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For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to move heat from a cool space into a warm, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house; during the cooling season, heat pumps move heat from your cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide up to 4 times the amount of energy they consume.
The most common type of heat pump is the air-source heat pump, which transfers heat between your house and the outside air. If you heat with electricity, a heat pump can trim the amount of electricity you use for heating by as much as 30% - 40%. High-efficiency heat pumps also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months. However, the efficiency of most air-source heat pumps as a heat source drops dramatically at low temperatures, generally making them unsuitable for cold climates, although there are systems that can overcome that problem.
For homes without ducts, air-source heat pumps are also available in a ductless version called a mini-split heat pump. In addition, a special type of air-source heat pump called a "reverse cycle chiller" generates hot and cold water rather than air, allowing it to be used with radiant floor heating systems in heating mode.
Higher efficiencies are achieved with geothermal (ground-source or water-source) heat pumps, which transfer heat between your house and the ground or a nearby water source. Although they cost more to install, geothermal heat pumps have low operating costs because they take advantage of relatively constant ground or water temperatures. However, the installation depends on the size of your lot, the subsoil and landscape. Ground-source or water-source heat pumps can be used in more extreme climatic conditions than air-source heat pumps, and customer satisfaction with the systems is very high.
A new type of heat pump for residential systems is the absorption heat pump, also called a gas-fired heat pump. Absorption heat pumps use heat as their energy source, and can be driven with a wide variety of heat sources.
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If you struggle with installing and removing window air conditioners every summer and complain about losing the view out of your windows, or the convenience of opening them to fresh air, you are not alone in thinking there must be a better way.
In fact, there is. It's called ductless air conditioning. This technology can be used to heat or cool and is especially well-suited to homes and businesses built without central air systems. It is used increasingly in home improvement projects where a porch is enclosed or an attic is converted to bedrooms.
Every building and every situation presents its own problems with climate control. Architects and engineers have realized this for years and they have struggled to adapt air-conditioning technology to modern living and working demands. Ductless air conditioning systems now make the job much easier.
These systems use no ductwork or ducted air distribution. Because of that, there are few places where the systems cannot be installed. In addition to homes, the systems have been placed in thousands of offices, shops, motels and hotels, schools and universities, computer rooms, banks, hospitals, nursing homes and labs.
Going ductless can mean changing indoor climates from variable and unpredictable to comfortable and consistent, without expensive renovation work or compromising the integrity of the structure. And the work can often be done by a trained professional in a matter of hours.
Ductless systems are made up of four components: the condensing unit, located outside the building; the indoor unit, or units, which can be wall or ceiling mounted; thin refrigerant lines, which connect the outdoor unit to the indoor unit; and a wireless remote or wall monitor, which controls the entire system.
Simple copper tubing and electrical wiring connects the outdoor unit to indoor units. Refrigerant is pumped from the outdoor condenser coil and compressor through the tubing to the indoor unit or units. A fan then quietly distributes cool air drawn across the unit's evaporator coil.
According to the Air Conditioning and Refrigeration Institute, there are a number of benefits users get with a ductless system. These include:
- Easy and clean installation.
- Easy maintenance.
- Efficient and quiet operation, with heating too.
- Simple controls.
- Attractive and efficient design.
- Doesn't take up window space, which adds to the beauty and security of your home. |
Ductless mini-splits are the ideal air conditioning solution for installations where adding ductwork is impractical or too expensive. The matched combination of indoor air handler and outdoor condenser is efficient and easy to install.
Dual zone A/C units let you cool or heat two separate areas or one large area. They come in sizes of 18,000 and 24,000 BTUH total capacity. They include one outdoor condenser, two indoor air handlers and two remote controls.
The indoor units can be mounted on any outside wall - a 2-3/4" diameter hole is all that's needed for connecting the two units. A mini-split opens the view from a window that might otherwise be blocked by a window air conditioner.
The units are operated by LCD wireless remote controls and are packed with convenience and comfort features. |
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Ductless (Mini-Split) Heat Pumps
Combine the flexibility of room air conditioners with the whole house cooling of central systems
Summary
Installing central air conditioning in a home that does not have forced air ducts can be difficult. Ductless mini-split heat pumps provide a unique solution to bringing central air conditioning into homes. By piping refrigerant to individual coils within air handlers mounted throughout a home (rather than a single refrigerant coil/air handler and central ductwork), mini-split heat pumps do not require ductwork for central air conditioning. Because the refrigerant lines take up much less room than do typical ducts, much less effort is required in installation in a retrofit.
Ductless mini-split systems combine the flexibility of room air conditioners with the whole house cooling of central systems. Although some systems provide heating and cooling, ductless mini-split heat pumps are usually installed primarily for cooling.
In a conventional heat pump, a single indoor unit (refrigerant coil and air handler) and single outdoor unit (condenser and compressor) serve the entire house. Air is cooled at the evaporator coil and distributed around the house via ductwork. In ductless systems, there is (usually only) one outdoor unit serving multiple indoor units (each containing a refrigerant coil and blower). Refrigerant is piped from the outdoor unit through small-diameter insulated refrigerant lines directly to individual rooms or zones. Cooled air is blown into the room by a fan in the individual evaporator units. The term "mini" is used to describe the small indoor units located in each room or zone.
While distribution energy losses in conventional systems have been estimated as high as 30 percent, distribution losses for ductless systems are about one to five percent.
PATH Attributes
Because they do not rely on ductwork (which is often leaky and can account for a third of the energy usage for heating and cooling), mini-split heat pumps can boost energy efficiency. The ability to control each zone separately can also contribute to energy efficiency.
Ease of Implementation
Ductless heat pumps are installed using conventional methods for heat pump/air conditioner installation. However, extra care must be taken to prevent refrigeration leaks and to ensure proper operating pressures.
Initial Cost
The cost of ductless heat pumps has declined as the technology has become established in the marketplace. A 2004 polling of ductless heat pump suppliers showed costs for ductless heat pumps to run between $500 and $900 per ton, depending upon the type of system and the number of zones desired per unit.
Operational Cost
Ductless systems can reduce energy costs for heating and cooling over conventional heat pumps. Cost will vary with equipment efficiency rating and the leakiness (and location) of ducts to which it is compared.
U.S.Code Acceptance
Few, if any, code or regulatory barriers limit ductless technology. The National Appliance Energy Conservation Act of 1992 requires that split systems have a minimum SEER of 10.0 and HSPF of 6.8. In 2006, these minimum requirements will increase to 13 SEER and 7.7 HSPF. The Air-Conditioning and Refrigeration Institute provides a list of air conditioners and heat pumps and their rated efficiency.
Field Evaluations
Not Applicable
Installation
Ductless systems are relatively easy to install. It takes two installers about a day to install a system having up to three zones. Wiring for power and controls is easier than with a conventional unit since wires can be run along with the refrigerant lines. Refrigerant lines from outdoor units can span up to one hundred feet to indoor units.
Indoor units are about six to eight inches deep and are mounted flush on a wall or ceiling, or recessed in a drop ceiling. A three-inch hole behind the unit is used for attaching wiring, refrigerant lines, control cables, and a condensate drain.
Warranty
Warranty varies with manufacture. A typical warranty is one year on indoor units and up to six years on compressors.
Benefits/Costs
Ductless system benefits include ease of installation-air ducts are bulky and require special structural attention, while split system piping can often be routed through walls and joists. Further, split systems allow zone control for increased comfort and efficiency. System energy losses are reduced because distribution takes place through insulated refrigeration lines rather than ductwork. Aesthetics are improved over window units and no windows need to be blocked. Each zone has its own thermostat, so occupants can modify temperatures in each zone.
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Ductless split air conditioning offer higher efficiency and reduced noise without a large hole in the wall or an open window. By separating compressor and condenser fan from indoor blower, the noisiest components are outside and away from the room. The indoor part of the ductless air conditioner has remote control capabilities and a timer to cycle the system only when needed.
Since mini split air conditioners have no ducts, they avoid energy losses associated with ductwork of central forced air AC systems. Duct losses can account for a significant portion of energy consumption for space conditioning, especially if the ducts are in a unconditioned space such as an attic.
Ductless air conditioning offers Higher Efficiency vs. window air conditioning, less noise, and no costly ductwork.
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