Duct Sizing

DUCT SIZING: Improperly-sized ductwork can cause multiple heating and cooling performance and service issues.

• Under-Sized Ductwork Symptoms
  • Inadequate airflow
  • Excessive noise
  • Cooling freeze-ups
  • Heat Pump high pressure
  • Furnace limit trips
  • Pre-mature motor failures
• Over-Sized Ductwork Symptoms
  • Low air velocity
  • Hot & cold spots
  • Multi-floor cooling problems

USING A DUCT SIZING CHART:

• Remember that duct sizes are "inside" dimensions (not outside).
• Need 400 CFM per Ton of cooling or blower capacity.
  • 2 ton = 800 CFM
  • 2 1/2 ton = 1000 CFM
  • 3 ton = 1200 CFM
  • 3 1/2 ton = 1400 CFM
  • 4 ton = 1600 CFM
  • 5 ton = 2000 CFM
  • 6 ton = 2400 CFM