described with respect to fig4 a triac triode for alternating current or igbt insulated gate bipolar transistor control method may be used for controlling the relay on off control of the heating elements particularly for a case of using a plurality of symmetric heating elements alternatively a combination of triac or igbt and a relay on off control is used for controlling a plurality of heating elements the triac and igbt control method uses a triac control circuit and an igbt control circuit respectively one or more aspects of the invention may be embodied in computer usable data and computer executable instructions such as in one or more program modules executed by one or more computers or other devices generally program modules include routines programs objects components data structures etc that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device the computer executable instructions may be stored on a computer readable medium such as a hard disk optical disk removable storage media solid state memory ram etc as will be appreciated by one of skill in the art the functionality of the program modules may be combined or distributed as desired in various embodiments in addition the functionality may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits field programmable gate arrays fpga and the like particular data structures may be used to more effectively implement one or more aspects of the invention and such data structures are contemplated within the scope of computer executable instructions and computer usable data described herein although.