Circuit Breaker Lock-On Devices

[JDBrown]

In the past we have specified breaker lock-on devices for branch circuits feeding fire alarm panels and emergency egress lighting, but I came across a customer spec today that had me scratching my head. In addition to the expected fire alarm panels and emergency lighting, they want lock-on devices on clocks, refrigerators and control wiring.

I can't figure out what they mean by "control wiring", since in my experience control wiring isn't directly connected to a breaker anyway, but that's a different issue.

My question is: Is it legal to put a breaker lock-on device on a circuit that feeds a refrigerator or a clock?

My understanding is that you're allowed to use a lock-on device for a fire alarm panel or for emergency exit lighting, because the danger of losing power to that circuit outweighs the danger of the branch circuit conductors getting too hot. I don't think you can make that argument for a refrigerator or a clock, though (even if the "clock" is really a lighting or HVAC controller). So does anybody have experience with this? I haven't been able to find it in the Code, but it doesn't seem like it would be allowed.

P.S. In case it matters, it's a commercial occupancy; small bar/restaurant.

 

[jim dungar]

The NEC requires, and has for decades (maybe 50 years), that all breakers be 'trip free' which means they must trip even though the handle is held in the On position.

This has been part of the UL489 listing for as long as it has been in the NEC.

 

[Jraef]

All circuit breakers are required to be "Trip Free" meaning that nothing that you do with the handle will affect the trip mechanism; you cannot hold a handle in the closed position and expect that the breaker will not trip. So a Lock On device does NOT (cannot) interfere with the breaker TRIPPING, it only affects MANUAL operation of the breaker. they are very common on any circuit that might have dire consequences of being inadvertently flipped off. I use them a lot in Lighting Panels where the breakers are used to switch lighting on and off, but there are other critical loads fed from the same panel. You don't want the 18 year old doofus killing your fridge over night because he was too lazy to pay attention to WHICH breakers he was flipping off at the end of the shift, and just turned them ALL off...

And yes, control power is often fed from a panelboard breaker, especially if there is a "Master Relay" connected to an E-Stop circuit that kills everything at once.

 

[roger]

The NEC requires, and has for decades (maybe 50 years), that all breakers be 'trip free' which means they must trip even though the handle is held in the On position.

This has been part of the UL489 listing for as long as it has been in the NEC.

And along with Jim's post, breakers are not intended to be emergency disconnects even though I have had some safety people want to think they are.

Roger

 

[JDBrown]

Thanks a bunch, guys. Learn something new every day, I suppose -- I had no idea about the trip free requirement.

 

[jim dungar]

...the trip free requirement.

NEC 240.80