21
DOMITOP HF 24 - 30 E
FERELLA GOLD HF 24 - 30 MEL
Version - 09.2002
2.4 Burner unit
Operation
The burner unit comprises a manifold and 12/16 nozzles (depending on the capacity), the burner mount,
electrodes and the burner assembly.
Manifold - nozzles
The valve sends gas at a suitable pressure to the manifold, which
homogeneously distributes the gas to the single burner stages at the nozzles.
It is secured directly to the burner mount. Its positioning must be exact since
it affects the air/gas mixture. In addition, the threaded holes forming the seat
of the nozzles must be aligned with the respective Venturi tube of the burner.
If it were not so, the air/gas mixture would be wrong and there would be poor
combustion with an unstable flame. The nozzles are made of brass and
machined extremely precisely for their dimensions. There is a seal between
the nozzles and the manifold.
Ignition electrode
The ignition electrode is made of a metal alloy (Kanthal) that withstands high
temperatures and oxidation. Its base is composed of a ceramic composite of
glazed alumina whose purpose is to protect and electrically insulate it. Once
the ignition procedure begins, the card powers the electrode with a pulsating
voltage of a few kV, a series of electrical discharges is set off between the
electrode and the head of the burner (set at a distance of 3.5 mm). Clearly,
these sparks are the trigger for the air-gas mixture. It is important for the
distance between the electrode and the burner head to be 3 - 4 mm and the
discharge to be made at the centre.
Checks
If there is no discharge:
Check whether the boiler shuts down, in which case check
the connection of the electrode to the card or whether it
discharges at other points; if necessary, check the safety
thermostat and the card.
If the boiler does not shut down and the fan keeps on
working, check the air pressure switch.
If there is a discharge, but no ignition and after 10 seconds
the boiler shuts down, check the gas valve and, if necessary,
the card.
If there is a discharge and then a flame, but the boiler still
shuts down after 10 seconds, check the detection electrode
and its connection.
3.5
±0.5
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