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Sizing DC circuits for breaker contorl

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rockman7892

Electrical
Joined
Apr 7, 2008
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1,179
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Does anyone have a good rule of thumb for determining sizes of branch circuit breaker for breaker control? With a typical breaker you'll have trip coil current rating, close coil current rating, charging motor (AC or DC but lets assume DC in this case), and any relays and control devices (LOR's etc....)

Lets use an example where breaker has a charging motor run amps of 4A, and close/trip coil ratings of 7A.

Most of these breaker ratings are momentary with the exception of the charging motor (which may be a few seconds) so I've always been curious what value is used for basis of circuit size? It it typically using the largest momentary value and adding on any continuous values for relays etc..? So in this case if breaker has 7A trip coil rating would we use this as the largest breaker rating plus add any additional value for continuous loads such as relays, etc.?

How are lockout relays or other momentary control devices usually factored in?
 
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