Response Threshold «Q - Siemens RWF40.000A97 User Manual

5.6 Response threshold «Q»
HVAC Products
The response threshold «Q» defines for how long and how low the actual value is
allowed to drop before the system switches to high-fire operation.
An internal mathematical calculation using an integration function determines the sum of
all the areas Q = Q1 + Q2 + Q3, as shown in the diagram. This only takes place when
eff
the control deviation (x-w) falls below the value of the switching threshold «HYS1». If
the actual value increases, integration is stopped.
If «Q » exceeds the preset response threshold «Q» (can be adjusted on the parameter
eff
level), this causes the second stage of the burner to switch on or - in the case of a
floating controller / modulating controller – the actuating device to open.
If the actual boiler temperature reaches the required setpoint, Q
Temperature (°C)
x
w
HYS1
Q
7865d19e/1199
Monitoring of the actual value ensures that the switching frequency is kept low in the
transitional range from low- to high-fire operation, aimed at reducing wear.
CC1B7865en
Q
1
2
05.12.2002
5. Operating modes
is reset to 0 .
eff
Q
3
Q = 0
eff
t
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