CHAPTER XI 



HOT WATER INSTALLATION 



General Principles. Before discussing 

 the installation of a hot water heating sys- 

 tem it is necessary to have in mind the phy- 

 sical and mechanical principles involved. 

 Briefly they are these: Water increases in 

 volume as it is heated and it is consequently 

 lighter in weight. When a fire is lighted un- 

 der a water boiler the water around the heat- 

 ing surface expands and, being lighter, is 

 forced upward by the heavier, colder water. 

 Popularly speaking, the hot water "rises." 



The practical problem is to conduct the 

 hot water from the boiler to the coils where 

 the large radiating surface permits the water 

 to give up its heat to the air in the house 

 and then, as it becomes colder and heavier, 

 to conduct it back to the boiler where it will 

 displace the warmer and lighter water there. 

 Gravity is the force utilized to produce cir- 

 culation. It acts with a force proportional 

 to the difference in weight between the col- 

 umn of warm water and the column of cool 

 water. 



167 



