5
Boiler functions
5.1
Boiler switching behavior
The
Minimum activation and deactivation time parameters have priority over all other parame-
ters described in following.
To be able to keep the cooling off periods between two activation phases, a boiler is first
switched on when the time entered in
Minimum deactivation time has passed since the last de-
activation.
To ensure the burning of residues left over during the start-up phase, a boiler is switched off first
after the time entered in
Minimum activation time has elapsed.
Parameters
WE
Parameter level / Range of values
Minimum activation time
1 min
PA1, PA2* / 0 to 90 min
Minimum deactivation time
2 min
PA1, PA2* / 0 to 90 min
* Only in systems Anl 4 to 7
On/off boiler
A boiler is activated when the flow temperature falls below the flow temperature set point by
the
Hysteresis (Fig. 3). After the operational feedback message (burner firing –> section 5.10),
the
Lockout time must elapse before the boiler is switched to the next stage. If the flow tempera-
ture is expected to reach the set point range within the
Tolerance time, the boiler does not switch
to the next stage.
A boiler stage is switched off when the flow temperature exceeds the flow temperature set point
by the
Hysteresis.
Modulating boiler
A boiler starts to operate with its minimum capacity if the flow temperature falls below the flow
temperature set point by the
Hysteresis (Fig. 2). After the operational feedback message (burner
firing –> section 5.10), the
Lockout time must elapse before the modulation is enabled. The con-
troller modulates the boiler capacity to match the actual energy requirement according to the
flow temperature set point.
Parameters
WE
Parameter level / Range of values
Hysteresis
3 °C
PA5 / 1 to 20 °C
Tolerance time
30 min PA5 / 0 to 99 min
Lockout time
2 min
PA5 / 0 to 99 min
Boiler functions
32
EB 5474 EN
