Breaker lock-on

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pete m.

pete m.

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Ohio
Does anyone know where there is documentation from the breaker manufacturers that show a breaker with a "lock-on" device will still trip under an overcurrent and/or overload condition.

Thanks in advance for any help.

Pete
 
I'm unsure about documentation but I have seen tripped CB's with the lock-on devices installed.
 
pete m. said:
Does anyone know where there is documentation from the breaker manufacturers that show a breaker with a "lock-on" device will still trip under an overcurrent and/or overload condition.

Thanks in advance for any help.

Pete
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Check out 240.80, it requires to be of trip free design, meaning even if the handle was glued in the on position the breaker would still operate.
 
The operating mechanism of a circuit breaker must be designed to ensure positive opening of the circuit breaker, and circuit interruption must occur whether the tripping or opening signal is received with the circuit breaker fully closed or in any partially closed position. The operating mechanism must also be capable of closing, re-closing, and latching the circuit breaker closed.
 
240.80 2005 NEC, Method of operation.Circuit breakers shall be trip free and....Assumimg that these are C/B's built since that rule went into effect. (checked a 1971 NEC & was NOT in effect then).
 
I attended a Sq D class quite some time back, and the thermo mechanical trip mechanic's inside, were of a bi-metallic metal that would de-energize the circuit regardless of what the handle on the outside was doing. Just a tidbit of info there.
 
weressl said:
You would want to look at the applicable ANSI Standards and UL test requirements for each class of circuit breakers.
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See post 5 by norcal, all you need to do with circuit breakers after the trip free requirements is to look at the time of installation. All the newer circuit breakers shall be trip free. :smile:
 
According to my 1986 version of NEMA AB-1, the standard for molded case circuit breakers, paragraph 3.3 "The internal operating mechanism of a circuit breaker shall be trip-free."

My 1960 catalogs use the phrase "trip-free" when describing breakers that meet UL, NEMA, and Fed Spec WP-131a, but I have no proof that it was required back then.
 
I once arrived at residential job (in the 1970's) and found a 2 X 4 jammed under a FPE 2 pole 30 amp on the t-pole to keep it from tripping. Much to my dismay it worked but the thing was red hot :mad: Another reason why you don't see them much any more.
 
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