Appliances covered by this European Standard include one or a combination of the following: - gas-fired sorption chiller; - gas-fired sorption chiller/heater; - gas-fired sorption heat pump. This European Standard applies to appliances designed to be used for space heating or cooling or refrigeration with or without heat recovery. This European Standard applies to appliances having flue gas systems of type B and C (according to CEN/TR 1749) and to appliances designed for outdoor installations. EN 12309 does not apply to air conditioners, it only applies to appliances having; - integral burners under the control of fully automatic burner control systems; - closed system refrigerant circuits in which the refrigerant does not come into direct contact with the water or air to be cooled or heated; - mechanical means to assist transportation of the combustion air and/or the flue gas. The above appliances can have one or more primary or secondary functions (i.e. heat recovery - see definitions in EN 12309-1:2014). In the case of packaged units (consisting of several parts), this standard applies only to those designed and supplied as a complete package. The appliances having their condenser cooled by air and by the evaporation of external additional water are not covered by EN 12309. Installations used for heating and/or cooling of industrial processes are not within the scope of EN 12309. All the symbols given in this text should be used regardless of the language used. This part of EN 12309 deals particularly with the specific provisions of hybrid heating appliances based on gas-driven sorption heat pumps as defined in Part 1. The heating appliances covered by this European Standard are of a hybrid type, an encased assembly or assemblies combining a direct or indirect-fired sorption heat pump for base load and a peak load condensing boiler with only one flue system, electrical supply cable and human machine interface to the end user. The direct- or indirect-fired sorption heat pump integrated in the hybrid appliances in this European Standard could be intermittent or continuously operating ab or adsorption heat pump. The control system of hybrid heating appliances decides on the transition between the heat pump operation mode to/from the mixed operation mode (heating by both sorption heat pump as well as the peak boiler) and the direct heating mode (only peak boiler) depending on the heating fluid inlet or return temperature, temperature of brine entering the indoor heat exchanger (evaporator) of the heat pump, the required outlet or supply temperature dependent on the outdoor temperature as well as the target value of the indoor or room temperature. Upon transition from the heat pump operation mode to the mixed operation mode, the control system decides also on the degree of mixing based on the above mentioned parameters.