SATK22
17
Primary Flow Rate Limitation
Primary flow rate limitation in heating mode.
DEFAULT SETTING: no limitation (technical parameter t03 =
100)
During start-up of the heating cycle from cold, e.g. on change
over from night-time ambient set point to the daytime set
point, the HIU may demand a significantly higher primary flow
rate than the design one, because of the low temperatures of
the secondary medium.
This effect is far greater with high temperature systems in
which, during the transient to the design operating condition,
high thermal power values may be transferred from the primary
circuit to the secondary circuit. This effect can be restricted by
lengthening the transient, setting a limit on the maximum
primary flow rate that can be withdrawn in heating mode.
The flow rate limitation is imposed by controlling the
maximum opening of the primary circuit modulating valve.
The relationship between the degree of opening (%) and Kv of
the circuit that connects the primary flow to the secondary
flow is shown in the graphs.
Primary flow rate limitation in DHW mode.
DEFAULT SETTING: no limitation (technical parameter t04 =
100)
Likewise, you can establish a limit to the primary flow rate that
can be tapped for instantaneous DHW production.
The flow rate limitation is imposed by controlling the
maximum opening of the primary circuit modulating valve.
Since latter is controlled by a differential pressure limiter, it is
possible to supply direct correspondence between the opening
position of the valve and the circulating flow rate
(*)
.
N.B.
Any limitation must be assessed in accordance with the
effective thermal characteristics of the residential unit served.
(*)
The correspondence between valve position and flow rate is
indicative. Graphs obtained with pressure head upstream of the
HIU = 50 kPa.
A maximum degree of opening (%) can be set via technical
menu parameter t03
Max opening (%)
Kv (m
3
/h)
70
60
50
80
100
90
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
A maximum degree of opening (%) can be set via technical
menu parameter t04.
Max opening (%)
Flow rate (l/h)
70
60
50
80
100
90
0
200
400
600
800
1000
1200
