1.4 AFO: Fire Optimisation
Note: This basic function cannot be activated or deactivated manually. But, it is activated automatically
with each combustion.
When AFO is activated, AFO will be displayed.
Opening the door(s) (refuelling) in the operation mode “Boiler ON” is not advisable.
Recommendation: Do not refuel unless the “Refuel” sign is lit up.
Effect: AFO consists of several parameters programmed by the manufacturer, depending on the boiler
type and the fuel properties.
Function: After firing, the boiler will automatically enter the “AFO mode”. AFO-Output and duration depend
on the required primary and secondary combustion temperature and ash amount to keep minimal
emission to burn on a reduced output.
Use: Each combustion is carried out under practically the same – ideal conditions.
1.5 KLA: Reduced Boiler Output
Note: This basic function is not available for every boiler type.
KLA (▼) can be activated as required.
KLA is only useful, if more than one combustion are carried out per day – which is not possible in
some cases.
KLA is automatically deactivated at the beginning of each new combustion. By pressing the (▲)
button KLA can be deactivated during combustion. When KLA is activated, KLA is displayed.
Function: If the (▼) button is pressed while in “Boiler ON” mode, the system will be regulated to the
smallest boiler output possible once completing the AFO mode – regardless of the heat demand.
This might result in a reduced flue gas temperature (see chapter 1.16).
Use: Depending on the boiler type and the fuel, the burning cycle can be extended, which can simplify
burning the remaining coal and/or remaining amber.
KLA is not available for all boiler types.
1.6 AAO: Combustion and Burnout Optimisation
Along with BSB AAO is the most important function – it regulates fuel properties, which are not always ideal in practice.
Note: This basic function cannot be activated or deactivated manually.
When AAO is activated AAO displays.
Effect: If the combustion temperature is too low, the controller automatically increases the boiler output
to meet the minimum combustion temperature required. A too low combustion temperature
reduces the efficiency of the firing and can lead to increased emissions.
Possible reasons for an activation of AAO:
● Fuel is too large or too wet.
● If the fuel amount is running low in part load operation (burnout), AAO increases the boiler
output in order to reduce emissions.
● If the fuel chamber is “large” and the fuel is “wet”, AAO is also activated during the
combustion. The high vapour content in the flue gas, resulting from wet fuel (when the
amount of fuel is high), reduces the temperature of the embers. Therefore, AAO
automatically increases the boiler output. This can temporarily require combustion with ≥
35 kW from a boiler type with a rated power of 30kW.
Function: The controller recognizes this problem when the secondary air flap is in the position of the
minimal airflow and the current O
2
value is 1% higher than the set O
2
value. In that case the set
boiler output is ignored and the output is increased. Thanks to this automatic function not ideal
fuel properties are compensated in order to prevent combustion errors.
Use: Achieving the highest degree of efficiency with low emissions.
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