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Quick setback
constant (KON)
Benefit
Impact
Example
Generating the
temperature demands
With fixed value control or
emergency operation
With weather compensation
78/171
Siemens Building Technologies
HVAC Products
• Making use of the building's ability to store heat
The duration of quick setback will be changed.
Entry:
Increase:
Longer setback time;
for well insulated buildings that cool down rather slowly
Decrease:
Shorter setback time;
for poorly insulated buildings that cool down quickly
Without room influence
Quick setback is started as soon as changeover to a lower room temperature setpoint
takes place.
The heating circuit pump will be deactivated until the quick setback time has elapsed.
That quick setback time is generated based on the setting of the composite outside
temperature and the room temperature setpoint step.
The quick setback time is limited to a maximum of 15 hours.
The example applies to a setpoint step of 4 K (e.g. from TRw 20 °C to 16 °C):
TaGem
0
- 20
0
- 10
0
0
0
+ 10
0
Heating circuits 1 and 2 generate heat demands Hz1 and Hz2.
The heat demands are generated in different ways, depending on the configuration.
Also, the temperature demands are determined. They result from the user settings and
environmental conditions.
Fixed value control
The temperature demands result from the potentiometer position of the HMI.
Emergency operation
The temperature demands result from the calculation of the heating curve based on an
assumed outside temperature of 0 °C. This means that parameter «Slope» can be used
to exert an influence on the temperature demand.
There are different sources of weather compensation:
• LMU...-internal weather compensation:
LMU...-internal weather compensation will be activated when the outside sensor is
present, but no RU is connected. The heating curve parameters of the LMU... will be
used (STH1, STH2, DTR1, DTR2)!
• Weather compensation with the QAA73...:
The weather compensation of the QAA73... follows from the plant configuration.
In the case of weather compensation via the QAA73 ., the heating curve parameters
of the latter will be used which means those of the LMU... are not relevant!
For detailed information on the assignment of setpoints, refer to «Compensation
variants heating circuits».
Basic Documentation LMU54... / LMU64...
3 Functions
KON
4
8
0
0
0.5
1
3
6
5
11
Values are given in hours
12
15
0
0
1.5
2
9
11
15 (16.5)
15 (21)
20
0
2.5
15
15 (27)
CC1P7494en
07.11.2002
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