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100 amp feeding 100 amp 250' away #10025
05/26/02 11:01 AM
05/26/02 11:01 AM
J
joeh20  Offline OP
Member
Joined: Mar 2002
Posts: 95
Tullahoma, TN, 37388
Good morning to the ECN thinktank.
My question: yesterday we refed a cabinet shop main panel, the panel is a GE 100 main breaker 20 circuit box. It was fed from a pole mounted 100amp meter and 100 amp disconnecting breaker underground about 50 feet away, 2 #2 al hots and 1 #2 al neutral, ground rod at pole #4 bare copper to meter nuetral bar, no ground from pole to shop 50 feet away. this week the pole has to come down.
We had a 200 amp panel in a building near the shop just lights and 20 recept, total load 25 amps max, we installed a 100 amp QO breaker in this panel and ran 250' 2 #2 al and a #4 neutral in conduit underground to existing GE 20 circuit panel in cabinet shop, we drove 8' ground rod and ran #4 bare to panel in shop and left out ground wire between buildings,
the question is with that distance and 100 amp breaker feeding 100 amp main with #2 al rated at 100 amps which breaker is the first to trip, and is that wire adequate to keep good voltage in the shop, the shop only draws maybe 50 amps with all the stuff running , and is the placement of the ground rod near the shop the safest way to do this.
Something tells me that this circuit is only good for about 75 amps max should the main panel in the cabinet shop been downsized to have been fed with 100 amp breaker 250' away.


Lighting the way
Work Gear for Electricians and the Trades
Re: 100 amp feeding 100 amp 250' away #10026
05/26/02 12:23 PM
05/26/02 12:23 PM
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Is this cabinet shop a "dwelling"?

If not, the #2 isn't big enough for 100A.

Table 310-15(b)(6) is for dwellings only.


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Re: 100 amp feeding 100 amp 250' away #10027
05/26/02 02:42 PM
05/26/02 02:42 PM
J
joeh20  Offline OP
Member
Joined: Mar 2002
Posts: 95
Tullahoma, TN, 37388
it was an old house on the property, and with two additions now is a 1900 square foot cabinet shop. so it would be commercial by nature of the activity in it now.
I wondered about the wire size myself, the owner had purchased the material for the job and need someone to install, I felt he had the wire a bit small, especially with the distance.


Lighting the way
Re: 100 amp feeding 100 amp 250' away #10028
05/26/02 07:31 PM
05/26/02 07:31 PM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,371
joeh20
just some quick figures...
120V @ 250'>75deg USE>75deg term>in pvc>1 ph ac>=@5% drop using 250KCMIL al...


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