The Achill multi fuel Insert boiler is capable of heating up to 9/10 single radiators on the 17.1kw and 13/14 single radiators on the 21kw. It will fit most standard 16/18 fireplace openings and is Constructed from steel with a cast iron door with an efficiency level of over 75%. It is thermostatically controlled which combined with both primary and secondary air allows for exceptional control.