Heat pump laundry treatment apparatus and method of operating a heat pump laundry treatment apparatus

The invention relates to a heat pump laundry treatment apparatus, in particular a heat pump laundry dryer (2) or a heat pump washing machine having drying function, and to a method of operating such a heat pump laundry treatment apparatus. The laundry treatment apparatus (2) comprises a control unit (51) controlling the operation of the laundry treatment apparatus (2), a laundry treatment chamber (18) for treating laundry (19) using process air (A), a process air circuit (20, 20a - 20d) for circulating the process air (A), a heat pump system (4) having a refrigerant loop (6), in which the refrigerant fluid is circulated through a first and a second heat exchanger (10, 12), a compressor (14) for circulating the refrigerant fluid through the refrigerant loop (6), and a cooling fan unit (53) for cooling the compressor (14). During the operation the conveyance capacity of the cooling fan unit (53) is varied. The method comprises monitoring the conveyance capacity of the cooling fan unit (53), and if the monitored conveyance capacity is equal to or below a minimum conveyance capacity value, increasing the conveyance capacity.