SDC / DHC
Hydraulic Components
EN2H-0221GE51 R0808
137
The modulating burner stage is activated when the heat generator
temperature has dropped below the set nominal temperature by
more than 1 K. The burner is enabled through the burner relay. As
soon as the heat generator temperature crosses the switch-off
level the burner is deactivated, in contrast to the mixed heating
circuit parameters.
Adjustment to the setpoint temperature is realised through the
conventional 2-point output (activating the burner) and an
additional 3-point output for modulating the actuator in the burner.
The temperature is registered by the heat generator sensor. In
contrast to mixed heating circuit control, no end position function
is assigned to this actuator. The control algorithm is running
continuously.
The burner remains in operation for the duration of the set
minimum burner runtime irregardless of temperature-based
switch-off conditions.
If the heat generator maximum temperature is exceeded or the
heat generator minimum temperature is undershot, the same
functions apply as with conventional heat generators.
7.1.9 Modulation of P part (Xp)
The proportional part Xp defines how a step change of the
setpoint effects a change of the corresponding actuator according
to the new setpoint.
Example:
With a max. heat generator temperature of 70°C, the actuator in
the modulating burner must cover a temperature differential of 50
K (starting from a room temperature of 20°C). This corresponds to
a control deviation of 100%. The set value is calculated as
follows:
Xp (%)/K x 50 K = 100% or Xp = 2%/K
7.1.10 Modulation of sample time Ta
The sample time is a controller-internal quantity which defines the
time interval between two subsequent actuator pulses in the
presence of a control deviation. Shorter sample times allow finer
adjustments.
Activation of
modulation
Adjustment
Minimum burner run
time
Minimum and
maximum
temperature limit
Function
