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Siemens Building Technologies
Basic Documentation RVL471
CE1P2524E
HVAC Products
14 Function block "District heat"
23.10.2002
100
90
80
70
60
50
40
30
20
10
0
V
P
[%]
DRT
on
DRT
OFF
V
S
t
252
2
D
11
DRT
ON
DRT
OFF
t
V
P
V
S
With active maximum limitation of return temperature differential
Without maximum limitation of return temperature differential
Time
Volumetric flow on the primary side
Volume saved
14.2.3
Integral action time
With maximum limitation of the return temperature and maximum limitation of the return
temperature differential, the integral action time determines the rate at which the flow
temperature setpoint will be reduced.
•
Short integral action times lead to faster reductions
•
Long integral action times lead to slower reductions
With this setting, the effect of the limitation function can be matched to the type of plant.
14.2.4
Minimum stroke limitation (suppression of hydraulic
creep)
To avoid measurement errors in connection with heat metering due to extremely small
flow rates, the flow through the two-port valve in the primary return can be limited to a
minimum (Y
min
function). If the valve is supposed to open below the minimum stroke
position, it will be fully closed and remains closed until the set closing time has elapsed.
The first opening pulse after completion of the closing time will reopen the valve and
the control resumes normal operation.
The stroke assigned to the minimum volumetric flow must be acquired by an auxiliary
switch fitted in the actuator and delivered to the RVL471. When bridging terminals
H4
−
M, the valve will close and the waiting time commences.
If minimum stroke limitation is active, the display shows .
Minimum stroke limitation has priority over all other limitations.
Minimum limitation of stroke also acts during d.h.w. heating.
14.2.5
Limitation of the volumetric flow
The RVL471 does not provide limitation of the volumetric flow.
Function
Behaviour during d.h.w.
heating