Flow Temperature Set Point In Cooling Mode; Dew Point Monitor; Dehumidifiers - Rehau NEA SMART 2.0 Service Manual

4.4.2

Flow temperature set point in cooling mode

The calculation of flow temperature set point in cooling mode must
take into account the following demands:
- Avoid condensation on cooled surfaces
- Ensure user comfort
- Cooling system characteristics
General limit
The lowest set point of flow temperature is defined by a system-spe-
cific parameter.
Condensation topic
The system receives from the installed room units with humidity
sensor the information "relative humidity" and "dew point".
Remark:
Both values are used for dehumidifier control, see
chapter 8 Parameter.
The highest dew point from all rooms which belong to a mixed circuit
is selected and a safety offset is added. Flow temperature may not
drop below this limit.
Relevant parameters
Web page:
Home  Installer  Settings  Mixed circuits
App:
Settings  Installer  Control parameter  Cooling  Circuits
User comfort
Surfaces which are too cold will cause uncomfortable conditions,
especially in floor cooling systems. To avoid this, the minimum flow
temperature is set according to the cooling system characteristics.
Note:
An additional sensor can be connected to the room unit to monitor the
temperature of the cooled surface. User may set a limit value; the
temperature of the cooled element will not fall below this value in
cooling mode.
A sufficient safety margin to calculated dew point must
be selected according to the conditions in the installation.
It has to be taken into account that
- as a matter of principle, all measured values have a certain
degree of inaccuracy
- the surface temperature of the cooled areas may be close to
the flow temperature, depending on ambient conditions
- a correction of flow temperature due to a rapidly increasing
room humidity has not an immediate effect on the surface
temperature. Depending on the system used the reaction will
only take place after a certain period of time
- condensation on cooled elements can damage structure,
surface and appearance of these elements
- condensation on cooled floors can cause accidents due to
slippery surface
4.4.3

Dew point monitor

The potential free output contacts of dew point monitors can
connected to Base, R-Module and U-Modules configured for mixed
circuit control.
They shall be installed on pipes which carry water with the lowest
temperature. It must be ensured, that the mounting position allows air
circulation and that the humidity conditions are representative for the
cooled environment.
When the dew point monitor is triggered, the reaction is:
- Dew point monitor connected to U-Module of mixed circuit stops
mixed circuit and closes valves of all rooms which are supplied by
this circuit
- Dew point monitor connected to Base or R-Module closes all valves
of all cooled rooms
- Dehumidifiers belonging to rooms or mixed circuit are started
4.4.4

Dehumidifiers

The maximum configuration of the system is able to control up to
9 dehumidifiers. Dehumidifiers are controlled by the Base (1 dehumi-
difier) and by U-Module (2 dehumidifiers per U-Module).
Dehumidifiers are assigned to rooms, whereby several rooms may
have access to the same dehumidifier. It is not possible to assign
more than one dehumidifier to one room.
A dehumidifier is started when:
- Relative humidity is above a limit value, or
- Calculated dew point is above a limit value, or
- There is a dew point alarm by a dew point monitor
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