Compensation Of Heat Losses Through Control - Siemens RVD230 Basic Documentation

General
Caution!
Mode of operation
Settings 0 and 1
Setting on operating
line 2
Example
Setting on operating
line 3
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HVAC Products

17.3.6 Compensation of heat losses through control

Generally, heat losses due to d.h.w. consumption are always compensated for through
control.
In addition, when using a flow switch and a circulating pump, it is possible to configure
whether the control shall also be active outside periods of d.h.w. consumption, that is,
whether heat losses due to radiation, circulation, etc., shall be compensated for.
The configuration is to be made on operating line 54.
If a flow switch is used, the primary valve will temporarily be controlled by an opening
signal at the beginning of d.h.w. consumption, and by a closing signal at the end of
d.h.w. consumption.
To ensure no excessive temperatures occur and the response of the control is fast, a
QAE21.93 immersion sensor must be used in the case of configurations with no flow
switch, since that sensor immerses into the heat exchanger.
B32
Plant without flow switch
Operating Operating
line 55 line 54
0
≠ 4
1, 2, 3
4 0, 1
4 2
4 3
Explanations relating to the settings on operating line 54:
There is no d.h.w. heating when no d.h.w. is consumed. This is true also when the
circulating pump runs. Since heat losses are not compensated for, the d.h.w. tempera-
ture will drop to the room temperature level eventually.
A temporary drop of the d.h.w. flow temperature is accepted. Heat losses are only
partially compensated for; the flow temperature may drop by a maximum of 20 %. Sub-
sequent heating up to the d.h.w. setpoint always takes a minimum of 5 minutes.
For the compensation of heat losses, the circulating pump must be released. If it is not
released, no control is provided independent of the d.h.w. flow temperature.
D.h.w. setpoint T = 50 °C
BWw
Cold water temperature T
Permissible reduction ∆T = 20 %
Minimum d.h.w. flow temperature T
– ∆T × (T
T = T
BWV BWw BWw
The aim is to maintain the d.h.w. setpoint and all heat losses will be fully compensated
for. A circulating pump is used.
Basic Documentation RVD230
17 D.h.w. heating
Plant with flow switch
Function
Full compensation of heat losses
No compensation of heat losses
Partial compensation of heat los-
ses, maximum flow temperature
reduction by 20 % permitted
Full compensation of heat losses
= 10 °C (fixed value):
Nx
= ?
BWV
– T ) = 50 – 0.2 (50 – 10) = 42 °C
Nx
B32
Flow switch circulating
pump
No
No
Yes
No No
Yes Yes
Yes Yes
CE1P2383en
27.05.2004