DEVICES USED FOR HEATING 



133 



rents enter and leave the furnace, and the type with, 

 pipes (Fig. 210) conducting the heated air to the vari- 

 ous rooms in the house. The pipeless furnace is the 

 cheaper to install. 



The chief advantages of the hot-air furnace are 

 the low cost of installation, the ease with which it can 

 be adjusted to sudden changes in temperature on the 

 outside, and the combination of heating and ventila- 



COOl AlftfROT-l LIVING-ROOM 



SMOKE 

 PIPE 



G-RATE 

 ASH PIT 



UVING-ROOM FLOOR 

 COLD-AIR CHAMBER 



WARM-AIR CHAMBfR 



'AIR SPACE BETWEEN 

 WARM-AIR AND COLO-AIR 

 CHAMBERS 



RADIATOR 

 CLEAN OUT 

 FOR RADIATOR 



HOT BLAST DRAFr 



HUMIDIFIER 



DRAFT DOOR 



FIU 208 PIPELESS FURNACE 



tion which it furnishes. Its chief disadvantages are 

 the difficulty, often encountered, of heating the wind- 

 ward side of the house, leakage of gases and smoke 

 into the air supply, and the cost of operation. Some 

 of these disadvantages can be overcome if painstak- 

 ing attention and study are given to the installation of 

 the furnace. 



How is a home heated by means of a hot-water 

 heating plant? In this type of heating plant (Fig. 211) 

 the heat of combustion is applied to water in the fur- 

 nace which is carried by convection currents through 

 pipes to radiators in various rooms of the house. The 

 radiators absorb some of the heat from the water and 

 in turn heat the layers of air next to them, setting in 

 motion air convection currents. Part of the heat is 

 also radiated through the room ; however, it is by 

 convection currents that the room is heated evenly. 

 The hot-water heating plant is more efficient than a 

 hot-air furnace and it maintains a more even tempera- 

 ture. It is more expensive to install, however, and it is 

 slow to heat. 



How is a home heated by means of a steam heating 

 plant? The parts of a steam heating plant (see Fig. 

 212) look very much like the parts of a hot-water 

 system. They differ considerably, however, in opera- 

 tion. In the steam heating system the boiler is only 

 partly filled with water, which is converted into steam 

 by the fire. As steam forms in the boiler, the pressure 



that is created is sufficient to force the steam through 

 steam pipes to the radiators. In the radiators the 

 steam condenses to water. As much heat is given to 

 the radiators as was required to convert the water to 

 steam in the boiler of the furnace. The radiators in 

 turn heat the room by convection and radiation. The 

 condensed water in the radiators returns to the boiler 

 to be changed again to steam. 



A steam heating system costs less to install than a 

 hot-water system and gives more heat in proportion 

 to the amount of fuel burned. As with the hot-water 

 system, it provides no means of ventilation for the 

 house. Therefore fresh air must be supplied through 

 windows and doors or by some special entrance pro- 



5TEAM SUPPLY PIPE-""- 



PRESSURE _ 

 GAUGE 



SAFETY VALVE- 



DAMPER 

 EGULATOR 



SMOKE 



WATER 

 LEVEL 



BOILING 

 WATER 



FIRE BOX 



RETURN PIPE 



DRAFT DAMPFIU 



GRATE 



ASH DOOR 



FIG. 209. BOILER OF STEAM HEATING SYSTEM 



vided in the building. Steam heating systems are used 

 very successfully in heating large buildings or in 

 heating groups of buildings by a central heating plant 

 because steam can be more successfully transported 

 long distances than can hot water or hot air. 



Oil burners which are attached to furnaces have 

 been gaining in popularity in recent years. They are 

 clean and efficient heating devices, producing an even 

 and automatically controlled heat. 



In sections of the United States where natural gas 

 is abundant, gas jets automatically controlled are 

 sometimes used in the furnace. This method provides 

 clean and efficient heating, but in most communities 

 it is more expensive than oil or coal. 



Electric heaters and ranges are probably the most 

 convenient and cleanest of all heating devices, but the 



