| Home | Terms of Use | Site Map | Contact Us |
IndustryCommunity.com > Electrical and Electronic Community > Technical Forum > Message
Main Menu

[ List Subjects ][ Current Board ][ Post Message ]
[ View Followups ][ Post Followup ]

Subject: MCC sizing/upgrade

Date: 03/13/01 at 10:06 AM
Posted by: Stevan Simmons
E-mail: ssimmons@tomsfoods.com
Message Posted:

I need to add a fusible branch switch unit to an existing MCC (Sq D Model 5). The unit is rated for 600 amps horizontal and 300 amps vertical at 480 VAC. I currently have two units in this 300 amp section. A Size 4 starter with 250 amp short circuit protection and supplying a 75 hp motor at 96 FLA. and a Size 2 starter supplying a 20 hp drive at 25 FLA with a 30 amp(this seems to be too small also) short circuit breaker. I am assuming that the vertical capacity limit is based on supplying 125% of the largest motor + the FLA of the smaller motors. This would be an existing amperage of 120 + 25 = 145 amps. As the vertical bus is rated at 300 amps I calculate 155 amps of spare capacity. I need 160 amps to feed two 80 amp panels using TW 4/0 conductors. Am I getting close here or am I way off base with this calculation? Thanks for the help!

Follow Ups:

Post a Follow-up:


Message to Post:


1999-2001 Sunlit Technology Co., Ltd. All rights reserved.