Document KJbO5L4qoM7RwkrNQQvBbqy0N

HEATINC VENTILATING AIR CONDITIONING GUIDE 1943 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, D _ 50.000 X (40 - 0) _ TMco __ R ---------- 2208---------- 9058 Sq ft' For row 2, O _ 50,000 X (65 - 40) R--------- 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 so 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 Loads * (EDR) 2265 1415 849 Connection LoADb (EDR) 2265 or 1132 1415 or 708 849 or 425 One quarter of total row load. bOne 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 ruin 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). Horizontal return pipes may be carried past doorways and other ob structions by using the scheme illustrated in Fig. 17: . It will be noted that the large pipe, in this case, runs below the obstruction and the smaller one over it... Branches from steam mains in one-pipe gravity steam systems should use the prefiried. connection shown in Fig. 18, but where radiator condensa tion does not flow back into the main the acceptable method'shown in the same figure may be used. This acceptable method has the advantage of giving a perfect swing joint when connected to the vertical riser or radia tor connection, whereas the preferred.connection does not give this swing CHAPTER 15. PIPINC FOR STEAM HEATINC SYSTEMS without distorting the angle of the pipe. Runouts from the steam main are usually made about 5 ft long to provide flexibility for movement in the main. Offsets in steam and return piping should preferably be made with 90-deg ells but occasionally fittings of other angles are used, and in such cases the length of the diagonal offset will be found as shown in Fig. 19. Fig. 15. Dripping Main Where it Rises to Higher Level Fig. 17. Looping Dry Return Main Around Opening Acceptable method Preferred method Fig. 18. Methods of Taking Branch from Main To find length C-muftiply A by constant for angle 9 Fig. 19. Constants for Determining Length Offset Pipe "rt H pockvs rT Wet return Fig. 20. Dirt Pocket Connection Fig. 21. Dripping End of Main into Wet Return Fig. 22. Dripping End of Main into Dry . Return Fig. 23. Dripping Heel of Riser into Dry . Return Dirt pockets, desirable on all systems employing thermostatic traps, should be so located as to protect the traps from scale and muck which will interfere with their operation. Dirt pockets are usually made 8 in. to 12 in. deep and serve as receivers for foreign matter which otherwise would be carried into the trap; They are constructed as shown in Fig. 20. On vapor systems where the end of the steam main is dripped down into the wet return, the air venting at the end of the main is accomplished 309