Product Overview
Data sheet AVDO
Automatic By-pass Valve
VD55K622 © Danfoss 04/10
3
Fig. 1 Fig. 3
Example 1
Bypass control across heating system
Given:
System, see fi g. 1•
Insignifi cant pressure loss in pipe from boiler •
to bypass.
Pump characteristic, see fi g. 2.•
2.2 psi (0.15 bar) system diff erential pressure •
at max. system load.
Required:
Bypass circulation beginning at 2.2 psi (0.15 •
bar) pump pressure.
Min. 8.8 gpm (2.0 m•
3
/h) boiler circulation
Seek:
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. 8.8 •
gpm (2.0 m
3
/h) boiler circulation at min.
system load
Solution:
An 8.8 gpm (2.0 m•
3
/h) fl ow corresponds to a
3.6 psi (0.25 bar) pump pressure - see
“Capacity”.
On closing radiator valves or zone valves•
AVDO ensures a minimum of 8.8 gpm
(2.0 m
3
/h) circulation at 3.6 psi (0,25 bar)
diff erential pressure across AVDO.
Choose AVDO 25 that provides 12 gpm
•
(2.7 m
3
/h) at 3.6 psi (0.25 bar) diff erential
pressure across valve.
Set AVDO to #1.5 (2.2 psi, 0.15 bar) opening•
pressure.
Example 2
Bypass control across circulating pump
Given:
System, see fi g. 3•
Pump characteristic, see fi g. 4•
Required:
Bypass circulation beginning at 1.5 psi (0.1 •
bar) pump pressure
Max. system diff erential pressure with•
closed radiator valves or zone valves must
be limited to 3.6 psi (0.25 bar)
Seek:
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 max.•
system diff erential pressure not to exceed
3.6 psi (0.25 bar) at min. system load
Solution:
The max. permissible diff erential pressure•
3.6 psi (0.25 bar) across the system
corresponds to a 8 gpm (1.8 m
3
/h) water
volume (fi g. 4). At min. load AVDO must
ensure 8 gpm (1.8 m
3
/h) in circulation through
the bypass. In this example AVDO 20 must
be used - see “Capacity”.
As circulation is not to begin before•
diff erential pressure across system has
exceeded 1.5 psi (0.1 bar), AVDO is set to
# 1.0 (1.5 psi, 0.1 bar) - see “Setting.
Sizing
Fig. 2
Fig. 4