Immergas EOLO Star Export Manual page 21

Technical documentation Technical documentation
MODULATION BOARD
Inside the EOLO STAR control box is a microprocessor controlled electronic board that integrates
ignition and adjustment functions and, by means of LEDs, shows the operating condition of the
appliance, indicating any tripping of safety devices.
- OPERATION
Heating request
When the main switch (IG) is in WINTER position and the system water pressure switch (SP) is closed,
operation is enabled in heating phase.
When the room thermostat contact (TA) closes, the adjustment circuit starts the circulator (MP) by
means of the PUMP RELAY.
If the temperatura read by the Central Heating NTC sensor (NM) is below that set using the heating
potentiometer (RISC), the board powers the fan (MV) by exciting the FAN RELAY.
Consequent operation of fan (MV) causes the fume pressure switch contact (SV) to close, thereby
permitting the adjustment circuit to excite the REQUEST RELAY.
This way, the board ignition circuit is enabled. This first of all triggers the ignition electrode (E1) and
then, by means of the RELAY V/G, the main coils of gas valve (VG).
During the ignition phase, current to the modulation coil is gradually raised, in 8 seconds, from
minimum to a value equal to about 50% of maximum.
Subsequently, the signal is returned to minimum value for 20 seconds and then increased so as to reach
maximum heating power in 100 seconds.
If during this time, the difference between the temperature set by means of the heating potentiometer
(RISC) and that read by the NTC supply sensor (NM) is such as to cause flame modulation, the signal to
the modulation coil is limited and changed according to effective need.
Subsequently, the signal varies in a way directly proportionate to the difference between the temperature
set using the heating potentiometer (RISC) and that read by the supply sensor (NM).
The modulation range (maximum and minimum) during operation in heating phase is adjusted by
means of the "C.H. MIN POWER" and "C.H. MAX POWER" trimmers.
When the set temperature is exceeded, the REQUEST RELAY contact is opened with consequent
switching off of the burner, the relighting of which for the same request is prevented for a time of 180 s /
30 s.
19
STES ed 07/01 EOLO STAR