Ground Electrode at Ground Mounts / 690.47(A)

[am1954]

Am I interpreting 690.47(a) of 2017 NEC correctly in assuming that our ground mounted arrays should now have two ground electrodes installed (since the rack is considered a 'structure supporting PV array')? We usually build them on helical piles and galvanized pipe, but the piles usually only go about 4' or 5' into the ground.

Also, in scenarios where we have more than one ground mounted arrays located near each other (less than 10' or so), should we be putting (2) grounding electrodes at each array? The arrays are bonded to each other via an EGC.

(A) Buildings or Structures Supporting a PV Array. A building or structure supporting a PV array shall have a grounding electrode system installed in accordance with Part III of Article 250.

 

[jaggedben]

Yes, if you are using rods then you need two of them to fulfill NEC requirements.

Personally think it's a bit ridiculous if you also have a whole bunch of steel helical piers in the ground, since they make a lot more electrical contact and should also be bonded anyway. But unless you make one of them 10ft deep then the rods is what the code requires.

 

[solarken]

I interpret the 250.52(A)(2) one or more metal in-ground support structures in direct contact with the earth vertically for 10ft or more as being met by two helical piles at a depth of 5 ft, and they are bonded together by the metal structure. So the only other thing needed is the EGC run with the PV conductors to the inverter. I suppose to be safe you could drive an 8 foot electrode as well and bond that to the structure.

 

[jaggedben]

I interpret the 250.52(A)(2) one or more metal in-ground support structures in direct contact with the earth vertically for 10ft or more as being met by two helical piles at a depth of 5 ft, and they are bonded together by the metal structure. So the only other thing needed is the EGC run with the PV conductors to the inverter. I suppose to be safe you could drive an 8 foot electrode as well and bond that to the structure.

Unfortunately 250.52(A)(2) quite explicitly refers to 'at least one structural member' that is 10ft in the earth. You cannot combine the lengths of multiple members.