer ground, that's another case - but you do an ufer ground when you pour cement foundation - not an afterward thing like when you do a solar install - so I'm sure it's not an ufer ground)

[samotlietuvis]

All main panels have a grounding bar - someplace to connect ground wires to.
A ground rod is a piece of steel ~8' long 5/8" diameter, with a copper coating. (and is labeled and sold as "ground rod")

Many panels have a wire that leaves the panel and connects to a grounding rod.
Not all.
For my house the main grounding is the water pipe coming into the house. The only reason I have a grounding rod at my house is that I put one into the soil myself - before that it didn't have one - just had the copper pipes.



EGC connects to the ground bar in the main panel.
EGC includes bare copper wires in your 12-3 romex, ground bar in subpanel, etc.

GEC connects to the ground bar in the main panel.
GEC is the wire to your grounding mechanism (ground rod, plumbing clamp, or ufer ground)

The "rebar rod" should actually be a 5/8" copper covered steel rod (maybe 1/2" copper covered if your AHJ lets you)
If it's actually rebar, just buried in soil that's not up to code. (If it's rebar that's part of an ufer ground, that's another case - but you do an ufer ground when you pour cement foundation - not an afterward thing like when you do a solar install - so I'm sure it's not an ufer ground)

Thanks for information. It does look like a "rebar rod", but probably it is a copper covered steel rod. Not enough day light to open my Main to see what I got. That will have to wait until the weekend. My SMA 3000TL-US just arrived. Feels like Christmas come early .