6
Hoval STU Wood Pellet Boiler
Each boiler is supplied with a fully integrated pellet-burning stoker comprising combustion retort(s), modulating delivery auger(s), a
transfer box, fully modulating primary (FD), secondary (ID) fans and lambda control. The transfer box is integrated with a bulk pellet store
via either angled pick-up auger(s) or a flexible centreless auger arrangement depending on site layout. The stoker can be arranged to
deliver the fuel into the rear (standard supply) or the front of the boiler depending on site layout, the pick-up arrangement being designed
to suit site requirements.
The stoker connects the boiler and the bulk pellet store via the Transfer Box. Wood pellet is collected at the outlet of the store and moved
to the Transfer Box via a Pick-Up Auger (or a Centreless Flexible Auger - see typical layout drawings), and then delivered into the retort
within the boiler via a Delivery Auger.
The stoker automatically adjusts the fuel feed to match the boiler load. Continuous O
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monitoring of flue gases ensures close combustion
control as the air supply is adjusted to match the fuel feed.
The standard stoker design incorporates an airless kindle feature. This allows the boiler under normal operation, to be held in "stand-by"
mode when heat is not required for up to 72 hours and maintains a small ignition source within the stoker retort to allow quick response to
a sudden call for heat outside normal operation. An electric ignition system is available as an option. If it is anticipated that the available
heating load would lead to any boiler kindling in excess of this period, then it should be switched off .
Each Stoker Control Panel displays the boiler-operating condition and set points along with boiler operating temperature, flue gas
temperature (optional) and O
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readings. Individual readings can be displayed or combined and shown as a trend.
Each Delivery Auger is fitted with two separate safety features to detect and correct any pellet burn back; an overheat burnback thermostat
linked to the stoker control and a water dosing device independent of electric supply. Pellet level in the transfer box is controlled via two
proximity sensors to give an additional firebreak. A motorised burnback protection damper is also fitted between the transfer box and
the pick-up auger which will close in the event of the burnback thermostat been initiated. It will also close in the event of a power failure.
Stoker Detail
Note : LAMBA OXYGEN
SENSOR FITTED
INTO ID FAN CASING
