3342
7
GB
3.6
FAN ADJUSTMENT
Modulation is based on variable-speed technology. Combustion air delivery can be adjusted by varying the
motor's speed (rpm). The proportioning gas train, depending on the pressure detected in the purging cir-
cuit, delivers the right amount of fuel. Hence the output delivered is adjusted by varying the motor's speed
of rotation. Motor speed can be adjusted by means of the 3 ≈Trimmers∆ (see figure 5).
4.
OPERATION
4.1
ADJUSTMENT PRIOR TO IGNITION
The following adjustments must be made:
- Open the manual valves located upline from the gas train.
- Purge air from the gas line by means of the screw in test point START.
- Connect the software diagnostics kit to the control box: via this kit, you can view the motor's rpm.
- Check the settings chosen with the trimmers located on the control box (fig. 5) referring to the table given
below.
4.2
BURNER START-UP
Close the thermostat and switch on the burner's power.
The burner starts in pre-purging mode at top speed.
Speed subsequently decreases to the START value and the burner fires.
If the fan starts but no flame has appeared by the end of the safety time, the control box allows the start-up
programme to be repeated: up to 3 attempts are made.
If there is no firing by the fourth attempt, the burner locks out.
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 screw V1 on the gas valve mixer anticlockwise slightly.
Once the burner has fired, the next step is to complete the burner's other adjustments.
D7238
D7237
3-pin terminals
MAX:
maximum output
START:
ignition speed
setting
Terminals for connecting
output regulator
Fig. 5
power adjustment
MIN:
minimum output
power adjustment
Trimmers
