A conventional central air conditioning system normally operates at a fixed speed. When the full cooling or heating capacity is not required, the system turns itself on and off to keep the room temperature at the selected level. This system has a single indoor unit connected to a network of ducts. A fan distributes hot or cool air to different parts of a building through these ducts and brings air back into the central system. This is not as efficient as a VRF system, as it heats or cools the entire building uniformly to a selected temperature. Moreover, energy losses in the fan and ducts of a conventional system can add 30% to the energy bill.

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