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© Baxi Heating UK Ltd 2012
The Gas Adaptive System
The Baxi GA range of boilers are fully ‘Gas Adaptive’. This means the system automatically monitors the flame and adjusts
the gas valve to achieve the correct combustion at all times.
Explanation of Set Flames on GA
The Set Flame is a value that is used to achieve the desired combustion and is set at either during manufacture or by an
engineer on site. The value of this is different for each model because of fan speeds, mixers, nozzles, heat exchangers etc.
hence each model has different Set Flames.
This value relates to the ionization signal (e.g. 35 = 350 kOhms), and it simply tells the boiler what ionization it should
achieve at that fan speed.
If it is set incorrectly the boiler will always try to achieve that signal. It must be set correctly at manufacture, and by an
engineer if any gas carrying parts or R.D.S. are changed, to achieve 9.0% +-0.2 CO2 on N.G. (10.5% +-0.2 CO2 on N.G. )
The adjustable Set Flames are at three fixed fan speeds:-
00 (min)
IGN (ignition) Displayed as 33, 41 etc. It is a % of maximum fan speed or ‘power’.
100 (max)
From these three points, a curve is drawn and the values for the entire RPM range are calculated.
When the Set Flame is changed at one of the fan speeds above, the RPM will always stay the same, but the PCB will send a
signal to the valve to open or close the solenoid to alter the gas flow so that the ionization signal matches the Set Flame
value just inputted.
As the ionization signal changes, so does the combustion.
Boiler Cycle: From Factory to Installation
Installed
Commissioning
Function
Service Due - 1
Service Due - 2
Boiler set
automatically to
achieve 9.0% CO2
Boiler fitted by installer
Before use boiler must
complete C.F.
After 11 months ‘Sd’
shown on boiler
display
After 11 months ‘Sd’
shown on boiler
display
‘SD’ function reset at annual service
1.0 Gas Adaptive System
Manufactured & Set
on N.G.
