Tenants were supplied with heating and cooling from the base buildings AHUs and VAV boxes located on each floor. Any additional cooling or heating requirements were provided to the tenants by local condenser water package units.

Sydney Central's traditional tenant condenser water system was consuming large amounts of energy. The system was static and offered no flexibility when building loads varied leaving the building owner with high operating costs for tenancy owned/maintained systems.

The challenge was to reduce energy consumption, and increase Sydney Central's building star rating and capital value, while performing system upgrades in a live building without affecting tenant control.

• Supply and install condenser water shut-off valves that isolate whole floors or individual packaged air-conditioning units when not required, reducing demand on the base building condenser water system.

• Supply and install variable speed drives on pumps and fans to allow speed modulation and turn down in low load scenarios.

• Ensure that sufficient water flow through package units and computer room air conditioning units are maintained at all times.

• Formulate and implement an operational pumping and cooling tower fan sequence that minimises electrical consumption.

• Fine tune the condenser water system ensuring minimal electrical consumption without affecting tenant comfort or critical air conditioning for the computer rooms.

The building had an Optergy Enterprise EMS with over three years of energy consumption data and the ability to track and tune any strategies in real time. The energy consumption from the base building tenant condenser water system reduced by 69% and over the next 12 months yielded a total of 250 MWh energy savings or the equivalent of $50,000 at 0.2c per kWh, with a ROI under two years.

The tenants were extremely satisfied with their reduced energy costs and increased energy star rating of the building. The landlord was equally pleased with the increased energy star rating for the buildings as this meant an increase in capital value as well as an opportunity to attract potential tenants.