NOTES ON WINTER GARDENING. 93 



In modern green house heating we have only to consider two 

 general systems — steam and hot water in closed circuits. Each 

 system has its ardent champions; each has its advantages and 

 its faults. Both claim economy of fuel and ease of control as 

 specially strong points. It is claimed that the hot water 

 heaters require less attention than steam heaters. This, how- 

 ever, is a doubtful advantage save at night as frequent atten- 

 tion to the fires is essential to the most economical use of fuel. 

 On the other hand, fewer boilers are required to heat a large 

 plant if steam be used and the first cost of piping for steam is 

 very much less than for hot water. There is no doubt that in 

 the economy of construction and in efficiency, when the circuit 

 is very crooked, steam has the advantage. On the other hand, 

 there is less fluctuation in temperature with hot water. 



In selecting a hot water heater, observe the amount and 

 arrangement of direct heating surface, the arrangement of water 

 sections in the heater, the ease of cleaning and the readiness 

 with which leaks may be mended. Horizontal sections are 

 usually most efficient. 



For steam heating an ordinary second-hand horizontal flue 

 boiler, condemned for high pressure work, will be found cheap 

 and satisfactory. 



7. Pipes and Piping. 

 The common practice both with steam and hot water at 

 present is to carry the "riser" or flow pipe to the farther end 

 of the house and there distribute heat by means of smaller 

 return pipes. If practicable there should be a gradual ascent 

 in the flow pipe from the furnace to the point of distribution in 

 the returns. There should then be a gradual descent of the 

 return pipes to the furnace. The size of pipe best suited for 

 returns depends upon the length of the coils and also to a cer- 

 tain extent upon their height above the heater. In general, 

 two inch pipe is to be preferred if hot water is used and one 

 inch or one and one-quarter inch with steam. We sometimes 

 use one and one-half inch pipe for hot water circuits, but unless 

 the coils are very short the friction reduces the efficiency of the 

 apparatus. 



