Air Conditioning: Complete Technical Reference

Air conditioning operates on the vapor-compression refrigeration cycle: liquid refrigerant evaporates in the indoor coil (absorbing heat), compresses to gas, condenses in outdoor coil (rejecting heat), then expands back to liquid. This cycle repeats 60-120 times per hour. Efficiency depends on temperature difference between indoor and outdoor: a 20°C difference yields COP (Coefficient of Performance) ~3.5; a 35°C difference yields COP ~2.0. In Kenya's 45°C climate, AC operates at inherent efficiency penalty—proper system design accounts for climate stress.

Refrigerant Charge is Critical: Undercharge reduces cooling capacity and increases compressor current; overcharge increases pressure and reduces efficiency. Proper charge verified by superheat (10-15°C at evaporator outlet) and subcooling (8-12°C at condenser outlet) using gauge manifold. Many systems operate at ±20% incorrect charge, wasting energy. Annual professional verification prevents inefficiency.

Airflow Velocity Essential for Heat Transfer: Evaporator velocity 2-4 m/s, condenser velocity 2-3 m/s. Undersized ducts or clogged filters increase velocity, causing temperature drop but with increased friction losses. Oversized ducts reduce velocity and heat transfer. Proper ductwork balances heat-transfer rate with pressure drop and noise.

Thermal Management in 45°C Ambient: AC capacity derates 10-15% per 5°C above 35°C ambient. A 10kW AC at 35°C provides only 8-9kW at 45°C. Climate derating must be included in load calculations; oversizing by 20-30% ensures adequate capacity in peak summer. Undersized AC never achieves set-point during heat waves.

Humidity Control Important as Temperature: AC removes ~0.7 liters water per kW daily. Oversized AC cycles on/off without sufficient dehumidification runtime, leaving spaces damp despite low temperature. Proper sizing ensures adequate runtime. Extremely hot/humid climates benefit from separate dehumidification systems.

Electrical Requirements Substantial: 10kW AC draws ~43A at 230V single-phase (or 17A per phase at 380V 3-phase). Cable must be sized correctly: undersized cables increase voltage drop and reduce starting ability. 50-meter run at 43A in 2.5mm² cable incurs 4V drop (2% of 230V), acceptable. Proper breaker sizing protects without nuisance tripping during startup (5-8× FLA inrush).

Installation Quality Directly Impacts Efficiency: Poor duct sealing wastes 15-25% cooling; improper insulation causes condensation/mold; incorrect refrigerant lines increase friction losses. Professional installation includes pressure testing (400 psi × 30 min) to verify zero leakage, evacuation to remove moisture, and charging to specifications. DIY installation often fails within 2-3 years.

Noise Sources: Compressor (40-50dB normal, 60+ dB = wear), fan (proportional to speed), refrigerant flow. Inverter compressors quieter than fixed-speed. Installation location and vibration isolation affect perceived noise. Proper installation with isolators reduces noise 5-10dB.