Greenhouse Heating 



feet of radiating surface. If a fireman is on duty all night, the proportion 

 of radiating surface can be somewhat increased. 



Firebox or Locomotive Boiler 



The "firebox boiler" has many friends among florists. Its efficiency 

 is fair. It is easy to fire, and is safe. It has, however, some weak points. 

 The legs of a locomotive firebox have much surface exposed to the atmos- 

 phere, and, in consequence, are very vulnerable to corrosive effects. A green- 

 house boiler is out of commission about half the year. During this period 

 of rest the firebox is in a condition of extreme exposure. If the grates are 

 left in, with an accumulation of ashes either on the grate or in the pit, in 

 contact with the boiler legs, they will absorb moisture from the air and 

 mcite active corrosion wherever they touch the boiler. A little care would 

 practically obviate these defects, but the average florist stops firing as soon 

 as warm weather renders it unnecessary, and probably does not look at 

 his heating apparatus again until the approach of winter. He who neglects 

 a locomotive firebox boiler in this manner will soon find in it numerous 

 holes. 



While the circulation of water in the locomotive type of boiler is not 

 ideal, it is, however, fairly good. In this type of boiler there should be 

 not less than three openings, or inlets, for return water ; that is, one inlet 

 in each of the three sides of the firebox, which openings should be near 

 the bottom, or below the grate. It will improve the circulation if these 

 openings are connected into one trunk. 



Horizontal Tubular Boilers 



The horizontal tubular boiler is probably the most efficient, and the 

 safest heater for general florists' use. It should be set higher at the front 

 than at the back. This elevation should be not less than twelve nor more 

 than twenty-four inches. The boiler should be built longer than the regu- 

 lar type. It should have no drum on top. The tubes should be of iron, and 

 not steel. The shell would undoubtedly last longer if made of iron rather 

 than steel, but it is now practically impossible to build boiler shells of iron, 

 as iron plates cannot be had except after months of waiting, and then at 

 a prohibitory cost. 



During the inactive season steel tubes corrode much faster than iron, 

 for which reason the increased cost of iron tubes may well be afforded. 

 This type of boiler, which is the ideal one for hot-water circulation, is effi- 



179 



