Square D Tandem Breaker Won't Fit - Mystery Solved - RELECTRIC
https://www.relectric.com/blog/2018/04/16/understanding-tandem-twin-breakers-for-qo-load-centers/
Apr 16, 2018 · QO (e.g., QO2020) are circuit breakers are designed for use in the older “non-class CTL” QO load centers that were manufactured before the change in code. However, this is not always the case. At various points in time, Square D has labeled tandem circuit breakers with part numbers that did not hold true to this rule.
DA: 45 PA: 8 MOZ Rank: 90