692 



GREENHOUSE 



form a number of vertical coils, each containing from 

 six to ten pipes. Tlie upper ends of the manifolds are 

 joined at the front end of the heater and connect with a 

 flow pipe, while the lower ends of the rear manifolds 

 are joined to the returns. As a rule, the grate is of the 

 same width as the coil, and from one-half to two-thirds 

 as long. Although a box coil is much cheaper than a 

 cast-iron heater, when we add to its cost the expense for 

 grate, doors and other fittings, and of bricking it in, the 

 amount saved will not be large, especially as the coil 



999. Flow and supply pipe for under-bench flows. 



toilers are, as a rule, not more than one-half as lasting 

 »3 cast-iron boilers, most of which are complete and re- 

 quire no brick work or trimiiMii-^. 



Mot (Foier jPi'pinjr. — Moil. I n \,.,\ v,:.iir heating sys- 

 tems do not differ partimlirly ir<ii.i tlmse in which 

 steam is iised, except tliat larj. r -i ■> <1 i>iiM s are required 

 to afford til- I,.-. . -iir;, .-.mI, ,■! .1,, [ ..n,:. ily 4-inch cast- 

 iron pi I" ... I . .i i:; ! : I I , :i ..I ' . t . iidiouses, but 

 asthej-i: ; ! . ,! . .. iM at or iron fil- 



ings, till I . i i.iiig, and it is 



much 111" I '. 1 . . ■! 1 .11 .i repairs than 



when -111. ' rrwjoints are 



used. < I 1 . r in the pipes, 



the circ'iii ;' 1 ), . i. .,.i.. ..i_^. h, and it is not 



<'.-isv til -' .1. :li. lij-li I., iii|,.,r;inu-u 111 the water that 



i!m iI i>v^ .h . ill. -ad, as is often desirable. 



Will II till tl.iw pipes supply a number of houses, or 

 if the heater is at some distance from the Greenhouse 

 to be warmed, it is best to start from the boiler with one 

 large pipe, or with two pipes leading out from different 

 sides of the boiler, rather than to carry independent 

 pipes to each house. If there are several houses to be 

 heated, it is advisable to have the heater located at the 

 north end or side of the houses, as near the center as 

 possible, and carry the flow pipe along the ends of the 

 houses just over the doors, although, if necessary, they 

 may be beneath the level of the doorways. From this 

 main pipe one or more supply pipes can lead into each 

 of the houses. The size of the main feed pipe, as well 

 as of the branch pipes, should be in proportion to the 

 amount of radiation that they supply; and, in determin- 

 ing the amount that can be handled by pipes of different 

 sizes, it is advisable to use somewhat larger supply 

 pipes when all of the radiation, both flow and return, 

 is under the benches than when the flow pipes at least 

 are overhead. A similar allowance should be made when 

 the boiler is partly above the level of the returns, as 

 compared with a system in which the radiating pipes are 

 a number of feet above the top of the boiler, since in 

 the latter case a much smaller supply pipe will sufiice. In 

 a general way, the following sizes can be used as sup- 

 ply pipes: I^-inch pipes for 75 to 100 square feet of 

 radiation; 2-inch pipes for 1.50 to 200 square feet; 2K- 

 inch for 250 to 350; 3-ineh for 400 to «00; 3K-inch for 

 COO to 800; 4-inch for 1,000 to 1,200; and 5-inch for 1,500 

 to 2,000 square feet of radiation. The supply pipes 

 should, if possible, rise vertically from the heater to a 

 point higher than the highest point in the system and 

 then should have a slight fall, say 1 inch in 20 feet, so 

 that there will be no opportunity for the pocketing of 

 air in the pipes. It will, however, make but little dif- 



GREENHOUSE 



fi-iiiiii- uIm 111. r ihe pipes run up-hill or are given a 

 .sli;^lit .liiwiiwaiil sl.j|ie. and the former arrangement may 

 l)t.' ti-'il wlii-if it wiii lii/st suit the conditions. Incase 

 thi- |ii|H'.s an- .at 11. li iinili-r the benches, and it is im- 

 po>sil.l.- 1" viiik 111.- I..iil.rs much below the level of the 

 I-. Ill-, i' will I,.- \\.\\ ii. 1 1 II \ .■ the flow pipe run vertically 

 tniiM 111. 1.1 li' 1 : . .1 M. 1 1,1 1 if 8 or 10 feet (Fig. 999), and 



till 1 ' ' iitally along the ends of the 



lim. [ily pipes for each and drop- 



I'iii- nil- 1(11 M- . 1 1 ..f the benches. 



li 1- ...lull il.-.-.iiaMK- I... have some or all of the flow 

 pipes overhead, as this will greatly improve the circula- 

 tion and will aid in preventing cold drafts of air upon 

 the plants. Some make use of a single large flow pipe 

 in each house. This is located upon the [losts. a f.n.t or 

 so beneath tin- iI.Il;.-. ami .■arri.-s tin- wat.T t.. 1 h.- farthc-r 



end of the I -.■, V'.L. r.. I.ianrli pipi^ .■.mnril wiili tin- 



coils, but u liitli r .!i-tn!.iiti..ii ..1 t li.. Iir.it .an l.r >. .iir.al 



are used. These can be upon the ridge and purlin posts, 

 and it is often desirable to have one upon each of the 

 wall plates. The number and size of these flow pipes 

 will depend upon the width of the houses and the size 

 of the coils that they supply. The ammiiit of radiating 

 surface in the flow pipe itself should \<i- a. 1. 1. .1 t.. that in 

 the coil, in determining the size of Mi|.|iiv |.i|" that 

 will be required. For long houses it will ..It. n I.,- m .is- 

 sary to use one or more 3-inch pipes, hut ordiuarily 2- 

 inch or 2^-inch pipes distributed upon the posts and 

 wall plates will give the best results. 



The size of pipe used for the returns will depend upon 

 the length of the coils and their height above the boiler, 

 as the pipes for elevated short coils may be smaller 

 than those of considerable length that are below the top 

 of the boiler. Ordinarily 2-inch pipe will be desirable 

 for coils more than 75 feet in length, and will be prefer- 

 able to a smaller size when they are only 50 feet in length, 

 if the flows are under the benches and the lowest part 

 of the coils are below the top of the boiler. For short 

 coils, pipes as small as IK-inch may be used where they 

 are .i..iii.'wliiit i-lovated, but for ordinary commercial 

 Gr. . iilii.ii. - I', iiifh pipe is better up to 50 to 75 feet, 

 ami r all others, as, while small pipe fur- 



iii-l . 1 iii.-tiveradiation, the increased friction 



iiii|.. ill.. 111. .in Illation. 



If a sin;;]!' lartre flow pipe is used, it is often desirable 

 to have one or more of the returns elevated upon the 

 purlin posts and wall plates, but ordinarily the radiating 

 -surface should be distributed upon the walls (Fig. 1000), 

 and under the benches in houses where, as is now gen- 

 erally the case, there are walks along the side walls. In 

 houses in which it is undesirable to have bottom heat, all 

 of the pipes may be upon the walls; and this is also the 

 usual arrangement when solid bf.ls nrr- \isfd. except in 

 wide houses, in which case a ]...iti..ii ..|' tl..- i-.-turns may 

 he upon the sides of the b.-.K, i,. m ath tli.' walks, or 

 elevated upon the purlin and ri.lL-.' |.i.t-. i'lic pipes in 

 the coils maybe connected at th. ir in.l.'^ .itli.r by means 

 of manifolds or by tees and close nipples, but in either 

 case provision should be made for the expansion of the 



pipes, which may be done in the case of vertical coils 

 by running them partly across the ends of the houses 

 and in the horizontal coils by the same means, or by 

 placing the header at the lower end of the coil and a 

 foot or so lower, and connecting it with the ends of the 

 pipes by means of nipples and right and left ells. 



