Withstand rating of non-fused disconnect switch (safety switch)
Withstand rating of non-fused disconnect switch (safety switch)
(OP)
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).
h ttp://ecat alog.squar ed.com/pub s/Electric al%20Distr ibution/Sa fety%20Swi tches/3100 CT9801.pdf
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).
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RE: Withstand rating of non-fused disconnect switch (safety switch)
See the following page on SqD's web site which seems to contradict your link, but I think is probably newer.
http://
Ratings vary between manufacturers. 10K is common. Some rate their NF disconnects for use with some circuit breakers. Others only allow use with fuses.
RE: Withstand rating of non-fused disconnect switch (safety switch)
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.
RE: Withstand rating of non-fused disconnect switch (safety switch)