Calculation motor

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hhsting

Senior Member
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Glen bunie, md, us
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Junior plan reviewer
I am trying to size breaker for Make Air Unit kitchen and commercial kitchen exhaust fan. Manufacturer does not have MOCP

I am stuck as to what percentage of full load I would take. Looked at 430 still confuse.

Make up air unit is 1.5HP, 120V single phase
Exhaust fan is 1HP, 120V single phase

Any thoughts in regards to breaker sizes from panelboard?
 
Do a search for Sq D motor data calculator is an on line
Program that will give realistic answers. The code maxiums are too large, IMO.
 
The code tells you to size the conductors at 125% of the full load current as found in the tables at the end of Article 430. 430.52 will tell you what size the branch circuit short circuit and ground fault protective device.
 
Table 430.148 is for single phase motors.
1HP @ 120V = 16A FLC, x 1.25 =20A so a 20A circuit and breaker (could be larger if the motor has thermal protection)
1-1/2HP @ 120VAC = 20A FLC x 1.25 = 25A, so a 25A circuit and breaker minimum (same issue).
 
I like the Sq D motor data calculator, eady and good starting point. Siemens fhas a similar one. I used to buy them 100 at a time from the american slide chart company, gor my classes.
 
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