CHAPTER XVIII 



Greenhouse Heating 



As a rule, the florist should consult a practical heating engineer when 

 installing his heating plant. Every greenhouse establishment fur- 

 nishes its own problems and peculiarities in heating. These can be 

 best studied out and provided for by a practical man experienced in heat- 

 ing problems. For this reason I will not attempt to give advice as to laying 

 out and installing heating apparatus, but will briefly describe the most im- 

 portant systems in general use among florists. In writing this chapter I 

 have been ably assisted by Mr. E. S. Titus, of Hempstead, Long Island, 

 who has had ample experience in installing greenhouse heating apparatus, 

 and who erected the one in operation at the Cottage Gardens. 



Modern greenhouse heating is accomplished by two systems, steam and 

 hoi-water, and these are varied in several ways. 



Hot Water Systems 



There are a number of hot-water systems which are more or less distinct 

 in character. Three of these are widely used among florists. 



The Open Expansion Tank Method 



The first to be described is the old system, with open expansion tanks, 

 which is operated under low pressure. In the beginning, a type of heater made 

 of cast iron, technically called a one-piece boiler, was almost universally used. 

 This type of heater, although somewhat crude in design, was fairly efficient. 

 The radiating surface employed was made of a four-inch heavy cast-iron 

 pipe. The expansion of water was taken care of by numerous open cast- 

 iron tanks connected to the highest and most distant points of the heating 

 pipes. These tanks also formed a medium for the liberation of air from 

 the water contained in the apparatus. 



On account of the low expansion tanks this system necessarily required 

 a low head of water, and correspondingly low water temperature, the 

 actual boiling point being only slightly above the normal, or 212 degrees 

 Fahr. In practice, a radiation temperature of 150 degrees is rarely exceeded. 



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