Operating Principle - DeDietrich 310 ECO Series Installation And Operating Manual

De Dietrich Gas 310/610 ECO
e. Flue gas damper (optional for Gas 310
boiler, standard for Gas 610 boiler)

3.2 OPERATING PRINCIPLE

Combustion air is drawn into the inlet connection from the plant room (room ventilated version) or from outside via
the eccentric flue system (room sealed) by an air supply fan.
On the inlet side of the fan is a specially designed chamber (venturi unit) which takes gas from the multi-block and
mixes it in the correct proportions with the incoming air. This mixing system ensures that the correct gas/air ratio
is delivered to the pre-mix burner at all times.
Depending on demand (under the dictates of flow/return sensor and other external/internal control inputs) the
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'abc®' system determines the required boiler output. The 'abc® control then varies the speed of the air supply
fan which alters the volume of air being drawn into the venturi, this change in volume is measured using air
pressure differential which directly controls the volume of gas also being delivered to the venturi. The resultant
controlled mixture is delivered to the premix burner.
This mixture is initially ignited by the combined ignition/ionization probe which monitors the state of the flame.
Should the flame be unstable or not ignite within the pre-set safety time cycle the controls will (after 5 attempts)
shut the boiler down requiring manual intervention to reset the boiler. The digital display will indicate a flashing
fault code confirming the reason for the failure.
The products of combustion in the form of hot flue gases are forced through the heat exchanger transferring their
heat to the system water, (the flue gas temperature is reduced to approximately 9-14° F [5-8° C] above the
temperature of the system return water) then discharged via the condensate collector, to the flue gas outlet
connection, to atmosphere.
Because of the low flue gas exit temperature there will be a vapor cloud formed at the flue gas terminal – this is
not smoke -, simply water vapor formed during the combustion process.
If the flue gas temperature falls below dew point 131°F [55°C], water vapor (created during the combustion
process) will begin to condense out in the boiler, transferring its latent heat into the system water, thereby
increasing the output of the boiler with-out increasing the gas consumption.
Condensation formed within the boiler and flue system is discharged from the boiler to an external drain via the
drain pan and siphon supplied.
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