Indicator light Circuit Breakers


Senior Team Emeritus
Premium Member
Mar 29, 2003
So I blew up a neon lamp indicator light as part of a circuit breaker last night. Spectacular explosion and spark. I remember there was some detail about this bin full of of these breakers... just couldn't remember what it was.

Turns out, this after finding a sub-note following a lot of web-surfing with the breaker manufacturer that there needed to be a resistor added to the indicator light. Yea, I saw that note on resistors, but thought such a thing was already in there... Because it was a 250v circuit breaker, the end user was to add a properly sized one so that dependant upon the actual voltage the breaker was seeing, that resistor could be changed dependant upon voltage. Oops, I now remember a detail about these breakers I forgot long ago.

Simple enough, yet how could a resistor really play a factor in say a 120v line voltage system?

Neon indicator lamp saw 120v, and instantly exploded. Added the proper resistor and it works just fine (once I replaced the breaker). How is such a thing working in concept?
Last edited:


Active Member
Jun 7, 2004
Tacoma, WA USA
Kinda like LED's then, a current limiting resistor is required to keep the LED from burning itself up. As the temperature rises, the resistance drops, which increases the temperature more, which drops the resistance more, etc....until it draws so much current it burns up.