A pre-charged heating/cooling system is shown for installation by unlicensed personnel. An outside unit includes an outside coil, outside fan, compressor and a reversing valve. An inside unit has an inside coil, inside fan for drawing air through the inside coil and discharging the conditioned air into the enclosed space, and a power cord connection. A cable sheath contains all connections from the inside unit to the outside unit with electrical connections being secured in position on the outside unit by a cover and a bracket. An expandable window sill holds and seals the cable sheath in a window opening.