The NEMA 6-20 receptacle shown in the picture is rated for 208 or 240 VAC and 20A of current
. It does not provide 110VAC when properly wired.
The NEMA 6-20 receptacle will permit
someone at any time to connect a 240 VAC appliance drawing 20A of load.
and breaker are already rated at 15A, so the better choice would be the NEMA 6-15 receptacle, to retain the existing wiring
and breaker AND have a fully compliant system.