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Siemens Building Technologies Basic documentation RVD240 CE1P2384en
HVAC Products 16 D.h.w. heating 27.05.2004
16.2.2 D.h.w. heating
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.
With plant type 2–6 (with intermediate circuit), the storage tank charging pump is acti-
vated only when the common flow temperature B1 has exceeded the actual 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 pump and the storage tank charging pump operate during the defined pump
overrun times; the storage tank charging pump by an adjustable period of time longer
than the intermediate circuit pump (operating lines107 and 108).
However, both the charging process and pump overrun can be stopped by the protec-
tion against discharging.
16.2.3 Feeding the circulating water into the heat exchanger
It is possible to configure the feeding of circulating water into the heat exchanger (oper-
ating line 54). The following settings are available:
Setting Circulating
pump
Feeding the circulating
water into…
Function, action
0 No – No control
1 Yes the storage tank No control, no compensation of heat
losses
2 Yes the heat exchanger 80 % of the heat losses will be com-
pensated
3 Yes the heat exchanger Full compensation of heat losses;
constantly aiming for the d.h.w. flow
temperature setpoint
A flow temperature drop of 20 % is accepted. The behavior is the same as that with
d.h.w. heating directly via heat exchanger (setting on operating line 54 = 2). When a
d.h.w. charging cycle is completed, the circulation will first be charged for 5 minutes
before the demand for d.h.w. becomes invalid.
16.3 Direct d.h.w. heating
16.3.1 General
Direct d.h.w. heating via heat exchanger is covered by plant types 1–4 and 4–4.
16.3.2 D.h.w. heating
D.h.w. heating takes place directly via heat exchanger, which can have a flow switch
fitted on the secondary side. Use of a circulating pump is optional. The relevant settings
are to be made on operating lines 54 and 55.
The regulating unit is always 2-port valve Y5 in the primary return of the d.h.w. heat
exchanger; it is controlled according to temperature B3 in the secondary flow of the
heat exchanger.
To ensure a good control performance, a fast actuator with a running time of
10...35 seconds is required; its opening and closing times may be different.
Setting 2
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