Document jyxXknqe4aVLOdwN33dLw4OpN

Heating Ventilating Air Conditioning Guide 1939 larger sizes are frequently located externally to the occupied and con ditioned space and are connected thereto by means of delivery and return ducts. Such an arrangement permits the location of the conditioning unit convenient to either the source of refrigeration or outside air or both It frequently permits the use of the basement or of space less valuable than that on the level or floor of the occupied zone. The design then approaches that of a Central System, (see Chapter 21). Oftentimes the same type of unit may find application in an exposed position for one job and in a concealed location for another. Thus it can be seen that it is not possible to define a unit merely on the basis of its location. Frequently conditioning units are built into the structure or into the architectural design of a room so that they are entirely concealed except for the dis charge and return grilles which are designed so as to correspond to the decorative scheme of the room. Air Distribution With self-contained units, or any units exposed within the conditioned space, the aiir distribution is usually through grilles or louvres built into the equipment. The grilles or louvres are usually adjustable to assist in directing the air properly. The discharge of the air from this type of unit is usually directed upward at some angle with respect to the horizontal so that the cool air is not directed at the occupants, but at the same time is. carried to the most remote part of the room. In general, the air discharge should be designed to distribute cool air over the entire zone, dropping slowly and returning to the unit below the breathing line and along the floor. The location of doorways, air vents and heat-exposed walls should be carefully observed as they have a marked effect on the direction of air flow and on its uniformity of temperature. ' With the suspended type of unit, located within the conditioned space, sufficient outlet air velocity should be provided to give adequate induction and mixing with the room air thereby preventing the immediate dropping <jf the air stream and resulting objectionable cold drafts. Where the units are located outside the conditioned space, air dis tribution is more frequently provided through multiple outlets located in ducts from the conditioning unit. The location of these outlets is quite critical and is influenced both by the building construction, economies of connections and by the distribution of load. There are a wide variety of outlet types used, and most of these have fixed delivery characteristics, thus requiring careful consideration in their location. Some types of outlets are now available with adjustable vanes thereby permitting some alteration in the delivery of the air stream after installation. This frequently eliminates objectionable down drafts re sulting from the impingement of the air stream against posts, pillars, lighting fixtures, and beams. TYPE* OF UNITS Several types and designs of air conditioning units in production and proposed are available for selection. New designs are constantly ap- ^ .pearing, with, new improvements, greater capacities,. wider range of ., application:and .superior construction... It will. be.impossible to cover in 452 Chapter 22. Unit Heaters. Ventilators. Air Conditioning, Cooling Units this chapter the many types of construction on the market. Illustrations of current makes and models will be found in the Catalog Data Section. A few typical designs of conditioning units will be described in detail. An all-year floor type heating and cooling unit for an exposed location and with direct expansion coil supplied with refrigerant from a remotely located compressor is shown in Fig. 12. A cooling coil for use with chilled water may be substituted for the direct expansion coil indicated. The fans below the separate cooling and heating elements deliver the air against deflectors thereby obtaining distribution across the face of the element and preventing condensate from dripping down into the fans. The plate upon which the fans are mounted serves as the drip pan from which the water is conducted to the drain. Separate elements are used for heating and for cooling. Thus this unit may be used automatically for Fig. 12. Floor Type Heating and Cooling Unit heating and cooling without manual control. When the unit is used for summer conditioning only, the heating coil may be omitted for the installation. The illustration indicates an evaporative type humidifier and drain pan. Other units are available in which a target spray humidifier is sub stituted for the evaporative type thereby providing a unit for summer cooling and dehumidification, at the same time supplying humidification in winter for application in rooms with other existing heat sources. Still another unit is available in which the fans are mounted at the top of the unit delivering directly through a grille and drawing their air supply through the cooling and heating coils. Other variations in pro portion and details of construction of this general arrangement are common. With this type of unit, ventilation is usually provided by means of a separate duct connected to the inlet of the unit. eniirely different arrangement shown in Fig. 13 places both the air inlet and the discharge at the top of the unit. The fan at one side diszn^fi8 a*r downward to the bottom where it turns and passes horiontally through an atomizing spray air washer. The path then, con- 453