39 



Heating Pipes. 



The four-inch cast-iron pipe for heating greenhouses has been 

 almost entirely discarded and in its place wrought-iron gas pipe is 

 used. Within the past few j'ears small pipes from one to two 

 inches in diameter for radiating surface have come into almost uni- 

 versal use in hot water heating, with one or more flow pipes 

 large enough to supply many of the smaller radiating pipes. "With 

 the latter more radiating surface is obtained, the water circulates 

 more rapidlj', because the smaller the pipe the less water there is to 

 heat. The pipes now used are practically of the same size as those 

 used for steam, and the system of arrangement is ver}' similar. 



Arrangement of the Pipes. — To obtain the best results the pipes 

 should be placed at nearly equal intervals through the house (Figs. 

 2, 3 and 4) and not in large coils or stacks. Most of them should 

 be above the benches, especially for those plants whose roots are 

 liable to injury by too much heat and moisture like the carnation, 

 etc. Plants much subject to leaf diseases should have some of the 

 pipes under the benches, as should also cutting benches and seed 

 beds where the root growth is to be encouraged. Two methods 

 of arrangement are most in use. Fig. 15, where the heated water 

 rises to the highest point at once and falls continuously to the 

 boiler, and Fig. 16, where the pipes continue to rise from the boiler 

 to the farthest end of the house and then fall by a regular grade 

 to the boiler. Both of these give good results, but in neither case 

 should the pipes go below the grade and rise again to above the 

 last level. The amount of pipe required will depend upon location, 

 construction and the kind of crop to be grown, the quantity vary- 

 ing from one foot of heating surface of pipe to three feet of glass 

 surface, to one foot to ten feet of glass surface. 



In all cases the diameter and the heating surface of pipe should be 

 larger than would be required to keep up tlie required heat when 

 the heating plant is run at its fullest capacity, for it is not economy 

 to force the boiler to its utmost. Two boilers are often put in, so 

 that one only may be run during the fall and spring, and both 

 together during the winter when needed, and that in case of the 

 breakdown of one the other one can do tlie work while repairing 

 is being done. 



Ventilating Fixtures. 



Of the many ventilator " lifters" in use, those that apply the 

 force by means of a light siiaft directly against the lifting end of 

 the sash are perhaps the best. Some of tliis type are very expen- 

 sive, while many are low in price. Tlie lifters that work with the 

 shaft and elbow joint are largely in use, but greater force is re- 

 quired with them than with the first-mentioned types. 



