A very low velocity system was required to ensure low noise, but it also had to treat and deliver large volumes of air. As well as undergoing acoustic tests, these AHUs were also tested for fan pressure, volume and air integrity. Fan and motor speed and motor efficiency were also checked. All tests were passed.
Chilled water is supplied to the air-handling units by roof-mounted chillers working with ice storage. Hot water for the heating coils is provided by gas-fired boilers. Run-around coils enhance energy efficiency.
Ventilation is demand controlled, with temperature sensors in the space and carbon-dioxide sensors in the return-air ducts.
Some of the air-handling units are inverter controlled, so that components such as fans can operate at variable speed to respond to the enormously variable capacity requirements in the different parts of the building at different times.
