The. Steam ONE-PIPE STEAM SYSTEMS

Transcription

1 FULL-COLOR TRAINING GUIDE SERIES The of Steam ONE-PIPE STEAM SYSTEMS

2 ONE-PIPE STEAM SYSTEMS PIPING AND TROUBLESHOOTING

3 ONE-PIPE STEAM SYSTEMS ONE-PIPE STEAM SYSTEMS A. HOW ONE-PIPE SYSTEMS WORK 1. movement in the system and radiators a) vent design and operation b) Main vent and riser vent installation c) must move out through vent for steam to enter. d) Main and riser vents must work first to provide steam to all radiators at the same time. 2. Condensate movement in the radiators a) Radiator supply valves b) The condensate must flow back through the same valve where the steam is entering c) One-pipe radiator valves cannot be throttled 3. vent shut-off a) Float prevents water from escaping b) shuts off when internal element heats up 4. Dimension A condensate movement and return to the boiler in One-Pipe Systems a) The lowest steam carrying pipe must be at least 28 inches above the normal boiler water line. B. SYSTEM CHECKLIST 1. The system piping must provide dry steam wet steam causes water hammer, component damage and water level problems. 2. Make sure air vents are working. a) The most important vents are the main and riser vents. b) Make sure they are working and piped to protect them from water hammer. c) Check the radiator vents. 3. If replacing an old, large boiler, consider the need for a boiler feed system to provide the water storage needed until the condensate returns. 4. One-pipe gravity systems cannot be zoned with zone valves. a) When the zone valve closes, the whole pressure of the boiler pushes back on the returns. b) This requires 30 inches of height over the water level for every PSI at the boiler. c) Most one-pipe systems will have to be equipped with drip traps and feed pumps to allow zoning with zone valves. C. THE NEAR-BOILER PIPING 1. The near boiler piping is the first line of defense for a reliable system. a) Correctly installed, the near boiler piping acts as a moisture separator and boiler water level stabilizer. b) Incorrectly piped or undersized near boiler piping will cause carryover the system components may be damaged and poor heat distribution and noise will occur. D. SIZING THE BOILER 1. The boiler output must be large enough to satisfy all connected radiators. 2. Size the boiler by doing a radiator count, totaling all of the connected Square Feet. 3. Select a boiler with a Steam Net Load Rating (in square feed of EDR) greater than the total connected radiation. 4. If the boiler is undersized, the radiators furthest away will not heat. 5. If the boiler is severely oversized, the steam flow in the mains will cause too much pressure drop. The water in the returns will rise and water hammer can occur. E. COUNTERFLOW SYSTEMS 1. Basic system piping and operation a) Condensate must flow against the flow of steam b) The boiler header must enter the top of the main on counterflow systems. 2. Pipe sizing one pipe counterflow systems a) Mains are sized one size larger than they would be for parallel flow piping. This allows room for the condensate to flow along the bottom of the pipe. F. PARALLEL FLOW SYSTEMS 1. One pipe parallel flow with wet return a) Operation b) Pipe Sizing 2. One pipe parallel flow with dry return a) Operation b) Pipe Sizing 3. One pipe parallel upflow system a) Operation b) Upfeed Riser and Runout piping c) Pipe Sizing 4. One pipe parallel downflow system a) Operation b) Downfeed riser piping c) Pipe Sizing G. TROUBLESHOOTING 1. Water hammer on start-up 2. Water hammer during mid-cycle 3. Water hammer on shut-down 4. Hammering in the boiler 1

4 A. HOW ONE-PIPE SYSTEMS WORK A. HOW ONE-PIPE SYSTEMS WORK Seat AIR VENT TYPICAL Float Float Support Excerpt: Hoffman Steam Heating Systems, ITT Figure 1: Construction The float prevents water from escaping. The float can be damaged by water hammer, preventing the vent from operating correctly. The thermal element expands when heated to close off the vent. 2

5 A. HOW ONE-PIPE SYSTEMS WORK Figure 2: Explanation of Ratings Note that it is important for the boiler cut-out pressure to be lower than the Drop-Out pressure of the vents on the system. Otherwise, they cannot function after the initial cycle. The pressure in the system would keep them closed. 3

6 A. HOW ONE-PIPE SYSTEMS WORK Figure 3: Selection and Application of s Use adjustable vents when you want proportional venting. The larger the radiator, the larger the vent opening. This way each radiator heats in proportion to its size as intended. 4

7 A. HOW ONE-PIPE SYSTEMS WORK Figure 4: Main Installation You will often find the main vent piped as shown on the right. This allows water hammer at the end of the main to slam into the vent. The float will quickly collapse, causing the vent to fail in the closed position. Pipe the Main as shown on the left. This protects the vent from the hammer at the end of the main and provides an air cushion against the shock. If the main vent doesn t work, the radiator vents must remove the air from the system piping. This will cause the closest radiators to heat first and the furthest radiators may not heat at all when the thermostat shuts down the boiler. The Main (and Riser s) is the heart of a one-pipe system. It must work to provide uniform heat in the building by removing the air from the steam distribution piping. When it works, all the radiators receive steam at the same time. 5

8 A. HOW ONE-PIPE SYSTEMS WORK OFF CYCLE s serve as vacuum breakers. When steam condenses, it causes a vacuum. The vents let air back in to fill the void. The system fills with air. The water level in the return finds the same level as the boiler since there is no pressure difference in the piping. Main Water Line Water Hartford Loop Wet Return Burner Off Figure 5: Stand-by Conditions in the System At the end of each heating cycle, the thermostat shuts off the boiler. With no steam being supplied, the steam in the system condenses and creates a vacuum. This vacuum causes air to be pulled in through the vents until the system fills with air. 6

9 A. HOW ONE-PIPE SYSTEMS WORK THERMOSTAT CALLS FOR HEAT Boiler fires. Water boils in boiler, creating steam. Surface level rises slightly because the steam bubbles displace water. Pressure builds in system as steam pushes on the air. Pressure pushes air out through Main and Radiator vents. Water begins to back up in the return riser because flow causes pressure drop in piping. So pressure is lower at end of piping than at boiler. Main Steam Water Line Water Hartford Loop Wet Return Figure 6: Call for Heat The thermostat closes, the boiler fires and the cycle begins. 7

10 A. HOW ONE-PIPE SYSTEMS WORK THE MAIN VENT When the Main works right it exhausts air quickly from the steam piping. So all branch lines receive steam at about the same time. This makes heating uniform throughout the building. If the main vent doesn't work, the first radiators get steam first, causing poor heat distribution. The Main vent closes as steam reaches it. Radiator vents are smaller. They must vent slowly to match the radiation. If they vent too quickly, condensate will back up in the radiator and cause water hammer. The radiator vents continue to vent air as steam pushes up toward the radiators. Water backs up higher in the return as the pressure difference from beginning to end of piping increases with flow and condensate begins to form. Steam Main (Closed) Steam Water Line Water Hartford Loop Wet Return Figure 7: Importance of the Main The Main must quickly evacuate all air from the steam piping. This way all branches receive steam at about the same time. And the building will heat evenly. 8

11 A. HOW ONE-PIPE SYSTEMS WORK HEATING BEGINS IN RADIATORS Steam pushes into the radiators. The radiators cool the steam. Steam begins to condense. The radiators begin to heat up and give off heat to the room as the steam gives off 970 BTU per pound in condensing. Condensate starts to build up in the bottoms of the radiators and flow out through the radiator valves. Condensate runs down the branch piping to the main, flowing against the steam coming up the branches. Steam Steam The heavy start-up condensate load adds to the pressure difference, raising the water level in the return to its highest point during the heating cycle. Boiler water level slightly lower because water has been steamed off and condensate has not returned yet. Steam Condensate Condensate Condensate Main (Closed) Steam Water Line Water Hartford Loop Wet Return Figure 8: Heating Begins in the Radiators When steam pushes into the radiators it starts to condense and heat the radiators. The radiators begin to give off this heat. 9

12 A. HOW ONE-PIPE SYSTEMS WORK STEADY STATE HEATING Steam fills radiators until it reaches the radiator vents. The radiator vents close when exposed to the steam temperature. The boiler continues to fire, providing steam to the system, until the thermosat is satisfied. The riser level drops as the start-up condensate load passes back to the boiler. The steady level is just enough to overcome the pressure loss through the steam piping and return piping. Boiler water level is lower because of condensate out in the system. In some cases the water level may go out of the gauge glass when the boiler shuts down. This is because the steam bubbles in the boiler collapse, so the surface level drops. And the condensate has not returned from the system. Steam Steam Condensate Closed Condensate Steam Condensate Closed Main (Closed) Steam Water Line Water Hartford Loop Wet Return Figure 9: Steady State Heating Conditions The steam has pushed into the radiators and reached the radiator vents. They shut off when exposed to the steam temperature. The heating cycle continues until the thermostat shuts off the boiler. 10

13 A. HOW ONE-PIPE SYSTEMS WORK STEAM SYSTEM OPERATION CYCLE START AIR IN RADIATOR STEAM AT RADIATOR INLET Figure 10: Radiator at Start of Cycle Radiator is full of air. If Main works, all radiators receive steam at the same time. 11

14 A. HOW ONE-PIPE SYSTEMS WORK STEAM SYSTEM OPERATION AIR VENT ALLOWS AIR TO BE PUSHED OUT BY THE STEAM CONDENSATE STARTS TO FORM RADIATOR BEGINS TO BE WARMED BY CONDENSING STEAM Figure 11: Radiator Begins to Receive Steam If Radiator works, the steam pressure pushes air out through the vent, allowing steam to enter. Condensate begins to form and roll back through the radiator valve. 12

15 A. HOW ONE-PIPE SYSTEMS WORK STEAM SYSTEM OPERATION AIR VENT CLOSES AS STEAM REACHES VENT CONDENSATE LOAD INCREASED Figure 12: Steam Reaches the The vent closes as its element is heated and expanded by the steam temperature. 13

16 A. HOW ONE-PIPE SYSTEMS WORK RADIATOR SUPPLY VALVE CANNOT BE USED TO CONTROL FLOW Valve must be kept fully open when in use Partially closed valve restricts condensate Excerpt: Hoffman Steam Heating Systems, ITT Figure 13: Radiator Supply Valve One-Pipe Radiators Do not throttle the valve. This will restrict condensate flow and cause hammer in the radiator. 14

17 A. HOW ONE-PIPE SYSTEMS WORK DIMENSION "A" GRAVITY RETURN SYSTEMS 28" A Note: Return line loss includes safety factor Figure 14: Gravity Return Systems Dimension A The only way water can be pushed back into the boiler is for the return water to raise to a height high enough to overcome the line losses and the difference in pressure between the boiler and the end of the main. Allow 28 inches as shown for most existing gravity systems. 15

18 A. HOW ONE-PIPE SYSTEMS WORK DIMENSION "A" GRAVITY RETURN SYSTEMS System Size Over 100 MBH Under 100 MBH Steam Piping Pressure Drop Wet Return Pressure Drop Wet Return Pressure Drop Safety Factor Overall Safety Factor Start-up Condensate Allowance TOTALS 14" 4" 2" 8" 28" 3.5" 3.5" 7" 14" Figure 15: Dimension A Adding Up the Drops Most gravity systems were piped for a 1/2 psig (14 inches) drop through the main. If the drop is higher, increase the 28" minimum. If the pipe insulation has been removed and not replaced, increase the 8" start-up condensate allowance. 16

19 B. SYSTEM CHECKLIST B. SYSTEM CHECKLIST THE SYSTEM 1. The system must provide dry steam for performance and system component life. 2. Wet steam will cause water hammer, resulting in damage to vent valves or anything else in the way. 3. Water carryover to the system will cause the boiler water level to drop too quickly. This will cause overfilling and flooding. CHECK DIMENSION A 4. Make sure the lowest steam carrying pipe (or dry return) is at least 28 inches above the normal boiler water line. If the piping pressure drop is more than 1/2 psig, increase this minimum as needed. 5. Dimension A may have been correct at one time, but it could have changed if the piping was modified over the years. 6. The new boiler water line may not be the same as the old boiler. If the new water line is higher, be very careful that you still have the 28 inches minimum to any steam carrying pipe or dry return. CHECK ALL AIR VENTS 7. Make sure all main and riser vents and all radiator vents are working. 8. Make sure the main vent is piped correctly. COMPARE NEW BOILER TO OLD 9. If you are replacing an old, large boiler, you may need to install a boiler feed system to provide the storage needed. a) The old, large boilers had more water content. So they could steam longer before they needed water added. b) New, high efficiency boilers don t have as much water content. So they can usually only steam for about 15 minutes before they drop to the low water point. c) A boiler feed system tank holds enough water to allow a long time for condensate to come back. It can supply water to the boiler when needed while the condensate makes its rounds in the system. BE CAREFUL WHEN ZONING 10. Gravity return systems usually don t have enough height from the boiler to the lowest steam carrying pipe to provide 30 inches for every psi pressure at the boiler. a) One-pipe systems should operate around 2 psig at the boiler. This would be 60 inches (5 feet) of pressure applied on the returns when a zone valve is closed. 11. If you are installing zone valves, you will probably have to also install a boiler feed system or condensate receiver system and install drip traps on the main and return risers. The system will no longer be gravity return. CHECK THE SYSTEM HISTORY 12. Ask the owner and maintenance personnel about any problems the system had before. This will give you a good lead on repairs or replacements that may be needed. CHECK ALL THE PIPING 13. Make sure the wet returns are not plugged or leaking. If there are signs that the old boiler used a lot of make-up water it could be that the wet return is leaking. Replace the wet returns. 14. Make sure all pipes are sloped in the right direction. If they are pitched the wrong way or sagging, hammer will occur. 15. If additional heated space has been added to the building, make sure the pipes are large enough for the connected radiation. 17

20 B. SYSTEM CHECKLIST DIMENSION "B" GRAVITY RETURN SYSTEMS Steam Supplies Zone Valve Pressure = 0 when valve closes Water Line 30" per PSI at Boiler B Returns Boiler pressure acts on water in returns Figure 16: Dimension B Result of Zone Valve or Trap on Gravity System When the zone valve closes, all of the boiler pressure pushes back on the returns. This raises the water level in the returns above the boiler water level 30 inches for every psi pressure at the boiler. This will usually require the addition of drip traps and a feed system. 18

21 C. THE NEAR-BOILER PIPING C. THE NEAR-BOILER PIPING NEAR-BOILER PIPING Steam Supply 2" Skim Connection Offset Header Required to Prevent Damage to Boiler From Expansion of Header Figure 17: Return Typical Near-Boiler Piping 19

22 C. THE NEAR-BOILER PIPING 1. Follow the boiler manufacturer s guidelines on nearboiler piping and pipe sizing. 2. Pay special attention to the number and location of risers off of the boiler. 3. Too few risers or risers in the wrong locations can cause a sloped water line in the boiler and/or heavy carryover to the system. a) Sloped water line can actually result in dry firing some sections of the boiler and result in severe damage. RIGHT Water separates from the steam when it turns up into the take-off. EQUALIZER HEADER CONNECTIONS FOR MULTIPLE BOILER RISERS WRONG Water pools under the take-off, causing heavy carryover to the system. EQUALIZER Figure 18: Correct Piping of Steam Take-Off from Boiler Header 20

23 D. SIZING THE BOILER D. SIZING THE BOILER TUBULAR RADIATION RATING Square Feet per Section Height 3 Tube 4 Tube 5 Tube 6 Tube 7 Tube 14" " " " " " " COLUMN RADIATION RATING Square Feet per Section Height 1 Column 2 Column 3 Column 4 Column 5 Column 14" " " " " " " " " " " RADIANT CONVECTOR Width Height Square Feet Per Section 5" 20" /2" 20" 3.40 CAST IRON BASEBOARD Width Height Square Feet Per Linear Foot 2 1/2" 10" 3.40 SIZE THE BOILER TO HANDLE THE RADIATION Figure 19: Select a Boiler with a Net Load Rating Greater Than the Total Connected Radiation 21

24 E. COUNTERFLOW SYSTEMS E. COUNTERFLOW SYSTEMS ONE-PIPE COUNTERFLOW SYSTEM Steam main feeds steam to system and condensate back to boiler. Condensate flows against the steam in the main. The main pitches upward away from the boiler twice as much as a parallel flow system. No return riser is used since the condensate feeds back to the equalizer pipe. No Hartford Loop is needed since the return is above the water line. The boiler header must enter the top of the main, unlike parallel flow systems, where the main feeds off the top of the boiler header. Note that Dimension A is at the lowest point of the steam main as shown. But Dimension A doesn't have to be 28 inches for counterflow systems. There is almost no pressure drop from the boiler to the point of condensate return. The only loss is the piping loss for the condensate. Main Steam A Condensate Water Line Pitch up 1" per 10 ft Maximum Header Length 100 ft Figure 20: Schematic Piping Typical Counterflow System in Operation 22

25 E. COUNTERFLOW SYSTEMS PIPE SIZING ONE-PIPE COUNTERFLOW SYSTEMS STEAM SUPPLY SIZING - ONE PIPE COUNTERFLOW MAIN PITCHED MINIMUM 1 INCH PER 10 FEET 2 1/2" , " , " 1, , " 2, , " 4,546 1,091,040 1,137 Note: Pipe capacities based on recommended increase one pipe size for counterflow one-pipe mains RUNOUT SIZING FOR RUNOUTS UNDER 8 FEET (ADD ONE PIPE SIZE FOR LONGER RUNOUTS) 1" 28 6, /4" 64 15, /2" 64 15, " 92 22, /2" , " , RADIATOR SUPPLY VALVES AND VERTICAL CONNECTORS 1" 28 6, /4" 64 15, /2" 92 22, " , BOILER EQUALIZER CONNECTION 1 1/2" , /2" 6,400 1,536,000 1,600 Figure 21: Minimum Pipe Sizes One-Pipe Counterflow Systems Use this chart to compare the size of existing piping and to determine sizing of lines for added zones and branches. 23

26 F. PARALLEL FLOW SYSTEMS F. PARALLEL FLOW SYSTEMS ONE-PIPE PARALLEL SYSTEM with WET RETURN Steam main feeds steam to system and condensate to Return. Condensate flows with the steam in the main. The main pitches downward away from the boiler at least 1 inch per 20 feet. The return riser feeds condensate to the wet return. Steam Radiator Radiator Dimension A must be 28 inches for most systems. Check the main and return sizes against the chart to be sure this is enough. Condensate Condensate Main Steam Steam Water Line Condensate Pitch down 1" per 20 ft A Water Hartford Loop Wet Return Figure 22: Schematic Piping One-Pipe Parallel Flow System with Wet Return 24

27 F. PARALLEL FLOW SYSTEMS PIPE SIZING ONE-PIPE PARALLEL FLOW SYSTEM WITH WET RETURN STEAM SUPPLY SIZING - ONE PIPE PARALLEL FLOW MAIN PITCHED MINIMUM 1/2 INCH PER 10 FEET 2" , /2" , " 1, , " 2, , " 4,546 1,091,040 1,137 6" 7,642 1,834,080 1,911 RADIATOR RUNOUT SIZING FOR RUNOUTS UNDER 8 FEET (ADDONEPIPESIZEFORLONGERRUNOUTS) 1" 28 6, /4" 64 15, /2" 64 15, " 92 22, /2" , " , RADIATOR SUPPLY VALVES AND VERTICAL CONNECTORS 1" 28 6, /4" 64 15, /2" 92 22, " , WET RETURN SIZING 1" , /4" 1, , /2" 1, , " 4, ,000 1,000 BOILER EQUALIZER CONNECTION 1 1/2" , /2" 6,400 1,536,000 1,600 Figure 23: Minimum Pipe Sizes One-Pipe Parallel Flow System with Wet Return Use this chart to compare the size of existing piping and to determine sizing of lines for added zones and branches. 25

28 F. PARALLEL FLOW SYSTEMS ONE-PIPE PARALLEL SYSTEM with DRY RETURN Steam main feeds steam to system and condensate to Return. Condensate flows with the steam in the main. The main and dry return pitch downward away from the boiler at least 1 inch per 20 feet. The dry return feeds condensate to the return riser. Locate the Main near the end of the dry return. Steam Radiator Radiator Dimension A must be 28 inches for most systems. Check the main and return sizes against the chart to be sure this is enough. Condensate Condensate Pitch down 1" per 20 ft Steam Main Condensate Steam A Dry Return Water Line Water Hartford Loop Wet Return Figure 24: Schematic Piping One-Pipe Parallel Flow System with Dry Return 26

29 F. PARALLEL FLOW SYSTEMS PIPE SIZING ONE-PIPE PARALLEL FLOW SYSTEM WITH DRY RETURN STEAM SUPPLY SIZING - ONE PIPE PARALLEL FLOW M AIN PITCHED MINIMUM 1/2 INCH PER 10 FEET 2" , /2" , " 1, , " 2, , " 4,546 1,091,040 1,137 6" 7,642 1,834,080 1,911 RADIATOR RUNOUT SIZING FOR RUNOUTS UNDER 8 FEET (AD D O N E PIPE SIZE FO R LO N G ER RU N O U TS) 1" 28 6, /4" 64 15, /2" 64 15, " 92 22, /2" , " , RADIATOR SUPPLY VALVES AND VERTICAL CONNECTORS 1" 28 6, /4" 64 15, /2" 92 22, " , D R Y R ETU R N S IZIN G 1" , /4" , /2" 1, , " 2, , W ET R ETU R N S IZIN G 1" , /4" 1, , /2" 1, , " 4, ,000 1,000 BOILER EQUALIZER CONNECTION 1 1/2" , /2" 6,400 1,536,000 1,600 Figure 25: Minimum Pipe Sizes One-Pipe Parallel Flow System with Dry Return Use this chart to compare the size of existing piping and to determine sizing of lines for added zones and branches. 27

30 F. PARALLEL FLOW SYSTEMS ONE-PIPE PARALLEL UPFEED SYSTEM Steam main feeds steam to Upfeed Risers and Branches. Main and dripped risers feed condensate to returns. The main pitches downward away from the boiler at least 1 inch per 20 feet. Note that dripped riser connections pitch down from the main. Undripped riser connections pitch upward from the main. Dimension A must be 28 inches for most systems. Check the main and return sizes against the chart to be sure this is enough. The lowest steam carrying pipe, either a main or a riser or branch line, determines the smallest Dimension A. Provide a Main at the top of each riser and at the end of the steam main. Radiator Main Radiator Main Radiator Give good pitch to long feeds Supply Main Riser Not Dripped Main Riser Dripped A Hartford Loop Boiler Water Line Wet Return A Riser Drip Dirt Pocket Figure 26: Schematic Piping One-Pipe Parallel Upfeed System Steam feeds up the risers to the radiation. Condensate flows down the risers to the main or to drip legs as shown. 28

31 F. PARALLEL FLOW SYSTEMS PIPE SIZING ONE-PIPE PARALLEL UP-FLOW SYSTEM STEAM SUPPLY SIZING - ONE PIPE PARALLEL FLOW MAIN PITCHED MINIMUM 1/2 INCH PER 10 FEET 2" , /2" , " 1, , " 2, , " 4,546 1,091,040 1,137 6" 7,642 1,834,080 1,911 UPFEED RISER RUNOUT SIZING WHEN RISER IS DRIPPED RUNOUT SLOPED DOWN 1/2" PER 10 FT 1" 68 16, /4" , /2" , " , /2" , UPFEED RISER RUNOUT SIZING WHEN RISER IS NOT DRIPPED RUNOUT SLOPED UP 1/2" PER 10 FT 1" 28 6, /4" 55 13, /2" 81 19, " , /2" , RADIATOR RUNOUT SIZING FOR RUNOUTS UNDER 8 FEET (ADD ONE PIPE SIZE FOR LONGER RUNOUTS) 1" 28 6, /4" 64 15, /2" 64 15, " 92 22, /2" , " , UP-FEED RISER SIZING 1" 45 10, /4" 98 23, /2" , " , /2" , " , " 1, , UP-FEED RISER DRIP SIZING Riser Size Drip to Wet Return Drip to Dry Return (With Loop Seal) 1" 3/4" 3/4" 1 1/4" 3/4" 3/4" 1 1/2" 3/4" 1" 2" 1" 1" 2 1/2" 1" 1" 3" 1" 1" WET RETURN SIZING 1" , /4" 1, , /2" 1, , " 4, ,000 1,000 DRY RETURN SIZING 1" , /4" , /2" 1, , " 2, , RADIATOR SUPPLY VALVES AND VERTICAL CONNECTORS 1" 28 6, /4" 64 15, /2" 92 22, " , BOILER EQUALIZER CONNECTION Pipe Size Square Ft EDR Btu/Hr Net 672Pounds/Hr 1 1/2" , /2" 6,400 1,536,000 1,600 Figure 27: Minimum Pipe Sizes One-Pipe Parallel Upfeed System Use this chart to compare the size of existing piping and to determine sizing of lines for added zones and branches. 29

32 F. PARALLEL FLOW SYSTEMS UP-FEED RUNOUT WHEN NOT DRIPPED Up-Feed Riser Pitch 1/2" per Foot & Increase Pipe One Size One size larger than riser Steam Main 3 Ft Approximately Figure 28: Upfeed Riser and Runout When Not Dripped 30

33 F. PARALLEL FLOW SYSTEMS UP-FEED RISER WITH DRIP LINE Up-Feed Riser Steam Main Pitch 1/2" per 10 ft Wet Return Elevation End View Figure 29: Upfeed Riser Connection When Dripped to Wet Return 31

34 F. PARALLEL FLOW SYSTEMS UP-FEED BRANCH CONNECTION (NOT DRIPPED) Up-Feed Riser Steam Main Pitch 1/2" per 10 ft Elevation End View Figure 30: Upfeed Branch Connection When Not Dripped 32

35 F. PARALLEL FLOW SYSTEMS RUNOUT TO DOWN-FEED RISER Steam Main Pitch 1/2" per 10 ft Down-Feed Riser Elevation End View Figure 31: Downfeed Riser Connection to Steam Main 33

36 F. PARALLEL FLOW SYSTEMS ONE-PIPE PARALLEL DOWNFEED SYSTEM Express Steam Riser feeds top floor steam main. Steam main feeds steam to Downfeed Risers and Branches. Main and dripped risers feed condensate to returns. The main pitches downward away from the boiler at least 1 inch per 20 feet. Note that dripped riser connections pitch down from the main. Undripped riser connections pitch upward from the main. Dimension A must be 28 inches for most systems. Check the main and return sizes against the chart to be sure this is enough. The lowest steam carrying pipe, either a main or a riser or branch line, determines the smallest Dimension A. Provide a Main at the top of each riser and just above the lowest branch on each of the Downfeed Risers. Main Radiator Radiator Radiator Give good pitch to long feeds Main Express Steam Supply Riser Main A A Main Riser Dripped A Hartford Loop Boiler Water Line Wet Return Riser Drip Dirt Pocket Figure 32: Schematic Piping One-Pipe Parallel Downfeed System The main advantage of this system is that the condensate flows in the same direction as the steam in all of the downfeed risers. 34

37 F. PARALLEL FLOW SYSTEMS PIPE SIZING ONE-PIPE PARALLEL FLOW DOWN FEED SYSTEM S T E A M S U P P L Y S IZ IN G - O N E P IP E P A R A L L E L F L O W M A IN P I T C H E D M I N I M U M 1 / 2 I N C H P E R 1 0 F E E T P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 2 " , / 2 " , " 1, , " 2, , " 4, , 0 9 1, , " 7, , 8 3 4, , E X P R E S S R I S E R S I Z I N G - P A R A L L E L D O W N F E E D S Y S T E M P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 2 1 / 2 " , " 1, , / 2 " 1, , " 2, , " 4, , 0 0 8, , " 7, , 7 2 8, , " 1 5, , 6 0 0, , D O W N - F E E D R I S E R S & B R A N C H E S T O D O W N F E E D R I S E R S P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 1 " , / 4 " , / 2 " , " , / 2 " , " 1, , / 2 " 1, , " 2, , R A D I A T O R R U N O U T S I Z I N G F O R R U N O U T S U N D E R 8 F E E T ( A D D O N E P I P E S I Z E F O R L O N G E R R U N O U T S ) P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 1 " 2 8 6, / 4 " , / 2 " , " , / 2 " , " , W E T R E T U R N S IZ IN G P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 1 " , / 4 " 1, , / 2 " 1, , " 4, , , R A D I A T O R S U P P L Y V A L V E S A N D V E R T I C A L C O N N E C T O R S P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 1 " 2 8 6, / 4 " , / 2 " , " , B O I L E R E Q U A L I Z E R C O N N E C T I O N P i p e S i z e S q u a r e F t E D R B t u /H r N e t P o u n d s / H r 1 1 / 2 " , / 2 " 6, , 5 3 6, , Figure 33: Minimum Pipe Sizes One-Pipe Parallel Downfeed System Use this chart to compare the size of existing piping and to determine sizing of lines for added zones and branches. 35

38 G. TROUBLESHOOTING G. TROUBLESHOOTING Figure 34: How Water Hammer Occurs 36

39 G. TROUBLESHOOTING TROUBLESHOOTING WATER HAMMER ON START-UP LOOK FOR SAGS IN STEAM MAIN AND DRY RETURN PIPING, WHERE WATER CAN POCKET. LOOK FOR CONCENTRIC REDUCER WHICH WOULD CAUSE WATER TO POCKET. CHECK FOR LONG STEAM MAINS WITH NO DRIP LINES. CHECK DIMENSION "A". IF THE BOILER WATER LEVEL IS TOO HIGH, DRY RETURNS MAY NOW BE WET. Figure 35: Troubleshooting Water Hammer Which Occurs Shortly After Start-up 37

40 G. TROUBLESHOOTING TROUBLESHOOTING WATER HAMMER IN MID-CYCLE WET RETURN LINES MAY BE CLOGGED, CAUSING CONDENSATE TO BACK UP INTO STEAM PIPING. DIRTY BOILER WATER OR WRONG NEAR-BOILER PIPING COULD BE CAUSING WET STEAM. THE BOILER MAY BE OVERSIZED OR OVERFIRED. THIS CAUSES TOO MUCH PRESSURE DROP IN MAIN, SO CONDENSATE BACKS UP IN RISER. Figure 36: Troubleshooting Water Hammer Which Occurs During Mid-Cycle 38

41 G. TROUBLESHOOTING TROUBLESHOOTING WATER HAMMER IN MID-CYCLE Use close nipple only Hartford Loop CHECK THE HARTFORD LOOP. THE NIPPLE MAY BE TOO LONG. ONLY USE A CLOSE NIPPLE. MAKE SURE THE STEAM PIPING IS INSULATED. IF INSULATION HAS BEEN REMOVED, TOO MUCH PIPING CONDENSATE WILL RESULT AND CAUSE CONDENSATE TO BUILD UP IN THE PIPING. RADIATOR VENTS MAY BE TOO QUICK. THIS CAUSES CONDENSATE TO POOL AND BLOCK SUPPLY. Figure 37: Troubleshooting Water Hammer Which Occurs During Mid-Cycle 39

42 G. TROUBLESHOOTING TROUBLESHOOTING WATER HAMMER ON SHUTDOWN Top of Nipple 2 to 4" Below Boiler Water Line Hartford Loop CHECK THE HARTFORD LOOP. THE NIPPLE MAY BE TOO CLOSE TO THE BOILER WATER LEVEL. IT MUST BE 2 TO 4 INCHES BELOW. MAKE SURE THE STEAM PIPING IS INSULATED. IF BOILER ROOM PIPING INSULATION HAS BEEN REMOVED, BUT SYSTEM PIPING INSULATION REMAINS, A VACUUM WILL OCCUR IN THE BOILER ROOM PIPING ON SHUTDOWN, CAUSING WATER LEVEL TO BOUNCE. Figure 38: Troubleshooting Water Hammer Which Occurs On Shut-Down 40

43 G. TROUBLESHOOTING TROUBLESHOOTING HAMMERING IN THE BOILER Steam Pocket CHECK FOR FLAME IMPINGEMENT ON THE LEGS OF WET BASE BOILERS. THIS CAUSES STEAM POCKETS TO FORM. THE STEAM COLLAPSES AND CAUSES HAMMER. CHECK THE BOILER FOR SEDIMENT ACCUMULATION. SEDIMENT IN THE LEGS OR BOTTOM OF THE BOILER CAN SLOW CIRCULATION AND CAUSE HAMMER. OVERSIZED TANKLESS COILS CAN CAUSE THE BOILER WATER LEVEL TO COLLAPSE DURING HIGH POTABLE WATER FLOW. THIS CAN CAUSE HAMMERING. Figure 39: Troubleshooting Hammering in the Boiler 41

44 FULL-COLOR TRAINING GUIDE SERIES ONE-PIPE STEAM SYSTEMS Price $ CHOS396 R2 (12/10-1M)