Equipment grounding conductor sizes when tapping

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Tainted

Tainted

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1600 amp service switch with 1600 amp fuses feeds a switchboard. I 10 ft tap ahead of this switchboard and install a standalone 800 amp switch with 750 amp fuses to feed a load.

I know that on the load side of 800 amp switch the equipment grounding conductor needs to be 1/0.

But should the equipment grounding conductor between the switchboard and 800 amp switch be 1/0 or 4/0? (all conductors are copper)
 
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The tap is on the line side of the existing service equipment? There are no EGCs run with service conductors.
That would mean the 800 amp switch is also service equipment and has to be grouped with the 1600 service switch.
 
Tainted said:
1600 amp service switch with 1600 amp fuses feeds a switchboard. I 10 ft tap ahead of this switchboard and install a standalone 800 amp switch with 750 amp fuses to feed a load
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Sounds like the tap is after the 1600 amp switch?
 
If the conductors are on the load side of an overcurrent device you would size the EGC per 250.122 (based on the OCP device on the line side of the tap)with a full size in each raceway with the "exception" that the EGC does not need to be larger than the phase conductor.
 
Tainted said:
Correct, service switch and switchboard is seperate
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Your first post says "10 ft tap ahead of this switchboard". Being separate is not the question. The question is where the conductors to the 800 amp switch connect to the power.
 
Another question will be what type of conductors are being tapped? Busbars or multiple sets of wire conductors?
 
augie47 said:
If the conductors are on the load side of an overcurrent device you would size the EGC per 250.122 (based on the OCP device on the line side of the tap)with a full size in each raceway with the "exception" that the EGC does not need to be larger than the phase conductor.
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so does this mean it has to be 4/0?
 
As I read it, yes. (would not be my 1st mistake)
From 250.122 A (General)
.......................................shall not be smaller than shown in Table 250.122, but in no case shall they be required to be larger than the circuit conductors supplying the equipment...........................................
 
Tainted said:
got it, thanks! So let's pretend that the phase conductors are 2/0, this would be that the EGC needs to be 2/0?
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Parallel #2/0's are not the size of the phase conductors. It's the aggregate of the multiple sets not ths smallest conductors you can parallel together.
 
For conversations sake, if hr ran (4) sets of 2/0 to supply his 800 (750) amp switch then his EGC would only need to be 2/0, correct ?
(Even though a 1600 calls for 4/0)
 
augie47 said:
For conversations sake, if hr ran (4) sets of 2/0 to supply his 800 (750) amp switch then his EGC would only need to be 2/0, correct ?
(Even though a 1600 calls for 4/0)
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The EGC would be required to be #4/0. If the circuit conductors were a single set of #2/0's then #2/0 would be the largest required. According to T250.122 #2/0 is insufficient to carry the fault current for a 1600 amp OCPD ahead of the feeder.
 
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