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

Heat-Emitting Units

The hot water in both gravity and forced hot-water heating systems is circulated through the pipes to the radiators or other heat-emitting units, from which the heat is transferred into the room. Conventional cast-iron radiators (Figure 7-30) are often set on the floor or mounted to the wall. Many examples of these can still be […]

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Drainage

There should be a provision for adequate drainage facilities in a hot-water heating system during shutdown periods. Pitching all pipes to a central point is an important consideration in designing the system because it is essential to effective drainage. If drainage is not provided for, there is always the danger of the unheated water freezing […]

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Circulating Pumps (Circulators)

In forced-hot-water heating systems, circulating pumps (also some­times called circulators or booster pumps) are used to force the hot water through the piping or tubing. Figure 7-29 illustrates a typical location of one of these pumps on a return line. The operation of EXPANSION TANK Figure 7-29 Circulating pump is located on the return water […]

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Expansion Tanks

Expansion tanks (Figures 7-27 and 7-28) are installed in hot-water heating systems to provide for the expansion and contraction of the water as it changes in temperature. Water expands with the rise of temperature, and the excess volume of the water flows into the expansion tank. Another feature of the expansion tank is that the […]

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Pipe and Pipe Sizing

The tubing used in hydronic heating systems is made of copper, steel, plastic, or rubber. The size of the pipes or tubing used in these systems depends on the following two factors: (1) the flow rate of The water and (2) the friction loss in the tubing. The flow rate of the water is measured […]

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Control Components

The efficient and safe operation of a hot-water heating system requires the use of a variety of different types of controls, which can be roughly divided into either system-actuating controls (e. g., the room thermostat, burner controls, and circulating pump controls) or safety controls (e. g., high-limit controls, pressure-relief valves, and pressure-reducing valves). The safety […]

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Combination Water Heaters

A combination water heater is designed to produce both domestic (potable) and space heating hot water from the same source. As shown in Figure 7-24, an inner stainless steel tank containing the domestic hot water supply is immersed inside an insulated outer tank containing the prime water used for space heating. The prime water in […]

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Hydronic Furnaces

In a hydronic furnace, water is first heated in a boiler or water heater and then circulated through the coils of a liquid-to-air heat exchanger connected to the furnace air handler (Figure 7-23). Hydrotherm residential oil-fired hydronic boiler Hydrotherm residential MultiPulse AM Series Gas-fired hydronic boilers Figure 7-20 Examples of boilers used in hot-water heating […]

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Hot-Water Boilers

The boilers used in hot-water heating systems are made of cast iron or steel (Figures 7-19 and 7-20). The cast-iron boilers generally dis­play a greater resistance to the corrosive effects of water than the steel ones do, although the degree of corrosion can be significantly reduced by chemically treating the water. Gas (natural or propane), […]

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Forced-Hot-Water Heating Systems

Water as a medium for transmitting heat to radiators and other heat-emitting units gives up only sensible heat, as distinguished from steam systems, which heat principally by the latent heat of evaporation. The result is that the temperature of the heat-emitting units of a steam system is relatively high as compared with hot water. In […]

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