PV20a / PV30a pellet burner
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DK9902A1 www.pelltech.eu
1.Melting hose
To avoid the reaching of fire during back-burning to external auger, a melting hose is put between
external auger and pellet burner. The hose will melt when air temperature in it’s inside reaches 100
o
C.
2.Temperature sensor
A temperature sensor is mounted on burners input tube. If the burner is not regularly cleaned, part of
burning gases start to move through fuel line. The sensor detects temperature rise in fuel line and shuts
down the burner when temperature inside burner exeeds 60
o
C. This safety device is not meant to
replace regular cleaning by the user.
3.Controller
Software supervison made by controller monitors continuously all inputs and outputs and shuts down
the operation of burner in case of abnormal condition occur. Controller has watchdog timer WDT to
reset the controller in case program lock up. It also has a brown-out detection and reset circuit to reset
the controller when power supply voltage falls below threshold. Burner makes self-testing after applying
power. Following is checked:
-
Existence of feeder auger motor current (motor is turned on for a moment)
-
Existence of speed signal from fan (fan is turned on for a moment)
-
Voltage level on backup battery is > 11V when loaded with feeder auger motor
or last error message is displayed.
To ensure there are no explosive gases inside the boiler, the fan is ran for short duration before
loading/ignition starts.
4.Backup battery
If mains supply is lost, the burner runs on backup battery power and feeder auger transports pellets
from feeder’s tube to the burning chamber, where they burn finally with help of natural draught. Fan
rotation and all other functionalities are stopped. Battery voltage is checked allways at startup and
continuously monitored during the operation.
5.Safety thermostat
In case back-burning has reached into feeder auger, safety thermostat cuts mains power off and feeder
auger is unloaded by using battery
power. Thermostat acts at 65
o
C and has to be reset manually.
Figure 2 Safety devices
