Rules for MC motor whip

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Jamesbond

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Hey Guys,
My company installs industrial ceiling fans and I have a question regarding a specific set up.
The fans are assembled with a 10’ 12/3 MC whip, but it is usually cut down to 5’ or 6’.
In this scenario there will be 3 fans on one circuit.
We intend to use a 30amp breaker and 10 awg THHN ran in 3/4” EMT to a junction box mounted at each fan location where we will tie in the 12/3 whip and continue the 10awg on to the next fan.
Is this considered up to code? Since 12/3 is rated for 20amps but there is a 30amp ocpd?
Any help is appreciated. Thanks
 
The 12ga needs to be protected by a 20A OCPD. There is no problem running #10 from a 20A cb for the circuit to reduce VF, then take the final whip down to #12, so long as the 12 is properly protected. How big are the fans? Can 3 of them fit on a 20A circuit? Does the fan have an MOCP shown? That might be an issue as well.

Alternatively you could add a suitable breaker at/as the junction, but that would be expensive.
 
Jraef said:
The 12ga needs to be protected by a 20A OCPD. There is no problem running #10 from a 20A cb for the circuit to reduce VF, then take the final whip down to #12, so long as the 12 is properly protected. How big are the fans? Can 3 of them fit on a 20A circuit? Does the fan have an MOCP shown? That might be an issue as well.

Alternatively you could add a suitable breaker at/as the junction, but that would be expensive.
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OK, no one else has jumped in here, and I know you are a moderator so that makes me question myself but I think this installation is just fine. Starting at TABLE 310.15(B)(16) we are directed to 240.4(D) for which table 240.4(G) sends us to 422 if you define this as an appliance or 430 if you define this as a motor. Article 422.11(G) sends us back to 240.4 so that would limit #12 to 20 amps. However, 430 allows #12 to be protected per table 310.15(B)(16) So, is a Big Ass Fan an appliance or a motor? I believe the MC connects directly to the motor head, so I argue that it is a motor covered by article 430 therefor the proposed installation it fine.
 
don_resqcapt19 said:
Where is the motor controller, and motor overload protection?
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Yes, that's a critical issue. The reason the rules change in 430 is because it ASSUMES there is a protection device somewhere else in the circuit, be it a motor controller or in the motor itself. In the absense of any of that, it defaults to the other rules.
 
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