Document KJ3Q5er7BeZjbN40YORMjagNw

HEATING VENTILATING AIR CONDITIONING GUIDE 1941 Typical connections to manifold coils having more than 6 pipes Fig. 9. Typical Pipe Coil Connections Trap Fig. 10. Typical Piping Connections to Concealed Heating Units with Wet Returns Fig. 11. Dirt pocket Trap Piping Connections to Indirect Radiators 286 CHAPTER 14. PIPING FOR STEAM HEATINC SYSTEMS where EDR = equivalent direct radiation, square feet. Q = volume of air, cubic feet per minute. 4 = the temperature of the air entering the row of heating units under con sideration, degrees Fahrenheit. tl = the temperature of the air leaving the row of heating units under considera tion, degrees Fahrenheit. 60 = the number of minutes in one hour. 55.2 = the number of cubic feet of air heated 1 F by 1 Btu. 240 = the number of Btu in 1 sq ft of EDR. Example 4- Assume that the heating units shown in Fig. 14 are handling 50,000 cfm of air and that the rise in the first row is from 0 to 40 F, in the second row from 40 to 65 F, and in the third row from 65 to 80 F. What is the load in EDR on each supply and return connection? Solution. For row 1, R 50,000 X (40 - 0) 220.8 9058 sq ft. For row 2, R 50,000 X (65 - 40) 220,8 5661 sq ft. For row 3, R 50,000 X (80 - 65) 220.8 3397 sq ft. Each row of heating units consists of four stacks and each stack has two connections 90 that the load on each stack and each connection of the stack is as follows: Row i 2 3 Total Load (EDR) 9058 5661 3397 Stack Load* (EDR) 2265 1415 849 ` Connection Load<> (EDR) 2265 or 1132 1415 or 708 849 or 425 One quarter of total row load. SOne half of stack load if two steam connections are made: otherwise, same as stack load. The pipe sizes would then be based on the length of the run and the pressure drop desired, as in the case of radiators. It generally is considered desirable to place the in direct heating units on a separate system and not on supply or return lines connected to the general heating system. DRIPS A steam main in any type of steam heating system may be dropped to a lower level without dripping if the pitch is downward with the direction of steam flow. Any steam main in any heating system can be elevated if dripped. Fig. 15 shows a connection where the steam main is raised and the drain is to a wet return. If the elevation of the low point is above a dry return it may be drained through a trap to the dry return in two-pipe vapor, vacuum and sub-atmospheric systems. Horizontal steam pipes may also be run over obstructions without a change in level if a small pipe is carried below the obstruction to care for the condensation (Fig. 16). 287