ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (Scott35), 263 guests, and 18 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#99636 08/22/06 11:47 AM
Joined: Mar 2005
Posts: 399
A
Member
This is the situation.
Portable classroom composed of two halves, (think of a double wide mobile home) each with a 100 amp main breaker panel that controls the circuits in that half of the building.
The electrician brings TWO 100 amp feeders out to the panels. Each originates in the same service panel with a 2pole 100 breaker.
Based on 225.30 (formerly 225.8 & 9[1996] and 230.84[1990]) only ONE feeder or branch circuit, with exceptions for firepumps etc.
To comply with the Code should the electrician (1) use a 200 amp breaker listed for two conductors per pole (2) handle tie the two 100 amp breakers, (3) either or (4)something else ?
Note the panels inside are ten feet apart.
We build them around here and use them but, I'm just not sure. [Linked Image]
Alan--


Alan--
If it was easy, anyone could do it.
Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

#99637 08/22/06 12:56 PM
Joined: Dec 2003
Posts: 751
E
Member
I would supply a small 150-200 amp main breaker panel mounted on the outside of the classroom, then feed each panel with a 100 amp feeder. Maybe even supply a branch circuit for outside lighting.

It may be, that when the calculations are done for the combined load of both halves, that a 100 amp feeder would suffice. If so, then you could feed the closer panel, and subfeed the other from the first.


Earl
#99638 08/22/06 03:44 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
I'm thinking a single 200 amp feeder run to a 200 amp disconnect mounted inside or outside the structure. If you feel that the two inside panels are "grouped" as required by 225.34(A), then the feeder can be run to the structure and then tapped at that point.


Few things are harder to put up with than the annoyance of a good example.
#99639 08/24/06 02:09 PM
Joined: Mar 2005
Posts: 399
A
Member
Problem solved [Linked Image]
One disconnect, (service or not) rated 200 amps (225.30 & 34) with one feeder to each double classroom.
At the classrooms a W.P. junction box with two 100 amp taps (per 240.21 tap rule) to the panels.
Done & Done.
Alan--


Alan--
If it was easy, anyone could do it.
#99640 08/24/06 03:13 PM
Joined: Dec 2003
Posts: 751
E
Member
And don't forget to install a couple of ground rods.


Earl

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5