Rinnai Vent-Free Fan Convectors push heat to the farthest reaches of the room, evenly warming larger spaces. Each model is 99.9% efficient for hard-to-heat rooms, maximizing cost savings and comfort. FC824N is a flexible, easy to install vent free fan convector with 24KBTU Natural Gas from Rinnai is the perfect solution for rooms and spaces that are hard to heat.