I am trying to use a 400A molded case circuit breaker as the disconnecting means for a combined load of motors and heaters. Unfortunately this breaker does not carry a horsepower rating. So my question is will this breaker that has the necessary current rating for the total load pass inspection, or do I need to use something else due to the breaker's lack of a horsepower rating?
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MCCB as Disconnect for Combined Loads
- Thread starter nep
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Re: MCCB as Disconnect for Combined Loads
Disconnect or control? A breaker is self protecting in that it has both overload and short circuit protect unlike a switch that has no protection. The concern is if the "disconnecting device" has the ability to close in and withstand the motor inrush/LRA and break the counter EMF when opening the circuit. With a TM breaker this is not an issue.
The breaker will do fine as a disconnect. UL489 "listed" thermal magnetic breakers are commonly used in combination starters all the time both as a disconnect and for short circuit protection. TM breakers do not provide motor overload protection. There is no need to be HP rated.
Disconnect or control? A breaker is self protecting in that it has both overload and short circuit protect unlike a switch that has no protection. The concern is if the "disconnecting device" has the ability to close in and withstand the motor inrush/LRA and break the counter EMF when opening the circuit. With a TM breaker this is not an issue.
The breaker will do fine as a disconnect. UL489 "listed" thermal magnetic breakers are commonly used in combination starters all the time both as a disconnect and for short circuit protection. TM breakers do not provide motor overload protection. There is no need to be HP rated.
john m. caloggero
Senior Member
Re: MCCB as Disconnect for Combined Loads
See Section 430.110(C).Molded case Circuit breaker are tested and listed as suitable as motor disconnects, provided it has a rating of not less than 115% of the ampere rating based on the motor tables in Article 430. The rating of the circuit breaker must not be less than 115% of the motor amperes plus the heater load. NO HP rating is necessary for the Circuit breaker.
See Section 430.110(C).Molded case Circuit breaker are tested and listed as suitable as motor disconnects, provided it has a rating of not less than 115% of the ampere rating based on the motor tables in Article 430. The rating of the circuit breaker must not be less than 115% of the motor amperes plus the heater load. NO HP rating is necessary for the Circuit breaker.
AG-electric
Member
Re: MCCB as Disconnect for Combined Loads
GOOD JOB GUYS
GOOD JOB GUYS
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