A heating arrangement, in which the circulating heat transfer medium for radiators is heated by condensation of a refrigerant in a heat pump, is controlled by relays in the energizing circuits of the several, independently driven pumping units of the compressor in the heat pump in response to the difference between the temperature of the atmosphere outside the heated area and the temperature of the circulating heat transfer medium to reduce the pumping energy consumed in response to the rising temperature of the heat transfer medium, and thereby to improve the efficiency of the heating arrangement.
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