Siemens Building Technologies
Basic Documentation RVL470
CE1P2522E / 30.03.2000
Landis & Staefa Division
Function block "Space heating"
23/68
where:
ln
Natural logarithm
kt
Building time constant in hours
t
Duration of setback
TAM
Composite outside temperature
TRw
Setpoint of the NORMAL room temperature
TRw
Setpoint of the REDUCED room temperature
8.4.7. Optimum start control
During the building’s non-occupancy times, the RVL470 maintains the setpoint of
REDUCED heating. Toward the end of the non-occupancy time, optimization switches
the control to boost heating. This means that the selected boost will be added to the
room temperature setpoint. Optimization calculates the changeover time such that, at
the start of occupancy, the room temperature will reach the setpoint of NORMAL heat-
ing.
When the room temperature is simulated by the room model, that is, when using no
room temperature sensor, the forward shift in time is calculated as follows:
t [ min ] = ( T
Rw
– T
RM
)
*
60
where:
t
Forward shift
TRw
Setpoint of the NORMAL room temperature
T
RM
Room model temperature
Optimum start control with the room model takes place only if a quick setback was pre-
viously effected.
Optimum start control can be deactivated by entering 0 hours as the maximum heating-
up period.
8.4.8. Boost heating
For boost heating, a room temperature setpoint boost can be set. After changeover to
the NORMAL temperature, the higher room temperature setpoint applies, resulting in an
appropriately higher flow temperature setpoint.
t
25
22
D
0
8
T
R
T
Rw
T
Rx
T
Rw
T
Rw
T
Rw
t
Time
T
R
Room temperature
T
Rw
Setpoint of NORMAL room temperature
T
Rw
Setpoint of REDUCED room temperature
T
Rx
Actual value of the room temperature
T
Rw
Room temperature setpoint
∆
T
Rw
Boost of room temperature setpoint (with boost heating)
Duration of boost:
•
When using a room sensor, boost heating is maintained until the room temperature
has reached the setpoint of normal heating. Then, that setpoint is used again
