TAC Xenta 102 Handbook
Appendix A: Setpoint calculation
TAC AB, 1999-08-18
0-004-7516-1 (GB), App A:1 (2)
Appendix A: Setpoint calculation
Definitions:
Deadband
= Neutral zone
Occupied
= Comfort mode
Standby
= Economy mode
Unoccupied
= Off mode
nviSetPoint
= Input temperature setpoint (
nviSetpoint)
nciSetPoints
= Six basic setpoints for temperature (
nciSetpoints)
Occupied_cool
= Cooling setpoint comfort
Standby_cool
= Cooling setpoint economy
Unoccupied_cool = Cooling setpoint off
Occupied_heat
= Heating setpoint comfort
Standby_heat
= Heating setpoint economy
Unoccupied_heat = Heating setpoint off
Effective
= Existing
In
nciSetpoints, the cooling and heating setpoints for comfort and economy mode are set. nviSetpoint gives
you the possibility to move all four setpoints with only one value. The mean value of the comfort setpoints
in
nciSetpoints can be regarded as the basic setpoint for comfort mode, and the mean value of the econo-
my setpoints can be regarded as the basic setpoint for economy mode. The temperature scale for the
setpoints must be as follows:
unoccupied_heat < standby_heat < occupied_heat < occupied_cool < standby_cool < unoccupied_cool.
There are two methods to calculate the setpoints: Method A and Method B.
Method A:
When
nviSetpoint receives a valid setpoint, this value becomes the new, common setpoint. The cooling
and heating setpoints are recalculated to be at the same distance from the new, basic setpoint as they
were from the earlier basic setpoint. Therefore, method A removes the existing asymmetry (see the ex-
ample on the next page).
The controller calculates the different setpoints for heating and cooling in comfort and economy mode,
from
nviSetpoint, plus or minus half the neutral zone in the comfort and economy modes, which are calcu-
lated from the
nciSetpoints. The controller takes the differnet heating and cooling setpoints in off mode
from
nciSetpoints.
deadband_occupied
= occupied_cool –
occupied_heat
deadband_standby
= standby_cool – standby_heat
effective_occupied_cool = nviSe 0,5 (deadband_occupied)
effective_occupied_heat = nviSetPoint – 0,5 (deadband_occupied)
effective_standby_cool = nviSe 0,5 (deadband_standby)
effective_standby_heat
= nviSetPoint –
0,5
(deadband_standby)
Method B:
In economy mode you can chose method B to calculate the existing setpoints. In this case, the setpoints’
distance from the existing setpoint, is as far as the distance they were from the old, basic setpoint in
comfort mode. Method B only has influence when the two setpoints from
nciSetpoints do not have the
same value, i.e. when the four setpoints are not placed symmetrically around one value. With Method B
the asymmetry is therefore kept, as the old comfort setpoint is used (see the example on the next page).
The controller calculates the different setpoints for heating an cooling in comfort and economy modes
from
nciSetpoints. Also, the actual, absolute setpoint deviation is calculated as the mean value of the
occupied_heat setpoint and the occupied_cool setpoint. The controller gets the different heating and coo-
ling setpoints in off mode from
nciSetpoints.
effect_abs_setpoint_ offset = nviSetpoint – (occupie occupied_heat) /2
effective_occupied_cool = occupie effect_abs_setpoint_offset
effective_occupied_heat = occupie effect_abs_setpoint_offset
effective_standby_cool
= standby_cool
+ effect_abs_setpoint_offset
effective_standby_heat
= standby_heat
+ effect_abs_setpoint_offset
