PTAC units that are to be used at 277 volt require an optional sub-base kit from the manufacturer that contains the receptacle within. This makes it compliant. The premises wiring connects to the kit.We have a motel that is installing room air conditioners. They are rated 265 volt and come with an attachment plug made for 277 volt. These are UL listed units. It would seem to me the units violate NEC 440.60 as they are over 240 volt and are required to be hardwired.
I sent you a message.Frigidaire model # FFRP092LT6 265 volt
See here: http://manuals.frigidaire.com/prodinfo_pdf/Specsheets/FFRP092LT6_0117_EN.pdfFrigidaire model # FFRP092LT6 265 volt