# How many grounds for 52 x 20A plug circuits in a warehouse?



## denny3992 (Jul 12, 2010)

1- and if u feel fancy, make it a #10


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## CRStarbird (Jun 16, 2014)

NEC will allow one? Any chance you can cite the section of the code book?


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## 480sparky (Sep 20, 2007)

CRStarbird said:


> NEC will allow one? Any chance you can cite the section of the code book?
> 
> Sent from my iPad using Tapatalk


Nothing to cite. NEC is a permissive document. If it doesn't say otherwise, it would be legal. Since there's no requirement to install a separate ground for each individual circuit, one is all that's required.


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## CRStarbird (Jun 16, 2014)

Well that makes my life easier than I thought. Thanks for the help!


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## TQuade (Jan 22, 2010)

It says in the nec you can run just 1 look under 250.122 (c) Multiple Circuits. Where a single equipment grounding conductor is run with multiple circuits in the same raceway,cable,or cable tray, it shall be sized for the largest over current device protecting the conductors in the raceway,cable,or cable tray. 

Then if you see 250.122(1) it references you to the chart for wire size.

Max circuit breaker feeding your raceway is 20a you run 1-#12 for all 52 of your circuits just set some ground bars every couple feet in your trough and jump them out to carry the bond down the length of your trough and bring all your grounds to them.


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## ElectricJoeNJ (Feb 24, 2011)

How many conduits are feeding the trough or is the trough going straight to the panel?


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## CRStarbird (Jun 16, 2014)

Single pipe straight from the panel to the trough


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## ElectricJoeNJ (Feb 24, 2011)

CRStarbird said:


> Single pipe straight from the panel to the trough Sent from my iPad using Tapatalk


 Single pipe with 104 CCC's or 78 if your sharing neutrals. That's a lot of derating. Hell of a lot of 6 wire


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## 480sparky (Sep 20, 2007)

ElectricJoeNJ said:


> Single pipe with 104 CCC's or 78 if your sharing neutrals. That's a lot of derating. Hell of a lot of 6 wire



52 circuits can be 70 conductors if it's 3-phase.


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## Pete m. (Nov 19, 2011)

Don't forget this little gem:

*376.22 Number of Conductors and Ampacity.* The number of conductors and their ampacity shall comply with 376.22(A) and (B).

*(A) Cross-Sectional Areas of Wireway.* The sum of the cross-sectional areas of all contained conductors at any cross section of a wireway shall not exceed 20 percent of the interior cross-sectional area of the wireway.

*(B) Adjustment Factors.* The adjustment factors in 310.15(B)(3)(a) shall be applied only where the number of current-carrying conductors, including neutral conductors classified as current-carrying under the provisions of 310.15(B)(5), exceeds 30. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.

Pete


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## CRStarbird (Jun 16, 2014)

So does the NEC define EMT and the wire trough the same way? If I split the conductors up, will I need to derate the same once they come together in the trough as if they were all in the same pipe?


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## ElectricJoeNJ (Feb 24, 2011)

480sparky said:


> 52 circuits can be 70 conductors if it's 3-phase.


I didn't bother mentioning that because once your over 41 it's maxed at a %35 derate factor


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## ElectricJoeNJ (Feb 24, 2011)

CRStarbird said:


> So does the NEC define EMT and the wire trough the same way? If I split the conductors up, will I need to derate the same once they come together in the trough as if they were all in the same pipe? Sent from my iPad using Tapatalk


 No. It applies to circular raceways. The article for metal wire ways was posted above, but it would still apply in your case because your over 30 CCC's


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## TQuade (Jan 22, 2010)

CRStarbird said:


> So does the NEC define EMT and the wire trough the same way? If I split the conductors up, will I need to derate the same once they come together in the trough as if they were all in the same pipe? Sent from my iPad using Tapatalk



Look in the code book and find out.
310.15(b)(3)(a) adjustment factors for more than three current carrying conductors.
Table 4 conduit or tubing fill
366.22 (a) and (b) tells you how to calculate the trough size
366.23(a) and (b) tells you how to derate the amps of your wires, 30 or less 310.15(b)(3)(a) don't apply but it does apply to the pipe you fed it with and what you get when you derate for that applies for the whole run.


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## CFL (Jan 28, 2009)

Is the wireway listed as suitable for grounding. Not sure if I worded that correctly, but if it is you don't need any grounding conductor.


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## varmit (Apr 19, 2009)

If your conduit from the panel to the wireway is more than 36 inches long, you would need to do some major derating.


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## 480sparky (Sep 20, 2007)

varmit said:


> If your conduit from the panel to the wireway is more than 36 inches long, you would need to do some major derating.



36"?


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## varmit (Apr 19, 2009)

Even if you divided the conductors from the panel into two conduits you would still derate down to 40% for the conduit portion. (25 amp x .4 =10 amp limit)


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## TQuade (Jan 22, 2010)

varmit said:


> If your conduit from the panel to the wireway is more than 36 inches long, you would need to do some major derating.


It's 24"


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## TQuade (Jan 22, 2010)

And at 24" adjustment factors don't apply up to 60% fill


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## varmit (Apr 19, 2009)

TQuade said:


> It's 24"


Brain cell misfire. Oops


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## Southeast Power (Jan 18, 2009)

CRStarbird said:


> Hey everybody, I am running 52 x 120v 20a circuits with SO cable drops throughout a warehouse. I have 165' of wire trough, piping out every 20' to 2 4S boxes on each side of the trough. I have a neutral for each box, and 2 circuits per box. I'm trying to figure out the minimum number of ground wires to pull through the trough from the 120/208v 3-phase panel while still being up to code. Any ideas? An NEC book section would be awesome too!
> 
> Thanks!
> 
> ...


No ground required. If you want to go crazy use one.
The problem I see here is with the design. 
I think it might be an issue with the neutrals more than anything we have discussed.
You will have about 8 locations, two at each location each sharing a neutral?
32 phase conductors and 16 neutrals I get 48 conductors.
What did I miss?
165' one box on each side one setup on each side with 2 phase conductors and a neutral. Maybe I missed a drop.
I think it would be fun to set up the wire pull.


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## 480sparky (Sep 20, 2007)

jrannis said:


> ........
> 32 phase conductors and 16 neutrals I get 48 conductors.
> What did I miss?
> ........


20 circuits....... that's what you missed.


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## TQuade (Jan 22, 2010)

Not sure about the no ground required. Pipe I can understand using as a ground path but I would use a ground busing with a tail or pull a ground regardless. I don't believe you can use trough as a path because of how thin it is your gonna have to have it thick enough to drill and tap holes to have at least 2 threads for proper grounding based off the NEC correct me if I'm wrong, just shooting from memory.


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## ElectricJoeNJ (Feb 24, 2011)

jrannis said:


> No ground required. If you want to go crazy use one. The problem I see here is with the design. I think it might be an issue with the neutrals more than anything we have discussed. You will have about 8 locations, two at each location each sharing a neutral? 32 phase conductors and 16 neutrals I get 48 conductors. What did I miss? 165' one box on each side one setup on each side with 2 phase conductors and a neutral. Maybe I missed a drop. I think it would be fun to set up the wire pull.





CRStarbird said:


> I have 165' of wire trough, piping out every 20' to 2 4S boxes on each side of the trough. I have a neutral for each box, and 2 circuits per box


 two 4 squares on each side


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## 480sparky (Sep 20, 2007)

tquade said:


> not sure about the no ground required. Pipe i can understand using as a ground path but i would use a ground busing with a tail or pull a ground regardless. I don't believe you can use trough as a path because of how thin it is your gonna have to have it thick enough to drill and tap holes to have at least 2 threads for proper grounding based off the nec correct me if i'm wrong, just shooting from memory.



*250.118 Types of Equipment Grounding Conductors.* 
The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
(13) Other listed electrically continuous metal raceways
and listed auxiliary gutters.


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## TQuade (Jan 22, 2010)

480sparky said:


> 250.118 Types of Equipment Grounding Conductors. The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following: (13) Other listed electrically continuous metal raceways and listed auxiliary gutters.


That's what I'm saying I can't see what he's using but all the trough that's listed for grounding has grounding locations on it either holes or tails


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## 480sparky (Sep 20, 2007)

TQuade said:


> That's what I'm saying I can't see what he's using but all the trough that's listed for grounding has grounding locations on it either holes or tails



No holes or tails required. The EGC can be the EMT between the trough and the panel.


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## TQuade (Jan 22, 2010)

480sparky said:


> No holes or tails required. The EGC can be the EMT between the trough and the panel.


I see what your saying but since it's a metal raceway it's gonna have to have provisions for connecting an equipment grounding conductor if it is one that's listed for being used as such.

Article 386
Surface metal raceways
386.60 grounding Surface metal raceway enclosures providing a transition from other wiring methods shall have a means for connecting an equipment grounding conductor


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## TOOL_5150 (Aug 27, 2007)

varmit said:


> Brain cell misfire. Oops


Thats the strapping requirement. :thumbup:


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## Bad Electrician (May 20, 2014)

Just my opinion but it seems some additional thought should be put into this layout to avoid a hack stamp.


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