User Manual

55
AUTOMATIC CONTROL
4 VENTILATION AND AIR CONDITIONING
CONTROL
BT Reason for energy savings
4.3 Coordination of room air temperature control by
ventilation and by static system
Interaction of the different systems has to be
coordinated.
0
Interaction is not coordinated:
E.g. closed loop controllers are dedicated to each
system to maintain the room air temperature
independently.
Without coordination there is a risk of having
independent control loops working against each
other and inner and external heat gains cannot
be taken into account. This leads to
unnecessary energy consumption and at times
to uncomfortable room temperatures.
1
Interaction is coordinated:
I.e. only one system is controlled by a closed
loop controller for the room air temperature and
the other system conditions the room only to that
extent that allows the closed loop controller to
benefit from internal and external heat gains.
3
With that the various system parts work in a
coordinated way with each other to always
provide a comfortable room temperature. The
energy consumption will be kept low with this
approach.
4.4 Outside air flow control
This control function is applied to ventilation
systems that allow varying the OA ratio or flow
respectively.
0
Fixed OA ratio/OA flow:
The system runs according to a given OA ratio,
e.g. modified manually.
Often there is an unnecessarily hight outside air
flow to the plant that will be conditioned.
Experience shows that outside air rates that
have been set too high will not be reset which
leads to a constantly high energy consumption
for the conditioning of the outside air.
1
Staged (low/high) OA ratio/OA flow:
Depending on a given time schedule
The outside air rate will be adjusted in stages
(e.g. a time schedule reduces the outside air
rate over lunch, late in the afternoon, …). W ith
that the energy consumption for the conditioning
of the outside air will be reduced accordingly.
Whether this provides an appropriate outside air
rate from an occupancy perspective depends on
the quality of the time schedule and its flexibility
for adjustments.
2
Staged (low/high) OA ratio/OA flow:
Depending on the occupancy, e.g. light switch,
infrared sensors etc.
With presence detection there will only be a high
outside air rate if the rooms are occupied. With
that the disadvantages of a preefined time
schedule are eliminated and the energy
consumption for the air conditioning will be
somewhat reduced. The outside air rate often is
still too high compared to the demand.
3
Variable control:
The system is controlled by sensors which detect
the number of people or indoor air parameters or
adapted criteria (e.g. CO
2
, mixed gas or VOC
sensors). The used parameters shall be adapted
to the kind of activity in the space.
4
There will always be only as much outside air
brought to the plant and conditioned as
necessary. This leads to the minimally required
energy consumption for the conditioning from an
outside air flow perspective.