Dimensions (inches) - Model HD/HDS Performance Data - Model HD/HDS Model Size 30 45 60 75 100/125 Model Size 30 45 60 75 100 125 A (length) 26.8 26.8 26.8 26.8 35.5 BTU/Hr Input* 30,000 45,000 60,000 75,000 100,000 125,000 B (height) 12.2 12.2 18.0 18.0 20.5 BTU/Hr Output* 24,600 36,900 49,200 61,500 82,000 102,500 C (depth) 22.0 22.0 25.0 25.0 31.