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Ductless Heat Pumps -- An Energy-Efficient Way to Heat and Cool Your New Addition

Ductless heat pumps cool and warm your home more efficiently by eliminating one of the major sources of wasted energy in a conventional HVAC system—the ductwork. Like a conventional heat pump, ductless units function by transferring heat outside in summer and moving heat indoors in winter. When the expense of installing ductwork as well as the potential costs of energy losses from the ducts are removed from the equation, ductless heat pumps add up to greater energy conservation and lower operating costs. Though ductless technology is relatively new to the U.S., it was first marketed in Japan over 40 years ago and quickly adopted by Europeans. Ironically, Americans initially introduced conventional air conditioning to post-war Japan. However, the bulky systems and need for invasive ductwork made it a poor match for Japanese high-density residential housing. A more compact and quieter alternative, capable of cooling a house room-by-room instead of using ducts became the objective of research conducted by the Mitsubishi Electric Corporation in the 1960s. Because energy costs were much higher in Japan than in the U.S., the solution also had to be more energy-efficient than the conventional central A/C or window units Americans brought to the country. After many years of research and development, Mitsubishi introduced the world's first ductless wall-mounted mini split air conditioner to the market in 1968.

How It Works

Ductless heat pumps represent the integration of two functions, cooling and heating, into a single compact system consisting of only three major components:

  • Indoor: A space-saving air handler mounts high on the wall or ceiling of a single room to be cooled and heating. This unit comprises an indoor refrigerant coil and a blower to distribute air. The indoor component doesn't require ductwork, a window mounting or any direct opening to the outdoors.
  • Outdoor: The outdoor unit in a ductless system consists of a compressor, outdoor coil and coil fan integrated into a compact cabinet normally located next to an exterior wall behind or at one side of the house.
  • Connections: The indoor and outdoor unit are linked by an insulated conduit that incorporates two refrigerant lines and the thermostat control wiring. The conduit requires only a three-inch hole in an exterior wall for installation.

All-Year Comfort

While ductless A/C only provides cooling, a ductless heat pump handles both cooling and warming functions without the necessity for a conventional gas-fired furnace. A reversing valve installed in the refrigerant circuit reverses the flow of refrigerant when the system switches from cooling mode in summer to winter heating mode.

  • Summer cooling - When the weather’s warm, the indoor coil in the wall-mounted unit extracts heat energy from inside the room where it’s installed and transfers it to refrigerant circulating between the coil and the outdoor unit. Conveyed outside through the refrigerant conduit, the heat energy is compressed by the compressor and then dispersed into the air by the outdoor coil and coil fan.
  • Winter warmth - In winter, the system reverses and the coils trade functions. Down to about freezing, there is enough latent heat in outdoor air to warm an interior space. The outdoor coil utilized in ductless heat pumps becomes the heat extractor, harvesting heat energy from cold winter air and transferring it to refrigerant. After the molecules of heat are concentrated by the compressor cycle, the hot refrigerant travels through the conduit to the wall-mounted indoor coil where it is dispersed into the room by the blower fan.

Why Some Homeowners Choose Ductless Heat Pumps

Ductless heat pumps and air conditioners were a late arrival to the American scene. However, the acceptance of the technology has been rapid. While the market for central air conditioning has remained static in recent years, manufacturers of ductless systems reported double-digit sales increases in 2011 and 2012. Over the past five years as a whole, industry stats show a yearly growth rate of 12 percent for ductless systems, despite a lagging economy. The reasons behind the increasing preference for ductless as an alternative to central A/C and window units can be attributed to many factors:

  • Remodeling and renovation - Ductless has made its greatest impact in remodeling and add-on scenarios. Frequently the cost of extending ductwork from an existing central A/C into a remodeled area or a new addition is prohibitive. Window units, on the other hand, are inefficient, intrude on interior design and still leave heating issues unaddressed.
  • Convenience and simplicity - Ductless heat pump technology consolidates both the cooling and heating functions into a single unit. This creates a smaller equipment footprint and simplifies upkeep and routine maintenance.
  • Energy efficiency - Because you are cooling only the specific rooms that need it and not wasting energy on other spaces, ductless units have a jump on efficiency that central A/C cannot equal. In cooling mode, ductless heat pumps are 40 percent more efficient than a central air conditioner and 25 to 50 percent more efficient than conventional gas-fired or electrical resistance heating. Ductless heat pumps are now commonly available with seasonal energy efficiency ratio (SEER) ratings above 20, while most high-efficiency central A/C units average in the 16 to 18 SEER range. Because the system operates without ducts, the inevitable efficiency declines due to duct leakage and thermal loss over the years are not a factor. 
  • Low-impact installation - The expansion of ducted central A/C to a renovated area or a new addition creates a lengthy disruption in your home, as walls and ceilings must be opened up for ducts and supply and return grilles have to be installed in every room. By comparison, a ductless heat pump installation requires only interior mounting of the air handler/coil unit and routing of the refrigerant conduit through a three-inch hole in an exterior wall. The outdoor unit is an uncomplicated installation that needs only connection to the conduit and a power source. The unit can normally be installed in any inconspicuous spot up to 50 feet away from the indoor component. A ductless unit for a single room can usually be installed by a two-person crew in just one day.
  • Safety and clean air - Because there is no combustion involved anywhere in the heat pump process, no dangerous combustion byproducts are produced that need to be vented to the exterior of the house. This includes, most notably, carbon monoxide (CO) gas that can be deadly if it accumulates in the enclosed interior spaces of the home. The absence of combustion also means no fire danger from gas burners or electrical hazards from baseboard or space heaters.
  • Low-key design - A ductless system blends into interior decor easily. The profile of a typical ductless air handler extends only about seven inches out from the wall and the external cover presents a sleek, high-tech appearance. All controls are recessed behind doors and most daily operation is executed with a handheld remote control. A ductless system offers mounting options for the air handler that include wall and ceiling installation or freestanding floor models. Furniture, wall hangings and rugs can be placed anywhere without concern about blocking the wall or floor vents required by conventional cooling and heating.
  • Enhanced security - Historically, the only alternative to central A/C in individual rooms used to be a window unit. However, the installation of window air conditioners represents a weak link in home security. Easily removed from the exterior, a window unit provides intruders with quick access to your home and valuables.

The Ductless Zone

Ductless technology incorporates flexibility that allows each room with an air handler to become an independent temperature zone controlled by its own dedicated thermostat. Occupants of every room can now enjoy personalized interior comfort. A single outdoor unit in a ductless heat pump system can accommodate up to four indoor air handlers, delivering individualized temperatures to each zone.

Ductless technology requires the specialized sales, installation and service expertise available from a Mitsubishi Electric Diamond contractor. Mitsubishi Electric Cooling & Heating helps you locate the manufacturer-authorized contractor nearest to you anywhere in the state. Let us direct you to a reputable local expert qualified to explain the wide range of efficiency and performance benefits available from ductless heat pumps.

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