Engineered for easy maintenance and superior air delivery. Its compact size offers installation convenience. The Dometic DFSD20111 Small Furnace has a redesigned, durable stamped steel door, sold separately (select models only). Doored Furnace, 18,000 BTU, Uses LP Gas, 12 DC Voltage Horizontal or vertical configuration for flexible installation Quiet operation thanks to reduced air turbulence Low-profile, compact design: 7 in. x 12 in. x 20 in. (H x W x D) 12 V DC powered unit 18,000 BTU Outside access door required (sold separately)