27
Hoval STU Wood Pellet Boiler
Under normal operation the LRP controller monitors and regulates
the boiler water temperature. In addition to this, mounted in a pocket
on top of the boiler are two thermostats. The first of these has a
temperature dial, which can be adjusted in the range of 70-83
o
C, this
effectively acts as a first limit stat, and if the boiler water temperature
exceeds the set temperature the stoker will shut off and will only re-
fire once the water temperature has fallen. It should be set higher
than the programmed water temperature setting in the LRP controller.
The second stat is set at commissioning, usually 11
o
C above the first,
and is a second or high limit stat. If the boiler temperature exceeds
this limit then the stoker will shut off and the High Limit indicator will
be illuminated. The stoker will not re-fire until this second limit stat
is manually reset.
Under normal operation the Stoker Run (green) light should show
on the control panel.
A fuse fail or a motor trip would illuminate the appropriate light - if
illuminated the cause should be investigated prior to resetting.
The stoker control panel can be fitted or mounted on either side
of the boiler or where requested can be supplied separately for
mounting on a wall within the plant room. Site wiring will be re-
quired to connect the pellet auger feed motors, FD and ID fan
motors, each must be connected via individual isolating switches
that should be clearly labelled. In addition the flow temperature
sensor, damper control on both FD and ID fans, burn back stat,
burnback protection damper, door microswitch, combustion
chamber pressure switch and lambda control will also require
wiring back to the panel. This wiring is NOT generally part of the
stoker installation unless arranged at the time of order.
The Stoker Control Panel also houses a series of indicator lights as
follows:
•
Panel Live (Orange).
•
Fuse Failed (Red).
•
Stoker Run (Green).
•
High Limit (Red).
•
Trip (Red).
•
Low water level alarm (Red)
•
Burnout (Orange)
Control Details and Safety Features
Space for other optional
selector switch.
Optional Pick-up
auger(s) selector switch
(not standard item)
Note:
For Boilers fitted with the optional electric ignition system, a door microswitch is fitted which is linked
to a "latching relay" inside the control panel. This ensures that if the electric igntion process fails, then
the boiler door needs to be opened (& appropriate action taken), before the Auto/Igntion selector switch
can be reset. Please follow the operating and fault finding procedures in Appendix D of this manual if
this situation arises.
