NEC 2014 section 422

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hhsting

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Location
Glen bunie, md, us
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Junior plan reviewer
2.5kw heater at 277V single phase has full load of 9.025A.

Branch circuit breaker feeding it is 20A.
However 9.025x1.25=11.28A next standard size of breaker is 15A.

I am confused as to what the size of this breaker should be. NEC 2017 section 422.10 says branch circuit rating for appliance shall not be less than 125 percent of marked rating. NEC 2017 section422.211(a) branch circuit shall be protected agains overcurrent in accordance with 240.4. All that indicates 20A is ok however I am not sure if 15A is typically whats provided with manufacturer instructions.

Does anyone have any idea as to what the breaker size should be?
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
HH, you shoulduld review this recent thread of yours:

Heat trace

I have 208V single phase 4kVA heat trace 19.2A full load. Breaker provided is 30A Looked in NEC 2017 section 427.57 but its not clear and their is no other breaker sizing provided for heat trace. 19.2Ax1.25 = 24A next size would be 25A. However breaker provided is 30A. Is their a section NEC...
forums.mikeholt.com

The lesson in that was that you are mixing up the next size up rule. Generally, the next size up rule allows you to go to the next standard size ocpd above the ampacity of the conductors you are protecting. As I stated in that previous thread, there is no general requirement that you have to use the minimum size ocpd after next size up relative to an appliance/machine/equipment rating. See the article 422 section David posted for the appropriate ocpd size.
 
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