After reading this article:


and from it a link to this one:


ABSTRACT Test results presented in this paper demonstrate that some brands of residential molded case circuit breakers do not operate properly within the limits specified by the applicable standard. The samples tested are both used, from homes, and new, purchased at retail sources. The minimum trip current is determined for each breaker. The test procedure encompasses the basic overload trip requirements of the applicable standard. Breakers that do not open the circuit at or below 135% of rated current fail to meet the requirements of the standard. Test results vary substantially from brand to brand. The best brands are essentially failure free. The failure rate of the worst-case brands is in the order of 50% for both used breakers from homes and new breakers recently purchased. Some samples, primarily multi-pole breakers, do not open the circuit at any level of applied current. Failure of a circuit breaker in a home to operate properly when required poses an increased risk of fire and injury.

I am concerned. The second article written only a bit over a year ago says that the same defects in this style of breaker are still common.

I'm considering putting in a sub panel in my garage, and would like to do the right thing. The second article is weasel worded and doesn't identify the various brands, but by implication all of the Stab-Lok type circuit breakers are flawed.

What is the best alternative type of breaker?

  • 1
    The Federal panels in that article are old and no longer available. Any new, current breaker panels and breakers at a retail store should be safe.
    – JPhi1618
    Commented Jul 10, 2019 at 19:25
  • 2
    I am confused. Are you referring to your existing main panel that you'll be feeding the subpanel from? Are you planning to use a Federal Pioneer or Federal Pacific panel as your new subpanel, because you have one lying around? Or are you concerned about the reliability of new-stock subpanels now sold in stores? Please shoot us a photo of the panel which concerns you, you can edit it in to your question. Commented Jul 10, 2019 at 20:27
  • Also, you're in Canada, right? Commented Jul 10, 2019 at 23:46
  • Edited question to emphasize that the problem exists with current stab lok breakers. Commented Jul 11, 2019 at 12:31
  • Are you asking about Stab-Lok brand breakers or the generic class of breakers installed with a slot on the back? I see no language that implies that the entire class has failure issues.
    – isherwood
    Commented Jul 11, 2019 at 13:08

2 Answers 2


enter image description here

UBI is a 'replacement' stab-lok sold under various names. Chinese based company. 2/3 failed to trip below the 135% rated current.

Siemens/Murray looks about 2/3 passed at or very closely above.

Eaton, Square D and GE had no test failures.

This is NOT a huge test.

enter image description here

Second image is from testing 3000 breakers that were removed when renovations were done. Breakers had not been abused. (Wet, building hit by lightning, etc) and were all in service at the time of removal.

Based on this, I will go with a Square D sub panel and breakers.

Images is from the article: https://inspectapedia.com/electric/Circuit_Breaker_Failures.php


Your profile says you are in Alberta. Federal Pacific in Canada never had the same issues as FPE in the US and never lost their listing ability, eventually separating off as a totally separate company because of what happened to the US, changing their name to Federal Pioneer to try to distance themselves from it. That entire issue doesn't apply to you.

  • See abstract (added) from 2nd article. Commented Jul 11, 2019 at 12:35

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