Introduction

Selecting the right central HVAC system is one of the most critical engineering decisions during the design phase. A wrong decision means high energy consumption, costly maintenance, and occupant discomfort.

Step 1: Heat Load Calculation

Heat load is calculated per ASHRAE Handbook of Fundamentals and includes:

  • Internal loads: electrical equipment, lighting, occupant heat
  • External loads: solar radiation through glazing, outdoor temperatures
  • Ventilation loads: fresh air requirements per ASHRAE 62.1

Central System Types

1. Chiller Systems

Ideal for buildings exceeding 5,000 m². Chills water distributed to air handling units on each floor. Efficiency ranges 0.5 – 0.7 kW/ton.

2. VRF/VRV Systems

Uses variable refrigerant flow directly to indoor units. Suitable for mid-size buildings with zone-by-zone control. High efficiency makes them the most demanded in modern markets.

وحدة تكييف مركزية Chiller

Efficiency Standards

System Efficiency Standard
Chiller COP ≥ 5.5 ASHRAE 90.1
VRF/VRV IPLV ≥ 4.0 AHRI 1230
DX SEER ≥ 14 DOE