Load disconnect

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Electriman

Senior Member
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TX
Greetings,

NEC requires to have a local disconnect for motors and HVAC loads. Do we have the same requirement for other loads i.e. UPSs or other process load i.e. extruders ,...?
And if we have a load that is drawing more than 1000A and requires a local disconnect per NEC, does it need to have a disconnect for ground fault protection?

I appreciate it your feedback in advance.
 
You misread the ground fault requirement. Ground fault tripping is required. It typically uses a breaker but could be done with say a protection relay triggering a smart fuse. This would be necessary at short circuit currents where breakers are not available. It might be done with a disconnect with a motor operator but I’ve never seen one because those aren’t intended for fault duty.

OSHA requires either a lockable disconnect or plug for all loads (end devices) and this extends everywhere with rare exceptions for general maintenance. This does not extend to generation, transmission, or distribution, or to construction.

Motor disconnects are necessary because occasionally a motor starter can weld itself shut under short circuit conditions so that the motor cannot be shut off via the starter controls, and to replace fuses if a fused disconnect is used. This is over and above OSHAs requirements so it has a special place in NEC. Everything else has either a disconnect or circuit breakers because of the requirement for overcurrent protection. Granted this might amount to cutouts but it’s still there. At the distribution (utility) level NEC does not apply...we switch to NESC. At that level it’s legal to just use jumpers and sometimes done but only under controlled circumstances (unloaded).
 
Around here most industrials use the second part of the exception to 430.102(B)(2) to avoid a physical disconnect at the motor.
 
paulengr said:
You misread the ground fault requirement. Ground fault tripping is required. It typically uses a breaker but could be done with say a protection relay triggering a smart fuse. This would be necessary at short circuit currents where breakers are not available. It might be done with a disconnect with a motor operator but I’ve never seen one because those aren’t intended for fault duty.

OSHA requires either a lockable disconnect or plug for all loads (end devices) and this extends everywhere with rare exceptions for general maintenance. This does not extend to generation, transmission, or distribution, or to construction.

Motor disconnects are necessary because occasionally a motor starter can weld itself shut under short circuit conditions so that the motor cannot be shut off via the starter controls, and to replace fuses if a fused disconnect is used. This is over and above OSHAs requirements so it has a special place in NEC. Everything else has either a disconnect or circuit breakers because of the requirement for overcurrent protection. Granted this might amount to cutouts but it’s still there. At the distribution (utility) level NEC does not apply...we switch to NESC. At that level it’s legal to just use jumpers and sometimes done but only under controlled circumstances (unloaded).
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Thanks.

As far as distance between load and disconnect, I know it should be visible load vicinity but do we have a maximum space i.e. 25' or 50'?
 
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