Low ambient temperature heat pump water heater systems, heat exchangers, and methods thereto

A heat pump water heater system comprising:

• an evaporator configured to facilitate heat exchange between ambient air and a refrigerant;
• a condenser configured to facilitate heat exchange between the refrigerant and water;
• a vapor injection line comprising an expansion valve and configured to receive the refrigerant from the condenser, the expansion valve being configured to transition the refrigerant received from the condenser from a first pressure to a second pressure;
• a compressor configured to circulate the refrigerant through the evaporator, the condenser, the vapor injection line, and a multi-fluid heat exchanger, wherein the multi-fluid heat exchanger comprises:
• a first microchannel tube configured to receive the refrigerant at the first pressure from the condenser;
• a second microchannel tube configured to receive the refrigerant at the second pressure from the vapor injection line;
• and
• a housing having a plurality of plates configured to receive the water from a water source;
• wherein the multi-fluid heat exchanger is configured to facilitate heat exchange between the refrigerant at the first pressure, the refrigerant at the second pressure, and the water and wherein the first microchannel is disposed between the second microchannel and the plurality of plates, and the refrigerant at the first pressure heats both the refrigerant at the second pressure and the water;
• wherein the condenser is configured to receive the water that is output from the multi-fluid heat exchanger.