Data Sheet
Automatic Bypass Control AVDO
Application
AVDO is a self-acting constant flow control
primarily used either to maintain minimum flow
rates through e.g. a low-capacity gas boiler or to
control the differential pressure in a central
heating system.
AVDO:
opens on rising differential pressure
▪
has a setting range of 0.05 - 0.5 bar
▪
Low-capacity gas boiler where maintenance of a min.
flow is required
is dimensioned for pressure stage PN 10,
▪
max. 120 °C
DN 15 and DN 20
▪
operates without impulse tubes
▪
On delivery valve housing is fit onto AVDO with
one of the following fittings: internal socket
thread, internal socket thread/nipple or external
thread for compression fittings.
Differential pressure control
Danfoss Heating Solutions VD55K902 © Danfoss 02/2011 1
Q
[m³/h]
∆P [bar]
Q
[m³/h]
∆P [bar]
Data Sheet Automatic Bypass Control AVDO
Ordering
Type Setting range, Connection Code no.
bar Inlet Outlet
AVDO 15
AVDO 20
AVDO 25
AVDO 15
AVDO 20
AVDO 25
AVDO 15
AVDO 20
AVDO 25
AVDO 15
AVDO 20
AVDO 25
1)
According to ISO 7/1
2)
According to ISO 228/1
0.05 - 0.5
0.05 - 0.5
0.05 - 0.5
0.05 - 0.5
Rp ½
Rp ¾
Rp 1
Rp ½
Rp ¾
Rp 1
G ¾ A
G 1 A
G 1 ¼ A
Rp ½
Rp ¾
Rp 1
1)
1)
1)
1)
1)
1)
2)
2)
2)
1)
1)
1)
R ½
R ¾
1)
R 1
R ½
R ¾
1)
R 1
G ¾ A
G 1 A
G 1 ¼ A
R ½
R ¾
1)
R 1
1)
1)
1)
1)
1)
1)
2)
2)
2)
003L6002
003L6007
003L6012
003L6003
003L6008
003L6013
003L6020
003L6025
003L6030
003L6018
003L6023
003L6028
Accessories (supplied in boxes of 10)
Copper tube fittings Code no.
AVDO 15
AVDO 20
Ø 16 x 1 013U0131
Ø 18 x 1 013U0132
Ø 18 x 1 013U0134
Ø 22 x 1 013U0135
AVDO 25 Ø 28 x 1 013U0140
Technical Data
Capacities
Setting range: 0.05 - 0.5 bar
Max. differential pressure 0.5 bar
Max. flow temperature 120 °C
Max. leakage at closed valve 50 l/h
Operation pressure PN 10
AVDO 15 AVDO 25
2 VD55K902 © Danfoss 02/2011 Danfoss Heating Solutions
Q
[m³/h]
∆P [bar]
Data Sheet Automatic Bypass Control AVDO
AVDO 20
A = set opening pressure
∆P = ∆p for valve
– - – = Upper limit graph
for recommended
application area with
almost noiseless
installation.
Measurement conditions
according to ISO 3743.
Design
Installation
Setting
Materials
Setting handle Pom-plast
1.
2. Base Ms 58
3. Spring guide PPS plastic
4. Spring Stainless steel
5. Valve cone PPS plastic
6. Valve body Ms 58, hot-pressed
7. Setting pin Stainless steel
O-rings EPDM
The valve body must be mounted with flow in
direction of the cast-in arrow.
The control is set by turning the setting dial.
AVDO has a setting scale on which the opening
pressure in bar or mwg can be directly read.
The differential pressures stated for a given
setting are indicative.
The scale gives the differential pressure across
the AVDO when it just begins to open.
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1
1
Data Sheet Automatic Bypass Control AVDO
Sizing
Fig. 1 Fig. 2
Example 1:
Bypass control across heating system
Given:
System, see fig. 1.
▪
Insignificant pressure loss in pipe from
▪
boiler to bypass.
Pump characteristic, see fig. 2.
▪
0.15 bar system differential pressure at max.
▪
system load.
Required:
Bypass circulation beginning at 0.15 bar
▪
pump pressure.
Min. 2.0 m³/h boiler circulation.
▪
Seek:
A constant flow control that opens
▪
concurrently with falling load across the
system (closing radiator thermostats).
A constant flow control that ensures min. 2.0
▪
m³/h boiler circulation at min. system load.
Solution:
A 2.0 m³/h flow corresponds to a 0.25 bar
▪
pump pressure. On closing radiator
thermostats AVDO is to ensure min. 2.0 m³/h
circulation at 0.25 bar differential pressure
across AVDO. Choose AVDO 25 that
provides 2.75 m³/h at 0.25 bar differential
pressure across valve. Set AVDO on 0.15 bar
required opening pressure.
Example 2:
Bypass control across circulation pump
Given:
System, see fig. 3.
▪
-Pump characteristic, see fig. 4.
▪
Required:
Bypass circulation beginning at 0.1 bar
▪
pump pressure.
Max. system differential pressure at closed
▪
radiator thermostats must be limited to 0.25
bar.
Seek:
A constant flow control that opens
▪
concurrently with falling load across the
system (closing radiator thermostats).
A constant flow control that ensures max.
▪
system differential pressure not exceeding
0.25 bar at min. system load.
Solution:
The max. permissible differential pressure
▪
0.25 bar across system corresponds to a 1.8
m³/h water volume (fig. 4). At min. load
AVDO must ensure 1.8 m³/h pump bypass
circulation. In this example AVDO 20 must
be used - see "Capacity".- As circulation is
not to begin before differential pressure
across system has exceeded 0.1 bar, AVDO is
set on 0.1 bar - see "Setting.
Fig. 2
Fig. 4
1. Pump characteristic
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Data Sheet Automatic Bypass Control AVDO
Dimensions
Fig. 1 Fig. 2
Fig. 3 Fig. 4
Fig. 1
DN Type
1)
a
1)
b
L3 L4 L5 H1 S1 S2
min max
15 AVDO 15 RP ½ R½ 40 69 33 83 112 28 30
20 AVDO 20 RP ¾ R ¾ 42 74 37 83 112 34 37
25 AVDO 25 RP 1 R 1 46 81 46 85 114 43 40
Fig.2
DN Type
1)
a
L3 L5 H1 S1
min max
15 AVDO 15 RP ½ 40 33 83 112 28
20 AVDO 20 RP ¾ 42 37 83 112 34
25 AVDO 25 RP 1 46 46 85 114 43
Danfoss Heating Solutions VD55K902 © Danfoss 02/2011 5
Data Sheet Automatic Bypass Control AVDO
Fig. 3
DN Type a, mm
2)
b
L1 L2 H1 S
min max
15 AVDO 15 15/16/18 G ¾ A 87 111 89 113 30
20 AVDO 20 18/22 G 1 A 93 120 90 114 37
25 AVDO 25 28 G 1¼ A 106 136 95 119 45
Fig. 4
DN Type
1)
a
1)
b
L1 L2 H1 S1 S2
min max
15 AVDO 15 RP ½ R½ 87 116 89 113 28 30
20 AVDO 20 RP ¾ R ¾ 93 125 90 114 34 37
25 AVDO 25 RP 1 R 1 106 141 95 119 43 40
1)
According to ISO 7/1
2)
According to ISO 228/1
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Data Sheet Automatic Bypass Control AVDO
Danfoss Heating Solutions VD55K902 © Danfoss 02/2011 7
Data Sheet Automatic Bypass Control AVDO
Danfoss A/S
Heating Solutions
Haarupvaenget 11
8600 Silkeborg
Denmark
Phone:+45 7488 8000
Fax: +45 7488 8100
Email: heating.solutions@danfoss.com
www.heating.danfoss.com
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already on order provided that such alterations can be made without subsequential changes being necessary in specifications already agreed. All trademarks in this material are property of the respective
companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.
8 VD55K902 © Danfoss 02/2011 Danfoss Heating Solutions
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