Air-to-air heat pump defrost bypass loop

A heat pump having a means for defrosting a coil, the heat pump being reversible between a heating cycle and a cooling cycle, comprising:

• a compressor;
• an indoor coil;
• an outdoor coil;
• an expansion means between the indoor coil and the outdoor coil, the expansion means being in fluid communication with the indoor coil and the outdoor coil to allow flow of the refrigerant fluid between the indoor coil and the outdoor coil;
• a sensor for detecting a condition of the outdoor coil and providing a signal indicative of the condition of the outdoor coil;
• a programmable controller including predetermined set points, the controller including means for receiving the signal from the sensor indicative of the condition of the outdoor coil, the controller further including means for providing signals when the predetermined set points are achieved;
• means for defrosting the outdoor coil, wherein the means for defrosting the outdoor coil includes a refrigerant bypass circuit that provides hot refrigerant to the outdoor coil at an elevated temperature, the refrigerant bypassing the expansion means, the bypass circuit comprising a valve operable between a first closed position to a second open position in response to a first signal from the controller, and the second open position to the first closed position in response to a second signal from the controller, a refrigerant fluid supply means, the supply means providing hot refrigerant fluid to the valve, the supply means located upstream of the expansion device between the compressor and the expansion device, a refrigerant fluid discharge means providing refrigerant discharge fluid passing through the valve to the outdoor coil, the refrigerant bypass circuit defrosting the outdoor coil when the bypass circuit valve is open;
• and
• an auxiliary heat source, the auxiliary heat source being activated in response to a third signal from the controller and inactivated in response to a fourth signal from the controller.

A heat pump having a means for defrosting a coil, the heat pump being reversible between a heating cycle and a cooling cycle, comprising:

• a compressor;
• an indoor coil;
• an outdoor coil;
• an expansion means between the indoor coil and the outdoor coil, the expansion means being in fluid communication with the indoor coil and the outdoor coil to allow flow of the refrigerant fluid between the indoor coil and the outdoor coil;
• a sensor for detecting a condition of the outdoor coil and providing a signal indicative of the condition of the outdoor coil;
• a programmable controller including predetermined set points, the controller including means for receiving the signal from the sensor indicative of the condition of the outdoor coil, the controller further including means for providing signals when the predetermined set points are achieved;
• and
• means for defrosting the outdoor coil, wherein the means for defrosting the outdoor coil includes a first refrigerant bypass circuit that provides hot refrigerant from the condenser to the outdoor coil at an elevated temperature, the first refrigerant bypass circuit bypassing the expansion means, the first refrigerant bypass circuit comprising a valve operable between a first closed position to a second open position in response to a first signal from the controller, and the second open position to the first closed position in response to a second signal from the controller, and a second refrigerant bypass circuit that provides hot refrigerant from the compressor to the outdoor coil at an elevated temperature, the second refrigerant bypass circuit bypassing the expansion means, the second refrigerant bypass circuit comprising a valve operable between a first closed position to a second open position in response to a third signal from the controller, and the second open position and the first closed position in response to a fourth signal from the controller.