Small Duct, High-Velocity Air Conditioning Systems
A unique feature of the SDHV systems is the air distribution system. The air distribution system, together with the blower-coil unit, is usually installed in attic spaces of older homes that were not designed for forced-air circulation heating or cooling.
Thus, installation of a SDHV system helps satisfy the air conditioning needs for older homes, replacing less-efficient window air conditioners. The outdoor condensing units used in SDHV systems are identical to those used in conventional split systems.
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Another advantage of using of SDHV systems is the use of small, 2-inch insulated, flexible tubing to supply cooled air throughout your home. The ductwork weaves in between spaces in the walls, ceilings, or floors similar to a central vacuuming system. In fact, high velocity systems use small supply vents with cover plates the size and shape of CD-ROMs (or smaller). This makes the system popular in older homes where conventional ductwork would require much more demolition to the existing space.
A SDHV heat pump system is comprised of a conventional outdoor heat pump unit and an indoor blower-coil unit and duct system similar to the system used for cooling, except that the blower-coil unit is equipped with a larger coil for refrigerant management and a back-up heat source, such as a resistance heating element or hot water coil, is added.