The difference in grounding

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mto12345

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I know the NEC definition of these: Grounded conductor, EGC (Equipment grounding conductor) and GEC (grounding electrode conductor) and they are determined based on NEC Table 250.102(C)(1), Table 250.122 and Table 250.66, respectively. However, I am uncertain as to whether they are all required for my application. For instance, I know that when you have parallel runs then the ground wire is not required (what NEC Code is this?) but not certain with clarity what is needed. For instance, the service disconnect what ground is need (NEC code?), for the transformer secondary cable (4 #300kcmill) does one of the conductors act like a ground (NEC code?). Also a schematic drawing example would help, cause I have read a lot of explanations but nothing that really shows all these three grounds at a time pictorially.

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augie47

augie47

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From a utility transformer up to your service disconnect the grounded (neutral) conductor serves all grounding needs. Bonding jumpers might be needed to ground raceways (250.102)..
Your question mark on your GEC ..GEC are size per 250.66 with a 3/0 maximum size and reduced sizes are allowed to ground rods and UFER grounds.
Grounding on the load side of your service disconnect is governed by 250.122

I know of no Code Section that supports your statement "I know that when you have parallel runs then the ground wire is not required"
As noted above EGCs are not required on service as the neutral is also the ground but, on other than service, grounding conductors are normally required albeit the raceway may be he grounding conductor (250.118)

It might be worth noting on your diagram the "ground" on the secondary side of your 75kva transformer is shown as a #4. In fact, that conductor would be a SSBJ {250.30(A)(2)}and sized by 250.102and should be a #2 based on your 3/0 phase conductors and the transformer needs a GES (That appears to be mentioned in the notes below the transformer but is not shown on the diagram)
 
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mto12345

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Location
Atlanta
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Engineer
augie47 said:
From a utility transformer up to your service disconnect the grounded (neutral) conductor serves all grounding needs. Bonding jumpers might be needed to ground raceways (250.102)..
Your question mark on your GEC ..GEC are size per 250.66 with a 3/0 maximum size and reduced sizes are allowed to ground rods and UFER grounds.
Grounding on the load side of your service disconnect is governed by 250.122

I know of no Code Section that supports your statement "I know that when you have parallel runs then the ground wire is not required"
As noted above EGCs are not required on service as the neutral is also the ground but, on other than service, grounding conductors are normally required albeit the raceway may be he grounding conductor (250.118)

It might be worth noting on your diagram the "ground" on the secondary side of your 75kva transformer is shown as a #4. In fact, that conductor would be a SSBJ {250.30(A)(2)}and sized by 250.102and should be a #2 based on your 3/0 phase conductors and the transformer needs a GES (That appears to be mentioned in the notes below the transformer but is not shown on the diagram)
Click to expand...
Thanks for clearing this up, I really appreciate it.
 
T

Tulsa Electrician

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Tulsa
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Electrician
Note: the 3/0 ground (GEC) was clouded in.
Most likely a revision and hopefully a grounding detail.

Does no good to attach a SDS transformer GEC to the building unless it's part of the GES.
The grounding detail if available will help with that.

I do see in the upper right corner ground detail.
How about a pic of that
 
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