3425
7
GB
3.7
FAN ADJUSTMENT,
(see fig. 5)
Modulation is based on variable-speed
technology.
Combustion air delivery can be adjusted
by varying the motor's speed (rpm).
The proportioning gas train delivers the
right amount of fuel, depending on the
pressure detected in the purging circuit.
Hence the output delivered is adjusted by
varying the motor's speed of rotation.
The motor speed can be adjusted by
means of the “Trimmers” (see figure
below).
4.
OPERATION
4.1
ADJUSTMENTS BEFORE FIRST FIRING
The following adjustments must be made:
-
Open manual valves upline from the gas train.
-
Bleed the air from the gas pipes using the screw on the socket P1.
-
Assemble a pressure gauge on the pressure test point P2 located on the gas valve.
-
Connect the diagnostic software kit on the control box: this allows you to visualise the motor rpm.
4.2
BURNER START-UP
Close the thermostat and switch on the burner's power.
If the fan starts up, but no flame appears by the end of the safety time, the control box allows the start-up
programme to be repeated up to 3 times.
If firing does not occur upon the fourth attempt, the burner goes into lockout mode.
Reset and wait for a new start-up attempt.
If the burner still does not fire, the problem may be that gas is not reaching the combustion head within the 3-
second safety time.
Turn the screw V1 on the gas valve mixer slightly anticlockwise.
Check the pressure shown on the pressure gauge connected to the socket P2 of the valve, and compare it with
that indicated on the table below.
Once firing has taken place, proceed with global burner calibration operation.
Fig. 5
D8427
Trimmer for adjustment
of output supplied
D8425
Maximum gas flow
adjustment (
V1
)
Gas pressure downline
test point (
P2
)
