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12 - FACTORY OPTIONS AND ACCESSORIES
Operating cycle of the burner
■ Burner operation:
When the unit demands heat, the modulation PCB will start the
operation cycle. It authorises the fl ame monitoring equipment
to start.
The equipment will immediately start ventilating burner [A] and
prewashing the combustion chamber for a preset length of time.
After the prewash, the ignition phase starts: the equipment opens
solenoid EV1 and, in parallel, solenoid EVP which supplies gas
to the pilot burner [B].
After detecting the pilot fl ame, the equipment opens the main
gas valve EV2 [C] to supply gas to the main burner.
After a time of dual functioning of the two burners (pilot and
main), the modulation PCB removes gas from the EVP valve
and turns off the pilot burner [D].
A single electrode detects the fl ame both for the pilot burner
and the main burner.
The ignition program lights the burner to obtain an intermediate
level heat production capacity, which corresponds to about 30%
of the maximum capacity. Once the fl ame is stabilised for a few
seconds at ignition power, the burner begins to modulate its
output to reach maximum output, if required, in a variable length
of time programmed into the modulation PCB.
During operation, the modulation PCB will regulate the power
output of the burner proportionally to the voltage (0-10 Vdc) in
the terminals.
If there are multiple power modules, the 0/10 Vdc signal could
turn off one or more modules in cascade.
■ Turning off the burner:
When the demand for heating ceases, signalled by a voltage
lower than the preset limit (0.5 Vdc), the modulation PCB turns
off the burner [E]; the fan continues to purge the combustion
chamber, post-wash, for a preset length of time [F].
Opening a contact (see electrical diagram) always causes the
burner to stop without causing a fault.
■ Safety thermostats:
A safety thermostat with automatic reset and positive safety
setting is installed on the heater module. The breaking of the
sensitive element corresponds to a safety intervention.
When the thermostat intervenes, through the fl ame monitoring
equipment, the burner stops and the flame equipment is
blocked.
The block of the flame equipment, caused by the safety
thermostat, is signalled on the LCD display of the CPU PCB on
the machine with F20. The block is classifi ed as “non-volatile”
and requires a manual reset.
Near the safety thermostat, there is an NTC1 probe set to the
value of the ST1 parameter which reduced the burner’s heat
output independently from the incoming 0/10 Vdc signal when
is reaches the set point. The probe monitors the ratio of heat
capacity / cooling air fl ow. It is not advisable to change the
ST1 value.
On/off signal
Burner fan
EVP - pilot light flame
EV1 - 1st electromagnetic valve gas
EV2 - 2nd electromagnetic valve gas
A BC D E F
Analysis of combustion
Wait until the heater is switched on. Check that the heater is
running at maximum power by using one of the two methods below:
■ check that Tin input signal is equal to 10 V;
■ from the LCD display, access the REG menu, then use the Hi
and Lo controls to force operation at maximum or minimum
output (refer to the paragraph “Control of the gas burner”).
At maximum output, check again that the input pressure in the
valve corresponds to the value required; adjust if necessary.
Perform the combustion analysis to verify that the level of
CO
2
corresponds to the fi gures in the table in Paragraph “Gas
connection”.
If the measured value is diff erent, turn the adjustment screw on
the Venturi pipe. Loosening the screw will increase the CO
2
level,
screwing it down will decrease the level.
Set the heater to minimum output, and verify that the level of
CO
2
corresponds to the fi gures in the tables in paragraph “Gas
connection”. If the values do not match, screw or loosen the off set
screw respectively to increase or decrease the CO
2
level and
repeat the procedure.
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