What is a lock device on a circuit breaker for?

Saturday, August 4, 2018

The National Electric Code (NEC 422.30) requires that an installed electric appliance be able to be shut off by the a person servicing it and that the shut-off device either be within sight of the appliance, or lockable if not within sight—in other words, under their control. The intention of this requirement is to avoid the possibility of someone turning the electricity back on while the technician is handling the appliance wiring and liable to be shocked. 

   A lock device on the front of a breaker in an electric panel is usually for a water heater at a location that is not within sight of the panel, but it could be used for any other major appliance except an air conditioning condenser (outside unit), which the National Electric Code (NEC 440.14) requires that the shut-off device must always be within sight.

   Here’s a list of three other acceptable shut-off devices besides a circuit breaker lock:

  1. Cord plugged into a receptacle outlet within sight - The simplest of all solutions: pull the plug and you’re good.
  2. A wall switch within sight - This is handy for people that like to turn off their water heater when not home, and a switch that lights up when on is often used. A wall switch is also sometimes installed for furnaces and air conditioning air handlers, located on the wall near the unit. The only
    problem with this means of shut-off  is that occasionally a family member mistakes it for a light switch, turns it off, and then later the air conditioner mysteriously has stopped working. 
  3. A circuit breaker or pull-disconnect box within sight - This is the most common disconnect method for new homes. The circuit breaker switch may not have an amperage rating number on it, because it does not have to provide overcurrent protection if it is already provided by a breaker at the main panel.

    Another type of breaker locking device you might see is shown below.

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Here’s links to a collection of our other blog posts about ELECTRIC PANELS: 

What causes copper wires to turn green or black in an electric panel?  

What is the maximum number of circuit breakers allowed in an electric panel?

When should a corroded or damaged electric panel cabinet or disconnect box be replaced? 

What is a tandem circuit breaker? 

When did arc fault circuit interrupter (AFCI) breakers first become required?

Can an electric panel be located in a closet? 

Can an electric panel be located in a bathroom? 

Can you add circuit breakers by different manufacturers to an electric panel if they fit?

My circuit breaker won't reset. What's wrong?  

What is a split bus electric panel?

How do I identify a combination AFCI (CAFCI) circuit breaker? 

What does a circuit breaker with a yellow or white test button indicate? 

What is a Dual Function Circuit Interrupter (DFCI)? 

What is the difference between a Combination Arc Fault Circuit Interrupter (CAFCI) and an Arc Fault Circuit Interrupter (AFCI) circuit breaker?  

What is the difference between "grounded" and "grounding" electrical conductors? 

What does it mean when a wire is "overstripped" at a circuit breaker?

Why is an old fuse panel dangerous?  

Who is the manufacturer of those "bad" electric panels?

Why is the circuit breaker stuck in the middle? 

My circuit breaker won't reset. What's wrong? 

Why do some breakers in my electric panel have a "TEST" button on them?

What is the right size electric panel for a house?

    Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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