Furnace Size Calculator

Furnace Size Calculation Formula

\[ \text{size} = \text{BTU}_{\text{rec}} \times A \times F_s \times F_i \times e \]

Where:

Climate Zone and BTU Recommendation

Climate Zone Annual Average Temperature (°C) BTU Recommendation (Min) BTU Recommendation (Max)
Zone 1 21°C and up 30 35
Zone 2 16 to 20°C 35 40
Zone 3 11 to 15°C 40 45
Zone 4 6 to 10°C 45 55
Zone 5 -4 to 5°C 55 70
Zone 6 -9 to -5°C 70 80
Zone 7 -19 to -10°C 80 90
Zone 8 -24 to -20°C 90 100
Zone 9 -25°C and below 100 100+