Cooling Mode; Cooling Criterion - Rehau NEA SMART 2.0 Service Manual

4.4

Cooling mode

Cooling mode of the system may be started and stopped depending
on the following conditions or parameters:
- Selected operating mode by user
- Defined heating or cooling period
- Calculated cooling criterion
- External input signals which are defined as HEATING or COOLING
Selected operating mode
Cooling mode can be started only when the system is set to HEATING
/ COOLING, only COOLING or MANUAL COOLING.
Defined heating or cooling period
When there is a definition for cooling period, cooling mode is started
only during this period. Cooling mode is also not started when system
is in a defined heating period.
4.4.1

Cooling criterion

The cooling criterion is a value derived from a set of different
conditions – outside conditions and conditions in the pilot rooms – the
overall need to start cooling mode.
The cooling criterion is calculated out of the following values:
- Outside temperature (current value) and a reference value for this
- Filtered outside temperature and a reference value for this
- Pilot room temperatures and their set points in cooling mode
- Trend of the pilot room temperatures
- Weighting parameters for the above named values
1)
When no pilot rooms are defined, this influence does not exist.
By using the weighting parameters, it is possible to adapt the way that
cooling mode is started to the needs of the user and the characteri-
stics of the building. Of course, the setting has a decisive influence on
the energy usage of the building on one hand and the comfort
conditions on the other hand.
A weighting parameter may also be set to zero to eliminate the
influence of a certain value.
Standard-Referenzwerte
Die
Actual outside temperature:
Filtered outside temperature:
Relevant parameters
Web page:
not available
App:
Settings  Installer  Control parameter  Cooling  General
24
1)
sind:
24 °C
18 °C
Examples for cooling criterion settings
Example 1:
- Type of application:
Good insulated office building with heavy internal loads.
- Demands:
High importance of comfortable room temperatures.
- Conclusion:
Outside temperature has no decisive influence, the focus is on the
room temperatures.
- Setting:
Reduce reference values for actual value of outside temperature to
20 °C, for filtered value to 16 °C. Reduce weighting factors for both.
Increase weighting factor for pilot rooms.
Example 2:
- Type of application:
Very well insulated residential building
- Demands:
Energy usage for cooling mode should be reduced. Free cooling is
preferred. Temporarily too high room temperatures can be accepted.
- Conclusion:
Use cooling mode only when outside temperature is too high for free
1)
cooling.
- Setting:
Reduce weighting factor for pilot rooms.
Example 3:
- Type of application:
Show room with big glass fronts.
- Demands:
Energy usage for cooling mode is not so relevant. Room temperatu-
res have to be comfortable.
- Conclusion:
Allow cooling mode all the time outside heating period.
- Setting:
Set reference value for filtered outside temperature to 16 °C.
Note:
Minimum run time of cooling mode (default value 60 min.)
and blocking time for heating mode after cooling mode (default
value 12 hours) avoid wasting energy by switching between
heating and cooling.