jdelgado wrote:

Hello

What is the optimal X factor for disconnect switches. I assumed it is 2 because that’s the default value that ETAP gives you. I'm I correct for assuming this? Furthermore, It falls under the low voltage category (0.208-1), so it can be the value for MCC's and panels which is 1.473. Which value is optimal for Arc Flash calculations?

Thanks

IEEE 1584 suggests 2 for open air arcs, 1.641 for Low Voltage distribution equipment and 1.473 for Low Voltage power/switchgear equipment. 1.473 would be worst case since the incident energy would not decay as quickly as using 2 however most would probably use 1.641 since switches may be considered Low Voltage distribution. You will have to decide based on this, how to proceed.

*Disclaimer >>> This is based on my thoughts and may or may not reflect the views of IEEE 1584 or the IEC TC78 of which I am Secretary and International Chairman respectively.*