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#87839 04/22/04 11:51 AM
Joined: Mar 2003
Posts: 849
Y
Member
Per 695.4 A a fire pump motor may be connected directly to the fire pump controller, bypassing any disconnect sw.(straigt from utility transformer) as long as the controller is a service rated listed controller,
Per 695.4 B a disconnect well be PERMITTED ,
but not required.
If a disconnect was installed it would be required to comply with 695.4 B (1)
Any comments ?? Hooking direct saves installing a Large disconnect sw(locked rotor current)
Wire size 125% full load current(695.6 c)

2017 / 2014 NEC & Related Books and Study Guides
#87840 04/24/04 08:18 AM
Joined: Apr 2004
Posts: 201
Member
You have it correct already.

A disconnecting means or overcurrent protection is not required for the fire pump controller with the SUSE label since it already has the disconnecting means and overcurrent protection.

If you put in the overcurrent protection, it would have to carry locked current indefinitely. That would permit the fire pump motor to run to failure. Your overcurrent protection is only for short circuits and ground faults.

The controller will protect the wiring and the disconnect switch by interrupting the feed to the motor after 20 seconds of locked rotor current. At that point, the motor is already fried. That is why the switch and wire is sized the same as any other motor but the overcurrent protection is required to carry locked rotor current forever. [Linked Image]


Charlie Eldridge, Indianapolis Utility Power Guy

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