DUCTS 

The ductwork in a system has to be installed in a manner that conforms to the duct & heating / cooling manufacturer's requirements and the Plumbing Act. 

​Generally the more obstructed (via tight bends or being crushed) the duct, the worse the system performs and the quicker components fail within the heater / cooler / air-conditioning system. It is all about air flow as restricted air flow causes a heat rise in the heater / cooler / air-conditioning and ducts, which then radiates heat outside the system.

Minimum radius bends are 1.5 to 2 times the diameter of the duct, specifics of which are available from the manufacturers. 

Non-compliant work voids the heater/cooler/air-conditioner warranty and can be enforced by the manufacturer. 

i.e. Braemar recommend the minimum bend radii to be: 

• 150 to 300mm duct - 1.5 duct diameters
• 350 to 400mm duct - 2 duct diameters

Flexible ductwork should be run through spaces at least as large as the diameter of the duct inner core. The ductwork should be supported horizontally at intervals of not more that 1.5 meters and vertically at intervals of not more than 1.8 meters. More information regarding ductwork installation with various photo's can be found at:
www.airah.org.au/imis15_prod/Content_Files/HVACRNNation/2009/July2009/HVAC

​There is a new code for ductwork for both heating and cooling which is under NCC 2001 Building Code of Australia Volume 23.12.5.3.

Basically R1.0 duct is required for heating only system installations in Melbourne instead of R.6. which was  previously required. In some instances R1.5 may be required for combined heating and refrigerated cooling systems.