User Manual

53
AUTOMATIC CONTROL
4 VENTILATION AND AIR CONDITIONING
CONTROL
BT Reason for energy savings
This section is for building energy systems that bring
air into the building: both ventilation and air
conditioning systems. Heating and Cooling of air
requires additional heating and cooling devices.
Control functions related to heating/cooling systems
are defined in sections 1 and 3 resp.
4.1 Supply air flow control at the room level (e.g. fan
on/off)
1
By reducing the air flow energy for the air
conditioning and the distribution can be saved.
0
No automatic control:
The system runs constantly (e.g. manual
controlled switch)
There will always be a constant (high) air flow to
the room even though this is not necessary from
a comfort perspective (e.g. air quality). With
manual switching such plants are often switched
off too late or not at all – as experience shows.
This leads to an unnecessary high energy
consumption at the air handling unit and also for
air transportation.
1
Time control:
The system runs according to a given time
schedule
There will always be a constant (high) air flow to
the room, but based on a time schedule.
Whether ventilation is only done as required
from a comfort perspective with this approach
depends on the quality of the time schedule and
the possibilty to make adaptations to it.
As experience shows this approach often also
leads to unnecessary ventilation. This then
results in an unnecessary high energy
consumption at the air handling unit and also for
air transportation.
2
Occupancy detection:
The system runs dependent on the occupancy
(light switch, infrared sensors etc.)
By utilizing presence detection a room will only
be ventilated if it is used. With that the
disadvantages of a predefinded time schedule
are eliminated and the energy consumption at
the air handling unit and for transportation will be
reduced. The air flow however is still constant
(high).
4.2 Room air temperature control by the ventilation
system (all-air systems; combination with static
systems as cooling ceiling, radiators, etc.)
2
Room air temperature depends on air flow (4.1,
4.5) as well as supply air temperature (4.9). This
control function is related to a closed loop
controller for the room air temperature acting on
the air flow or supply air temperature. It can work
with or without an additional static heating
system (radiators etc.). Minimum air flow rates
are maintained.
0
On-off control:
Fixed air flow rate and fixed supply air
temperature at the room level; Room
temperature setpoints are set individually.
With that the room temperature can only be
influenced minimally by ventilation.
The room temperature will fluctuate accordingly
due to the on/off control. With that too much
heating/cooling power will be brought to the
room and the energy for transportation will be
consistently high.
1
Continuous control:
Either air flow rate or supply air temperature at
the room level can be varied continuously ; Room
temperature setpoints are set individually
The air flow or the supply air temperature will be
adjusted by the room temperature control.
When adjusting the air flow, a reasonable supply
air temperature (4.9) must operating at the
superior level.
When controlling the supply air temperature at
the room level the air flow is constant. This leads
to a correspondingly high transportation energy.
2
Optimized control:
Minimum energy demand by optimized control.
Both air flow rate as well as supply air
temperature at the room level are controlled
dependent on heating/cooling load.
With that the minimally required air flow can be
provided as long as possible. Only if it is no
longer feasible to provide sufficient
heating/cooling power to the room with this air
flow will it be increased. By that the energy
consumption for air transportaton and also for air
conditioning will be optimized.