Siemens CTL Notch
I have a 20 year old Siemens main breaker panel and just purchased and installed a new Siemens sub panel. This sub panel has the capacity for 8 * 1 inch breakers or 16 half size (duplex) breakers. So I went ahead and ordered some of those: Q21515CT2, Q22020CT2 which are 220V quads (where the two outer breakers are together and the 2 inners are together).
When I tried to install them, they would not sit properly….So I did some research on the web and found in the Siemens documentation that these “QT breakers must be installed where the CTL notch is provided on the bus bar stab” The sub panel I just bought does not have any of those so called notches. I have been looking to find a sub panel (or main panel) that would have those notches with no success. I called Siemens and 2 different distributors and no one can help me. Can someone on this board lend me a hand please? (ie: how can I identify how many CTL notches a panel has before ordering it?)
Per the current codes, panels are approved for just so many breakers. That should be shown on the panel nameplate and can be determined by inspection whether there are spaces allowed for twin breakers.
I wouldn’t buy a new subpanel with the idea of installing twin breakers. Better to buy a panel with plenty of full-size spaces from the get-go.
Older panels did not have slots that would defeat installation of twin breakers. Twin breakers for those are still available from some manufacturers, but they are marked “for replacement only.” Even though they could physically fit in a new panel in defeated slots, they are not approved for that use.
