Dreizler marathon M 10001.1, Руководство пользователя

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Gas/air ratio control with pneumatic linkage
dreizler A 3001 E - 18.12.2015 | A 2035 - 1.09 | EN - 23.06.2009 30
10 Gas/air ratio control with pneumatic linkage
10.1 Description of gas/air ratio control
In the pneumatic gas/air ratio control, the air pressure PL downstream of the swirl plate in the burner hous-
ing is used as reference variable.
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The pressure-side air damper is actuated by the servomotor, which receives impulses from the modulating
burner regulator.
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When the air damper opens, air pressure PL increases, and initiates an immediate gas pressure increase
in the gas supply line downstream of the burner head by way of the gas pressure regulator. The gas pres-
sure adjustment is stepless, i.e. modulating. The combustion chamber pressure affects the air pressure,
taking into account the current air pressure during gas regulation.
10.2 Functionality of gas/air ratio control
The pneumatic gas/air ratio control works completely autonomously. A manometer is used for quick set-up
of the burner settings. The following operational parameters are compensated automatically:
•
Combustion chamber pressure fluctuations
• Chimney draught variations
• Changes in exterior temperature and air moisture
• Contamination of the fan impeller, leading to air flow fluctuations.
NOTICE:
The parameter 'frequency' can be set to control fan speed. The parameter 'frequency' will reduce power
consumption in the partial load range by up to 80%. Speed controlled combustion air fans can therefore
significantly lower overall operational costs and reduce the noise levels of the burner in the lower load rang-
es.
marathon
®
gas power burners are 'endurance runners'. They are equipped with a pneumatic gas/air ratio
control system. The air/gas ratio is set for each burner position automatically, and there are no mechanical
linkages. In marathon
®
gas power burners, burner load is set steplessly modulated up to a ratio of 1:5.
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Control impulses are received via an external burner control system or the dreizler
®
burner control unit
quattro pro, which is integrated in the burner control panel. The pressure-side air damper is actuated by the
servomotor directly to the positions OPEN and CLOSED.
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The servomotor moves the air damper with incremental impulses in the direction OPEN, once the capacity
controller requests more heat. The air pressure PL downstream of the burner head (swirl plate) increases,
and the gas ratio controller 'corrects' gas pressure PG immediately upwards on a gas/air control curve. This
curve must be configured at initial commissioning. A presetting of the gas/air ratio is preset ex works.
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With decreasing heat demand, the servomotor changes the air damper position towards CLOSED, while
the gas ratio controller throttles gas supply in reverse direction.
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The combustion chamber pressure PF counteracts air supply. It is connected to the gas ratio controller via
line PF. Its inclusion in the gas/air combination control is an important safety factor in terms of contamina-
tion in the boiler and burner area, also compensating for changes in the chimney draught.
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