Detached garage, 100 amp single phase 120/240v sub-panel, 360 feet away and I am figuring voltage drop. Got that but I was wondering if I had to also upgrade the GEC? Seems like I have seen this in the code that it must also be upgraded by I'll be darned if I can find it.
Voltage drop and GEC
- Thread starter Mtybee
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
The detached structure should have its own GES making the GEC quite short. If you meant EGC with the feeder than yes that needs to be increased in size if you increase the size of the ungrounded conductors. {250.122(B)}
Paul1955
Member
- Location
- Trinity, Alabama
You may be thinking of 250.122(B) in the 2014 NEC.
- Occupation
- Licensed Electrician
What are you using as a load value to figure your voltage drop?
kwired
Electron manager
- Location
- NE Nebraska
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- EC
250.66. Grounding electrode conductors are sized in accordance with the incoming service or feeder conductors to a building or structure.
You said you have 100 amp supply, but are likely increasing conductors size because of voltage drop. 250.66 don't care what the overcurrent protection is, it looks at the supply conductor size, so if you increased to 1 or 1/0 copper or 2/0 or 3/0 aluminum, what normally could have been an 8AWG GEC now must be at least 6 AWG. If you increased to 2/0 copper or 4/0 aluminum supply conductors you would need a 4 AWG GEC, even though you still have a 100 amp breaker on the supply side.
As others have mentioned already your EGC with the feeder needs increased as well if you increased ungrounded conductors because of voltage drop.
You said you have 100 amp supply, but are likely increasing conductors size because of voltage drop. 250.66 don't care what the overcurrent protection is, it looks at the supply conductor size, so if you increased to 1 or 1/0 copper or 2/0 or 3/0 aluminum, what normally could have been an 8AWG GEC now must be at least 6 AWG. If you increased to 2/0 copper or 4/0 aluminum supply conductors you would need a 4 AWG GEC, even though you still have a 100 amp breaker on the supply side.
As others have mentioned already your EGC with the feeder needs increased as well if you increased ungrounded conductors because of voltage drop.
publicgood
Senior Member
- Location
- WI, USA
EGC proportionally to upsize of ungrounded conductors. GEC by 250.66. Seems there is a consensus here.
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