Understanding AC Sizing
Proper HVAC sizing ensures optimal comfort and energy efficiency in your space.
- Load Calculation Factors Square footage: 600 BTU/100 ft². Ceiling height adjustment: +10% per ft over 8'. Window factor: 1000 BTU each. Occupancy: 400 BTU/person.
- Climate Considerations Hot-humid: add 30% capacity. Desert: +20%. Temperate: baseline. Altitude adjustment: -4% per 1000ft. Design temperature differential: 20°F typical.
- System Efficiency SEER 13 minimum standard. SEER 16+ for premium efficiency. EER = SEER ÷ 1.1 for peak load. COP = 3.5 typical for modern units.
- Sizing Guidelines 1 ton = 12,000 BTU/hr. Minimum 400 CFM/ton airflow. 20 BTU/hr/ft² average. Oversize limit: 15% max. Undersize limit: 10% max.
Installation Considerations
Ductwork Requirements
Supply: 0.1" WC pressure drop max. Return: 400 CFM/ton. Flex duct: limit to 25ft runs. Metal duct: size for 900 FPM velocity.
Energy Efficiency
Programmable thermostat: 10-30% savings. Proper insulation: R-8 minimum for ducts. Air sealing: test to 3% leakage max. Maintenance: bi-annual.
Cost Analysis
Equipment: $3000-6000/system. Installation: $2000-3000. Ductwork: $1000-3000 if needed. Annual operation: $200-600 typical.
Performance Metrics
Temperature split: 18-22°F. Static pressure: 0.5" WC max. Superheat: 8-12°F. Subcooling: 10-12°F. Run time: 70-80% on design day.