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© Baxi Heating UK Ltd 2012
Checking the Combustion - F304
At each service the combustion must be checked at three fan speeds:- ‘00’, ‘IGN’ and ‘100’.
00 =
Minimum
IGN = Ignition Speed (different for each model)
100 = Maximum Speed (D.H.W. power for Combi)
To check the combustion at these 3 speeds Function 304 must be activated.
To activate, press and hold the ‘ip’ and ‘CH +ve’ buttons together for 6 seconds.
‘304’ should be displayed and then the boiler will run at maximum when ‘100’ will be displayed. Allow a few moments for
the boiler to stabilize then measure the combustion.
To choose the next fan speed, press the ‘CH –ve’ button - the Ignition Speed will be displayed. To set at minimum press the
‘CH –ve’ again. ‘00’ will be displayed.
To de-activate this function, press and hold ‘ip’ and ‘CH +ve’ for 6 seconds or isolate power to the boiler for several seconds.
Note: If at ‘100’ the boiler temperature reaches 85°C, the burner will be extinguish and it will start again. To prevent this
from happening, open one or two D.H.W. taps whilst in F304 and the boiler will automatically dump the heat through the
D.H.W. circuit. In the case of System models it is recommended that any stored hot water is depleted prior to
commencement.
Limited Combustion Adjustment - F304
• A limited adjustment of the combustion can be performed whilst Function 304 is activated.
• By pressing the ‘ip’ button at any of the three fan speeds above an adjustment value is accessed. This adjustment is
limited in that a deviation of only -3 or +3 from the original value of 0 is permitted. The combustion can be
altered by approxi/- 0.6% in this mode.
• Changing the value by 3 increases or decreases the CO2 value by approximately 0.6%.
• Positive adjustment equates to richer combustion and negative adjustment results in weaker combustion.
• Once the combustion has been changed, press the ‘ip’ button to toggle back to the fan speed and now, by
pressing the ‘CH +ve’ or ‘CH -ve’, the fan speed can be changed.
• Once completed press and hold the ‘ip’ and ‘CH +ve’ buttons for 6 seconds to de-activate Function 304.
7.0 Checking the Combustion
