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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.
A B C
D
On/off signal
Burner fan
EVP - pilot light flame
EV1 - 1st electromagnetic valve gas
EV2 - 2nd electromagnetic valve gas
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
■ Safety thermostats
E
F
■ Fxx faults
■ Air/gas premixing operation:
Control of the gas burner
■ Unit electronic control:
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.
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.
The modulation PCB can distinguish between 30 diff erent types
of faults. This ensures accurate diagnostics. Also, codes and
possible causes of faults are listed in this manual.
For more serious faults that require a manual reset, use the
LCD display to reset the CPU PCB on the machine by pressing
the arrows at the same time.
The PCH heater is fi tted with a burner that completely premixes
air and gas. The air/gas mixing occurs inside the impeller on
the motor-fan.
The air taken into the impeller through the venturi tube,
calibrated, creates a vacuum. The vacuum in the venturi is
rebalanced by the gas valve, which is pneumatically controlled.
The air pressure - gas pressure ratio is 1:1. This ratio can be
corrected by turning the off set adjustment screw (on the gas
valve). The heater is supplied with the off set regulated and the
screw sealed.
A second adjustment can be done with the screw on the venturi,
which regulates the value of maximum gas capacity and
determines the amount of carbon dioxide (CO
This adjustment is also made at the factory. The screw is not
sealed to permit conversion to another type of gas, if desired.
The modulation PCB, mounted on the heater, manages the
motor rotation (in c.c.) depending on the heating capacity
required by the environment. Varying the rotation speed of the
motor changes the air fl ow capacity and therefore also the gas
fl ow capacity. Minimum and maximum rotation values of the
fan are programmed into the PCB and cannot be modifi ed by
the user or installer.
Important: All the connections to be established by the
client are featured on the wiring diagram included with
the unit.
The "50FC" control has a proportional output 0/10V (Y2) where
a natural gas or propane gas proportional actuator can be
connected.
The burner connection is managed by the control, in HEATING
mode, through an ON/OFF signal of the digital output NO5.
) in the fl ue gases.
2
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