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An economizer is a type of additional intermediate heat exchanger in the refrigerating circuit of brine-to-water and water-to-water heat pumps. After the heat has been transferred to the heating system by the liquid refrigerant, the economizer transfers part of the heat remaining in the liquid refrigerant to the overheated gaseous refrigerant upstream from the compressor. The economizer ensures that the refrigerating circuit process functions smoothly and at the same time contributes to increasing efficiency. Economizers are not only used in heat pumps. They are also, for example, implemented in similar types of refrigerating systems and power plants for extracting thermal energy from various different types of flue gases.

This refers to the heat exchanger of a heat pump in which heat is extracted from a heat source (air, ground water or ground) by evaporating the working medium at a low temperature and with low pressure.

Exhaust gas loss refers to the heat lost, together with the hot smoke gases, via the chimney. It is calculated and recorded as a percentage by the chimney sweep when carrying out the annual emission measurements. Because exhaust gas loss occurs mainly during burner operating times, its measured quantity can be seen as directly equal to the fuel loss.

For example: an annual fuel consumption of 4,000 litres o foil and a measured exhaust gas loss of 12% equals 0.12 × 4,000 litres = 480 litres.

However, the actual loss is in fact higher, since this measurement does not include the water vapour in the dry exhaust gas with its condensation heat. This accounts for an additional “latent” heat loss of approx. 11% for gas and 6% for heating oil. The measured gas loss of 12% of an oil boiler actually amounts to 12 + 6 = 18% or 12% + 11% = 23% for gas.