Greenhouse Heating 



In recent years a type of heater, made of cast iron, in sections, or the so-called 

 sectional boiler, has been employed quite largely. Notwithstanding its 

 crudeness, and the cumbersome appearance of this system, it has enjoyed 

 a remarkable popularity among florists, and its simplicity of operation, and 

 general durability, have kept it in the front rank for heating florists' estab- 

 lishments of moderate size. 



The Pressure Method 



In the second, a "pressure system," with open tanks, which are set 

 from twenty-five to forty feet above the heater, two-inch and two and one- 

 half-inch wrought pipe is generally used. The practical working of this 

 system differs in reality from the first only in that the expansion tank is set 

 at a higher elevation, thus increasing the pressure and boiling point. 



Assuming the water line in the expansion tank to be thirty-five feet 

 above the top of the heater, a pressure of fifteen pounds per square inch 

 in the boiler would be obtained, thereby raising the boiling point to 250 

 degrees Fahr. While the old style of one-piece heater, in some cases, is 

 not sufficiently strong to safely withstand this increased pressure, the sectional 

 boilers possess ample strength to do so. 



The cast-iron sectional boiler is so well known that little comment 

 thereon is necessary. It is efficient, fairly economical and durable, and safe 

 as well. Wrought-iron or steel tubular boilers of several different types 

 are also largely used in the hot-water system. The two most frequently 

 met with are the horizontal-return tubular and the firebox boiler, of loco- 

 motive or similar type. 



Sectional Boilers 



A sectional boiler for hot-water heating should be designed with the 

 greatest care. If the sections are bolted together, the bolts should in no 

 case pass through the water spaces, but through the legs, outside of the 

 water spaces. It is very important in hot-water apparatus that friction 

 should be reduced to the minimum. It has been found by actual experience 

 that the efficiency of some apparatus is much impaired by these bolts. If 

 the sections are connected together by drums and nipples, particular atten- 

 tion should be given to the size of these, for if the openings in the con- 

 necting drums are unduly small the circulation will be retarded, and this 

 means a serious impairment in the efficiency of the heater. This type of 

 boiler should have about one square inch of grate surface for every 1.3 square 



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