Heat-Emitting Units
A heat-emitting unit is a device that transmits heat to the interior of a room or space. The two heat-emitting units used in steam heating systems are radiators and convectors. Simply defined, a radiator is a heat-emitting unit that transmits heat from a direct heating surface principally by means of radiation. A convector may be defined as a heat-emitting unit that transmits heat from a heating surface principally by means of convection. The heating surface of a convector is usually of the extended finned tube construction.
A detailed description of the heat-emitting units used in steam heating systems is contained in Chapter 2 of Volume 3, “Radiators, Convectors, and Unit Heaters.”
Air Supply and Venting
Two types of venting occur in heating systems. One deals with passing smoke and gases resulting from the burning of com- bustible fuels (e.g., coal, oil, and gas) to the outdoors and is described in the various chapters on furnaces and boilers. Another type of venting deals with the relief of pressure in steam heating systems by allowing a certain amount of air to escape (i.e., be vented) from the radiators. Venting radiators is described in Chapter 2 of Volume 3, “Radiators, Convectors, and Unit Heaters.”
Unit Heaters
A unit heater is essentially a forced draft convector. A centrifugal fan or propeller is used to force the air over the heating surface and into the room or space through deflector vanes. The principal operating components of a steam unit heater are shown in Figure 8-61. Unit heaters find their widest application in industrial and commercial buildings, gymnasiums, field houses, auditoriums, and other types of large buildings.
All unit heaters are described in considerable detail in Chapter 2 in Volume 3, “Radiators, Convectors, and Unit Heaters.”
Air Conditioning
Central air conditioning can be added to a steam heated structure by installing a water chiller or a separate forced-air cooling system (i.e., a split system).
The water chiller and steam boiler may be installed as separate units, or a complete package containing both units may be used. Water chiller installations are very rarely used in residential air con- ditioning. Split-system air conditioning dominates this field (i.e., with respect to steam heated residences).