BN32
Member
- Location
- Chicago, IL
- Occupation
- Design
I'm inspecting a panel for UL 508A compliance and am confused on how to correctly size the main panel disconnect.
The panel is feeding a 480V/120V transformer, a 3phase 24V power supply, and multiple VFDs.
I've calculated a 180FLA.
The customer is using a 400A molded case circuit breaker as the main disconnect.
Based off of 30.2.1 this would be acceptable since its not loaded at over 80%.
The problem I'm having is with 32.3.
If I use this calculation, then the OCPD cannot exceed 210Amps.
The customer is using a lug kit and has multiple 10 awg runs to the branch circuits so using 32.3.1 (b) to an advantage is out of the question. (would this be different if they had 400A conductors run to a distribution block?)
I'm not sure what the correct fix would be here.
Any insight would be appreciated. Thanks in advance.
The panel is feeding a 480V/120V transformer, a 3phase 24V power supply, and multiple VFDs.
I've calculated a 180FLA.
The customer is using a 400A molded case circuit breaker as the main disconnect.
Based off of 30.2.1 this would be acceptable since its not loaded at over 80%.
The problem I'm having is with 32.3.
If I use this calculation, then the OCPD cannot exceed 210Amps.
The customer is using a lug kit and has multiple 10 awg runs to the branch circuits so using 32.3.1 (b) to an advantage is out of the question. (would this be different if they had 400A conductors run to a distribution block?)
I'm not sure what the correct fix would be here.
Any insight would be appreciated. Thanks in advance.