Rotex Controller Series Product Documentation page 91

EbV
Operation:
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
Note on operation
..2.., ..22.., ..C..
Selection of heat generator type
(depends on controller type)
Select sensor mode
Outdoor temp. locking
Basic load offset
..2.., ..22..
Switching differential I
(not at H-GEN setting 5)
Reset stage I
..22..
Switching differential II
(only for 2-stage H-GEN)
Time delay stage II
(only for 2-stage H-GEN)
Enabling mode stage II
(only for 2-stage H-GEN)
DHW charging mode stage II
(only for 2-stage H-GEN)
Reset stage II
Deviation (K)
Setpoint
Product documentation THETA NORM/UNIT
Key / parameter tree
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
HEAT GENER.
Switch-off line
Parameter
PARAMETER 01
PARAMETER 06
PARAMETER 25
PARAMETER 26
PARAMETER 08
RESET ST-1
PARAMETER 09
PARAMETER 10
PARAMETER 11
PARAMETER 12
RESET ST-2
Switch-on line
8-7