Tandem breakers don't sit flush in panel -

The duplex breakers provide two single pole breakers in the space typically required for only one standard breaker These duplex, 12-Inch frame breakers

When two breakers are interconnected in various systems the simultaneous closure thereof may be dangerous, or even disastrous Thus, in a multiphase alternating

two slot When two breakers are interconnected in various systems the simultaneous closure thereof may be dangerous, or even disastrous Thus, in a multiphase alternating

two slot shelving You can certainly use a 2-pole breaker If it is larger than 20amps please use the correct gauge of wire to hook into Tandem breakers are on the same phase so