Leave, remove, ignore?

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Industrial is expanding a building and local codes have changed enough that they are now required to provide at least a single line drawing of the electrical system to the city. We put the service in years ago and the plant electrician has done the work since then. They had installed a 601 amp feeder in preparation for this expansion and to feed some equipment along the way. Three 2" emt conduits with 3/0 phase conductors and a #4 EG in each. I mentioned that they should have had 1/0 EGs, if used. Their question is "Remove the EGs completely, cut them off, or just leave it alone?" (Most likely the building officials won't catch it anyway.)
 
I have run into similar situations a few times and when discussed with other inspectors, the majority have voted to "remove".
 
ptonsparky said:
Industrial is expanding a building and local codes have changed enough that they are now required to provide at least a single line drawing of the electrical system to the city. We put the service in years ago and the plant electrician has done the work since then. They had installed a 601 amp feeder in preparation for this expansion and to feed some equipment along the way. Three 2" emt conduits with 3/0 phase conductors and a #4 EG in each. I mentioned that they should have had 1/0 EGs, if used. Their question is "Remove the EGs completely, cut them off, or just leave it alone?" (Most likely the building officials won't catch it anyway.)
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Is a feeder that is 3 sets of 3/0 rated for 601 amps?

3/0 @ 75?c is good for 200 amps.

600 amp is a standard size.

I think that for a rating of 601 amps, 4/0 would have to be used.
 
Going against the majority, I'd try and push it through with them left in place. Then remove them, if that failed.

I'd still take three undersized wire EGC's in conjunction with the EMT, than EMT alone. I've seen way to many arced locknuts at boxes and panels to trust everyone to tighten ALL their locknuts and couplings/connectors EVERY time. But that's just my opinion...
 
tkb said:
Is a feeder that is 3 sets of 3/0 rated for 601 amps?

3/0 @ 75?c is good for 200 amps.

600 amp is a standard size.

I think that for a rating of 601 amps, 4/0 would have to be used.
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Looking at Table 250.122 I see that if my overcurrent device does not exceed 800 Amps I can use 1/0 cu for an equipment ground. 601 is less than 800.

I see what you saying about the 600 amp, but throw in that we are suppling motor loads and that should help.
 
ptonsparky said:
Looking at Table 250.122 I see that if my overcurrent device does not exceed 800 Amps I can use 1/0 cu for an equipment ground. 601 is less than 800.

I see what you saying about the 600 amp, but throw in that we are suppling motor loads and that should help.
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I agree on the EGC that it should be 1/0 for a 601 amp feeder.

ptonsparky said:
I don't understand how you came up with 4/0,
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The 3 x 3/0 parallel feeder conductors are only rated for 600 and not 601.
To be correct for 601 amps, and since there are 3 sets paralleled, the phase conductors should be 4/0 since 3/0 is only good for 200 amps @ 75?c.

Per 240.4(B) the conductor cannot be sized larger that the next standard size.
Since the parallels are good for 600 amps you cannot go up the the next size of 601 amps without increasing the size to 4/0 per parallel.

If you are going to use the logic that it's close enough, then #1 would be good enough for the EGC.
 
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ptonsparky said:
Be they 3/0, 4/0, or 500s they are still fused at 601 amps, which is no more than 800.
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240.4(B) only allows you to protect a conductor up to the next highest standard size.
Since 600 is a standard size, you cannot protect a parallel feeder that has an ampacity of 600 amps at higher than the standard size of 600 amps.
 
You gotta be kidding me.
You gonna trip over ONE WHOLE AMP?
And we're not talking a 5A fuse, we're talking a 600A. ONE WHOLE AMP means 1/600th of the rating. I SERIOUSLY DOUBT the breaker has that low of a tolerance. Are you telling me a 600A fuse/breaker has that awesome calibration that it works on 1/600th ???
Give me a break.
Breakers and fuses are inverse proportional, meaning the lower the amperage over, the longer it takes to trip, and vice versa, the higher the amperage over the rating the faster it takes to trip. Most breaker fuses will go a good 20% over their rating for 10-15 min. So yeah, that 1 WHOLE AMP will really make a difference.
But Hey, let's spend an extra thousand on fuses just because we've lost our freaking loving mind about COMMON SENSE.


tkb said:
If you are going to use the logic that it's close enough, then #1 would be good enough for the EGC.
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Strife said:
You gotta be kidding me.
You gonna trip over ONE WHOLE AMP?
And we're not talking a 5A fuse, we're talking a 600A. ONE WHOLE AMP means 1/600th of the rating. I SERIOUSLY DOUBT the breaker has that low of a tolerance. Are you telling me a 600A fuse/breaker has that awesome calibration that it works on 1/600th ???
Give me a break.
Breakers and fuses are inverse proportional, meaning the lower the amperage over, the longer it takes to trip, and vice versa, the higher the amperage over the rating the faster it takes to trip. Most breaker fuses will go a good 20% over their rating for 10-15 min. So yeah, that 1 WHOLE AMP will really make a difference.
But Hey, let's spend an extra thousand on fuses just because we've lost our freaking loving mind about COMMON SENSE.
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601 amp would be a fuse so they can use an 800 amp disconnect for a 600 amp feeder much like using a larger frame breaker with a smaller trip setting and according to the NEC it is a violation, but I thought we we talking about the NEC and not common sense. :roll:

Why would you size the EGC for an 800 amp feeder if the phase conductors are sized for a 600 amp feeder?
 
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I say leave and ignore.... what's it gonna hurt? I would think it would be an improvement over not existing.
 
NEC is written by people.
Again my question is: Do you really believe a fuse has 1/600th tolerance? That's almost 1/10th of a percent.
I don't know why they have 600A and 601A fuses, but do you really believe that (taking 1000 fuses of each) the 600A fuse will trip any faster (for any practical and safe purpose) than a 601A?

tkb said:
601 amp would be a fuse so they can use an 800 amp disconnect for a 600 amp feeder much like using a larger frame breaker with a smaller trip setting and according to the NEC it is a violation, but I thought we we talking about the NEC and not common sense. :roll:

Why would you size the EGC for an 800 amp feeder if the phase conductors are sized for a 600 amp feeder?
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Strife said:
NEC is written by people.
Again my question is: Do you really believe a fuse has 1/600th tolerance? That's almost 1/10th of a percent.
I don't know why they have 600A and 601A fuses, but do you really believe that (taking 1000 fuses of each) the 600A fuse will trip any faster (for any practical and safe purpose) than a 601A?
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You quoted the reason for the 601 amp fuse, below

tkb said:
601 amp would be a fuse so they can use an 800 amp disconnect for a 600 amp feeder much like using a larger frame breaker with a smaller trip setting and according to the NEC it is a violation, but I thought we we talking about the NEC and not common sense. :roll:

Why would you size the EGC for an 800 amp feeder if the phase conductors are sized for a 600 amp feeder?
Click to expand...
 
realolman said:
I say leave and ignore.... what's it gonna hurt? I would think it would be an improvement over not existing.
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As I understand 250.122(F) the EGC is sized in each raceway so that it could carry the total amount of fault current for a sufficient time to allow the OCPD to clear the fault and do so without damaging the other conductors within the raceway.

If the EGC is undersized (as the example from the OP) it could damage the surrounding conductors. Not trying to say that it WILL happen but that is my understanding.

Pete
 
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Cow said:
Going against the majority, I'd try and push it through with them left in place. Then remove them, if that failed.

I'd still take three undersized wire EGC's in conjunction with the EMT, than EMT alone. I've seen way to many arced locknuts at boxes and panels to trust everyone to tighten ALL their locknuts and couplings/connectors EVERY time. But that's just my opinion...
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I would tend to lean that way too.
 
pete m. said:
As I understand 250.122(F) the EGC is sized in each raceway so that it could carry the total amount of fault current for a sufficient time to allow the OCPD to clear the fault and do so without damaging the other conductors within the raceway.

If the EGC is undersized (as the example from the OP) it could damage the surrounding conductors. Not trying to say that it WILL happen but that is my understanding.

Pete
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Isn't the EMT sufficient for the EGC without the undersized EGC's
 
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