Rotex Controller Series, Product Documentation

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EbV Product documentation THETA NORM/UNIT
8-7
8.1.8 Switching for modulating burners
Modulating burners are controlled in a way similar to mixer control, through a PI control algorithm, since in
this case an actuator integrated in the burner regulates the air/fuel ratio according to the heating power.
However, in contrast to the control of conventional burners, control of modulating burners is subject to the
following criteria:
Switching differential
In contrast to conventional ON/OFF burner control systems with their switching differentials symmetrical
around the respective setpoint, the switching differential for modulating burners is an asymmetric interval
where the switch-on value is always 1K below the setpoint. This offers the advantage that, in case of a
possible overshoot through the P-band, the burner is not switched off, because the switch-off point lies
above the setpoint by a wider margin than the switch-on point is below the setpoint (overshoot reserve).
Also, when the heat demand is low (especially in the low-load range) the temperature will drop only slightly
because the burner is switched on again as soon as there is a deviation of more than 1 K.
Example:
Current setpoint = 50 K
Switching differential = 6 K
Switch-on at (50°C - 1K) = 49 °C
Switch-off at (49°C +6K) = 55 °C
Operation:
Note on operation Key / parameter tree Parameter
..2.., ..22.., ..C..
Selection of heat generator type
(depends on controller type)
HEAT GENER. PARAMETER 01
Select sensor mode
HEAT GENER. PARAMETER 06
Outdoor temp. locking
HEAT GENER. PARAMETER 25
Basic load offset
HEAT GENER. PARAMETER 26
..2.., ..22..
Switching differential I
(not at H-GEN setting 5)
HEAT GENER. PARAMETER 08
Reset stage I
HEAT GENER. RESET ST-1
..22..
Switching differential II
(only for 2-stage H-GEN)
HEAT GENER. PARAMETER 09
Time delay stage II
(only for 2-stage H-GEN)
HEAT GENER. PARAMETER 10
Enabling mode stage II
(only for 2-stage H-GEN)
HEAT GENER. PARAMETER 11
DHW charging mode stage II
(only for 2-stage H-GEN)
HEAT GENER. PARAMETER 12
Reset stage II
HEAT GENER. RESET ST-2
Deviation (K)
Switch-off line
Setpoint
Switch-on line