We installed security lighting on a number of storage shed buildings. These are buildings consisting of individual storage areas (ex: 8 per building) The lighting circuit is taken from a main building underground and comes up at each building with the light fixture controlled by a photo cell. There is no wiring inside of the storage sheds except for one that has a receptacle. The local inspector wants two ground rods installed at each building. I cannot find any requirement for this in the code and I'm wondering if any of you out there can shed (no pun intended)a little light on this situation. I feel no ground rods would be required since there is only one circuit and none of the wiring is installed inside of the sheds. Thanks in advance Ron
Thank you, Ryan. Your info was of great help. Not sure what you mean by using a multiwire branch circuit and call it one circuit. To me a multiwire branch circuit is two or more circuits which would require the ground rods at each building in which I would install the multiwire branch circuit. Thanks again Ron
Re: Ground rods at each building#89569 10/08/0412:49 AM10/08/0412:49 AM
Exception: A grounding electrode at separate buildings or structures shall not be required where only one branch circuit supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the conductive non–current-carrying parts of all equipment.
Sounds like you need a ground wire too, for that exception. But I see a multi-wire as one ciruit if they are a tied breaker, as well. Good luck, or it sounds like a a time to rent a 50lbs jack hammer, they drop rods fast!
Mark Heller "Well - I oughta....." -Jackie Gleason
Re: Ground rods at each building#89570 10/08/0402:17 AM10/08/0402:17 AM
A multiwire branch circuit is considered a single circuit for this application. Read the last sentence in 225.30. Multi-pole breakers or handle ties on individual breakers are not required. If only one multiwire circuit supplies each building a grounding electrode is not required. A disconnect is required for each building (255.33).
Re: Ground rods at each building#89571 10/08/0409:33 AM10/08/0409:33 AM
Take a look at 210.4, where is says that a multiwire is permitted to be considered multiple circuits. If that is permitted, than by using the english language, the contrary is true as well...a multiwire branch circuit can be considered one circuit.
Ryan Jackson, Salt Lake City
Re: Ground rods at each building#89572 10/09/0412:07 PM10/09/0412:07 PM
If we look at the Article 100 definition of mutiwire branch circuit we see that it is defined as a circuit not circuits
Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.
Bob Badger Construction & Maintenance Electrician Massachusetts
Re: Ground rods at each building#89573 10/09/0405:28 PM10/09/0405:28 PM
As Bob has noted, a multiwire branch circuit is just that 'a' branch circuit as per Art 100. There are other locations in the NEC that permit the use of a multiwire branch circuit as more than one circuit. Knowing these locations and how to understand them is a good benefit to understanding the NEC. 210.4 permits the use of a multiwire branch circuit as more than one - a good place we see this regularly is in kitchens for the small appliance branch circuits.