HVAC Load Sizing Equations and conversions

Airside Load Equations:

For H listed in BTU/Hr

Hsensible  = 1.085*CFM*ΔT
HLatent   = 0.68*CFMHTotal*ΔWLB
Hlatent  = 4840*CFM*ΔWGrains/LB
H Total  = H Sensible + H Latent
HTotal  = 4.5*CFM*ΔhEnthalpy
SHR  = Hsensible/HTotal

 

Water/Hydronic Load Equations:

MBH  = .5*GPM*ΔT
GPMEvaporator  = 24*TONS/ΔT 
GPMEvaporator  = 30*TONS/ΔT

Where:

  • Δ = Delta
  • CFM = Cubic Feet Per Minute
  • GPM = Gallons Per Minute
  • Tons = Air conditioning load (=12,000 BTU/Hour)
  • SHR = Sensible Heat Ratio
  • *Note 1.085 is the Density specific Heat Product DSHP and subject to change by location!)