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Interfaces for the LMU...
Sensor
Frost protection
Overtemperature
protection
Mixing circuits
U
Determining the flow
temperature setpoint
Handling the locking signal
Handling the forced signal
Flow temperature
control
80/171
Siemens Building Technologies
HVAC Products
• Connect X50 of the LMU... and AGU2.500... via cable AGU2.104
• Connect AGU - X52 - 01 to X1 - 02 of the LMU... (mains supply)
If the sensor becomes faulty (open-circuit or short-circuit), it must be noted that the flow
temperature will no longer be controlled. The mixing valve will be driven to the fully
closed position (from V1.01).
The mixing valve clip-in module has its own frost protection function. This frost
protection of the heating circuit only covers the mixing circuit.
The frost protection for the heating circuit can only become active when a flow sensor is
connected to the mixing valve clip-in module.
If such a flow sensor is not present, or if it does not function correctly, the function
cannot be performed.
In mixing circuits, the maximum flow temperature that can occur will be limited:
- 55 °C
up to V1.01
TvSmax
V1.02 and higher
In the case of underfloor heating systems, a separate external limit thermostat must be
fitted to ensure protection against overtemperatures!
When there is an active demand for heat, the flow temperature setpoint is generated
from the temperature demand plus a boost when there is an active forced signal, or
minus a reduction when there is an active locking signal.
The forced signal has priority over the locking signal.
When frost protection for the heating circuit is active, the flow temperature setpoint is
generated from the switch-off threshold for frost protection.
If the heat demand for heating circuit 2 is not set, but a forced signal is present, the flow
temperature setpoint will be placed in the middle between «TvSmin» and «TvSmax».
The basic unit generates locking signals when the current heat consumption is limited
by the consumers.
The purpose of these locking signals is to shut down or throttle individual load circuits to
enable the boiler temperature to rise more quickly.
If the locking signal exceeds a threshold value (5 %), the heat demand of all pump
heating circuits will be reset, thereby deactivating the pump of heating circuit 2.
If the second heating circuit is a mixing circuit (and is parameterized as such), any
locking signal causes the flow temperature setpoint to drop.
The basic unit generates a forced signal if there is a need for the boiler to carry surplus
heat away.
With the help of the forced signal, the heat shall reach the consumers as quickly as
possible.
When the forced signal is active, the basic unit sets the heat demand for all heating
circuits (including that for heating circuit 2).
The control used is 3-position control with delayed checkback. In connection with the
actuator, the control loop provides PI mode.
The flow temperature is controlled to the setpoint of the determined flow temperature
plus the boost.
Basic Documentation LMU54... / LMU64...
4 Clip-in AGU2.500... for additional heating circuit
CC1P7494en
07.11.2002
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