Document jVEb0g9OEdXVpyv6KdNw5oy2

Heating Ventilating Air Conditioning Guide 1938 Example 5. Assume that the heating units shown in Fig. 26 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? Chapter 16. Piping for Steam Heating Systems 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. DRIPPING Any 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 steam flow. Any steam main in any heating system can be elevated if dripped (Fig. 27). Steam mains also may be run over obstructions without a change in level if a small pipe is carried below the obstruction to care for l Fig. 26. Typical Piping for Atmospheric and Vacuum Systems with Thermostatic Control (Central Fan System) Solution. For row 1, D _ 50,000 x (40 - 0) r. R ~ ---------2208------------- 9058 " ft` For row 2, R,, = -5--0-,-0--0-0- 2X20(685--------4-0-1) = 5661` 8(1 ft- For row 3, D _ 50,000 X (80 - 65) ,,,,,,,, R------------- 2208--------- = 3397 " 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 Load* (EDR) 2265 1415 849 Connection Load**. (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. 326 Fig. 27. Dripping Main Where It Rises to Higher Level Fig. 28. Looping Main Around Beam Fig. 29. Looping Dry Return Main Around Opening Fig. 30. Methods' of Taking Branch from Main To find length C-muttiply A by constant tor angle B Fig. 31. Constants for Determining Length Offset Pipe om 9pocket , _ E"K-----Wet return Fig. 32. Dirt Pocket Connection the condensation (Fig. 28). Return mains may be carried past doorways or other obstructions by using the scheme illustrated in Fig. 29; in vacuum systems it is well to have a gate valve in the air line. Branches from steam mains in one-pipe gravity steam systems should use the preferred connection shown in Fig. 30, 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 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 327