400/320 Installation with 2 x 200 amp panels

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AverageGuy

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Cotopaxi, CO USA
I intend to install a 400/320 240v single phase service to my shop. (metal building, concrete slab)

I intend to use a tapped feed to install 2 x 200 amp panels each equipped equipped with a 200 amp OCPD.

I am planning 400 kcmil CU feed from the meter base / 400 amp OCPD to be tapped. (trough)

I plan a #3 CU GEC.

I plan a 2/0 CU conductor (THHN) from the taps off the 400 kcmil feeder from the 400 amp OCPD.

3 inch EMT conduit to be used between the 400 amp OCPD and the trough.

2 inch EMT conduit to be used from the trough to the indoor 200 amp OCPD's.

Both 200 amp panels bonded.



Its been many years and I didnt really have much experience with this type of install.

Does anyone see an issue with my logic?
 
AverageGuy said:
I intend to install a 400/320 240v single phase service to my shop. (metal building, concrete slab)

I intend to use a tapped feed to install 2 x 200 amp panels each equipped equipped with a 200 amp OCPD.

I am planning 400 kcmil CU feed from the meter base / 400 amp OCPD to be tapped. (trough)
Click to expand...
Since this is not a dwelling 400 KCMIL will not get it

AverageGuy said:
I plan a #3 CU GEC.
Click to expand...
Read all of 250.66, you may or may not need a larger GEC and possibly be allowed to use a smaller GEC

AverageGuy said:
I plan a 2/0 CU conductor (THHN) from the taps off the 400 kcmil feeder from the 400 amp OCPD.
Click to expand...
These will have to be 3/0

AverageGuy said:
3 inch EMT conduit to be used between the 400 amp OCPD and the trough.

2 inch EMT conduit to be used from the trough to the indoor 200 amp OCPD's.

Both 200 amp panels bonded.
Click to expand...
All fine.



Roger
 
roger said:
Since this is not a dwelling 400 KCMIL will not get it

Read all of 250.66, you may or may not need a larger GEC and possibly be allowed to use a smaller GEC

These will have to be 3/0

All fine.



Roger
Click to expand...
I greatly appreciate the valuable input.


As to the 400kcmil cu THHN in a raceway, would not the 90c rating of 380A -> 310.15(B)(16) apply above ground in EMT outdoors?
 
Where supplying more then one service disconnecting means a "common" conductor only needs sized according to the calculated load it supplies. Individual "taps" to a single service disconnecting mean need sized according to the overcurrent device, next size up is allowed 800 amps or less as long as calculated load is equal or less then the conductor ampacity.

Even though OP has 2-200 amp service disconnecting means if he only had 250 amps of calculated load a common supply conductor only needs a minimum ampacity of 250.

2/0 cu to each 200 amp panel is only acceptable when applying provisions of 310.15(B)(7), since OP is not dealing with a dwelling it doesn't apply at all, 3/0 is minimum size copper conductor allowed in this case.
 
kwired said:
Where supplying more then one service disconnecting means a "common" conductor only needs sized according to the calculated load it supplies. Individual "taps" to a single service disconnecting mean need sized according to the overcurrent device, next size up is allowed 800 amps or less as long as calculated load is equal or less then the conductor ampacity.

Even though OP has 2-200 amp service disconnecting means if he only had 250 amps of calculated load a common supply conductor only needs a minimum ampacity of 250.

2/0 cu to each 200 amp panel is only acceptable when applying provisions of 310.15(B)(7), since OP is not dealing with a dwelling it doesn't apply at all, 3/0 is minimum size copper conductor allowed in this case.
Click to expand...

Read OP again and missed the first time that there was a 400 amp OCPD in there, so that changes some of what I said as we now need 400 amp conductor to the single 400 amp device, can go next standard size OCPD higher though as long as calculated load is equal or less then conductor ampacity.

I think OP has wrong table for GEC. #3 is correct size EGC for a 400 amp circuit, but GEC needs to come from 250.66 in which his proposed 400 or the 500 copper he likely does need requires 1/0 GEC either way.
 
kwired said:
I think OP has wrong table for GEC. #3 is correct size EGC for a 400 amp circuit, but GEC needs to come from 250.66 in which his proposed 400 or the 500 copper he likely does need requires 1/0 GEC either way.
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Only if the table is applicable and since he didn't say what his GES is comprised of you might want to read 250.66(A),(B), and (C)

Roger
 
roger said:
Only if the table is applicable and since he didn't say what his GES is comprised of you might want to read 250.66(A),(B), and (C)

Roger
Click to expand...

Based on load calcs ill go all CU with 600kcmil to 3/0 on current carrying conductors.

At the 400a disconnect a GEC of 1/0 CU to 3 x 10' rods staked at 20' spacing exothermic. Metal building grounded. Dont think i need to tie the slab as its on a gravel bed but im not opposed to a concrete encased electrode additional.
 
AverageGuy said:
At the 400a disconnect a GEC of 1/0 CU to 3 x 10' rods staked at 20' spacing exothermic. Metal building grounded. Dont think i need to tie the slab as its on a gravel bed but im not opposed to a concrete encased electrode additional.
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You will have to use all Electrodes that are present and in most cases an inspector would probably consider gravel as being earth. Did you read 250.66(A) and (B)?

Roger
 
The grounding electrode conductor for a 400 amp service with 2-200 amp panels is #2. If you have a meter main then you would need 1/0--- T250.66 notes 1 & 2

You could run #4 to each panels also
 
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