Heating With Stratification Storage Tank; General; Heating With One Flow Sensor; Heating With 2 Flow Sensors - Siemens RVD230 Basic Documentation

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17.2 D.h.w. heating with stratification storage tank
This section only describes the functions used in addition to d.h.w. heating with storage
tanks.

17.2.1 General

D.h.w. heating with stratification storage tanks is covered by plant types x–6, x–7, x–8,
x–10 and 2–12. With these types of plant, separate heat exchangers are used for
space heating and d.h.w. heating. They can be connected either parallel to or in series
with the heating circuit.
The d.h.w. flow temperature can be controlled with the help of one or 2 flow sensors;
variable speed control of the storage tank charging pump is also possible.
These types of plant require no flow switch.
17.2.2 D.h.w. heating with one flow sensor
The d.h.w. flow temperature is acquired at the secondary output of the heat exchanger,
using sensor B3.
If the d.h.w. temperature at storage tank sensor B31 or B32 drops, d.h.w. heating
commences in that both the intermediate circuit pump and the storage tank charging
pump are activated (not with plant types x–6, x–8, 2–12 and 3–7).
With plant types x–6, x–7 and x–12, which use an intermediate circuit (with or without
mixing valve), the storage tank charging pump starts only when flow temperature B1
exceeds the actual value of the d.h.w. temperature by at least 2 K. It stops with no
pump overrun when the flow temperature has dropped below the actual value of the
d.h.w. temperature.
D.h.w. heating is terminated when the d.h.w. setpoint is reached. Both the intermediate
circuit and the storage tank charging pump operate during the defined pump overrun
times; the storage tank charging pump by an adjustable period of time (operating li-
nes107 and 108).
However, both the charging process and pump overrun can be stopped by the protec-
tion against discharging.
17.2.3 D.h.w. heating with 2 flow sensors
The temperature of the intermediate circuit is acquired with sensor B3, that of the d.h.w.
flow at the secondary output of the heat exchanger with sensor B12.
If the d.h.w. temperature at storage tank sensor B31 or B32 drops, d.h.w. heating
commences in that the intermediate circuit pump is activated. The procedure is the
following:
• First, the intermediate circuit is heated up until the temperature acquired with sensor
B3 has reached the setpoint. Then, the storage tank charging pump will be activated
and the d.h.w. circuit heated up until, at sensor B12, the setpoint is reached also.
If the temperature acquired with sensor B12 lies above the setpoint, it will deliver a
locking signal which acts on primary valve Y5.
• As an alternative, the speed of the storage tank charging pump can be controlled de-
pending on the temperature acquired by sensor B12. Primary valve Y5 is controlled
depending on the temperature acquired with sensor B3. If the temperature acquired
with sensor B12 lies above the setpoint, it will deliver a locking signal which acts on
primary valve Y5.
D.h.w. heating is terminated when the temperature at the storage tank sensor has
reached the d.h.w. setpoint. Both the intermediate circuit and the storage tank charging
Basic Documentation RVD230
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CE1P2383en
27.05.2004