Every cooling season, split systems across Melbourne move indoor heat to the outside air. That rejected heat is normally wasted. A split system for strata hot-water heat-rejection captures part of that heat and uses it to pre-warm the building’s domestic hot water. In a building with central gas hot water, this can cut common hot water gas use by around 12 per cent.
How split-system heat rejection works
In cooling mode, the indoor unit absorbs heat from room air and sends it to the outdoor condensing unit via refrigerant. The condenser then releases that heat into the outside air. A split system does not create cold; it moves heat out of the space. Because the compressor adds its own heat to the refrigerant, the total rejected heat is larger than the cooling capacity on the indoor rating label.
Without heat recovery, all of that thermal energy leaves the building. The condenser fan runs, the outdoor coil gets warm, and the heat dissipates. This is the normal path for almost every residential and small commercial split installation.
The normal path outside
Standard units have no water connection. The only reason to modify the refrigeration circuit is to capture heat before the condenser releases it. That modification is what makes a split system for strata hot-water heat-rejection different from a standard split install.
Why strata hot-water heat-rejection fits
Apartment buildings often have a central gas hot water plant. A central boiler heats water in a large storage tank, then a circulating loop delivers it to apartments. The boiler fires whenever the stored water drops below a set temperature. If the incoming cold water is preheated from 15°C to 35°C or more, the gas boiler does less work to reach its final set point.
Strata buildings are a good fit because the hot water system is already centralised. One heat exchanger and one preheat tank can serve the whole building. You do not need a separate heat recovery device in every apartment.
Central plant creates one point
A central loop gives a single integration point for a refrigerant-to-water heat exchanger. The recovered heat can enter the cold-water feed to the storage tank or a dedicated preheat tank. This keeps the installation simpler than trying to recover heat from dozens of small split systems.
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