PURPOSE: To regulate the speed reliably and stably even upon exposure to high temperature, in thermal pump hot water supplier where a compressor is driven through engine in housing, by regulating the speed of engine through mechanical centrifugal governor mechanism.

CONSTITUTION: Machinery such as engine 1, compressor 42, etc. is contained in housing 62 of roughly closed space surrounded by noise-proof boards 60, 61 where the compressor 42 secured above the engine 1 is driven through a belt 63. Furthermore, muffler 49, starting motor 54, etc. are supported above the engine 1 and a cooling water pump 51 is arranged at the inside to achieve double structure of heatexchanger 52 in cooling water circuit and hot water heatexchanger 43 in hot water circuit. Although the inner ambient temperature of the housing 62 will be high, the speed can be regulated reliably and stably by means of the mechanical centrifugal governor mechanism employed as the speed regulation governor of engine.