Define Zone and Assumptions
Let’s assume you're designing HVAC for the Concourse Level of an elevated metro station.
Assumed Area (Zone):
Zone area: 25 m × 12 m = 300 m²
Floor Height: 4.0 m
Conditions:
Parameter
Value
Occupancy
1 person per 1.4 m²
Lighting Load
15 W/m²
Equipment Load
5 W/m²
Outside Temp (DB/WB)
40°C / 28°C
Inside Design Temp (DB/WB) 24°C / 17°C
Infiltration Air Change
1 ACH
Ventilation
10 l/s/person
Step 2: Heat Load Calculation
2.1 Occupant Load
No. of people = 300 / 1.4 = 214 persons
Sensible heat/person = 75 W
Latent heat/person = 55 W
Sensible Load = 214 × 75 = 16,050 W
Latent Load = 214 × 55 = 11,770 W
Lighting Load
= 15 W/m² × 300 m² = 4,500 W
Equipment Load
= 5 W/m² × 300 m² = 1,500 W
Infiltration Load (Ventilation)
ACH = 1 → Volume = 300 × 4 = 1,200 m³
Air Infiltration = (ACH × Volume) / 3600 = 1 × 1200 / 3600 = 0.33 m³/s
Sensible Heat = 1.2 × 0.33 × (40–24) = 6.35 kW
Latent Heat = 2500 × 0.33 × (0.013 – 0.009) ≈ 3.3 kW
Ventilation Air (Fresh Air)
10 l/s/person × 214 = 2140 l/s = 2.14 m³/s
Sensible = 1.2 × 2.14 × (40–24) = 41.06 kW
Latent = 2500 × 2.14 × (0.013–0.009) = 21.4 kW
Total Load Summary
Load Type Sensible (kW) Latent (kW)
Occupants 16.05
11.77
Lighting 4.5
Equipment 1.5
Infiltration 6.35
3.3
Ventilation 41.06
21.4
Total
69.46
36.47
Grand Total (TR):
Total Load = Sensible + Latent = 69.46 + 36.47 = 105.93 kW
1 TR = 3.517 kW → Required TR = 105.93 / 3.517 ≈ 30.1 TR
Equipment Selection
Indoor Units (Cassette Type):
Let’s select 4-Way Cassette Units:
Assume each unit = 3.0 TR (10.5 kW)
Required = 30.1 / 3.0 ≈ 11 units
Distribute equally across the concourse for uniform cooling.
Outdoor Unit (VRF/VRV type):
Total Required Capacity: 30.1 TR
Select outdoor units with combined capacity ≥30.1 TR
Consider diversity factor (typical for VRF systems: ~0.8 to 0.9)
Example:
Use 2 × 16 HP (each 16 HP = ~45 kW = ~12.8 TR) outdoor units
Total = ~25.6 TR × 2 = 51.2 TR, sufficient for connected 30 TR indoor load with
diversity
Summary:
Item
Quantity
Capacity
4-Way Cassette Units 11 Nos
3.0 TR each
VRF Outdoor Units
16 HP each (12.8 TR)
2 Nos
0
