Unigas HR92A, Manual Of Installation - Use - Maintenance

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PART III: OPERATION
33

At the end of the pre-purge time, the actuator is in the light oil ignition position: the ignition transformer is energised (lamp B4 on);
the ignitor gas valves and the light oil valves open. Few seconds after the valves opening, the transformer is de-energised and
lamp
B4 turns off.

The burner is now operating, meanwhile the actuator goes to the high flame position; after some seconds, the two-stage operation
begins; the burner is driven automatically to high flame or low flame, according to the plant requirements.Operation in high or low
flame is signalled by LED
B2 on the burner control panel.
The fuel is pushed into the pump to the nozzle at the delivery pressure set by the pressure governor. The solenoid valve stops the fuel
immission into the combustion chamber. The fuel flow rate that is not burnt goes back to the tank through the return circuit. The nozzle
is feeded at constant pressure, while the return line pressure is adjusted by means of the pressure governor controlled by an actuator..

AIR FLOW AND FUEL ADJUSTMENT
Adjustments - brief description
The air and fuel rates adjustments must be performed at the maximum ouptput first (“high flame”): see the LMV related manual.

Check that the combustion parameters are in the suggested limits.

Check the flow rate measuring it on the counter or, if it was not possible, verifying the combustion head pressure by means of a dif-
ferential pressure gauge, as described on par. “Measuring the gas pressure in the combustion head”.

Then, adjust the combustion values by setting the “gas/air” ratio” curvepoints (see the LMV related manual).

Set, now, the low flame output (according to the procedure described on the “Siemens LMV manual”) in order to avoid the low
flame output increasing too much or that the flues temperature gets too low to cause condensation in the chimney.
User interface
The AZL2x.. display is shown below:
The keys functions are the following:
WARNING! During commissioning operations, do not let the burner operate with insufficient air flow (danger of
formation of carbon monoxide); if this should happen, make the fuel decrease slowly until the normal combustion
values are achieved.
WARNING! the combustion air excess must be adjusted according to the values in the following chart.
Recommended combustion parameters
Fuel
Recommended (%) CO
2
Recommended (%) O
2
Natural gas 9,0 ÷ 10,0 3,0 ÷ 4,8
Light oil 11,5 ÷ 13,0 2,9 ÷ 4,9
LPG 11,0 ÷ 12,0 2,8 ÷ 4,3