October 10, 2025 in Our Experience
Presbyterian ladies' College — Electrical Services
The Joan Montgomery Centre is a new state of the art sports, aquatic and learning facility at Presbyterian Ladies’ College (PLC) in Burwood.
101 Collins Street — Electrifying an Icon
101 Collins Street is a Melbourne landmark attracting some of Australia’s blue-chip corporations to occupy its prestigious location. In an age of growing net zero carbon aspirations, converting this 57-storey icon into a fully electric powerhouse came with its own set of unique challenges.
When the doors first opened at 101 Collins Street, the World Wide Web was first announced, mobile phones were the size of house bricks and natural gas-heated buildings were the rule. Fast forward from 1991 and the use of fossil-fuel power within commercial buildings is under increasing pressure.
The management team and building owner of 101 Collins Street identified electrification as the way forward to meet their ambitions of carbon neutral certification to support the net zero requirements of tenants, and to future-proof their asset in line with upcoming changes to the NABERS Energy
rating system.
Concept to completion
A.G. Coombs Advisory was engaged in 2022 to undertake the original feasibility assessment of replacing the gas-powered plant with electric heat pumps and it was determined that this was to be carried out two stages, first the conversion of the domestic hot water (DHW) plant, followed by the more complex and much larger heating hot water plant.
A.G. Coombs Advisory prepared concept designs, design and construct tender packages and technical and installation administration services for the two projects.
Domestic Hot Water System Conversion
The first project converted domestic hot water (DHW) generation from the original calorifiers that were connected to the building’s natural gas-fired heating hot water (HHW) plant, to a system featuring highly efficient commercial heat pumps, smart thermal storage calorifier tanks and solar Photo Voltaic collectors to provide off grid DC electrical energy production as the primary form of heat generation.
8 kW of solar PV collectors were installed on the Level 55 roof area in addition to the existing solar PV feeding the building’s electrical supplies. The new solar PV system provides the primary form of heating for the
4 x 500 litre storage tanks via electric immersion heating elements.
Separating the systems will also enable the gas-fired heating hot water (HHW) plant to be able to be shut down during summer periods, further reducing gas consumption, pumping energy, plant operating costs and associated plant maintenance.
Through careful planning, coordination and staging, the new system was able to be cut over on a weekend so as to avoid any impact on tenants and occupant amenity.
During the initial period following commissioning, the new plant was found to have reduced energy consumption by 81 per cent compared to the previous plant and reduced associated greenhouse gas emissions.
This project was recognised at the Energy Efficiency Council’s 2022 National Energy Efficiency Awards with the Integrated Clean Energy Award.
This award recognises projects that have demonstrated excellence in integrating high levels of energy productivity and renewable energy at the site, portfolio, precinct or community level.
Heating Hot Water System Conversion
The initial concept and feasibility study for the second project evolved over
a two year period to concept design development, tender documentation, procurement, fabrication and installation.
Replacing the two existing 1,800kW (thermal) gas-fired water heaters with a combination of air-sourced heat pumps and water-sourced heat pumps to satisfy the building’s 75°C delivery temperature is the first time such an outcome has been delivered in Australia at this scale.
The solution required the installation of four 600kW air-sourced heat pumps installed outdoors operating in a new low-temperature heating circuit with temperatures between 25-32°C circulating water to the two 1,600kW water-sourced heat pumps installed indoors which extracts the heat from the loop and ‘boosts’ the water to the required 75°C.
But transitioning space heating within a fully occupied premium building without impacting tenants in the middle of a Melbourne winter is a challenging proposition.
Collaboration between the A.G. Coombs Advisory and A.G. Coombs Projects teams was pivotal to realising the successful conversion of the entire building’s space heating from a gas-fired system to electric heat pumps with zero impact on tenant comfort.
The month-long switchover process was aided by the use of backup electric systems that had been installed in the building following the 1998 Longford gas outage to mitigate any future gas shortages.
Heat pumps are ideally installed outdoors so they can readily extract energy from the surrounding air. Using technology similar to that found in a refrigerator, they transfer this heat to water for heating the building. Heat pumps are very efficient compared with gas boilers because they transfer rather than generate heat. The roof space on the adjoining 13-storey podium was identified as the ideal location for all external new plant.
This was advantageous as the outgoing gas boilers were located on Level 11 within the podium building, so it was possible to connect the existing infrastructure up to the new heat pumps on the rooftop without significant additional pipework infrastructure. This was space that wasn’t being utilised and there was no impact on the building’s lettable space. However, the podium roof was not designed to support the weight of new equipment.
A modular approach
Working with Arup and GHD structural engineers, the A.G. Coombs Prefabrication team developed a new steel platform that could be lifted
onto the rooftop in sections — a solution that would support the weight of new plant and receive the structural tick of approval.
This rooftop installation allowed for the prefabrication of heat pump and mechanical services modules that could be craned into position over allocated weekends. A.G. Coombs Projects played an important role, building the steelwork structure, four large heat pump modules
and separate pipework modules all built at the A.G. Coombs integrated
prefabrication facility. This approach also resulted in considerably reduced
on-site labour hours.
Prefabrication contributed significantly to minimising downtime, particularly
when lifting plant equipment onto a rooftop in completed modules rather than individual components. This prefabricated ‘plug and play’ approach minimised tenant impact because it didn’t require an on-site team building in situ over many weeks – an important factor in projects of this nature.
Powering up
Heat pumps require significant electrical capacity. A.G. Coombs collaborated with electrical consultancy, Compass Engineering, and the on-site electrical contractor Brolec Electrical, to design new electrical infrastructure. This included four new mechanical services switchboards and significant cabling to replace an existing switchboard, including the provisions for generator-backed power supplies for a majority of the new heat pump plant in line with standby power provisions for the site.
Careful consideration was given to how the power would be reticulated within the building to the plant locations.
Discover more at:
- The Future is Electrification – 100 sec video produced by 101 Collins.
- High Solar – AIRAH article published in Ecolibrium magazine.
- National Energy Efficiency Award – Integrated Clean Energy
Award winner.