....The difference is it is service rated and the regular double slot breaker isn't (lower AIC rating).
It was flaky and one of the reasons that drove my service upgrade.
Not true.
The only thing unique about the Q1 family was the Top-Feed Main Breaker version (Q12100TF) used in some loadcenters.
The Q1 family of breakers were not special. They were simply leftovers from the original introduction of the QO family, back in the 50's. By the 80's Square D had introduced the higher ampacity QO breakers that we know today.
If anything the newer QO breaker has higher AIC ratings, as well as series-combinations ratings. Service entrance ratings go with the panel/enclosure not the breaker.
