Our Furnace Transfer switch is a 1-circuit, 15 amp 125V manual transfer switch for powering just your furnace during an outage.  It is ideal for use with smaller generators and a standard extension cord.  This transfer switch comes prewired and can be surface mounted indoors next to the existing load center.  It includes mechanically interlocked breakers - one for Utility mode, and one for Generator mode.  When the power goes out, simply connect an extension cord from your generator to the inlet on this switch, and switch off the Utility breaker, slide the interlock and turn on the Generator breaker to begin powering the circuit with your generator.  The mechanical interlock prevents the circuit from being fed by the utility and generator at the same time. UL Listed.  Dimensions:  6" wide x 9" high x 4-7/8" deep.  Made in USA.