Technical Description; Advantages Of Down-Fired Boilers; Down-Fired Boiler Operation; Standard Components - LA NORDICA LNK15 Manuel Utilisateur

TECHNICAL DEsCrIpTIoN

ADvANTAgEs of DoWN-fIrED boILErs

Combustion in boilers is carried out at high temperatures on the principle of gasification that saves fuel and protects the environment.
The primary and secondary air is heated in the boilers at high temperatures and this ensures a hot and stable flame and constant fuel
quality. All models are equipped with a suction fan and are easily handled and manageable. A large fuel feeder provides the option to
burn logs of wood 500 mm long. All models are equipped with a D.S.A. cooling coil.

DoWN-fIrED boILEr opErATIoN

Burning wood with a traditional system defined as << direct flame >>, whether this is carried out on a fireplace, a cooker or a stove, all the
wood that is loaded will burn together since it is covered by the flame that envelopes it and rises from the bottom.
For this reason, it will not be possible to obtain longer fuel duration.
With a down-fired boiler, also known as << total gasification boiler >>, fuel is obtained with a completely different system, which almost
avoids the entire problem described above.
This boiler is divided into two parts: the upper part (loading chamber) is used to load the wood and its volume is such that it can contain an
amount to ensure operation (maximum continuous power) between 3 and 4 hours.
Combustion air, which is divided into primary and secondary, is fed through a fan connected immediately above the smoke discharge pipe
(SUCTION BOILER), which depressurises the bottom chamber by suctioning the smoke through the slot that opens at the bottom of the said
chamber.
The bottom part contains the actual combustion chamber with the ash collection drawer.
operation is as follows: load a moderate amount of the wood from the centre door. Wood that is in direct contact with the embers will heat
up immediately and develop fuel gas.
The primary air sucked up by the fan through the opening will filter through the pieces of loaded wood until it reaches the contact point
between the wood and the embers igniting this gas, thus causing partial combustion. This obtains a flame that is partly composed of carbon
monoxide, which, as known, is fuel gas.
When it passes through the nozzle opening that communicates the loading chamber with the bottom chamber, secondary air reaches the
flame (still input by the fan), which completes combustion.
During this phase, the temperature of the flame can increase significantly and go beyond 1100 °C, thus completely burning all substances, which
would otherwise remain partially burned in a traditional system. Moreover, excess air required will be much more contained (approximately
20 - 30%) compared to more than 100% required in other systems, thus limiting sensible heat dispersion in the smoke.
On the other hand, the upper chamber will hardly have a flame since this is sucked up by the fan and made to pass through the central
opening. The loaded pile of wood is not covered with the flame and it does not catch fire like a traditional system.
The wood will only burn when it is in contact with the remaining embers left from previous combustion.
ATTENTIoN
When the fan is off, the wood left in the boiler still remains in contact with the layer of embers and thus continues gasifying; however, the
gas produced is not burned. Since there is no combustion air, the most volatile part of the gas exits from the flue, whereas the less volatile
part deposits in the loading chamber and the surfaces touched by the flame, thus creating tar scaling that can, in certain cases, obstruct
the smoke passages.
The wood still burns and causes a significant reduction in the boiler's overall performance. Also, a large part of the moisture in the smoke
remains condensing inside the boiler, thus generating the onset of corrosion.
For these reasons, the system must be sized correctly to avoid long pause times that would cause significant problems like the ones mentioned
above.
for THEsE rEAsoNs, THE boILEr MUsT NEvEr bE ovErsIZED CoMpArED To ACTUAL sYsTEM rEQUIrEMENTs

sTANDArD CoMpoNENTs

The boiler is supplied complete with:
• digital display
• power supply cable (plug NOT supplied)
• cleaning set
• assembly and operating instructions
• identification plate
• suction fan complete with smoke fittings
• Puffer probe (storage tank technician)
ENgLIsH 39