zone valves on supply or return

2021/05/21

Higher power consumption. 0000001611 00000 n In this scenario, the controller operating the circulator is set to maintain a fixed temperature drop across the distribution system. In this way, applying power to the "open valve" terminal causes the motor to run until the valve is open while applying power at the "close valve" terminal causes the motor to run until the valve is closed. 0000680917 00000 n 0000003799 00000 n It's like a multiple lane bridge with all lanes open. At least two major pump manufacturers now have small variable speed circulators on the market. When you adjust a differential pressure bypass valve set the knob so the disc just starts to lift away from its seat when all zone valves are open, then increase the differential pressure setting just a tad. If flatter is better, what do you think an "ideal" pump curve would look like? It would be a straight horizontal line at some fixed value of differential pressure. All Rights Reserved BNP Media. Highly sophisticated systems may use some form of building automation such as BACnet or LonWorks to control the zone valves. In large commercial installations, vacuum or compressed air may be used instead. 0000001786 00000 n Unfortunately, no fixed speed centrifugal pump can yield this ideal pump curve. bga return agc zoning globalindustrial Visit our updated. That's right. This style of valves requires the use of an SPDT thermostat or relay.

55mm twistseal heatlink Anything that changes the flow resistance of the distribution system causes the system curve to either steepen, (for increasing flow resistance), or flatten (for decreasing flow resistance). 0000003447 00000 n

Air acts as an insulator and is a poor heat transfer media. When represented on a graph, the system always operates at the point where the system curve crosses over the pump curve as shown in Figure 3. 0000680270 00000 n 0000003230 00000 n I'd say that warm air rising from baseboards when the outside temperature is 90+ degrees F is legitimate cause for a complaint, wouldn't you? Look for one or more of these strategies to show up in the not too distant future on a hydronic system near you. All active zones operate at the same flow rate and differential pressure regardless of which zones are off. This decreased dissolved oxygen content minimizes air entrapment or free air in the coil and thus the potential for noise. To find the flow rate through the circulator, drop a line straight down from the intersection of the curves to the lower axis of the graph.

For example, in a house, the main floor may be served by one heating zone while the upstairs bedrooms are served by another. When a control valve is installed on the return side, the water is at a higher pressure through the coil, reducing off-gas, thereby lowering dissolved oxygen content compared to a supply installation. 0000012978 00000 n In either case, the motor is usually connected to the water valve via a mechanical coupling. Zone valves operated by electric timing motors aren't "fail safe" (failing to the "open" condition). To determine the differential pressure across the circulator, draw a horizontal line from the operating point to the vertical axis and read the head added to the fluid as it passes through the circulator. The system curve of the distribution system steepens each time a zone valve closes.

HW|WKKRW>k@YyaDfZAS=Jk{=mvY~X/=af)a{3&oe>M?xpqEt$cVWLnysbZ*Q06I/ }f3Q`Z.dg5GR,P! Figure 4 shows the curve of such a circulator as well as the curve of a "high head" circulator. When a zone valve closes less heat is released by the distribution system and, hence, the temperature drop from the supply to return header drops. 0000006931 00000 n They should also be used to prevent "dead heading" the circulator in systems where several parallel-piped heat emitters are controlled by thermostatic radiator valves. The system can be harder to design, requiring both "SPDT" thermostats or relays and the ability of the system to withstand the fault condition whereby all zone valves are closed simultaneously. The increased pressure differential increases the flow rate through these zones. If it fails, the system becomes completely inoperable. If the water pressure is reduced, the air is released. Additional information and resources for hydronic system design are available on Siegenthalers website, www.hydronicpros.com. 0000402841 00000 n The return side is preferable as it allows the valve and actuator to operate at a reduced temperature which can help protect valve seats and actuator electronics over the installation lifetime.

In most cases I would bet the installer didn't know if a standard 1/25 horsepower circulator had enough "humph" for a system with more than three or four zones. The zones that remain on don't sense that other zones have closed.

Using a circulator with a flat pump curve in zone valve systems is not a new concept. 0000001632 00000 n Some valves have a small "window" that let's you see as the valve begins to bypass flow. In both cases the zone circuits that remain on "feel" increased differential pressure as the other zones close, but far less in the system using the circulator with the flat pump curve. As the speed decreases, the pump curves shifts to the left and downward on the graph as shown in Figure 6. As the system curve shifts so does the point where it intersects the pump curve. Hb```g``U``cgb@ !V(GT *`jzAd:kEXj>2(=`Lapi``ePT` ex+ ".f,`9Pu}# \` pCPnw@ b|, endstream endobj 68 0 obj 208 endobj 28 0 obj << /Type /Page /Parent 13 0 R /Resources 29 0 R /Contents 35 0 R /MediaBox [ 0 0 666 855 ] /CropBox [ 0 0 666 855 ] /Rotate 0 >> endobj 29 0 obj << /ProcSet [ /PDF /Text /ImageC ] /Font << /F1 31 0 R /F2 40 0 R /F3 38 0 R /F4 39 0 R /TT1 30 0 R >> /XObject << /Im1 51 0 R /Im3 53 0 R /Fm2 61 0 R >> /ExtGState << /GS1 45 0 R /GS2 46 0 R /GS3 62 0 R >> /ColorSpace << /DefaultCMYK 34 0 R /Cs8 34 0 R >> /Properties << /MC1 64 0 R /MC2 66 0 R >> >> endobj 30 0 obj << /Type /Font /Subtype /TrueType /FirstChar 32 /LastChar 133 /Widths [ 278 296 389 0 0 0 815 204 333 333 0 0 278 333 278 0 556 556 556 556 556 556 0 0 556 556 0 0 0 0 0 444 0 722 722 722 778 722 667 0 0 407 0 0 667 0 0 778 0 0 722 630 667 815 0 981 0 704 0 0 0 0 0 0 0 556 556 444 574 500 333 537 611 315 296 593 315 889 611 500 574 556 444 463 389 611 537 778 537 537 481 0 0 0 0 0 0 0 0 0 0 1000 ] /Encoding /WinAnsiEncoding /BaseFont /CMGENC+CenturySchoolbook /FontDescriptor 32 0 R >> endobj 31 0 obj << /Type /Font /Subtype /Type1 /FirstChar 32 /LastChar 133 /Widths [ 352 512 577 704 704 1027 898 352 449 449 448 694 352 449 352 577 704 704 704 704 704 704 704 704 704 704 352 352 694 694 694 642 924 834 834 705 834 705 705 770 834 451 577 834 642 1027 834 834 834 834 834 704 707 834 770 1027 834 770 705 449 577 449 694 500 321 770 770 642 770 770 512 770 770 385 385 705 385 1155 770 770 770 770 512 642 577 770 705 1027 770 705 642 449 256 449 694 0 0 0 0 0 0 1000 ] /Encoding /WinAnsiEncoding /BaseFont /CMGENB+AntiqueOlive-Compact /FontDescriptor 33 0 R >> endobj 32 0 obj << /Type /FontDescriptor /Ascent 985 /CapHeight 0 /Descent -216 /Flags 34 /FontBBox [ -165 -307 1246 1201 ] /FontName /CMGENC+CenturySchoolbook /ItalicAngle 0 /StemV 0 /FontFile2 49 0 R >> endobj 33 0 obj << /Type /FontDescriptor /Ascent 746 /CapHeight 714 /Descent -136 /Flags 32 /FontBBox [ -164 -136 1147 972 ] /FontName /CMGENB+AntiqueOlive-Compact /ItalicAngle 0 /StemV 254 /XHeight 601 /StemH 254 /CharSet (/A/W/e/t/space/r/u/n/s/a/d/z/o/v/l/ellipsis/g/exclam) /FontFile3 43 0 R >> endobj 34 0 obj [ /ICCBased 47 0 R ] endobj 35 0 obj << /Length 3057 /Filter /FlateDecode >> stream Some of the lanes on the bridge are now blocked off, and it's simply not possible to get the same amount of traffic across, even though traffic moves slightly faster along each lane. Figure 2 shows this effect for a system having several identical floor heating circuits each controlled by its own zone valve.

The first principle to understand is that the amount of air in the water at a given temperature depends on pressure.

ASHRAE states that "water velocity noise is not caused by water, but by free air, sharp pressure drops, turbulence, or a combination of these, which in turn cause cavitation or flashing of water into steam" (2009 ASHRAE Fundamentals Handbook, Chapter 22). Far superior method of linking multiple heat sources. This zoning can be accomplished in one of two ways: Zone valves as used in home hydronic systems are usually electrically powered. The temperature sensors associated with the pump controller sense this change as it develops and reduces the speed of the pump downward to maintain a set temperature drop. Comparison with multiple circulator pumps, Learn how and when to remove this template message, https://en.wikipedia.org/w/index.php?title=Zone_valve&oldid=891891377, Articles lacking sources from January 2008, Creative Commons Attribution-ShareAlike License 3.0. 0000680552 00000 n 0000007505 00000 n

0000529578 00000 n Zone valves can also be constructed using wax motors and a spring-return mechanism. In a heating application, the water temperature leaving the coil is cooler than the supply temperature. Design, CMS, Hosting & Web Development :: ePublishing. 0000682235 00000 n Still, I wish I had a dollar for every time someone installed a "high head" pump in a system containing several zone valves, and eventually heard about the problem - literally! Such as gas and solid fuel in one system. (Q|g#7} 0000012204 00000 n Under design load conditions all space heating zones should, theoretically, need heat, and thus all zone valves should be open simultaneously. This allows the zone valves to be directly controlled by low-voltage thermostats and wired with low-voltage wiring.

At some point the increased flow velocity will probably cause noise in either the zone valve or the piping. In some systems the increased differential pressure generated by several inactive zones can partially open what are supposed to be closed zone valves. Another possibility is to vary to circulator's speed based on the temperature differential across the distribution system.

No inherent redundancy for the pump. John Siegenthaler, P.E., is a consulting engineer and principal of Appropriate Designs in Holland Patent, New York. 0000003760 00000 n 0000009223 00000 n 0000001312 00000 n 0000007235 00000 n Please click here to continue without javascript.. Modern Hydronic Heating and Cooling For Residential and Light Commercial Buildings, 4th Edition. DeltaP = pressure differential across pumpH = head added by circulator (in ft. of head)d = density of fluid being pumped (in lb./cubic ft.) (use 61.3 lb. When a control valve is installed on the return side, the water is at a higher pressure through the coil, reducing off-gas, thereby lowering dissolved oxygen content compared to a supply installation. 0000008059 00000 n A zone-valved system is dependent upon a single circulator pump. What remains is for manufacturers to develop a simple, low-cost differential pressure sensor that can serve as the eyes for the circulator, telling it when and by how much to vary its speed. When a zone valve closes, the system curve steepens forcing the operating point to slide upward along the pump curve. However, several smaller circulators operating in parallel can produce a decent approximation for systems needing relatively high flow rates. As zone valves close, the bypass valve shuttles increasing amounts of flow through a piping detour rather than forcing the pump to operate at higher pressure differentials trying to push flow through a more restrictive distribution system. This increases the pressure differential imposed on the zones that remain open. 0000683357 00000 n A major factor behind this standard practice is coil efficiency. A single circulator pump and zone valves. 0000680060 00000 n Removal of electrical power re-closes the valve. It's been described in many references over several decades for those willing to learn how to properly select hydronic circulators. Compare the changes in differential pressure as the operating point shifts upward along the "flat" pump curve to those that would occur along the pump curve of the high head circulator. For those that don't, you can determine the differential pressure across the system when all zones are operating by finding the head at the operating point and converting it to a differential pressure using Formula 1. 0000404082 00000 n This decreased dissolved oxygen content minimizes air entrapment or free air in the coil and thus the potential for noise. True, they do prevent the circulator from operating at high differential pressures and, hence, eliminate flow noise and valve seat leakage. 0000002633 00000 n Properly controlled, the circulator operates as a constant differential pressure device regardless of the flow passing through it. %PDF-1.3 % In the meantime, use a circulator with a flat pump curve and differential pressure bypass valve on those zone valve systems to keep both your piping and your complaint line quiet. The overall system flow rate decreases, but the flow rate through each open zone circuit increases. A zone valve is arguably one of the most commonly used control components in residential and light commercial hydronic systems. From the standpoint of fluid mechanics, all hydronic systems constantly seek equilibrium between the mechanical energy (head) input from their circulator and the head loss due to fluid friction in the piping. It's possible that a high differential pressure across the circulator when the DHW load is operating could lead to hot water "oozing" through the closed zone valves on the space heating circuits. Zone valves, by comparison, draw little power at any time and many designs only draw power while in transition from open to close or vice versa. RU2ghxE>|m;OH[TK+9)N~Ao )hoJMllj1/c@byK'i`jG)F][^ ?L'BcV9`NSX?|&. Imagine, for example, a system having several zoned space heating circuits and a separate circuit supplying an indirect water heater. You must have JavaScript enabled to enjoy a limited number of articles over the next 30 days. Lower total cost of ownership when zone valve failure and repair costs are taken into account.

0000681339 00000 n Simple mechanical and control design ("SPST thermostats"). In this mode the distribution system exhibits its lowest flow resistance. In partnership with HeatSpring, he has developed several online courses that provide in-depth, design-level training in modern hydronics systems, air-to-water heat pumps and biomass boiler systems.

A more elegant solution to controlling differential pressure as zone valves close is to reduce the speed of the circulator. trailer << /Size 69 /Info 24 0 R /Root 27 0 R /Prev 1231052 /ID[<6d5752131d918b84c73a5def00ee22e0>] >> startxref 0 %%EOF 27 0 obj << /Type /Catalog /Pages 13 0 R /Metadata 25 0 R /JT 23 0 R /PageLabels 12 0 R >> endobj 67 0 obj << /S 95 /L 225 /Filter /FlateDecode /Length 68 0 R >> stream Copyright 2022.

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John Siegenthaler, PE. Return side installations may not always be appropriate, as in the case of a 3-way diverting valve- these are commonly installed on the supply and is not critical to proper operation; both locations will work effectively. Just like a circulator with the "ideal" pump curve we discussed earlier. Circulator pumps cost more than zone valves. By visiting this website, certain cookies have already been set, which you may delete and block. 0000681200 00000 n Another technique for limiting the differential pressure across the circulator is to install a differential pressure bypass valve as shown in Figure 5.