STEAM INSTALLATION 



199 



are less complicated than the return traps. 

 A small, separate boiler is generally used to 

 operate the pump, and the exhaust and sur- 

 plus steam is turned into the general heat- 

 ing system after being reduced to low pres- 

 sure. Gas and electric motors are also used 

 to drive the pumps for returning the water 

 of condensation. 



Fig. 102. A type of steam return trap 



