Siemens RVL481 - Temperature and D.h.w. Switching Differential

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Siemens Heating and D.h.w. Controller RVL481 CE1P2541en
Building Technologies 19 Function block "D.h.w. storage tank" 20.05.2008
19.3 D.h.w. temperature and d.h.w. switching
differential
The kind of d.h.w. storage tank temperature acquisition must be entered on operating
line 126.
In plant types x–5
without solar heating, select setting 0, 1, 2 or 3 on operating line
126, although d.h.w. heating with electric immersion heater does not require either
sensor or thermostat.
The storage temperature can be acquired via
• 1 or 2 sensors
• 1 or 2 thermostats
• 1 or 2 sensors with solar function; this activates function "Solar d.h.w. charging".
If temperature sensors are used, the switch-on / off temperature for charging is deter-
mined as follows:
T
BWx
2524D02
ON
OFF
SD
BW
T
OFF
= T
BWw
T
ON
ON D.h.w. charging ON T
BWw
D.h.w temperature setpoint
OFF D.h.w charging OFF T
BWx
D.h.w. temperature
SD
BW
Switching differential of d.h.w. charging T
BWx1
Measured value d.h.w. storage tank sensor B31
T
ON
Switch-on temperature T
BWx2
Measured value d.h.w. storage tank sensor B32
T
OFF
Switch-off 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 Switching criterion
0 1 sensor T
BWx1
< (T
BWw
– SD
BW
)
1 2 sensors T
BWx1
< (T
BWw
– SD
BW
) and T
BWx2
< (T
BWw
– SD
BW
)
2 1 thermostat Thermostat contact B31 closed
3 2 thermostats Both thermostat contacts B31 and B32 closed
4
1 sensor, solar
d.h.w. heating
T
BWx1
< (T
BWw
– SD
BW
)
5
2 sensors, solar
d.h.w. heating
T
BWx1
< (T
BWw
– SD
BW
) and T
BWx2
< (T
BWw
– SD
BW
)
Determination of the switch-off temperature (end of d.h.w. charging):
Operating line 126 Measurement Switching criterion
0 1 sensor T
BWx1
> T
BWw
1 2 sensors T
BWx1
> T
BWw
and T
BWx2
> T
BWw
2 1 thermostat Thermostat contact B31 open
3 2 thermostats Both thermostat contacts B31 and B32 open
4
1 sensor, solar
d.h.w. heating
T
BWx1
> T
BWw
5
2 sensors, solar
d.h.w. heating
T
BWx1
> T
BWw
and T
BWx2
> T
BWw
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.