Little Chat on Greenhouse Heating 



J. N. MacARTHUR 



Heating Engineer 



NEED FOR HIGHEST EFFICIENCY IN HEAT PRODUCTION— HOW THE GREENHOUSE BOILER BECAME SPECIALIZED 



AND TYPES THAT FIT SPECIAL PURPOSES 



SOMEBODY, somehow, somewhere, came 

 to a hasty conclusion about greenhouse 

 heating; and then proceeded to spread 

 it broadcast as a conclusive conclusion. 

 The conclusion was that the heating of a 

 greenhouse was a most vexatious problem; 

 one as yet to be satisfactorily solved. In 

 that word "satisfactory" it turns out was 

 mainly the question of coal burned. 



Evidently, it loomed up as a great bugaboo, 

 quite as the question of gasolene used to, with 

 automobile owners. But what boots it, if 

 gasolene does cost 30 cents a gallon instead of 

 20, if with improved engines and carbureters, 

 you get an equivalent increase in power and 

 mileage? 



Whether it is a question of greenhouse coal, 

 or an auto's gasolene, it all simmers right down 

 to the basis of getting proportionate returns 

 for your expenditures. 



There is a man up at Port Chester, N. Y., 

 who has a greenhouse 18 by 50 feet, who grows 

 on the side bench enough spring bedding 



The modern square sectional type of greenhouse boiler. 

 It is easy to install, to repair, and to operate. And easy on 

 coal. All clean-out doors, dampers and other operating 

 parts are entirely on the front 



plants that he sells to his neighbors to entirely 

 pay for the coal he burns. 



But like the auto again, the genuine 100 

 per cent, pleasure you get out of it, is so far 

 and away ahead of the money you put in it, 

 that it's overshadowed. 



But you can burn a needless amount of 

 coal, just like you can use an unnecessary 

 amount of gasolene. The boiler might be 

 termed the carbureter of the heating system. 

 Just as a special type of carbureter must be 

 devised for each type of engine, so should a 

 greenhouse be heated by a specially designed 

 greenhouse boiler. 



Next to all out-doors, and church lobbies, 

 the greenhouse is the most difficult thing to 

 heat. When you think of that thin film of 

 glass, not more than an eighth of an inch thick, 

 which is the only thing between the flowers 

 inside and the zero weather outside, you won- 

 der it can be heated at all. 



Talk, for instance, with the owner of those 

 huge commercial Rose houses, covering, not 

 so many square feet, but acres; and you will be 

 surprised to learn the small amount of coal 

 required to heat them, compared with other 

 buildings. Due allowance, of course, being 

 made for the great difference in structural ma- 

 terial. 



Now consider the fact that in residence 



heating the pipes are run vertically. This 

 gives every advantage of the force of gravity 

 to insure the return of the water to the boiler, 

 and so make the circulation both rapid and free 

 from air pockets. 



Now compare greenhouse heating, with its 

 pipes running horizontally under the benches, 

 and you at once see why it is that a boiler 

 that may economically heat your house, is 

 not successful for your glass enclosed garden. 



In reverse, however, you at once appreciate 

 that a boiler which is economical for green- 

 house heating, is exceptionally so for all other 

 purposes too. 



Contrary to your impression, perhaps the 

 evolution of the greenhouse boiler reads quite 

 like a fairy tale. 



Like every worth while thing, its inception 

 started with one man. In this case, it was 

 an enthusiastic lover of flowers, an English- 

 man who came to this country, following the 

 lure of larger opportunity. 



In those days, more than 60 years ago, be- 

 fore the day of steam or hot water adaptation, 

 greenhouses were heated in what now seems a 

 ridiculous way. A sort of stove or furnace 

 was bricked in at one end of the greenhouse 

 and the chimney or flue carried along under 

 the centre of the house to the other end; 

 where it ended in the chimney proper. This 

 flue was made of brick and tile. The heat 

 radiating from it warmed the house excessively 

 at one end, and in opposite proportion at the 

 other. Incidentally, it often leaked gas, kill- 

 ing the plants. 



Of course, such a heating method devoured 

 coal most discouragingly. 



Our English flower lover, who was also a 

 heating engineer, seeing his opportunity, de- 

 signed a sort of half furnace, half boiler, by 

 putting a water jacket around part of it. 

 From it, he ran hot water pipes down one side 

 of the house, and the brick flue down the other. 

 This gave a more even distribution of the heat, 



Cutting the top off the square sectional boiler like you 

 would a boiled egg and cracking off some of the side makes 

 its construction clear. The fire comes into the upper 

 story through the side flues, between each section. Then 

 it starts back and forth on its three time passage or fire 

 travel. It is this long fire travel that has much to do with 

 its short coal bill. See the illustration of a single section 



127 



and also placed it at the sides of the house, 

 where it was most needed. 



But still it was at best a one-sided proposi- 

 tion, all being in favor of the hot water side. 



The latest improved type of round sectional boilers used 

 for heating greenhouses of moderate size. It has all the 

 economy advantages of its brother, the square sectional 



So next he designed a regular, full-fledged 

 boiler in which instead of having the fire and 

 hot gases simply heat the water that was 

 only directly over the fire, as it does in a tea- 

 kettle, he made a water jacket hump or V- 

 shaped extension on the back. Back and 

 forth through this water-jacketed extension, 

 the flames, hot gases, and smoke had to pass 

 before they could go out from the smoke box 

 and up the chimney. 



■ This so increased the efficiency that with 

 the same coal, three houses of the same size 

 could be heated instead of one. Pipes were 

 used on both sides of the house and the 

 chimney flue carried directly from the boiler 

 through the roof, like any rightly behaved 

 chimney. 



For the first time it was possible to heat 

 all parts of the house uniformly and, by putting 

 valves on the pipes, have full control of the 

 heat distribution. 



Not to this very day has there been de- 

 signed a boiler that surpasses this hump boiler 

 for economy. 



But as houses grew larger, it became a prob- 

 lem to cast the big humped boilers needed. 

 It was also difficult because of their size, to 

 handle them when installing. And so it was 

 that one of the pioneers in greenhouse build- 

 ing determined to design a boiler that had 

 all the advantages of the hump one and none 

 of its limitations. 



