HOT WATER HEATING 159 



It is not within my province to recommend any particular 

 make of generator, circulator, or pump, but I would advise, 

 as a means of saving money in the end, that you consult a re- 

 liable firm of greenhouse heating engineers and get them to 

 figure on your requirements. 



The returns should have a steady pitch back to the boiler 

 of about 10 in. in 100 feet, and there should be no low places or 

 pockets in the system. Vents should also be placed at the 

 highest points in a pressure system to allow the air to escape. 

 Water in a common gravity or open circuit system cannot be 

 heated above 212 deg. F., while water at 15 Ibs. pressure will be 

 234 deg. F. 



I have personally had little experience with hot water heating, 

 but the modern system is so well liked and so highly recom- 

 mended by parties who are using it, that it is well worth 

 considering. The best type of boiler for this purpose is the 

 saddle back, as this type holds a very small volume of water, 

 and it has an immense amount of direct heating surface, there- 

 fore heats up very quickly, and it is claimed that it operates 

 more economically than any other type of boiler construction 

 known. There is really no comparison between the old fash- 

 ioned gravity system with its clumsy 4-in. pipes and leaky 

 joints, and the modern pressure system with small threaded 

 pipes and rapid, forced circulation. It would certainly be wise 

 for the smaller places, where no regular night fireman is em- 

 ployed, to consider this method of heating. 



The accompanying illustrations show better than words can 

 describe a few of the places being heated today with hot water. 

 This would seem to be sufficient demonstration of the capa- 

 bility of this system. 



