A heat transfer medium of a heat transfer medium circulation circuit B is a non-burnable refrigerant that exchanges heat as latent heat in each of an inter-heat-transfer-medium heat exchanger 15 and a usage-side heat exchanger 26, and a plurality of pumps 21, 37 are configured as liquid pumps for suctioning in the heat transfer medium, which is in a liquid state, and circulating the heat transfer medium through the heat transfer medium circulation circuit B.
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