Can QO tandem circuit breakers be mounted in an NQ panelboard:
Can a tandem breaker be installed in an NQ panelboard to increase the number of available circuits?
The QO tandem breakers are not UL listed or tested for use in panelboards. They are only for installation in specific, residential QO load centers.
Use of them in a panelboard violates UL and can result in loss of warranty.