Data sheet AVDO Automatic By-pass Valve - Danfoss

1 Data sheet AVDO Automatic By-pass ValveVD55K622 Danfoss 02/13 AVDO self-acting constant fl ow controls are used to maintain a minimum fl ow rate ( through a low water content gas boiler) or to control diff erential pressure in a heating closing of radiator or zone valves due to reduced heating demand may result in low fl ow and increased system diff erential pressure (potentially dead heating pumps). AVDO valves open with a falling system load and allow fl ow through a bypass line whenever the diff erential pressure through the Valve exceeds set point; ensuring a minimum fl ow rate or a system diff erential pressure at minimum system : Opens on rising diff erential pressure. Setting diff erential pressure range of - psi ( bar). Designed for 145 psi (10 bar), max. 248 F (120 C). Operates without impulse tubes. Can be supplied with NPT or solder tail pieces.

2 ApplicationOrderingTechnical data1 Application Examples:The placement of the AVDO can be piped between the supply and return or parallel to the circulator as seen in the fi gures - psi ( - bar)Max. diff erential psi ( bar)Operation pressure145 psi (10 bar)Max. fl ow temperature248 F (120 C)Max. leakage when gpm ( m3/h)Figure 1: Low water content gas boiler where a min. fl ow is required through the 2:Manifold with zonedmultiple loopsFigure 3: Diff erential bypass control across a pump being used on a constant circulating NumbersTypeDescriptionSize/ConnectionAVD O 15 Straight Valve Body1/2 Union Solder1/2 Union Male, NPT003L602001003L602002 AVDO 203/4 Union Solder3/4 Union Male, NPT003L602501003L602502 AVDO 251 Union Male, NPT003L603002 Data sheet AVDO Automatic By-pass ValveVD55K622 Danfoss 02/13 DesignInstallationSettingCapacity2 Materials of parts in contact with water1. Setting handlePom-Plastic2. BaseMs 583. Spring guidePolyphenylene sulphide (PPS-plastics)4.

3 SpringStainless steel5. Valve conePolyphenylene sulphide(PPS-plastics)6. Valve bodyMs 58, forged7. Setting pinStainless steel8. O-ringsEPDM rubberAVDO 20 AVDO 15 AVDO 25A = set opening pressure p = p for valveUpper limit graph for recommended application area with almost noiseless installation. Measurement conditions according to ISO Valve body must be mounted with fl ow in the direction of the cast-in control is set by turning the adjustmentknob. AVDO has a setting scale on which theopening pressure can be set according to thetable to the right. The diff erential pressuresstated for a given setting are indicative. Thescale gives the diff erential pressure acrossthe AVDO when it just begins to 1 = 2 = 3 = 4 = 5 = sheet AVDO Automatic By-pass ValveVD55K622 Danfoss 02/133 Fig. 1 Fig. 3 Example 1 Bypass control across heating systemGiven: System, see fi g. 1 Insignifi cant pressure loss in pipe from boiler to bypass.

4 Pump characteristic, see fi g. 2. psi ( bar) system diff erential pressure at max. system : Bypass circulation beginning at psi ( bar) pump pressure. Min. gpm ( m3/h) boiler circulationSeek: A constant fl ow control that opens simultaneously with falling load across the system (closing radiator valves or zone valves ) A constant fl ow control that ensures min. gpm ( m3/h) boiler circulation at min. system loadSolution: An gpm ( m3/h) fl ow corresponds to a psi ( bar) pump pressure - see Capacity . On closing radiator valves or zone valves AVDO ensures a minimum of gpm ( m3/h) circulation at psi (0,25 bar) diff erential pressure across AVDO. Choose AVDO 25 that provides 12 gpm ( m3/h) at psi ( bar) diff erential pressure across Valve . Set AVDO to # ( psi, bar) opening 2 Bypass control across circulating pumpGiven: System, see fi g.

5 3 Pump characteristic, see fi g. 4 Required: Bypass circulation beginning at psi ( bar) pump pressure Max. system diff erential pressure withclosed radiator valves or zone valves mustbe limited to psi ( bar)Seek: A constant fl ow control that openssimultaneously with falling load across thesystem (closing radiator valves or zonevalves) A constant fl ow control that ensures diff erential pressure not to psi ( bar) at min. system loadSolution: The max. permissible diff erential psi ( bar) across the systemcorresponds to a 8 gpm ( m3/h) watervolume (fi g. 4). At min. load AVDO mustensure 8 gpm ( m3/h) in circulation throughthe bypass. In this example AVDO 20 mustbe used - see Capacity . As circulation is not to begin beforediff erential pressure across system hasexceeded psi ( bar), AVDO is set to# ( psi, bar) - see 2 Fig. 4 Data sheet AVDO Automatic By-pass ValveDanfoss can accept no responsibility for possible errors in printed materials and reserves the right to alter its products without notice.

6 All trademarks in this material are property of the respective companies. Danfoss and Danfoss logotype are trademarks of Danfoss A/S. All rights , MD Toll Free: 866-375-HVAC (4822)Tel.: 443-512-0266, Fax: , ONToll Free: 866-676-8062 Tel.: 905-285-2050, Fax: Danfoss 02 barmH2O 228/1 MinMax15 AVDO G 3/4 Amm87151121891133020 AVDO G 1 Amm93165137901143725 AVDO G 1 1/4 Amm106178-95119119 Dimensions