410 ENGINEERING ON THE FARM 



set in the walls between the studs. Over each opening in 

 the floor or walls is a register of perforated cast iron, as 

 shown in Figure 315. 



In each pipe leading from a furnace is a damper so that 

 any pipe may be closed at will. There is a return air duct, 

 to be used when the weather is too cold to allow the heated 

 and used air to pass out of the house. The rooms are full 

 of air at all times, and more air cannot be forced into them 



a 



by the small pressure exerted by the warm air in the pipes 

 below. In order to get this warm air into the rooms, a 

 way must be provided for the cold air to escape. This is 

 done by means of a return air duct, which may open into a 

 chimney and allow the air to pass out, or under the furnace 

 and permit the air to be reheated and returned to the room. 

 When this is done, the fresh-air duct may be closed or 

 partly closed. 



First-floor pipes should not be less than 12 to 16 inches 

 in diameter. Second-floor rooms must be reached through 

 rectangular ducts, about 4X14 inches in size between stud- 

 ding. Unless special construction allows a large pipe to the 

 second floor, it will be found difficult to heat upper rooms, 

 especially to windward. All pipes in cellar and in walls 

 should be covered with asbestos paper to protect the pipes 

 and to save heat. This covering should be water-proofed to 

 prevent absorption of dampness during summer months. 

 The dampness hastens the rusting of the sheet-metal pipes. 

 A damper in every pipe and also in the smoke flue will aid 

 materially in controlling and distributing heat. 



Hot-water system. A hot-water system is only a slight 

 elaboration of the principle illustrated in Figure 311. 

 Enlarge the base to inclose the fire and reduce the size 

 of the tube or pipe between the fire and the rooms to be 

 heated, make that part of the circuit in the room large, 

 to give enough radiating surface, and the result is the 

 system shown in Figure 316. The main body, A, cast in 

 sections for convenience in handling, is often made quite 



