Circuit breaker Selection

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electricalRookie

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Hi all,

I am selecting circuit breakers for a 120VAC to 24VDC power supply. I am currently selecting circuit breaker for the 24VDC side, I wonder if I need to select ul489 breakers with DC rating? From Eaton product catalog, I found they have breakers that are dedicated to DC circuits. However, other circuit breakers have rating for both AC and DC, please see the picture below. It is very hard for me to purchase the DC rating circuit breakers and I wonder if I can use the one shown in the picture below?

1667956114897.png

Big thanks!
 
Jraef said:
No, you do not need UL 489 listed breakers on the 24VDC side of a power supply.
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hey Jaref, thanks for ur reply. However, some sites(automation direct) mention they are dual rating(AC/DC)breakers, even in their product filter, you can see 480Y/277/96VDC.

Could u elaborate why they put 96VDC there?

Thanks!
 
electricalRookie said:
hey Jaref, thanks for ur reply. However, some sites(automation direct) mention they are dual rating(AC/DC)breakers, even in their product filter, you can see 480Y/277/96VDC.

Could u elaborate why they put 96VDC there?

Thanks!
Click to expand...
You can’t use AC only breakers on a DC circuit. With AC the voltage and current cross zero twice every cycle. That makes it easier for the breaker to open a fault.

Not so with DC. That’s why the DC rating is less.
 
They are just letting you know that if you WANT to use them on DC, the voltage rating is not the same. Interrupting a DC circuit is more difficult than AC, so even though the breaker is rated for 480/277VAC, it can’t be used at that high of a DC voltage.
 
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