Response Threshold "Q - Siemens RWF40 Series User Manual

5.6 Response threshold «Q»
Landis & Staefa Division
The response threshold «Q» defines how long and how low the actual value can drop
before the system switches over 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 for the switching threshold «HYS1». If
the actual value increases, integration is stopped.
If «Q » exceeds the pre-set response threshold «Q» (can be adjusted at the parameter
eff
level), this causes the second stage of the burner to be switched on or - in the case of a
3-position controller / modulating controller – the regulating unit to open.
If the actual boiler temperature reaches the required setpoint, Q
Temperature (°C)
x
w
HYS1
Q
7865d19e/1199
Actual value monitoring ensures that the switching frequency is kept low in the
transitional range from low- to high-fire operation in order to reduce wear.
CC1B7865E
Q
1
2
February 10, 2000
5. Operating modes
is set to 0 .
eff
Q
3
Q = 0
eff
t
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