2) Turn off power to the furnace/air handler. 3) Remove the existing filter from the furnace/air handler or return air grille. 4) Wiring to the on-board transformer or integrated furnace control: NOTE: ONLY A QUALIFIED ELECTRICIAN SHOULD PERFORM ELECTRICAL WIRING. If there is a terminal strip such as the one shown in figure 1, connect the black wire of the power cord to the “Common” terminal (typically the "C" terminal) and the black wire with the white stripe to the “Hot” 24vac terminal (typica