OCPD possible size exception for 208V, 3P, .75HP (3.5A) exhaust fan

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cohosilver

Member
Hello forum,

I am installing an exhaust fan for a commercial kitchen vent hood (Ansul) project. The exhaust fan is a 208V, 3-phase, .75 HP (3.5A) fan. I have sized the circuit breaker for the fan as follows:
Step 1 - Find the full load current from Table 430.250 which comes out to be 3.5A.
Step 2 - Use Table 430.250 to find the size of the inverse circuit breaker size (250%) so 3.5A * 250% = 8.75A
Step 3 - Go to 2406 for standard size OCPD size. Min size = 15A
Step 4 = Use 208V 3-pole 15 amp circuit breaker for the exhaust fan.

However, I am in a remote location in the Panshir Valley of Afghanistan and the 3-pole 15 amp circuit breakers have not come in. I do however have a 3-pole 20 amp circuit breaker. My conductor size is #12 THHN. I am wondering if there is a code compliant way to use the 3-pole 20 amp circuit breaker.

No, I do not have a fused disconnect available. And yes, the circuit is a dedicated circuit for the exhaust fan because it runs through the fire suppression panel.

Your expertise is sincerely appreciated.

Respectfully,

Cohosilver
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I know of no Code compliant way.
(It would not be the 1st such motor to operate on a 20 amp breaker for years.. if you have overload protection the breaker is GFSC protection and I would not be hesitant to use it temporarily)
 
kwired

kwired

Electron manager
Location
NE Nebraska
augie47 said:
I know of no Code compliant way.
(It would not be the 1st such motor to operate on a 20 amp breaker for years.. if you have overload protection the breaker is GFSC protection and I would not be hesitant to use it temporarily)
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Same here, I would use it for temporary purposes with little concerns if that was the only choice. You do need separate motor overload protection if you don't have it, as the 15 amp breaker is not going to provide that either.
 
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cohosilver

Member
OCPD possible size exception for 208V, 3P, .75HP (3.5A) exhaust fan

Thank you for your comments, you affirmed my suspicions. Very much appreciated.

Respectfully,

Cohosilver
 
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