Filter by BTUs 4,000 (1) 4,500 (2) 6,000 (3) 8,500 – 50,000 (1) 8,500 – 64,000 (1) 8,500 – 77,000 (1) 9,000 (3) 12,000 (3) 16,000 (3) 20,000 (3) 24,000 (2) 27,000 (1) 30,000 (1) 32,000 (1) 40,000 (1) 48,000 (1) 55,000 (1) 81,000 (1) 108,000 (1)