Tapping load side of main disconnect switch

Status
Not open for further replies.
A

AKB

Just wondering
Location
Hillsdale, NJ
Occupation
Contractor
Hi,
Attached is a single line diagram of set up.
600A main fused disconnect being tapped on the load side by 3-barrel lugs. Each barrel gets 3/0 Cu conductors, and terminated at subpanels with 200 A mains, 42-space.
Subpaneles are 5 ft, 50 ft, 55 ft away from main disconnect. Do you see a problem with lay out? AIC ratings are not a concern at this time.
 

Attachments

  • Diner.pdf
    92.4 KB · Views: 60
Are all of the feeders on the outside of the building? Otherwise you have a tap rule problem with two of them.
 
They are inside. If you look at the drawings, these are just feeders.
We can't find 600A MDP to install after CT cabinet. Delivery time is too long. So, I want to use disconnect so I can run feeders to the subpanels. But, I'm protecting 3/0 Cu feeders with 200A mains in panels.
 
AKB said:
They are inside. If you look at the drawings, these are just feeders.
We can't find 600A MDP to install after CT cabinet. Delivery time is too long. So, I want to use disconnect so I can run feeders to the subpanels. But, I'm protecting 3/0 Cu feeders with 200A mains in panels.
Click to expand...

Length of the 3/0 conductors are the issue. They are protected at 600 amps. You have to comply with one of the feeder tap rules in 240.21(B). The one 5 feet away shouldn't be an issue, but the ones 50 and 55 feet away are the problem.
 
I got that. 3/0 Cu feeders protected by 200A breaker at panels. 600A disconnect protects service wires.
 
I was hoping to find some exception in the code from experienced guys like you.
I thank you very much for your time and effort.
 
AKB said:
Last one, do you realize I'm coming off of the load side of 600A disconnect?
Click to expand...
Yes we do. You have a 600 amp OCPD protecting 200 amp conductors for more than 25'. That's the problem, you've violated the maximum conductor length requirement of the 25' tap rule. {240.21(B)(2)} So either move the 200 amp OCPD's closer (within 25') or use 600 amp conductors to feed each panels 200 amp OCPD.
 
Status
Not open for further replies.
Top