Can someone please help me understand the proper method of grounding/bonding pole mounted DC PV arrays. My experience is limited and I have observed several different installs, none have which have been quite the same when it comes to grounding. Most recently, I was at a site with a pole mounted system, which had a DC disconnect mounted to the pole. The EGC picked up the disconnect and went from there to the inverter, which was located in the house. The panels were weebed to the rails, and there was a #6 bare stranded that picked up the rails, then ran down the pole to a set of ground rods driven at the base of the pole. Is this correct? This tells me that the only thing considered "equipment" here is the DC disconnect, and that the #6 is being used as a GEC (and if so, does this GEC need to be tied into the AC GE system at some point?). Any code references would be greatly appreciated.
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Proper grounding of DC pole mounted systems
- Thread starter csoc64
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jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Grounding and bonding can get pretty complicated. It's hard to argue that there's one way to do it. But here are some comments in response to specific things you mentioned.
- Panels and racking are equipment. All metal parts of a solar array are required to have equipment grounding. WEEBs are a listed method of bonding, and as such are a substitute for a wire EGC.
- The 2008 code requires a grounding electrode at each array. (690.47(D)). Codes before and after do not require it.
- Yes, any grounding electrode at the array is required to be tied to the AC GES. (Not a requirement that everyone agrees with, but it's in the code.) A combined EGC/GEC or combined EGC/bonding jumper can be installed, as long as it meets all the requirements of both, including where it is terminated. Between the 2008 and 2011 code exact interpretations may vary, although I've heard Bill Brooks say that the changes were supposed to be for clarity and not actually change the requirements.
- The EGC and GEC in the installation you described should have been bonded together at some point.
- Panels and racking are equipment. All metal parts of a solar array are required to have equipment grounding. WEEBs are a listed method of bonding, and as such are a substitute for a wire EGC.
- The 2008 code requires a grounding electrode at each array. (690.47(D)). Codes before and after do not require it.
- Yes, any grounding electrode at the array is required to be tied to the AC GES. (Not a requirement that everyone agrees with, but it's in the code.) A combined EGC/GEC or combined EGC/bonding jumper can be installed, as long as it meets all the requirements of both, including where it is terminated. Between the 2008 and 2011 code exact interpretations may vary, although I've heard Bill Brooks say that the changes were supposed to be for clarity and not actually change the requirements.
- The EGC and GEC in the installation you described should have been bonded together at some point.
SolarPro
Senior Member
- Location
- Austin, TX
We just published an article that is relevant to this scenario (plus many others):
http://solarprofessional.com/articl...ompendium-for-pv-systems?v=disable_pagination
See in particular the content related to "Supplemental electrodes" and "Systems with ac and dc grounding requirements."
Also, note that the 2014 NEC will once again require additional electrodes for ground- and pole-mounted PV systems. The Code Making Panel has been going back and forth on this. But I suspect that this will be the final word on the topic.
If you'd like, I can send you a PDF version of the article, which is more conveniently formatted?more reader friendly?than the online version.
http://solarprofessional.com/articl...ompendium-for-pv-systems?v=disable_pagination
See in particular the content related to "Supplemental electrodes" and "Systems with ac and dc grounding requirements."
Also, note that the 2014 NEC will once again require additional electrodes for ground- and pole-mounted PV systems. The Code Making Panel has been going back and forth on this. But I suspect that this will be the final word on the topic.
If you'd like, I can send you a PDF version of the article, which is more conveniently formatted?more reader friendly?than the online version.
PDF would be appreciated
PDF would be appreciated
A PDF would be great. Please advise how I can get you my email address without having to post it on the forum.
PDF would be appreciated
We just published an article that is relevant to this scenario (plus many others):
http://solarprofessional.com/articl...ompendium-for-pv-systems?v=disable_pagination
See in particular the content related to "Supplemental electrodes" and "Systems with ac and dc grounding requirements."
Also, note that the 2014 NEC will once again require additional electrodes for ground- and pole-mounted PV systems. The Code Making Panel has been going back and forth on this. But I suspect that this will be the final word on the topic.
If you'd like, I can send you a PDF version of the article, which is more conveniently formatted?more reader friendly?than the online version.
A PDF would be great. Please advise how I can get you my email address without having to post it on the forum.
SolarPro
Senior Member
- Location
- Austin, TX
Just sent you a PM.
Grounding and bonding can get pretty complicated. It's hard to argue that there's one way to do it. But here are some comments in response to specific things you mentioned.
- Panels and racking are equipment. All metal parts of a solar array are required to have equipment grounding. WEEBs are a listed method of bonding, and as such are a substitute for a wire EGC.
- The 2008 code requires a grounding electrode at each array. (690.47(D)). Codes before and after do not require it.
- Yes, any grounding electrode at the array is required to be tied to the AC GES. (Not a requirement that everyone agrees with, but it's in the code.) A combined EGC/GEC or combined EGC/bonding jumper can be installed, as long as it meets all the requirements of both, including where it is terminated. Between the 2008 and 2011 code exact interpretations may vary, although I've heard Bill Brooks say that the changes were supposed to be for clarity and not actually change the requirements.
- The EGC and GEC in the installation you described should have been bonded together at some point.
Thanks for your help here. A few more questions if I may. I think conceptually I'm struggling with the purpose of the grounding electrode system here. What exactly does the GEC have to pick up? Just the pole? So if I hit my GE, then the pole, can I then run the GEC into my pole mounted combiner box and combine it with the EGC on a ground bar? If so, can I now run a properly sized EGC/GEC to my main panel?
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Thanks for your help here. A few more questions if I may. I think conceptually I'm struggling with the purpose of the grounding electrode system here. What exactly does the GEC have to pick up? Just the pole?
I'm not an engineer, but here's my understanding of the purpose of the GES.
What it does: minimizes the potential difference between ground and the array.
Why this is supposed to be good:
1) increases personal safety by minimizing the chance that someone touching the array will be a lower resistance path to ground for any fault current
2) reduces the chance that stray voltage from nearby lighting will cause damage to the array equipment (because such voltages will have a low resistance path to/from ground, instead of causing arcing across parts).
So far so good, but then comes the question of why it should be tied to the AC grounding electrode back at your house. This seems to be controversial as some people (on other forums) think that tying things together provides a path for lighting to come back to your house, and this is a bad thing. All I can really say on the matter is that the code requires tying them together.
So if I hit my GE, then the pole, can I then run the GEC into my pole mounted combiner box and combine it with the EGC on a ground bar? If so, can I now run a properly sized EGC/GEC to my main panel?
Short answers, yes, and yes. Technically the wire to your main panel is a bonding jumper and must be installed accordingly, see Article 250.
SolarPro
Senior Member
- Location
- Austin, TX
The 2011 and 2014 Code do not require a supplemental grounding electrode for roof-mounted installations.
However, a if you are using a grounded inverter, then you have to have a GEC for the dc side of the system. If the inverter is located on the roof, as might be the case on a commercial installation, then you need to tie into the building steel or install a GE to meet this requirement. Note that the GEC can be accomplished via one of the three methods described in 690.47(C).
However, a if you are using a grounded inverter, then you have to have a GEC for the dc side of the system. If the inverter is located on the roof, as might be the case on a commercial installation, then you need to tie into the building steel or install a GE to meet this requirement. Note that the GEC can be accomplished via one of the three methods described in 690.47(C).
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