Heating and Ventilating Systems

Many different methods have been devised for heating buildings. Each has its own characteristics, and most methods have at least one objectionable aspect (e. g., high cost of fuel, expensive equip­ment, or inefficient heating characteristics). Most of these heating methods can be classified according to one of the following four criteria:

1. The heat-conveying medium

2. The fuel used

3. The nature of the heat

4. The efficiency and desirability of the method

The term heat-conveying medium means the substance or com­bination of substances that carries the heat from its point of origin to the area being heated. There are basically four mediums for con­veying heat. These four mediums are:

1. Air

2. Water

3. Steam

4. Electricity

Different types of wood, coal, oil, and gas have been used as fuels for producing heat. You may consider electricity as both a fuel and a heat-conveying medium. Each heating fuel has its own char­acteristics; the advantage of one type over another depends upon such variables as availability, efficiency of the heating equipment (which, in turn, is dependent upon design, maintenance, and other

Factors), and cost. A detailed analysis of the use and effectiveness of the various heating fuels is found in Chapter 5 (“Heating Fuels”).

Heating methods can also be classified with respect to the nature of the heat applied. For example, the heat may be of the exhaust steam variety or it may consist of exhaust gases from internal com­bustion engines. The nature of the heat applied is inherent to the heat system and can be determined by reading the various chapters that deal with each type of heating system (Chapters 6 through 9) or with heat-producing equipment (e. g., Chapter 11, “Gas Furnaces”).

The various heating methods differ considerably in efficiency and desirability. This is due to a number of different but often interre­lated factors, such as energy cost, conveying medium employed, and type of heating unit. The integration of these interrelated compo­nents into a single operating unit is referred to as a heating system.

Because of the different conditions met within practice, there is a great variety in heating systems, but most of them fall into one of the following broad classifications:

1. Warm-air heating system (Chapter 6)

2. Hydronic heating systems (Chapter 7)

3. Steam heating systems (Chapter 8)

4. Electric heating systems (Chapter 9)

You will note that these classifications of heating systems are based on the heat-conveying method used. This is a convenient method of classification because it includes the vast majority of heating systems used today.

As mentioned, ventilating is so closely related to heating in its various applications that the two are very frequently approached as a single subject. In this series, specific aspects of ventilating are considered in Chapter 6 (“Ventilation Principles”) and Chapter 7 (“Ventilation and Exhaust Fans”) of Volume 3.

The type and design of ventilating system employed depends on a number of different factors, including:

1. Building use or ventilating purpose

2. Size of building

3. Geographical location

4. Heating system used

A residence will have a different ventilating system from a build­ing used for commercial or industrial purposes. Moreover, the

Requirements of a ventilating system used to provide fresh air result in fundamental design differences from a ventilating system that must remove noxious gases or other dangerous contaminants from the enclosure.

The size of a building is a factor that also must be considered. For example, a large building presents certain ventilating problems if the internal areas are far from the points where outside air would initially gain access. Giving special attention to the overall design of the ventilating system can usually solve these problems.

Buildings located in the tropics or semitropics present different ventilating problems from those found in temperature zones. The dif­ferences are so great that they often result in different architectural forms. At least this was the case before the advent of widespread use of air conditioning. The typical southern house of the nineteenth cen­tury was constructed with high ceilings (heat tends to rise); large porches that sheltered sections of the house from the hot, direct rays of the sun; and large window areas to admit the maximum amount of air. They were also usually situated so that halls, major doors, and sleeping areas faced the direction of the prevailing winds. Today, with air conditioning so widely used, these considerations are not as important—at least not until the power fails or the equipment breaks down.

Posted in Audel HVAC Fundamentals Volume 1 Heating Systems, Furnaces, and Boilers