locking breakers on
- Thread starter codeuser1
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ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: locking breakers on
700.12(E) requires it if the exception is used.
According to the listing standard, breakers are required to be "trip free", which means they will still trip under fault or overload conditions, even if the handle is locked closed.
700.12(E) requires it if the exception is used.
According to the listing standard, breakers are required to be "trip free", which means they will still trip under fault or overload conditions, even if the handle is locked closed.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: locking breakers on
You also asked about disconnects. Those devices have no capability to open on their own, such as to clear a fault or to open on an overload. So it is certainly acceptable to lock them on. Anyone who needs to open a disconnect for maintenance may have to take the extra time to find the person with the key, but that is not a safety issue. The NEC is only concerned with safety.
That being said, I recall some discussions about the use of a disconnect as an emergency shutoff (i.e., a person?s clothing is caught in a machine, and you need to turn it off now). Clearly, if a disconnect were locked on, it would not serve that function. But I don?t think it is an NEC issue anyway. I think the disconnects that the NEC requires to be installed (e.g., for motors and for controllers) are there for maintenance, not for use as emergency shutoffs. Anyone have a different opinion on this matter?
By the way, just our of curiosity, is there some controversy in your office that leads you to ask the question?
You also asked about disconnects. Those devices have no capability to open on their own, such as to clear a fault or to open on an overload. So it is certainly acceptable to lock them on. Anyone who needs to open a disconnect for maintenance may have to take the extra time to find the person with the key, but that is not a safety issue. The NEC is only concerned with safety.
That being said, I recall some discussions about the use of a disconnect as an emergency shutoff (i.e., a person?s clothing is caught in a machine, and you need to turn it off now). Clearly, if a disconnect were locked on, it would not serve that function. But I don?t think it is an NEC issue anyway. I think the disconnects that the NEC requires to be installed (e.g., for motors and for controllers) are there for maintenance, not for use as emergency shutoffs. Anyone have a different opinion on this matter?
By the way, just our of curiosity, is there some controversy in your office that leads you to ask the question?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: locking breakers on
There is a basic safety requirement for machinery requring the ability to shut power off to a machine that locking the disconnect in the "on" position would seem to violate unless there was some other means to do so (such as a monitored estop pushbutton).
There is a basic safety requirement for machinery requring the ability to shut power off to a machine that locking the disconnect in the "on" position would seem to violate unless there was some other means to do so (such as a monitored estop pushbutton).
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