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Hoval STU Wood Pellet Boiler
With the KINDLE/IGNITION switch in this position and with a
demand signal calling for operation of the Boiler and with the Flue
Gas Temperature registering <50 °C, then the following sequence
for Ignition occurs;
• Run Pellet Feed systems to prime or charge the retort
• This may take several minutes to complete and is site
specific and pre programed on comissioning
• Hot Air Ignition Gun switches ON (A)
• ID Fan switches ON
• Wait for a set period (Approx 5 minutes)
• Hot Air Ignition Gun switches OFF
• Wait for a period (approx 10 minutes) to achieve the
required Flue Gas temperature
• If the Flue Gas Temperature >50 °C then
• Switch ON FD fan
• Wait for a set period (approx 10 minutes)
• Stoker Pellet Feed system operates, initially on Low Fire,
before normal modulation based on demand.
• If after priming the retort and running Igntion Gun/ID Fan
the Flue Gas temperature remains <50 °C
• The Hot Air Ignition sequence (from (A)) is re initiated
• If after a further attempt (i.e. .the 3rd) to establish
combustion, the Flue Gas Temperature remains <50 °C
then the Stoker Control switches the stoker/boiler off.
If the Flue Gas Temperature is >50 °C when the demand signal is
received the system will not fire the Ignition gun.
3. IMPORTANT. Once the fire has been established the operator
should set KINDLE/IGNITION switch on the Stoker Control Panel
to Kindle position.
4. If after the above the boiler has failed to light or combustion has
not been established then the operator
MUST NOT RESET
the
KINDLE/IGNITION switch to Ignition.
Isolate the boiler
electrically and report the fault to Hoval Service.
Standard Ignition (Manual)
From a 'Boiler Out' cold condition it is relatively easy to bring the
boiler on-line within a few minutes by the introduction of an ignition
source into a primed retort.
To set in operation:
• The operator should check that all the isolator switches
associated with the motors on the stoker are in the ON
position and that there is power to the Stoker Control
Panel (ON/OFF to ON).
• On the Stoker control set the Wood Burner switch to
AUTO, ID Fan Switch also set to AUTO.
• After a short delay (when both ID and FD fans operate)
the pellet feed augers will begin to feed pellets into the
retort.
• Run the Stoker until the retort fills with fuel - the pellets
should be level or just below the last set of Turyres (or
airways within the retort. It may be necessary to open the
boiler door to check the level of fuel in the retort.
• Set Wood Burner Switch to OFF.
• Using the isolator switches on the motors, switch to OFF
bothe PICK-UP and CONVEYOR (OR DELIVERY) augers.
• Open Boiler door.
• Add two small firelighters to the top of the retort and
surround with some of the wood pellet fuel. Carefully ignite
the firelighters.
• Close the Boiler Door
• Switch the Wood Burner switch to AUTO. This will
operate the stoker without adding any further fuel into the
retort and will also allow combustion to establish, as both
the ID fan and then the FD fan start.
• After approx 10 minutes operation check the condition of
the fire within the retort to ensure that combustion is fully
established (using the sight glass on the front of the door
of the boiler).
• IMPORTANT. Once the fire has established the isolating
switches on both the PICK-UP and the CONVEYOR
augers must be switched back to ON. This allows the
resumption of fuel feed into the boiler.
• Leave Stoker operating in AUTO mode.
Ignition from 'Boiler Stand-By' or Kindle
In normal operation once ignition has taken place from cold (as
described above) the boiler would normally be held in 'Stand-By'
or kindle mode whenever there was no call for heat (e.g. overnight
or over a weekend period).
Combustion of the wood pellet fuel is brought to a virtual standstill
and a small permanent ignition source is held within the retort.
When the stoker control receives a demand signal to fire the pre
purge process with both the FD and ID fans in operation
re-initiates full combustion within a few minutes. The stoker control
then responds to suit the load.
Note once ignition has been established the boilers can be held
in Kindle (or stand-by mode) for up to 72 hours without the need
to re-light the boilers. The boiler might run normally during a day,
switch to kindle at the end of the day and kindle overnight (or over
a weekend). The following day(s) normal operation could resume
without any need for manual intervention
If the boiler is kindled for an extended 72 hours period, then the
BMS should be configured to operate the boiler for a short but
continuous period (minimum 1 hour). Once this has occurred the
boiler will resume kindle mode until next called by the BMS.
The BMS should also be configured to operate system pump(s)
during the above one hour period, followed by a suitable pump
run-on period (max 30 minutes). When the stoker operates
normally, a "Stoker Running" volt free signal is generated, which
the BMS can use to start the system pump(s).
We recommend, however that the boiler is not routinely kindled
for more than 72 hours. If this is the case, the boiler should be
shut down as described below and re lit when required.
Always ensure there is sufficient wood pellet fuel covering the
pick-up auger or available at the outlet of the pellet storage silo.
Boiler Shut Down
During Normal operation it is possible to temporarily interrupt the
feeding of fuel into the boiler. This is necessary whenever the
Boiler door is to be opened to access the combustion chamber.
E.G. To check and inspect the fire or to remove any ash from
around the retort within the Boiler.
With the boiler operating, to temporarily stop the boiler from firing
fresh fuel;
• On the Stoker Control Panel, set the KINDLE/OFF/AUTO
switch from AUTO to OFF. Set the ID FAN switch from
AUTO to ID FAN ONLY.
• This halts the feeding of fuel into the boiler, and switches
off the FD fan.
• The Boiler door can then be opened, by using the Tommy
bar to loosen the nuts fastening the door shut. CAUTION
the operator MUST stand behind the boiler door as the
nuts are unloosened and the door is gradually opened.
NEVER stand adjacent to the opening door.
Operating Instructions
Always ensure there is sufficient wood pellet fuel covering pick-up auger or available at the outlet of the pellet storage silo.
