Abstract: A heat pump including a fluid circuit and a control arrangement. The fluid circuit includes a first heat exchanger, a second heat exchanger, a third heat exchanger and a driver for driving fluid about the fluid circuit. The control arrangement has one or more modes of operation. The first heat exchanger is arranged to exchange heat between the fluid of the fluid circuit and further fluid. The control arrangement is configured to in at least one of the modes of operation control a flow control mechanism to control a flow rate of the further fluid of the first heat exchanger.