Disconnect Locked Closed

[spsnyder]

I had a question posed to me regarding a building with a disconnect for a exterior exhaust fan is locked closed. Does this violate the NEC. My first thought was yes, it does violate the NEC. However, in looking at

Definitions (Under Article 100: Definitions)
"Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth."

AND....


"430.107 Readily Accessible
At least one of the disconnecting means shall be readily accessible."

I have my doubts as to whether it is a code violation. What is the difference between locking the equipment and locking the room the equipment is in? Thank you very much for your thoughts.

Regards

 

[haskindm]

There is no section of the code that prohibits "readily accessible" equipment from being locked or located in a locked room. If equipment is required to be "accessible" then it may not be locked. Carefully read the definitions of accessible and readily accessible in article 100.

 

[masterelect1]

Locked Disconnect

Locked Disconnect

Assuming that you are talking about the disconnect being locked, I know first hand that OSHA would not be thrilled with the DS being locked in the closed position.

Real Scenario that took place- An enclosure with multiple A-B size 1 motor starters being fed form a 100 amp source and each of the 12 starters has supplementary OC protection in the form of 3 pole CB's sized as necessary.
All motors were either pump motors or agitators ( none above 3 HP). Supp CB's unable to be locked open sooo it was determined to open the circuit brkr of the pump/agitator and lock the enclosures' Main Disc switch in the closed position. Osha guy in the bldg. for another reason, decides to take a walk through, sees this, and fines us for unsafe work practice. I felt it was safe-I'm disconnecting a motor-he disagreed-case closed !!

 

[Jraef]

There is nothing saying you can't, and as far as OSHA having a problem with it, it all depends on the application. A lot of critical equipment supply power is locked in the "ON" position, either circuit breakers or disconnect switches. Leaving Fire Pumps out of it for now, think about something as mundane as a sump pump. If someone were to walk by and throw the switch off or lean on it and disconnect it, then a sump overflows and causes a major disaster, the "safety" aspect could potentially be worse. I see it a lot on high tech equipment for semiconductor manufacturing; inadvertent power cutoff could cause gas leaks etc. that could be potentially much worse than what may happen if power were not cut off. For systems were personnel protection from energized equipment is critical, a disconnect switch should not be the primary Emergency power Off device anyway. Sometimes an orderly shutdown is more appropriate.

 

[charlie b]

For systems where personnel protection from energized equipment is critical, a disconnect switch should not be the primary Emergency power Off device anyway.

I agree. Indeed, I don?t know of a single instance in which the NEC requires us to design a system in such a way as to enable human intervention to turn off equipment in an emergency.

For example, if a pump experiences a break in its casing and is spewing water (or worse stuff) all over the place, it certainly would be ?convenient? if the disconnect switch (i.e., the one that is required to be within sight of the motor) could be used to turn off the motor, and thus terminate the event. But what if that disconnect were to be in the ?locked closed? position? Well, you couldn?t use it for this ?emergency.? That?s just too bad; the motor will have to keep pushing the pump roundy-roundy, and the fluid will just have to keep flying about. That is not an NEC problem; it is not related to any NEC requirement.

The function of the disconnect, and the reason it must be within sight of the motor, is to provide a measure of safety to the technician working on the motor. That person must be able to look at the disconnect switch from their position at the motor, and be able to verify that nobody has turned it back on, or that nobody is fiddling with it. Having the ability to locking it open is the intent of the code. Having the ability to quickly open it is not the intent of the code.

 

[spsnyder]

Thank you all very much for your help. It makes sence to me now. My initial thought was incorrect. Thanks again.