HVAC Operations, Maintenance and Energy Efficiency
HVAC Operations, Maintenance and Energy Efficiency tests whether you can run the plant day to day: control sequences and setpoints, the maintenance that preserves capacity, and finding savings without putting IT at risk.
Run at the top of the envelope
Where the hardware permits, operate rack inlet temperatures toward the upper recommended range (roughly 24–27 °C). Reset chilled-water supply upward (rule of thumb: 2–3 % chiller power per K), reset condenser-water temperature down as wet-bulb allows, and reset plenum or duct static pressure with VFD-driven fans. Re-verify rack inlet temperatures after every reset; a saving that creates a hot spot is not a saving.
Fan and pump affinity laws
Flow scales with speed, power with speed cubed. Cutting a fan to 80 % speed gives 0.8³ = 0.51, about 49 % less power - the largest single lever in most air-side systems.
Maintenance that preserves capacity
Clean coils (fouling cuts capacity and raises air-side ΔP), change filters on measured pressure drop rather than the calendar, manage cooling-tower water treatment, cycles of concentration and blowdown, brush chiller tubes, verify refrigerant charge, check belts and bearings, stroke-test economizer dampers, and calibrate temperature and pressure sensors - drifting sensors cause overcooling that no setpoint change will fix.
Worked example
A 200 kW chiller runs 6,000 hours a year. Raising chilled-water supply temperature by 2 K at 2.5 % per K saves about 5 %, i.e. 10 kW, or 60,000 kWh a year. Before banking it, confirm the most demanding rack inlet stays within target and that coil valves still modulate rather than sitting fully open.
Traps
- Leaving economizer dampers stuck closed, which silently deletes free cooling.
- Running every N+1 machine, so all chillers sit at low load and poor COP.
- Humidifying and dehumidifying, or cooling and reheating, at the same time.
- Changing filters far more often than ΔP justifies - labour and filter cost outweigh the fan energy.
- Tuning for a lower PUE while creating local hot spots.