Equipment Grounding Conductor Used As Grounding Electrode Conductor

Status
Not open for further replies.
C

chris huckins

Member
Location
collinsville,il
In the 2011 NEC Article 250.121 says "An equipment grounding conductor shall not be used as a grounding electrode conductor". I'm thinking about a 480 volt, 3 phase combination motor starter that incorporates a step down, single phase control transformer 480v-120v. A jumper is installed on the secondary side from the grounded terminal (X2) to the case of the motor starter, so does this now violate 250.121 because we are using the equipment grounding conductor,wire, installed with the circuit feeding the motor starter as a grounding electrode conductor?
 
That helped a lot, thank you. Since I'm asking, I have another confusing topic causing discussion in my code class. Article 250.12 talks about additional bonding when encountering non-conductive coatings. On the same motor starter(we are using it as a trainer, no voltage applied) we are using 1/2" metallic flexible conduit from motor starter to motor as the raceway. We are using reducing washers at the motor starter(3/4" hole, 1/2" flex) and at the motor the flex connector is threaded into the pecker head. Does this flex require additional bonding at the motor starter due to reducing washers and painted surface for a 480v motor? 208v motor?
 
I would look at 250.97 which requires special bonding of circuits where the voltage is over 250V to ground. I don't believe you have an issue here unless the OCPD is greater than 20 amps. I would look at 250.118(7).
 
chris huckins said:
That helped a lot, thank you. Since I'm asking, I have another confusing topic causing discussion in my code class. Article 250.12 talks about additional bonding when encountering non-conductive coatings. On the same motor starter(we are using it as a trainer, no voltage applied) we are using 1/2" metallic flexible conduit from motor starter to motor as the raceway. We are using reducing washers at the motor starter(3/4" hole, 1/2" flex) and at the motor the flex connector is threaded into the pecker head. Does this flex require additional bonding at the motor starter due to reducing washers and painted surface for a 480v motor? 208v motor?
Click to expand...

250.96 Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non-current-carrying parts that are to serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating shall be removed at threads, contact points, and contact surfaces or be connected by means of fittings designed so as to make such removal unnecessary.

Also consider

250.118 Types of Equipment Grounding Conductors. The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:

If used to connect equipment where flexibility is necessary to minimize the transmission of vibration from equipment or to provide flexibility for equipment that requires movement after installation, an equipment grounding conductor shall be installed.
 
Just looking at the definitions of an EGC and GEC in the NEC 2008 while keeping your tongue from wrapping around your eye tooth which would blur your vision hence understanding and at the same time while comparing those to the OP.Thats the way we do it,always have,I don't think NEC 2011 changed anything,,,,,I'm not confused but I wouldn't bet that the world was round either.:huh:

dick
 
If the motor housing is non conductive you can scrape the paint or use a bonding bushing along with an egc. Many locknuts are suitable for grounding as they bite into the paint.
 
Status
Not open for further replies.
Top