User Manual

88
Remarks of Siemens
This section outlines how Siemens interprets the functions and processing functions according
to EN 15232-1:2017.
4.1
Here only air renewal in the room is considered.
Note: For the room temperature control the parts “Heating control” and “Cooling control” of the EN
15232 are to be considered.
4.3
1 With that it will be prevented that two control loops attempt to control the same control value.
This means e.g. the room heating is set to bring the room temperature to 15 °C, the supply air
temperature will then be provided depending on the room temperature in order to maintain the
desired room temperature. With that internal heat gains (e.g. from people, devices, lighting, …)
can be considered or compensated.
4.4
3 By taking air quality indicators (CO
2
, VOC/mixed gas) into account the rooms will always be
provided with the minimally required outside air flows. Because of this only this outside air flow
must be conditioned. This keeps the energy consumption low.
4.5
2 By switching stages the speed n of the fans and with that the air flow V

will be changed. With that
the power consumption of the fans changes too. For that, the following proportional (or affinity)
laws apply:
n
1
n
2
=
V
󰇗
1
V
󰇗
2
 und
P
1
P
2
=󰇧
V
󰇗
1
V
󰇗
2
󰇨
3
resp.
P
1
P
2
=

n
1
n
2

3


Example:
At half the speed, the air flow is reduced to its half (1/2) * also and the power consumption goes
down to an eighth (1/8) *.
Note:
* This applies under ideal (loss-free) conditions only. For practical purposes the fan vendor’s documentation should be
consulted. The reduction of the power consumption e.g. at half the air flow is substantial based on experience and
disproportionately high (e.g. 60 %)
3 This type of control is widely used. It provides for adjusting the air flow to the demand of the
rooms. However there is no direct connection between the controllers in the room and the air flow
control at the air handling unit. Changes from the rooms will be transmitted via the duct work and
will affect the air pressure (e.g. VAV-controllers close à pressure at the sensor increases). The
pressure control can react to that and adjust the air flow at the fan based on that e.g. with a
variable speed drive (VSD). Based on experience the set point for the supplied air pressure is
often set too high (be on the safe side, poorly balanced air duct work). This leads to continuously
and disproportionally high energy consumption for the air transportation (see proportional laws
under 2).
4 This control approach requires individual control of the air flow at room level based on
temperature and/or air quality (4.2, 2 and 4.4, 3). This functionality can be easily implemented in
the Siemens Desigo building automation system using the standard solution “AirOptiControl”.
Applying this solution required communicating room- and VAV-controller that provide the
necessary demand information.