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undarnental Series Item :Choosing the Best HVAC System file:///c~/windows/TEMP/0,263 7, I b287,00.h 28 Window-Mounted Air Conditioners and Heat Pumps Window-mounted air conditioners and heat pumps cool yr heat individual conditioner They have a low initial cost and are quick and easy to install. They are also used to s a central heating or cooling system or to condition selected spaces when the central shuts down. When used with a central system, the units usually serve only part of the conditioned by the central system. In such applications, both the central system and units are sized to cool the particular conditioned space adequately without the other In other applications, where window units are added to supplement an inadequate e~ system, they are selected and sized to meet the required capacity when both system Window units require outside air and cannot be used for interior reoms. Window units are factory-assembled with individual controls. However, when severs used in a single space, the controls may be interlocked to prevent simultaneous hea cooling. For energy management in hotels, motels and other hospitality applications, on/off control system_may be used to de-energize units in unoccupied rooms. Other consider when selecting window unit systems are that window units are built to appli; standards, rather than building equipment standards, so they may have a relatively s high energy usage. Through-The-Wall Mounted Air Conditioners and Heat Pumps, PT. PTHPs Through-the-wall air-conditioners, packaged terminal air conditioners (PTACs), heat packaged terminal heat pumps (PTHPs) incorporate acomplete selfi-contained air-c~ direct-expansion (DK) cooling system, a heating system (gas, electric, hot water, or controls, and fan in an individual package. They are designed to cool ar heat individ~ Each space is an individual occupant-controlled zone into which cooled or heated air discharged in response to thermostatic cantrol to meet space requirements. These systems are usually installed in apartments, assisted-living facilities, hospitals motels, office buildings, and schools. Units range from appliance grade to heavy-dut commercial grade. Unitary System Selection Guidelines Unitary systems are selected when it is decided that a central HVAC system is too la expensive for a particular project, or a combination system (central and unitary) is ne certain areas or zones to supplement the central system. For example, unitary syste frequently used for perimeter spaces in combination with a central all-air system that interior building spaces. This combination will usually provide greater temperature ar control, air quality, and air (conditioned air and ventilation air) distribution patterns, th possible with central or unitary units alone. As with any HVAC system, bath the adva the disadvantages of unitary systems should be carefully examined to ensure that th selected will perform as intended far the particular application. Factors to consider when selecting unitary systems include: Heating and cooling capability can be provided at all times, independent of otl in the building but basic systems do not provide close humidity control. Howe humidity control is not needed for most applications. Close humidity control, if computer room applications or the like, can be accomplished by selecting spE purpose packaged units. Only the one unit and one temperature zone is affec malfunctions. One drawback of unitary units is that the operating sound levels high. Another is that appearance can be unappealing. Otherdisadvantages ai filtration options may be limited and outdoor air economizers are not always a provide low cost cooling. Also, condensate can be a problem ifi proper remove provided. Individual room control (on/off and temperature) is simple and inexpensive. H because temperature control is usually two-position, there can be swings in rc temperature. The air distribution can be adjusted by the occupant, but is limits airtlow quantity is fixed by design. Ventilation air is provided whenever the cor