Grounding vs. Grounded
- Thread starter cmccabe
- Start date
- Status
- Location
- Massachusetts
You can make always one larger conductors than required.
If you are asking if there is any time the NEC requires a larger grounding than grounded conductor I would say no.
If you are asking if there is any time the NEC requires a larger grounding than grounded conductor I would say no.
mcclary's electrical
Senior Member
- Location
- VA
Welcome to the forum. 250.122 (a) states that the EGC shall not be required to be larger than the circuit conductors.
- Location
- Logan, Utah
Welcome to the forum.
This question is kind of like asking if an apple can be larger than an orange.
The equipment grounding conductor is sized based on the circuits overcurrent protective device in accordance with 250.122.
The circuits grounded conductor is sized based on the maximum unbalanced current of the circuit. (See 210.19(A) for branch circuits, 215.2(A)(1) for feeders and 230.42(C) for service entrance grounded conductors)
Chris
This question is kind of like asking if an apple can be larger than an orange.
The equipment grounding conductor is sized based on the circuits overcurrent protective device in accordance with 250.122.
The circuits grounded conductor is sized based on the maximum unbalanced current of the circuit. (See 210.19(A) for branch circuits, 215.2(A)(1) for feeders and 230.42(C) for service entrance grounded conductors)
Chris
mcclary's electrical
Senior Member
- Location
- VA
It doesn't.
And the grounded conductor normally is bigger than the grounding conductor
- Location
- Massachusetts
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The Nec does not state that at all. It states that the grounding conductor does not need to be larger than the ungrounded conductors.
There are cases where the grounding conductor can be larger than the grounded conductor but generally the grounded conductor is larger than the grounding conductor.
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
Okay, I will bite. When? I ask only to learn.
Hameedulla-Ekhlas
Senior Member
- Location
- AFG
I am agree with others but
There is an important note just below NEC Table 250.122 that is very often overlooked.
It states, "where necessary to comply with seciton 250.4(A)(5) or (B)(4), the equipment grounding conductor shall be sized larger than this table, "Section 250.4(A)(5) states that grounding conductor shall be sized larger than this table." Section250.4(A)(5) states that grounding conductors "shall be capable of safely carrying the maximum ground fault current likely to be imposed on it, "Too many times, equipment grounding conductors are sized according to Table 250.122 without considering these other facts. In this case, the conductor may not be able to safely carry the fault current. As was seen earlier, at a given value of current, the conductor will fuse(melt), the ground is now lost and the equipment case or enclosure would become energized, which would create a shock or electrocution hazard.
- Location
- Massachusetts
250.122(A) makes clear the grounding conductor shall not be required to be larger than the circuit conductors.
Hameedulla-Ekhlas
Senior Member
- Location
- AFG
just please read the given note under table 250.122 page-249 NEC-2008
- Location
- Massachusetts
I did before I posted the first time.
The note says we may need a larger conductor then shown in the table. But 250.122(A) tells us in no case will the EGC be required to be larger than the circuit conductors.
- Location
- Logan, Utah
Yes, but that note does not say the equipment grounding conductors ever have to be larger than the ungrounded conductors.
I can't imagine a scenario where to comply with 250.4(A)(5) or (B)(4) I would have to size the equipment grounding conductor larger than the ungrounded conductors.
That note just reminds a code user that for some installations a larger EGC than required in table 250.122 might be needed to comply with 250.4(A)(5) or (B)(4) for an effective ground fault current path.
Chris
- Location
- Massachusetts
Can you point out the NEC section that specifies exactly what an effective ground fault current path is?
Just how fast does the OCPD have to operate?
Just saying .....
Grounds start getting big when it gets to parallel runs per 250.122(F) - Each parallel grounding equipment conductor shall be sized on the basis of the amperage rating of the overcurrent device protecting the conductors in the raceway or cable in accordance with table 250.122
jumper
Senior Member
- Location
- 3 Hr 2 Min from Winged Horses
I did before I posted the first time.
The note says we may need a larger conductor then shown in the table. But 250.122(A) tells us in no case will the EGC be required to be larger than the circuit conductors.
HE,
I have to agree with Iwire on this. I read the footnote and I do not see where the EGC would need to be bigger than the ungrounded or grounded conductors.
Hameedulla-Ekhlas, thinking we have different sized code books...my Table 250.122 is on page 117. To keep clarity in mind, if we define it by Article and section number, it won't matter what page it is on, we will both be on the same page for gleaning the information.
And am in the boat that the grounded or grounding conductors will not be larger than any of the current carrying conductors that are protected by an ocpd.
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- Location
- Logan, Utah
Can you point out the NEC section that specifies exactly what an effective ground fault current path is?
Just how fast does the OCPD have to operate?
Just saying .....
I agree the requirements in 250.4(A)(5) and (B)(4) are vague and possible unenforceable.
Chris
Can you point out the NEC section that specifies exactly what an effective ground fault current path is?
Just how fast does the OCPD have to operate?
Just saying .....
Bob,
Are you evil?
I can imagine having the Corp. of Engineers hovering over me with documentation from IEEE #142 telling me what an effective ground fault path is....
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