AVTI Multifunctional self - acting controller Description / Application AVTI is a self - acting combined controller developed for controlling small heat units with a room heating system and a hot service water system. The controller is specially developed for flat systems supplied from a secondary connected District Heating System, a block heating system or a central located boiler system in a dwelling house. (See fig. 2) AVTI is connected to the primary heating system as well as the cold service water system. To avoid risk leaking from the one media to the other AVTI is equipped with a double sealing. Between the sealing there is a bore to the outside of the valve so that in case of leakage from one sealing, the media can escape through the bore. For a proper functioning of the AVTI it is recommended to use filter in the system according to the system drawing. Fig. 1 AVTI Fig. 2 SIBC VD.GB.B7.2 Danfoss 8/25 1
Ordering Type DN Setting range Connections ISO 228/1 Code No. AVTI 15 45-55 o C G ½ A 3L355 AVTI 15 6-65 o C G ½ A 3L3515 Spare parts Description Sensor element with complete gland Code No. 3L355 Function A schematic drawing in fig. (3 and 4) shows the principle of the valve. The control functions in the controller are: 1. Differential pressure controller 2. Hydraulic proportional controller for controlling of domestic hot service water 3. Thermostatic valve for controlling of domestic hot service water 4. Domestic hot water priority function The differential pressure controller controls the differential pressure across the room heating system. The basic function of the controller for Hot Service Water System is a hydraulic proportional controller, which controls the primary flow proportional to the hot service water flow rate. The control valve also contains a thermostatic valve parallel connected for adapting the Hot Water temperature according to set value. The setting range of the valve is 45-55 C (6-65 C). The thermostatic valve maintains a stand by temperature in the heat exchanger. Fig. 3 In case of domestic hot water taping, the priority function in the controller reduces the flow rate in the room heating system. Fig. 4 Principle of the system drawing 2 VD.GB.B7.2 Danfoss 8/25 SIBC
Technical data Type 3L355 3L3515 Pressure stage PN 1 PN 1 Max. test pressure 16 bar 16 bar Range of supply temperature 65-9 C 7-9 C* Temperature setting at domestic hot service water 45-55 C 6-65 C* k v (domestic hot service water) see fig. 6 see fig. 6.1 k v (room heating system) see fig. 5 see fig. 5.1 Max. sensor temperature 9 C 9 C Max. operating pressure in the heating supply net. 2 bar (2 kpa) 4 bar (4 kpa) Max. closing pressure 6 bar (6 kpa) 6 bar (6 kpa) Length of the capillary tube.5 m.5 m ΔP available for the heating system 12-2 kpa (see Fig. 8) 8-2 kpa (see Fig. 8) Approvals VA VA * T ww T prim - 1 K( C) : The set point of DHW must be 1 K( C) lower than the actual supply temperature. 3L355 3L3515 kvs(kv)/ Q1 [m3/h] 1.3 1.2 1.1 1..9.8.7.6.5.4.3.2.1 5 1 15 2 kvs(kv) Q1 25 3 35 4 45 5 55 6 65 7 75 8 85 9 95 1 Fig. 5 Full priority to room heating system (3L355) kvs(kv) / Q1 [m3/h] 1.4 1.2 1..8.6.4.2 1 2 3 4 5 6 7 8 9 1 Fig. 5.1 Full priority to room heating system (3L3515) kvs(kv)/ Q1 [m3/h] 1.3 1.2 1.1 1..9.8.7.6.5.4.3.2.1 1 2 kvs(kv) Q1 3 4 5 6 7 8 9 1 kvs(kv) / Q1 [m3/h] 1.6 1.4 1.2 1..8.6.4.2 5 1 15 2 25 3 Fig. 6 Domestic Hot Water (3L355) Fig. 6.1 Domestic Hot Water (3L3515) 35 3 25 Pv (kpa) 2 15 1 5 1 2 3 4 5 6 Q2[l/h] 7 8 9 Fig. 7 Pressure drop across the diaphragm element for the proportional valve (3L355, 3L3515). SIBC VD.GB.B7.2 Danfoss 8/25 3
Sizing Electronic valve sizing program avialable on request ΔP heating system The ΔP available for the room heating system can be seen from Fig. 8: Example: Heating system Capacity: 8 kw ΔT heating system: 3 C Circulated flowrate in the room heating system 8 86 1 = 229 l/h 3 ΔP available for the heating system is 15 kpa (see Fig. 8). p available in room heating system Pa [kpa] 25 2 15 1 5 1 2 3 4 5 6 Flow in room heating system [l/h] Fig. 8 p available in room heating system Noise approximation Δp diferential pressure over AVTI Q1 total flow on primary side (room heating system + hot water service) 45 p=4 bar p=2 bar Noise level db(a) 4 35 3 p=1 bar p=.5 bar 25 2 1 2 3 4 5 6 7 8 9 1 11 Maximum differential pressure for 3L355 is 2 bar. 4 VD.GB.B7.2 Danfoss 8/25 SIBC
Sizing Example 1: Δp v = 2 kpa Q 2 = 84 l/h Temperature conditions 7/2-1/5 Taping temperature will be 47 C Example 2: Q 2 = 84 l/h T set = 55 C Temperature conditions 7/2-1/5 Needed Δp over AVTI is 35 kpa Quick calculation diagrams* 3L355 7/2-1/5 2 9 8 7 6 5 4 Tset [ C] 55 5 45 1 3 2 1 1 8 6 4 2 1 2 3 4 5 6 7 8 9 Q2 [l/h] 9/25-1/5 9 8 7 6 5 4 Tset [ C] 55 5 45 3 2 1 1 8 6 4 2 1 2 3 4 5 6 7 8 9 Q2 [l/h] 3L3515 7/2-1/63 Tset [ C] 9 65 6 8 7 6 5 4 3 2 1 15 1 5 1 2 3 4 5 6 7 8 P v [kpa] Q2 [l/h] 9/25-1/65 Tset [ C] 9 8 65 7 6 6 5 4 3 2 1 15 1 5 1 2 3 4 5 6 7 8 P v [kpa] Q2 [l/h] *Xp can be up to ±3 C SIBC VD.GB.B7.2 Danfoss 8/25 5
Connections 1 Primary inlet in the heat exchanger 2 To room heating system 3 From primary heating system 4 Secondary inlet in the heat exchanger 5 Cold service water supply 4 5 1 3 2 6 VD.GB.B7.2 Danfoss 8/25 SIBC
Design Proportional actuator Pos. Description Material 1 Housing 2 Seat CuZn36Pb2As 3 Cone 4 Diaphragm EPDM/PA Differential pressure actuator 11 Cone CuZn39Pb3 12 Housing 13 Diaphragm EPDM/PA 14 Seat 1.435 Controller 18 Housing CuZn36Pb2As 19 Cone CuZn39Pb3 2 Stuffing box CuZn36Pb2As O-rings EPDM Thermostat 27 Rubber cone EPDM 28 Sensor 2.9 29 Sensor gland CuZn36PbAs 3 Sensor gasket EPDM SIBC VD.GB.B7.2 Danfoss 8/25 7
Dimensions 8 VD.GB.B7.2 Danfoss 8/25 SIBC