Concerned about the reliability of its chiller plant through the peak summer period, the team at Westmead Hospital in western Sydney decided to review redundancy options.

Knowing a risk management strategy was necessary, the engineering team called Active Air Rentals and asked for a design and construct solution.

With approval for the project given on December 16, 2017, the Active Air project team got straight to work, ensuring a backup system was in place before Christmas.

Installing 3,500kW of air-cooled chiller plant was a big ask, added to that was the need to supply temporary power to operate the system.

Five chillers, along with four generators, a custom-made switchboard and multiple sets of 240mm2 power lock cables were required to get the job done.

Active Air senior project manager, Jonathan Towe, was charged with planning and organising the logistics.

"The small footprint which we had to work with onsite meant that craning in equipment and setting it up was tight," he said.

"With upwards of 12 truck and semi-trailer movements, a traffic management plan had to be devised to allow for the transportation and positioning of equipment.

"We had people at five different points along the four-way intersection managing the situation and allowing for truck access. A 300m reversing path was also required to allow the trucks to turn back after making their deliveries."

With the crane lifts and positioning in progress outside, mechanical plumbers set about cutting into the existing chilled water system.

To accommodate chilled water from the temporary plant, 300mm diameter stainless steel pipe ran through the plant room and the adjacent wall where a set of custom-built headers were installed to accept water from the chillers outside.

Once the cranes and transports retreated, the 100mm flexible hose used to connect the chillers to the headers was laid out.

A team of electricians then began running out the 240mm2 cable sets that would be used to connect the chillers, switchboard, splitters, and generators.

The temporary system also required a certain amount of fine control; accepting communication over RS485 from the building management system (BMS) to the panel.

This allowed for managing generator starts, machine rotation and general step control of the chillers to meet the combined plant demand.

Once in a position to commission the machines, water flow and pressure drops were balanced across vessels to ensure that all machines had adequate flow and could contribute to the building system effectively.

This was achieved by using a combination of ancillary pumps and balancing valves.

The solution was commissioned by December 22 – just four working days after work orders were received.

What had begun as a 'just in case' exercise quickly became an integral piece of the building system as Sydney experienced one of its hottest summers on record.

The chillers and generators were put to the ultimate test, running effectively through the heat to help ensure the building plant was able to maintain chilled water supply temperatures through peak load times.

"The [Active Air] installation team are to be congratulated for their assistance in providing excellent service and advice that enabled this critical piece of infrastructure to perform exceptionally well during very testing conditions," according to David Dobson, WSLHD senior project manager capital works, Program Management Office (PMO).


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