Automatic Changeover Of Operating Mode; Giving Consideration To Heat Demand From The Rva; Locking And Forced Signals When Connecting To The Lpb; External Dhw Heating By Albatros Controllers - Siemens LMU54 Series Basic Documentation

Automatic changeover
of operating mode
Giving consideration to
heat demand from the
RVA...
Locking and forced
signals when connecting
to the LPB
Siemens Building Technologies
HVAC Products
Integration of the LMU... into the ALBATROS system includes automatic changeover of
the operating mode on the RVA.... .
It is activated when operating mode «Standby» or «Manually summer» was selected on
the BMU or was triggered via modem.
In that case, the heating circuit operating mode on the RVA... changes automatically
and is indicated by a flashing «Standby» button.
The LMU... always takes into account the external heat demand from an RVA... as long
as internal automatic summer / winter changeover does not call for summer operation
due to high outside temperatures .
This means that protective functions on the RVA..., such as frost protection for the room,
can become active also when, on the LMU..., the «Standby» mode (manual summer
operation) was selected.
Although the operating mode of RVA... controllers normally is autonomous, the LMU...
can make use of locking and forced signals to influence the heat consumption of the
external user.
Locking signals that reduce heat consumption of the external heating circuits are
generated by the LMU... when DHW heating with absolute priority is active in the system
(on the LMU... or on one of the RVA...).
In that case, the RVA... will shut down their heating circuit pumps and drive their mixing
valves to the fully closed position.
If, however, the boiler temperature reaches a crucial level (e.g. temperature limiter cuts
out), the LMU... will generate forced signals that force the consumers to draw more
heat.
In response, ALBATROS controllers will activate the heating circuit pumps and open
their mixing valves.
In addition, the LMU... uses forced signals to trigger pump overrun in external heating
circuits. The duration of pump overrun is determined by LMU... parameter 130 --
(ZqNach).

5.1.2 External DHW heating by ALBATROS controllers

In principle, application «External DHW heating» by an ALBATROS controller is not
much different from «Heating circuit extension». Nevertheless, a number of important
points need to be considered with this application.
In an interconnected system consisting of LMU...and RVA... controllers, several plant
components can manage DHW heating. At first, it does not matter whether one or
several units are involved in DHW heating.
Normally, a selection is to be made when the type of DHW heating is used as a
criterion. For example, ALBATROS controllers do not support instantaneous DHW
heating applications, but only storage systems.
DHW sensors, pumps and valves will be connected to the device that has been selected
for that function. This means that all settings required for DHW heating are to be made
there (setpoints, time switch programs, etc.).
Provision of external DHW heating by ALBATROS controllers means that an adequate
hydraulic diagram must have been selected on the LMU... .
Suitable choices are diagram 64 through 76.
Basic Documentation LMU54... / LMU64...
5 Clip-in module OCI420... for communication via LPB
83/171
CC1P7494en
07.11.2002