Obstruction detection for a heat pump water heater system

A heat pump water heater system, comprising:

• a compressor configured to compress a coolant;
• an evaporator including an evaporator fan that is configured to cause air to flow through the evaporator when the evaporator fan is actuated;
• a first heat exchanger fluidly interposing the compressor and the evaporator and configured to transfer heat between the coolant and water flowing through the first heat exchanger;
• a temperature sensor configured to detect a temperature of ambient air;
• a pressure sensor configured to detect an air pressure at the evaporator;
• and
• control circuitry in communication with the temperature sensor and the pressure sensor and configured to:
• determine presence of an obstruction on the evaporator;
• and
• determine a frost condition or a non-frost condition of the evaporator in response to the temperature of the ambient air.

A heat pump water heater system, comprising:

• a compressor configured to compress a coolant;
• an evaporator including an evaporator fan that is configured to cause air to flow through the evaporator when the evaporator fan is actuated;
• a heat exchanger fluidly interposing the compressor and the evaporator and configured to transfer heat between the coolant and water flowing through the heat exchanger;
• at least one valve fluidly interposing the compressor and the evaporator and moveable between an operating position and a defrost position;
• a temperature sensor configured to detect a temperature of ambient air;
• a pressure sensor configured to detect an air pressure at the evaporator;
• and
• control circuitry in communication with the temperature sensor and the pressure sensor and configured to:
• determine presence of an obstruction on the evaporator;
• determine a frost condition or a non-frost condition of the evaporator in response to the temperature of the ambient air;
• and
• control the at least one valve to position the at least one valve to the defrost position in response to determining the frost condition.

A method of operating a heat pump water heater system, comprising:

• compressing a coolant via a compressor;
• drawing air over an evaporator via actuation of an evaporator fan;
• transferring heat between the coolant and water flowing through a first heat exchanger fluidly interposing the compressor and the evaporator;
• detecting a temperature of ambient air via a temperature sensor;
• detecting an air pressure at the evaporator via a pressure sensor;
• determining presence of an obstruction on the evaporator via control circuitry in communication with the temperature sensor and the pressure sensor;
• and
• classifying the obstruction based on the temperature of the ambient air.