Combined air-conditioning and hot-water supply system

A combined air-conditioning and hot-water supply system comprising:

• a heat source unit provided with a compressor for air conditioning, channel switching means, and an outdoor heat exchanger;
• an indoor unit provided with an indoor heat exchanger and throttle means for air conditioning;
• a circuit for a hot-water supply heat source provided with a refrigerant-refrigerant heat exchanger and throttle means for the hot-water supply heat source;
• a branch unit that distributes a circulating refrigerant to said indoor unit and said circuit for the hot-water supply heat source;
• a refrigerating cycle for air conditioning in which said indoor unit and said circuit for the hot-water supply heat source are connected in parallel and connected to said heat source unit via said branch unit;
• and
• a refrigerating cycle for hot-water supply in which a compressor for hot-water supply, a heat medium-refrigerant heat exchanger, throttle means for hot-water supply, and said refrigerant-refrigerant heat exchanger are connected in series, wherein
• said refrigerating cycle for air conditioning and said refrigerating cycle for hot-water supply are connected so that a refrigerant for air conditioning and a refrigerant for hot-water supply exchange heat in said refrigerant-refrigerant heat exchanger,
• said heat source unit and said branch unit are connected via a high-pressure-side connection pipeline having a first check valve that allows communication of a refrigerant for air conditioning only in one direction and a low-pressure-side connection pipeline having a second check valve that allows communication of a refrigerant for air conditioning only in one direction,
• a portion on an upstream side from the first check valve of said high-pressure-side connection pipeline and a portion on an upstream side from the second check valve of said low-pressure-side connection pipeline are connected via a first connection pipeline having a third check valve that allows communication of a refrigerant for air conditioning only in a direction from said low-pressure-side connection pipeline to said high-pressure-side connection pipeline, and
• a portion on a downstream side from the first check valve of said high-pressure-side connection pipeline and a portion on a downstream side from the second check valve of said low-pressure-side connection pipeline are connected via a second connection pipeline having a fourth check valve that allows communication of a refrigerant for air conditioning only in a direction from said low-pressure-side connection pipeline to said high-pressure-side connection pipeline.