Withstand rating of non-fused disconnect switch (safety switch)

[RonShap]

Performing a short circuit study at a commercial facility. Many of the local disconnects at 5 and 20 horsepower motors are for disconnect purposes only. I have typically indicated that a non-fused disconnect would have a withstand rating of 5,000A. My short circuit calculations indicate 15,000 for many of the disconnects.
Is my assumption that 30 and 60A heavy duty safety switches have a relatively low withstand, like 5k?
I can't find withstand information on the manufacturers site for a disconnect without the use of fuses (which fuses are not installed anywhere in the circuit, just breakers, MCP's and overloads).

http://ecatalog.squared.com/pubs/Electrical Distribution/Safety Switches/3100CT9801.pdf

 

[alehman]

See pages 7 and 31 of the document you linked. According to this, it would seem the disconnects are not rated for use without fuse protection. I notice that this information is dated 1997-1999.

See the following page on SqD's web site which seems to contradict your link, but I think is probably newer.

http://ecatalog.squared.com/catalog/173/html/sections/03/17303006.html#997752

Ratings vary between manufacturers. 10K is common. Some rate their NF disconnects for use with some circuit breakers. Others only allow use with fuses.

 

[dpc]

You might do a key word search of this forum. I vaguely remember a similar thread a couple of years ago. My recollection is that a non-fused disconnect switch can have a surprisingly low withstand rating, or none at all.

The Cutler-Hammer safety switches I am familiar with have a 10 kA withstand rating when non-fused.

FWIW, we always specify fused disconnects, even for motor disconnects.

Let us know what you find out from Square D.

 

[SierraJ]

As correctly indicated by dpc, Cutler-Hammer heavy dutty safety switches are rated 10,000A without fuses and 200,000A @480V with class R or class J fuse options. (Information obtained from the 2003 Consulting Application Guide)