Heating, Ventilation and Lighting 



IQI 



to the top as shown. In Fig. 33 it comes 

 nearer to the indirect system, lacking only 

 the intervening duct which serves to mix 

 the cold and hot air before delivery into 

 the room. This system applied to the 

 wooden wall would force the radiator into 

 the room, and the fresh-air inlet would be 

 below it in the floor. 



Steam and hot-water systems have 

 many points of similarity. Both feed 

 their heating vehicle through compara- 

 tively small pipes, in which the heating 

 vehicle, whether in double or single pipes, 

 effects a current and returns to the seat of 

 its generation. 



A brief synopsis of the various sys- 

 tems of steam and hot water may serve 

 to show their several points of similarity 

 and difference. 



In the two-pipe steam system the 

 flow main rises from the boiler and 

 connects by small branches with the 

 several radiators, while the return pipes, 

 connected with each radiator opposite the 

 flow entry, are carried down independently 

 to the main horizontal return located 

 below the level of the water in the boiler. Although the independent return may 

 be preferable, it is the practice in a tier of radiators to connect with a common 

 vertical return pipe. The objection to the former method is in the extra expense 

 of piping, and, in some rooms above the first floor, the ungainliness of the added 

 piping in the rooms. 



In the one-pipe steam system the mains are carried up and make one 

 connection with each radiator, each pipe serving for flow and return. In this the 

 principle lies in the fact that the higher-temperatured vehicle flows in the upper 

 part of the horizontal pipes. (This principle is explained in chapter 12.) 



In the overhead supply steam system the flow main is carried upward to a 

 height above the topmost radiator, and is connected with the various heating 

 surfaces in the interval of its downward course. The return pipes are independent 

 of this circuit, at least until a level below that of the water in the boiler has been 

 reached. 



The perfect system of the two-pipe hot water type is one in which the flow 

 main is carried upward to a point above the radiators, where it enters the expan- 

 sion tank at the side, leaving room above for the expansion of water. The return 

 is connected with the bottom of the expansion tank, and it is this return pipe 

 which serves to supply the radiators in its passage to the heater. The overflow pipe 

 extends upward from the top of the expansion tank, either through the roof or 



A glazed-tile mantel. For ordinary use the addition of a 

 simple tile shelf, supported on consoles, would be desirable 



