Product Selection Toolbox

[kytsurfer]

Hey,

So i am having a little trouble understanding this SCCR stuff. Right now, my panel is note meeting a manufactures SCCR rating of 50kaic min. I am not fully understanding what products have been tested together to achieve higher scc ratings.

I am using a powerflex 4 drive (1hp 460vac) rated at 100 Kaic. This drive will run two 0.5hp/460v/1a motors (same motors and will start at the same time).So i need a contactor and O/L for each motor (load side of drive) and a single breaker for the line side of the drive.

All of these must equal a min of 50kaic

Is anyone able to help me understand how to achive greater sccr's?

[fordtt]

Ferraz-Shawmut has an excellent paper about getting higher SCCR for panel.   Go here:  http://us.ferrazshawmut.com/oem/resources/sccr_select_guide.cfm and look for the UL 508 guides.  Basically, the UL508 states that a panel cannot have a higher rating than the weakest link.  On the other hand, it does allow a panel to achieve a higher rating if the branch circuit is protected by an overcurrent device that has a higher AIC.  If you protect your branch circuits with class CC fuses, then you should be ok.  Also, we usually design our panels with a fusible disconnect switch using class J fuses on the feeder so the whole panel gets a higher rating.  SB3.2 of UL 508 states that the control circuit is equal to the interrupting rating of the OCPD (overcurrent protective device) protecting the control circuit.  This eliminates weak links inside the panel that can cause unnecessary de-rating of the panel.  Class J fuses allow our panels to be rated up to 100kA.  It still doesn't eliminate the need for good panel design, but  just like in your case, it's hard to find components that can withstand high AIC on their own.  Hope this helps.