Bonding PV ground to detached garage Grounding Electrode

[goldfinch.electric]

Hi, I am installing a DC PV system on a detached garage. The garage has a 100 amp sub-panel run from the house and an auxiliary grounding electrode. My question is about bonding the PV overcurrent/disconnect panel to the #6 bare copper going to the grounding electrode of the garage. We also have run a EGC back to the inverter in the main house, where all will be bonded. We are on 2020 code cycle. Question. I installed a bond from the DC disconnect in the garage to the AC garage sub-panel grounding conductor. Is this bond needed or recommended? Thanks in advance for any thoughts on this confusing topic.



690.47 "A building or structure(s) supporting a PV system shall utilize a grounding electrode system installed in accordance with Part III of Article 250."
Check. The garage has its own GE installed.

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690.43 Exposed noncurrent-carrying metal parts of PV module frames, electrical equipment, and conductor enclosures of PV systems shall be connected to an equipment grounding conductor in accordance with 250.134 or 250.136, regardless of voltage. Equipment grounding conductors and devices shall comply with 690.43(A) through (D).

 

[pv_n00b]

The DC equipment needs an EGC bonding all the metal together. You need to bond the PV equipment in the garage to the garage grounding electrode. You also need to run an EGC from the module rack with the DC conductors and land on the ground terminal in the inverter.
The problem is when you cross the line between buildings with part of the PV system in on and part in the other. Now you are interconnecting the ground electrode systems of the two buildings.

 

[jaggedben]

It seems like you are saying that you have a DC-output array on the garage and the inverter at a different building (the house), in which case I'd say the grounding electrode conductor you installed from the DC disconnect is code required. It's not necessarily great to create a ground loop like that, but for most purposes it shouldn't cause problems and the code arguably requires it.

 

[goldfinch.electric]

Yes, the inverter is in a different building and there is a EGC running with the DC conductors back to the inverter in the main house. If I need a grounding electrode conductor from the DC disconnect, and there is a Ufer 6" away for the AC subpanel, am I creating a hazard by tying into the buildings GEC rather than running my own. Thanks for the replies.

 

[jaggedben]

Yes, the inverter is in a different building and there is a EGC running with the DC conductors back to the inverter in the main house. If I need a grounding electrode conductor from the DC disconnect, and there is a Ufer 6" away for the AC subpanel, am I creating a hazard by tying into the buildings GEC rather than running my own. Thanks for the replies.

No you are not creating a hazard by tying everything to one electrode system. There is potentially more hazard in having separate electrodes that might develop a voltage between them. This is why the code requires all electrodes at a structure to be tied together, it generally prohibits having separated electrodes. (Auxiliary electrodes aside, but that doesn't apply here.)