Building Services and HVAC Systems
Core toolkit
M&E design is dominated by load, flow and pressure. Build the cooling load from fabric conduction, solar gain (area x SHGC x irradiance), internal sensible and latent gains (people, lighting W/m2, equipment) and outdoor air. Select the coil using psychrometrics: room condition, supply condition, apparatus dew point and coil bypass factor fix the supply air quantity; the room sensible heat ratio tells you whether humidity control needs a lower ADP or reheat.
Air side: velocity and equal-friction duct sizing, fan static build-up, and the fan laws (Q proportional to N, pressure to N squared, power to N cubed). Water side: primary/secondary pumping, coil delta-T and Q = m cp dT; check valve authority, and understand why a low chilled-water delta-T wastes pump energy. Fire and life safety: SCDF Fire Code requirements for smoke control, staircase pressurisation, fire dampers and fire-rated ductwork. Name the local references: SS 553 (air-conditioning and mechanical ventilation), SS 530 (energy efficiency of building services), SS 554 (indoor air quality).
Traps
- Mixing L/s, m3/h and cfm; 1 m3/s = 3600 m3/h; 1 RT = 3.52 kW.
- Quoting compressor COP as plant kW/RT - they differ by condenser and auxiliaries.
- Omitting fan and pump heat from the space load, and ignoring diversity and duct leakage.
- Designing VAV systems on peak load only, when most energy is spent at part load.
Rule of thumb
Chilled water flow (L/s) = capacity (kW) / (4.19 x delta-T in K). A 350 kW coil at 6 K needs 350/(4.19 x 6) = 13.9 L/s.