Suppression Of Hydraulic Creep; Mode Of Operation; Raising The Reduced Room Temperature Setpoint - Siemens RVD230 Basic Documentation

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28.3

Suppression of hydraulic creep

28.3.1 Mode of operation

To avoid measuring errors in connection with heat metering due to extremely small flow
rates, the flow through the 2-port valve in the primary return can be limited to a mini-
mum (Y function). This ensures that consumers will not be able to draw heat that
min
cannot be acquired and billed.
If the valve's stroke reaches the minimum limit value, the valve will be fully closed and
then remains closed until the closing time has elapsed.
The first opening pulse delivered by the control after completion of the closing time will
reopen the valve and the control resumes normal operation.
What must always be set is the closing time. This is made on operating line 188, where
the function can also be deactivated by entering --- .
The suppression of hydraulic creep always acts on the actuating device in the primary
return. This means:
• All plant types, with the exception 8–4: 2-port valve Y1 will be closed
• Plant type 8–4: 2-port valve Y5 will be closed
If minimum stroke limitation is active, the display shows
other limitations and acts on the types of plant with a common flow or with a precon-
trolled flow (2–x, 3–x, 5–x, 6–x and 7–2), also during d.h.w. heating.
There is no suppression of hydraulic creep in the d.h.w. circuit connected to the primary
side.
28.3.2 Mode of operation
The stroke corresponding to the minimum volumetric flow is acquired by an auxiliary
switch fitted in the actuator and is then delivered to the controller. The auxiliary switch
is connected to terminals B7–M. When the valve reaches the minimum limit value, the
auxiliary switch will close. When B7–M closes, the valve will be shut and the closing
time starts.
If the link is maintained although the controller delivers opening pulses of 20 % of the
running time, or if the flow temperature setpoint exceeds the setpoint by more than
10 K, the function will deactivate itself until the auxiliary switch in the actuator opens
again.
28.4 Raising the reduced room temperature set-
point
The reduced room temperature setpoint can be raised as a function of the falling out-
side temperature. This ensures that
• the change from the reduced setpoint to the nominal setpoint will not be too great
when outside temperatures are very low
• there will be no extreme peak loads during the heating up phase.
What can be set is a starting point in °C outside temperature (start of compensation,
operating line 189). The reduced room temperature setpoint is raised only at outside
temperatures below that starting point; raising is not required when outside tempera-
tures are higher. The degree of increase is to be set in the form of a slope (operating
line 190); the slope represents the setpoint increase per °C outside temperature drop.
The setting range is 0...10; the effective value is 10 times smaller.
The temperature used is the composite outside temperature.
The function can be deactivated (by entering 0 for the slope).
Basic Documentation RVD230
28 Function block Miscellaneous
. It is given priority over all
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CE1P2383en
27.05.2004