Temperature And D.h.w. Switching Differential - Siemens RVL471 Basic Documentation

Siemens Building Technologies
HVAC Products
With plant types 4–x, 5–x, and 6–x, setting 1 on operating line 125 makes no sense,
since there is no own heating circuit. In that case, changeover to the electric immer-
sion heater would take place at midnight at the latest, after 48 hours of operation.
19.3 D.h.w. temperature and d.h.w. switching dif-
ferential
The kind of d.h.w. storage tank temperature acquisition must be entered on operating
line 126. It can be measured with one or 2 sensors, or with one or 2 thermostats.
If temperature sensors are used, the switch-on / off temperature for charging is deter-
mined as follows:
SD
BW
ON
OFF
T
T
ON OFF
ON D.h.w. charging ON
OFF D.h.w charging OFF
SDBW Switching differential of d.h.w. charging
T Switch-on temperature
ON
T Switch-off temperature
OFF
TBWw D.h.w temperature setpoint
TBWx D.h.w. temperature
If the d.h.w. storage tank is equipped with thermostats, the switch-on / off temperature
is determined by the thermostats.
Determination of the switch-on temperature (start of d.h.w. charging):
Operating line 126 Measurement
0 1 sensor
1 2 sensors
2 1 thermostat
3 2 thermostats
Determination of the switch-off temperature (end of d.h.w. charging):
Operating line 126 Measurement
0 1 sensor
1 2 sensors
2 1 thermostat
3 2 thermostats
SDBW D.h.w. switching differential
(operating line 128)
TBWw Setpoint of d.h.w. temperature (operating line 26 or 28)
T Measured value d.h.w. storage tank sensor (B31)
BWx1
T Measured value d.h.w. storage tank sensor (B32)
BWx2
From the 2 tables above, it is obvious that when using 2 sensors, it is irrelevant which
of the 2 sensors is fitted at the top and which at the bottom of the d.h.w. storage tank.
Basic Documentation RVL471
19 Function block "D.h.w. storage tank"
T
= T
BWx
BWw
Switching criterion
T < (T
BWx1 BWw
T < (T
BWx1 BWw
Thermostat contact B31 closed
Both thermostat contacts B31 and B32 closed
Switching criterion
T > T
BWx1 BWw
T > T
BWx1 BWw
Thermostat contact B31 open
Both thermostat contacts B31 and B32 open
– SD )
BW
– SD ) and T < (T
BW BWx2 BWw
and T > T
BWx2 BWw
– SD )
BW
.
73/118
CE1P2524E
23.10.2002