Special Boiler Functions; Change Of Operating Mode; Loading The Setpoint/Actual Value - Siemens LMS14 User Manual

Key
260/617
Building Technologies Division

6.12 Special boiler functions

6.12.1 Change of operating mode

When there is a change between space heating and DHW heating, the controller
responds as follows:

DHW heating is ended and, at the same time, there is a request from space
heating:
The controller switches the burner off. DHW overrun is performed while the position
of the DHW controlling element is maintained

The request from space heating is overridden by a DHW request:
The controller adopts the new DHW setpoint and makes use of the DHW
thresholds. The DHW controlling element switches over to DHW heating. The
controller switches off the burner only if the DHW switch-off threshold is or will be
exceeded when changing from heating circuit to DHW operation mode. In general,
however, the DHW setpoint lies above the setpoint for the heating circuit so that
shutdown will not take place

6.12.2 Loading the setpoint/actual value

Depending on the operating mode, the respective setpoints/actual values are loaded to
the LMS14....
Heating mode
Setpoint Boiler temperature
setpoint
Actual value Actual value of
boiler temperature
Line no. Meaning
TwwIst1 Sensor B38 at outlet of instantaneous water heater
TwwSoll Setpoint DHW outlet/keep hot setpoint
TRueck Boiler return temperature
In the case of instantaneous water heaters, the DHW setpoint is used. Depending on
the configured type of instantaneous water heater, the respective actual value is
loaded. With instantaneous water heaters, this is dependent on the type of hydraulic
system, Outlet or Comfort mode and parameterization.
User Manual LMS14...
6 The settings in detail
DHW storage tank Instantaneous
charging water heating
Boiler temperature TwwSoll
setpoint/DHW
charging setpoint
Actual value of TwwIst1/TRueck/
boiler temperature/ actual value of
DHW charging boiler temperature
temperature
CC1U7471en
28.01.2015