User Manual

43
AUTOMATIC CONTROL
3 COOLING CONTROL BT Reason for energy savings
3.2 Emission control for TABS (cooling mode) 5
0
No automatic control of the room temperature The highest supply output is continuously
delivered to the TABS, resulting in the emission
of unnecessary cooling energy under part load
conditions.
1
Central automatic control
The central automatic control for a TABS zone
(which comprises all rooms which get the same
supply water temperature) typically is a supply
water temperature control loop whose set-point is
dependent on the filtered outside temperature,
e.g. the average of the previous 24 hours.
6
Supply output is controlled depending on the
outside temperature, for example (corresponding
to the probable heat demand of the consumers).
Energy losses under part load conditions are
reduced, but no advantage can be taken of
individual heat gains in the rooms.
2
Advanced central automatic control:
This is an automatic control of the TABS zone
that fulfils the following conditions:
This is a central automatic control of the TABS
zone that is designed and tuned to achieve an
optimal self-regulating of the room temperature
within the required comfort range (specified by
the room temperature cooling set-point).
“Optimal” means that the room temperatures of
all rooms of the TABS zone remain during
operation periods in the comfort range, to meet
comfort requirements, but also is as high as
possible to reduce the energy demand for
cooling.
7
Supply output is controlled depending on the
outdoor temperature (corresponding to the
probable heat demand of the consumers).
Taking advantage of self-regulating effects
during operating times fulfills comfort
requirements in all the rooms and reduces
refrigeration demand as much as possible.
Using different setpoints for heating and cooling
(e.g. through the use of a setpoint range for the
flow temperature) can prevent unnecessary
overheating or undercooling. Additional energy
can be saved by compensating for known heat
gains in the building (e.g. by adjusting the flow
temperatures over the weekend in office
buildings – if there are no internal heat gains).
Within a specified outside temperature range
(transition period), the changeover between
heating and cooling occurs (indirectly) based on
heat gains in the building. This may enhance
comfort and automate operation (no need for the
operator to manually change over).
3
Advanced central automatic control with
intermittent operation and/or room temperature
feedback control:
a) Advanced central automatic control with
intermittent operation. This is an advanced
central automatic control according to 2) with
the following supplement: The pump is
switched off regularly to save electrical
energy, either with a fast frequency - typically
6 hours on/off cycle time - or with a slow
frequency, corresponding to 24 hours on/off
cycle time. If the TABS is used for cooling,
intermittent operation with 24 hours on/off
cycle time can also be used to reject the heat
to the outside air if the outside air is cold.
b) Advanced central automatic control with
room temperature feedback control. This is
an advanced central automatic control
according to 2 with the following supplement:
The supply water temperature set-point is
corrected by the output of a room
temperature feedback controller, to adapt the
set-point to non-predictable day-to-day
variation of the heat gain. Since TABS react
slowly, only day-to-day room temperature
correction is applied, an instant correction
cannot be achieved with TABS.
c) Advanced central automatic control with
intermittent operation and room temperature
feedback control.
Even more electricity can be saved through the
pump cycling. In addition, the switch-on phases
can be executed in some cases if energy
efficiency can be gained or at times when
energy is available at lower rates (e.g. cooling at
night at lower outside temperatures or at lower
electricity rates).
Heat gains can be used to save energy through
the use of room temperature control in a
reference room by readjusting the flow
temperature setpoint. Room temperature control
automates the compensation of additional or
missing heat gains if required corrects
incorrectly set weather-compensated control in a
restricted range.