Gas furnace for indoor heating

A furnace comprising:

• a burner;
• an exhaust flow path;
• a recovery flow path;
• a blower that suctions indoor air from an indoor space through the recovery flow path and discharges the indoor air;
• a supply flow path that guides the discharged indoor air back to the indoor space after the discharged indoor air undergoes heat exchange in the exhaust flow path;
• and
• a fuel supply unit including a fuel supply line, a fuel discharge line, and a valve provided between the fuel supply line and the fuel discharge line,
• wherein the valve comprises a step motor and a blocking member coupled to a rotating shaft of the step motor, the blocking member moving in a straight direction via by driving the step motor,
• wherein an opening amount of the valve between the fuel supply line and the fuel discharge line is adjusted by the straight movement of the blocking member so that the heating power of the burner is linearly adjusted to various magnitudes,
• wherein the fuel supply unit further includes a guide that guides the straight movement of the blocking member between the fuel supply line and the fuel discharge line, and
• wherein the guide comprises a seat portion that is provided at one side of an inner circumferential surface thereof, whereby the seat portion protrudes inward of the guide so that a lower end of the blocking member contacts the seat portion.