Normally we design a small generator and one automatic transfer switch for life safety emergency lighting circuits for new project. The maximum AIC rating of small ATS (switch rating < 225A) is 25KAIC. The Available short circuit current at main service switchboard is much higher than 25KA for example 55KA. Most time the ATS is located next to service switchboard. How do you guys protect the automatic switch from damage of available short circuit current? Thanks.:-?
How to protect the automatic transfer switch
- Thread starter dahualin
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If you bump the switch to 260 amp, Asco's specific breaker rating jumps to 42kaic for 600v and 50kaic for 480v. The 200kaic rating with fuses is only valid if you are using Class J. If you go to a 30 amp transfer switch then you are only rated up to 100 kaic with class J fuses.
Best of Luck!
Best of Luck!
I believe using current limiting fuses with up-over-down method for lowing the SSCA for downstream equipment protection is not acceptable right now. But I couldn't think of any other methods to protect them.
But ASCO publishes specific ratings when used with specific breakers or a current limiting fuse:
http://www.ascopower.com/cgi-bin/redirect.pl?/main.htm
For example, click 7000 series, then "Manuals and Information", and select publication 1128, Withstand ratings.
That's not the same as using the up-down method for increasing the rating of a circuit breaker.
Steve
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ron
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Many of the manufacturerw will extend the back of the ATS cabinet and place fuses within, so that it comes with the needed withstand.
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