Breakers locked in the closed position

[Mark2916]

I was wondering if you lock a breaker in the "closed" position, or the on position. What happens if the breaker was to trip due to a fault? Everytime I have seen a breaker tripped the handel has moved towards the "open" position. Would the lock allow the handel to move, or would it stay in the "closed" position?



Thanks

 

[mcclary's electrical]

I was wondering if you lock a breaker in the "closed" position, or the on position. What happens if the breaker was to trip due to a fault? Everytime I have seen a breaker tripped the handel has moved towards the "open" position. Would the lock allow the handel to move, or would it stay in the "closed" position?



Thanks

Welcome to the forum. It would still trip internally as normal

 

[raider1]

Welcome to the forum.

Breakers are built with a trip free design that allows the breaker trip function to operate independent of the handle. This permits a breaker to be locked in the closed (on) position and still function properly.

Check out 240.80 for the code requirement for trip free design.

Chris

 

[mxslick]

Mark, welcome to the Forum. :grin:

As they have already said, a modern breaker is trip-free and will still trip with the handle locked open.

A bigger concern would be not being able to shut the breaker off quickly in an emergency.

But, there were some very old breakers which did NOT trip-free and that would of course be very bad. (I think it was the old Westinghouse and Frank Adams ones mainly.)

And the pushbutton breakers (like used in aircraft) CAN be held closed against a fault. As one of my colleagues in the Air Force found out, the results can be costly. (One damaged wire harness running the length of the plane and many hours of downtime to fix, total cost was estimated around $750,000)

 

[mcclary's electrical]

Mark, welcome to the Forum. :grin:

As they have already said, a modern breaker is trip-free and will still trip with the handle locked open.

A bigger concern would be not being able to shut the breaker off quickly in an emergency.

But, there were some very old breakers which did NOT trip-free and that would of course be very bad. (I think it was the old Westinghouse and Frank Adams ones mainly.)

And the pushbutton breakers (like used in aircraft) CAN be held closed against a fault. As one of my colleagues in the Air Force found out, the results can be costly. (One damaged wire harness running the length of the plane and many hours of downtime to fix, total cost was estimated around $750,000)

I think in a plane,,,the pilot should have the capability to override an overload for certain situations. If holding that button in allows him to safey land and smoke a harness,,,so be it

 

[mxslick]

I think in a plane,,,the pilot should have the capability to override an overload for certain situations. If holding that button in allows him to safey land and smoke a harness,,,so be it

That is exactly why the aircraft breakers are designed that way. :grin:

Better to smoke a harness or black box than crash for sure.

Problem is, you get some ground troops who are stupid and don't follow proper procedure and you end up with very expensive and unnecessary repair costs.

 

[iwire]

A bigger concern would be not being able to shut the breaker off quickly in an emergency.

There is only one "Emergency disconnect" required by the NEC that I am aware of {680.41} all others are simply service switches and are not required to be available for emergency use.

 

[hurk27]

There is only one "Emergency disconnect" required by the NEC that I am aware of {680.41} all others are simply service switches and are not required to be available for emergency use.

ya missed one: 547.9(A)(1)


But it does amaze me that I have heard disconnects being called this for years:roll:

 

[iwire]

ya missed one: 547.9(A)(1)

I am looking at it but I do not see it.

 

[mxslick]

There is only one "Emergency disconnect" required by the NEC that I am aware of {680.41} all others are simply service switches and are not required to be available for emergency use.

True, that's what the Code says..but is it really all that great of an idea?

What of otherwise compliant MLO panels? No main to throw in an emergency on the locked-on circuit. (Or the breaker for that panel is far away in a locked room.) If you've got an emergency (fire, or personnel caught in machinery or getting shocked {yes I know they should be using LOTO}) I would not want to be trying to find alternate ways of killing power.

A stretch perhaps but I'm thinking in real world terms, and how I would want access to my breakers to be.

 

[Mark2916]

Thanks. I was looking for the code reference and could not seem to find it.