200 amp sub panel

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san diego
Hi Guys, i am installing a new 3 phase 4 wire sub panel in a heavy equipment workshop, the main panel is outside the building so i am running in 60 feet of 2 inch emt and 4 #3/0 and a #6 grd. At the main panel i am fitting a 200 amp breaker does the new sub panel i am installing need a main breaker ?, and if i drop a grd rod at the sub panel will that do instead of pulling in 60 feet of #6 grd.
Also is a bolt in breaker panel required for Industrial, Commercial or will a stab in panel do. Thanks in advance for the replies.
 

Dennis Alwon

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Chapel Hill, NC
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Retired Electrical Contractor
When you say outside the building do you mean it is in a different structure unattached to the building with the main panel? If yes then it would need either a main or no more than 6 disconnects to disconnect the structure. It will also need ground rods.
 
Location
san diego
200 amp sub panel

The Main is outside the building but attached to the building therefore same structure do i need to pull the #6 grd or can i drop in a grd rod. Thanks for the quick response.
 

infinity

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New Jersey
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The Main is outside the building but attached to the building therefore same structure do i need to pull the #6 grd or can i drop in a grd rod. Thanks for the quick response.

You must have an EGC run with the feeder conductors. In this case your EMT can serve as the EGC. You can never use only a ground rod! It will not do anything to clear a fault.
 

Dennis Alwon

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Chapel Hill, NC
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A ground rod is not needed if it is attached to the structure. Whether you choose to run an egc in emt is up to you. It is not required .. 358.60
 
Location
san diego
200 amp sub and derating

200 amp sub and derating

I just realised another potential issue with my installation, if i have a 3 phase 4 wire 120/208 supply and i have a 2 inch EMT run to my 200 amp sub panel. There is only one 3 phase 208v 60 amp load on this system, and one single phase 208v 30 amp load the rest are single phase 120v loads to specific machines and general use outlets. Does this mean that i have to count the neutral as a ccc thererfore meaning that 3/0 are only rated at 180 amps.
 

Little Bill

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Tennessee NEC:2017
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Semi-Retired Electrician
I just realised another potential issue with my installation, if i have a 3 phase 4 wire 120/208 supply and i have a 2 inch EMT run to my 200 amp sub panel. There is only one 3 phase 208v 60 amp load on this system, and one single phase 208v 30 amp load the rest are single phase 120v loads to specific machines and general use outlets. Does this mean that i have to count the neutral as a ccc thererfore meaning that 3/0 are only rated at 180 amps.

Yep, sounds like you need 4/0 wire, IMHO.
 

Electroplaxes

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Location
Nunica, MI
I once had an engineer tell me he was able to balance out the neutral so he didnt have to count it as a ccc. I didn't agree with him so I up sized, but there might be traction to it, who knows.
 

kwired

Electron manager
Location
NE Nebraska
I just realised another potential issue with my installation, if i have a 3 phase 4 wire 120/208 supply and i have a 2 inch EMT run to my 200 amp sub panel. There is only one 3 phase 208v 60 amp load on this system, and one single phase 208v 30 amp load the rest are single phase 120v loads to specific machines and general use outlets. Does this mean that i have to count the neutral as a ccc thererfore meaning that 3/0 are only rated at 180 amps.

The neutral is still only carrying unbalanced current of the phase conductors. Unless you have a lot of non linear load it can be sized as small as the required EGC if you can prove it will never carry more current than the EGC is rated for, otherwise it needs sized to max calculated current that will be connected to it.

Unless you will have 200 amps on phase A 200 amps on phase B and no load on phase C and all of this load is 120 volt you will not need the neutral the same size as phase conductors. If you add 120 volt load to phase C in this situation the current on the neutral will decrease.
 

augie47

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Tennessee
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State Electrical Inspector (Retired)
Take a look at 310,15(B)(4). You would only have to count your neutral if the major portion of the load is nonlinear. That is an extremely rare condition.
The fact that you have a relative large % of your load on the 120v is not relevant unless it is vastly nonlinear.
In all probability you will find you actual neutral current to be very low.

(sorry kwired, I posted on top of you accidently)
 

kwired

Electron manager
Location
NE Nebraska
The neutral is considered a current carrying conductor if you have a circuit that uses only two phases and the neutral of a wye system. If you have all line to neutral load, and the current of the two lines is the same then the neutral will be carrying approximately the same current as the phase conductors also. Connect the same loads to a single phase source and the neutral carries zero current if the lines are the same.

This fact can create problems with existing wiring if the service is changed from single phase to 3 phase wye, or 3 phase delta to 3 phase wye.
 
Location
san diego
200 amp sub panel

So if i dont count the neutral then 3/0 is good for the 200 amp breaker to protect the feeders, would anyone pull a # 6 grd with this or is the 2 inch good enough to use. Thanks for all the replies
 

kwired

Electron manager
Location
NE Nebraska
So if i dont count the neutral then 3/0 is good for the 200 amp breaker to protect the feeders, would anyone pull a # 6 grd with this or is the 2 inch good enough to use. Thanks for all the replies

You will get support either way on the EGC on this forum. According to NEC the metal raceway is all that is required.
 

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
Will 4 x 4/0 and a #6 be good in a 2 inch Emt


Mute point since we decided you can use the 3/0, but, for reference, unless I did the math incorrectly, NO.
(4) 4/0 THWN 0.3237 X 4 = 1.2948
(1) #6 THHN .0507
Total = 1.3455
2" EMT @ 40% (Table 4) 1.342

so, that pull would not meet Code. You could omit the #6 and it would be compliant but possibly a MEAN pull.
 

Little Bill

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Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Mute point since we decided you can use the 3/0, but, for reference, unless I did the math incorrectly, NO.
(4) 4/0 THWN 0.3237 X 4 = 1.2948
(1) #6 THHN .0507
Total = 1.3455
2" EMT @ 40% (Table 4) 1.342

so, that pull would not meet Code. You could omit the #6 and it would be compliant but possibly a MEAN pull.

Good point Gus, I didn't even look at the size of the conduit. I was just looking at derating for the more than 3 ccc.:slaphead:
Your coffee worked good today!:thumbsup:
 

infinity

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Location
New Jersey
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Journeyman Electrician
A 180 amp conductor (after derating) is permitted on a 200 amp OCPD if the connected load is 180 amps or less. So you #3/0's might still be OK if you had 4 CCC's, which you do not making the point moot.
 
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