G92 GREENHOUSE 



form a number of vertical coils, each coiitainin;,' from 

 six to ten pipes. The upper ends of the manitul.i^ :ui- 

 joined at the front end of the heater and connect witli ;, 

 'flow pipe, while the lower ends of the rear nj:imiil.i~ 

 are joined to the return^. As a rule, the grate is <•! tli.- 

 same width a- tlir r,.,\. mnl from one-half to two-ttiinls 

 as long. AIili'n-li :> !■ . -mI is much cheaper than a 

 ' ' '- Hs cost the expense for 

 rt of bricking it in, the 

 especially as the coil 



GREENHOUSE 



firciice whether the pipes run up-hill or are given a 

 sli^'bt downward slope, and the former arrangement may 

 111 u ed where it will best suit the conditions. In case 

 till pipes are carried under the benches, and it is im- 

 possible to sink the boilers much below the level of the 

 coils, it will be well to have the flow pipe run vertically 

 from the boiler to a height of 8 or 10 feet (Fig. 999), and 

 then branch and run horizontally along the ends of tho 

 houses, taking off the supply pipes for each and drop- 

 ping them below the level of the benches. 



It is often desirable to 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 posts, a foot or 

 so beneath the ridge, and carries the water to the farther 

 end of the house, where branch pipes connect with the 

 coils but a better distribution of the heat can be secured 

 ill houses more than 10 feet wide if two or more pipes 

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

 unci 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 

 .if tlie coils that they supply. The amount of radiating 

 surface in the flow pipe itself should be added to that In 

 till- coil, in determining the size of supply pipe that 

 will lie required. For long houses it will often be neces- 



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



boilers are, as a r 

 as ast b 1 m t fwh 



1 e no 1 k -n I or t nm n 

 H t n t Pi I -Mod rn hot water he 



g til > 

 nuch no 

 when sm I 

 used Ow 



If 



tl 



th fl 11 



When tie fl w p I I 



f the heat r at e d 

 to be war el t s be t to 

 laro-e p pe o th i i 



s les of tl 1 1 I 



the 



J ill.. . luls of the 

 if necessary, they 

 ways. From this 

 an lead into each 

 frid pipe, as well 

 ,.r.,,„,riioM to the 

 ;, ;:i .1,-termin- 

 . : of different 

 ;,i laiu'or supply 

 flow and return, 



heated till 



north end 1 1 1 



possible, and carry tli- i' 



houses just over tlir . I t 



may be beneath th" h i i 



main pipe one or iiiop 



of the houses. Tlio ^ ■ i i 



as of the braiicli i.i].. -. s| , ■, 



amount of radiation that t\,.", 



ing the amount that .-an !..■ lia 



sizes, it is ailvisal.lr io us,. 



]>ipes when all of the- ra-iiaii 



is under the benches than win n thr How pi] 



are overhead. A similar allowai should be 



the boiler is partly nl.ovo ihr l.v.l of the 

 compared with a systiiii in which the radiating pipes are 

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

 the latter case amuch smaller supply pipe will suffice. In 

 a general wav. the following sizes can be used as sup- 

 ply pipps: I'i-inch pipes for 75 to 100 square feet of 

 ridiiti.in- ■' inrli j.ipes for 150 to 200 square feet; 2%- 

 i„.h i.r ' ,0 lo :;-,n; 3-inch for 400 to GOO; 3^-inch for 

 cait. ^ II 1 in-li lor 1,000 to 1,200; and 5-inoh for 1,500 

 tl LMiiiM s.piaiv f.'ct of radiation. The supply pipes 

 should, it 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- 



sarv to use one or more 3-inch pipes, but ordinarily 2- 

 inoii or 234-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 p pes f r ele ted short co 1 may be smaller 

 tl an those of co s leral le length that are below the top 

 of the 1 1 O 1 n 1 h p p will be desirable 



f 1 1 f n length and will be prefer- 



1 1 1 tl ev are onlj 50 feet in length, 



11 11 benches and the lowest part 



1 1 1 e top of the boiler. For short 



I J [ 111 nch may be used where they 



1 t 1 te 1 but for or 1 nary commercial 

 1 scs 1/ nch p pe s better p to 50 to 75 feet, 

 1 ch p pe for all otl ers as wh le small pipe fur- 

 1 the mo t effect e ra 1 at on the increased friction 

 I les tl e c r ulat on , , . . , 



If a s ngle 1 ge flow p pe s sed t is often desirable 

 to 1 ave one or more of tl e retu ns elevated upon the 

 1 1 po ts an 1 wall plate but ord narily the radiating 

 f e lo llled t 1 d pon tl e walls (Fig. 1000), 

 \ 1 tl 1 n 1 1 e where, as is now gen- 



ii 1 tl II long the side walls. In 



1 nwh 1 t ul 1 le to ha 'e bottom heat, all 



ot tl e p pe m J 1 e p n the will and this is also the 

 al arr nge nent when sol d be Is are used, except in 

 w le house n wh ch ca e a port on of the returns may 

 be pon the s les of the beds beneath the walks, or 

 elevated upon the purlin and ridge posts. The pipes in 

 the coils may be connected at their ends either by means 

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

 case provision should be made for the expansion of the 



heatine. A wall coil. 



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. 



