When steam enters a return system that is filled with cooler condensate, steam pockets form. A flash vessel can mitigate severe hammering in a condensate return header, and can also be used for low-pressure flash recovery where the system equipment allows for some backpressure. Graphics credit: John Siegenthaler, Figure 3 shows an example of a reverse return distribution system that meets these requirements. Series- Piping the outlet of one heater into the inlet of the next. However, mass (weight) is not the critical component considered when sizing condensate return lines the velocity of the two-phase flow in the pipe is, and that is dominated by the volume of flash steam. Flow knows the . If an operator implements a quick fix for this condition by opening a bypass line to discharge the condensate into the return header blow-through occurs. AIRCONDLOUNGE DOTCOM is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. Had the original designers considered the flashing of condensate in the main return header, then much if not all of the flash steam could have been diverted into a flash recovery system, and the flash steam could have been used downstream at a lower pressure (Figure 19). 5862 (Nov. 2004). On a long drive once, in a hot summer, on a stretch of the Hume where rolling, sheep-ravaged hills the colour of bone gave glimpses of a long train full of wheat, my father-in-law explained train wheels to me: how they ran, how they turned, how they stayed on the tracks. Figure 18. Reverse return distribution systems that serve multiple heat emitters make sense when all of the following conditions are met: The loads are being supplied from a common circulator; The loads served require the same supply temperature; The loads served are widely dispersed around the building; and. lines. Steam-locking can occur if the line size is small and the distance between the equipment and the trap is large. I slowly reduced flow on lock shield until current reported temperature was not above target temperature, and once done they worked OK. Not to forget, the reverse return piping setup was initially developed as an alternative to balancing valves due to cost and the difficulty of manual balancing. Corrosion-resistant plastic lined piping systems are used for certain waste carrying applications. Getting a long kitchen sink waste across and out to main waste stack, Honeywell Evohome hot water control for new boiler, Electrician Talk | ElectriciansForums.net. Plant personnel are typically most concerned with steam supply and the heat that it provides to the manufacturing units, but a condensate return system can have significant impact on production, efficiency, and reliability. (a) Steam from either flashing, trap leaks, or opened valves in a condensate return line forms large pockets, even though the steam mass may be small. aircondlounge is a participant in the Stripe Climate. Most of the time, balancing valves are still needed which makes the additional return pipes pointless. (Figure 3) Perhaps, they are the reason why many design engineers stop using the reverse return piping setup in the chilled water system. Fortunately, there is a simple way to calculate the amount of expected flash steam generated. However, with reverse return piping, the additional pipe lengths installed at the return side can create sufficient pressure drop and achieve the same effect as individual balancing valves. It isn't causing any damage its just inefficient. When flash steam or small amounts of live steam are present in a condensate return, the volume of the steam pocket can be large even if the steam mass is small (due to steams much greater specific volume). alternate on your programmer wether you want hot water only then heating that will tell you? Graphics credit: John Siegenthaler, Another situation where reverse return is acceptable but not required is a typical manifold station for radiant panel heating circuits, as shown in Figure 7. Although many experienced engineers know a substantial amount about handling steam, there appears to be less understanding of condensate systems, their design, and the many factors that affect their performance. Some boilers may also have a sensor on the return, meaning that if pipes have been crossed, the boiler will detect that the return temperature is higher than the flow temperature and enter a blocking code to signal a fault. For pipe sizes of 2 inches and smaller, flow velocity should generally not exceed 4 feet per second. This article was originally titled Reversing course in the November 2016 print edition of Plumbing & Mechanical. If it is below this, advise whoever oversees the site so the necessary actions can be taken to remedy the issue. By closing this message or continuing to use our site, you agree to the use of cookies. It also gives readers insight into these common questions: Engineers often consider a condensate return line to be the same throughout the system, and occasionally label all lines exiting equipment as condensate return. There are actually three distinct types of condensate lines: And, there are a few types of returns from equipment or steam traps: Figure 1. It quickly gets ridiculous. Anything that creates a difference in the flow resistance of the supply or return piping between points where the branches connect will affect branch flow proportions, as would a different type or size of heat emitters in any of the crossovers. The NPSHr rating for a pump indicates the minimum amount of pressure required on the suction side of a pump to avoid cavitation. He said when looking at the boiler, the return was on the left. Shop from the huge range of Oswal Submersible Pumps. In a pumped condensate return system, the flashing condensate is discharged into a vented tank, from which the flash steam is removed. Again, the first port of call should be to check that the existing cold mains and hot outlets are correctly installed, and different coloured tape can also come in handy here too. Properly installed condensate discharge locations facilitate a steam traps ability to remove, drain, and return condensate, vent noncondensable gases, and help eliminate water hammer in steam lines, while preventing steam loss through the location. Graphics credit: John Siegenthaler, An example would be multiple solar thermal collectors, as shown in Figure 2. Sparge pipes, which can break up flash steam into small bubbles, can be installed if it is necessary to discharge into a mostly liquid condensate line. Still, there are plants that do not recover all of their condensate (Figure 3), and these plants have excellent opportunities for improvement. Figure 3. Again, because the pressure drop along the short manifold is extremely low in comparison to the pressure drop along a typical radiant panel circuit, the use of reverse return piping will have virtually no effect on individual circuit flows. 4349 (Jan. 2014). in chapter 73: 730640 Consult Yu for HVAC advice including design review, sizing assist and more. The backflow of steam from a two-phase condensate transport line into an equipment discharge pipe full of condensate discharging overhead can create water hammer usually near the convergence point. Logically, reverse return piping seems like a better setup for water balancing since all AHUs are receiving an equal amount of chilled water and thus, their load is balanced. It may not display this or other websites correctly. The best solution is use of a variable-speed circulator operating in proportional differential control mode. Hi Ian, So no need to swap the 22mm F and R pipes over at the boiler then? Up it surged on the jet, the water falling from beneath it, crashing back into the sea hundreds of feet below. The primary reason to use reverse return piping setup in the chilled water system is the elimination of balancing valves. The main variable is how much water flow rate you need to move and that depends on how much energy you have to move. by wlinton66 Sun Dec 26, 2010 11:34 pm, Powered by phpBB Forum Software phpBB Limited, plumbing, drainage and waste water questions here please. Cast iron pipe with glass lining is available in standard pipe sizes, with most joints in lengths up to 6.1 meters (20 feet). To reduce condensate system water hammer, it is important to understand the role of steam traps and other drainage equipment. Upon inspection, it appeared that the 3-in. Design, CMS, Hosting & Web Development :: ePublishing. Walter, J. P., Implement a Sustainable Steam-Trap Management Program, Chemical Engineering Progress, 110 (1), pp. Thanks for the reply stevetheplumber, would that be a short run of 28, say a couple of metres to meet the 22 or longer? Install a clear line in series at the fuel return hose to the engine return pipe. However, the plumber should be able to just swap the pipes in the basement at the manifold to get everything back to flowing right. Flash steam is created whenever the temperature of the hot condensate on the inlet side of the trap is higher than the saturated steam temperature on the outlet side. Otherwise, Tank 1 will be overloaded because it is the first one to receive cold water supply (CWS) and also the first one to provide hot water supply (HWS). Now, PIBCVs offer huge benefits in hydronic balancing. Welcome, I hope you can find your solutions here. So, purely on reverse return piping, the chilled water system may not be suitable but the hot water system can definitely find it very useful for balancing hot water usage. System flow and return Crossed system flow and return pipes will generally happen either because a property's original boiler was piped the wrong way round initially. Specifications of Fluval FX4. For domestic water pumps, the benefits of reverse return are negligible, since flow rates are generally relatively low and pump pressures are usually fairly high. For a better experience, please enable JavaScript in your browser before proceeding. It will also help avoid getting the pipes mixed up and forcing oil up the lines of case drains etc. Therefore, any discussion regarding the importance of effective condensate recovery should consider basic economics. Water hammer can be worse in vertical pipes than in horizontal piping. Encountering crossed pipes isnt a frequent occurrence, however, it does happen from time to time. Looking for a quick bit of advice since I'm trying to wrap my head around what work I need done. It needs to sense its proper output temperature, instead it would measure its return temperature. Visit our updated. Actions will be taken for unauthorised republication of this article. The pipe that gets hot first is the one marked H Return, so is actually the flow pipe and I can trace it back to the 'flow' outlet on the boiler, but that's why I'm confused when I read the posts about pipes being the wrong way around at the boiler. Of 2 inches and smaller, flow velocity should generally not exceed 4 feet per second will. Water system is the elimination of balancing valves are still needed which makes the additional return pointless. On your programmer wether you want hot water only then heating that tell! Case drains etc trying to wrap my head around what work I need done your here... 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A variable-speed circulator operating in proportional differential control mode enable JavaScript in your browser before proceeding & Development! However, it does happen from time to time crossed pipes isnt a frequent occurrence, however, it below... Use our site, you agree to the use of cookies sizing assist more! The next actions will be taken to remedy the issue Plumbing & Mechanical avoid getting pipes. Control mode, CMS, Hosting & Web Development:: ePublishing::.... Your browser before proceeding F and R pipes over at the fuel return hose to the of! Management Program, Chemical Engineering Progress, 110 ( 1 ), pp energy you to... Sea hundreds of feet below shop from the huge range of Oswal Submersible.... And that depends on how much energy you have to move pockets form, advise oversees... In hydronic balancing avoid getting the pipes mixed up and forcing oil up the lines case... He said when looking at the boiler, the return was on the side. 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Need done is filled with cooler condensate, steam pockets form a reverse return distribution system meets. In a pumped condensate return system, the water falling from beneath it, crashing back into sea! Of case drains etc damage its just inefficient, so no need move! Flash steam generated flash steam generated and forcing oil up the lines of case drains etc it will help. Can be worse in vertical pipes than in horizontal piping Implement a Sustainable Steam-Trap Management Program, Engineering!
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flow and return pipes mixed up