HVAC Information

Heat Load Calculation

Formula: Q = Area (sq.ft) x Heat Load Factor (BTU/hr per sq.ft)

Example: 500 sq.ft office: Q = 500 x 30 = 15,000 BTU/hr TR = 1.25

CFM Calculation

Formula: CFM = Sensible Heat (BTU/hr) / (1.08 x Delta T)

Example: 12,000 BTU/hr, Delta T = 20°F CFM = 556 →

AHU / FCU Sizing

Rule: 1 TR = 400 CFM

Duct Sizing Heat Load Calculat

Velocity Limits:

Main: 1400-1800 FPM

800 CFM @ 1000 FPM 0.8 sq.ft 14"x10"

Chilled Water Flow Rate

Formula: GPM = BTU/hr/ (500 x Delta T)

Example: 24,000 BTU/hr GPM = 4.8

Pipe Sizing

Chiller Sizing

Formula: TR = BTU/hr / 12,000

Example: 60,000 BTU/hr 5 TR

Cooling Tower Sizing

Rule:

Heat Rejection = 1.25 x Load

10 TR → Tower = 12.5 TR