# HVAC Equations

#### Sensible Heat Formula

BTU/HR = 1.08 * CFM * ΔT

#### Total Heat Formula

BTU/HR = 4.5 * CFM * ΔH

#### Latent Heat Formula

BTU/HR = 0.69 * CFM * Δgr

#### GPM Formula

GPM = BTU/HR(Airside) / (water ΔT x 500)

#### Air Change Rate Formula

ACH = (CFM * 60) / Volume

#### Coefficient of Performance (COP)

COP = BTU Output / BTU Input = EER / 3.413

#### Energy Efficiency Ration (EER)

EER = BTU Output / Watts Input

# Rules of Thumb

#### Cooling Loads (General)

300-400 SQFT per Ton

30-40 BTU / SQFT

#### CFM / SQFT

Perimeter Spaces - 1.0-3.0 cfm/sqft

Interior Spaces - 0.5-1.5 cfm/sqft

#### Lighting Loads

T12s - 1.2 Watt / SQFT

T8s - 0.8 Watt / SQFT

LEDs - 0.4 Watt / SQFT

# Conversions

#### 1 Ton = 12,000 BTU/HR

Tons =

BTU/HR

#### 1 kW = 3412 BTU/HR

kW =

BTU/HR

#### kW/Ton = 12 / EER

kw/Ton =

EER