Low ambient cooling kit for variable refrigerant flow heat pump

Abstract

Systems and methods for low ambient air temperature cooling in air-source based heat pump systems wherein an outdoor heat pump unit includes a discharge hood positionable over its fan. The hood including a damper that is openable and closeable as a function of outside temperature. The outdoor unit may also include wind deflectors positioned over the coil openings of the disclosure. During cooling operations below 23° F., the damper assembly partially closes to reduce airflow across the condenser coil of the outdoor unit to a level below that which is possible at minimum fan speed. As the outdoor temperature continues to drop, the damper assembly continues to close to further reduce airflow.

1 . An outdoor heat pump unit of a heat pump based air conditioning and heating system comprising
 an enclosure with openings formed in its side and back panels,   a condenser fan mounted on the top of the enclosure and in communication with an interior of the enclosure, the condenser fan configured to draw air in through the openings in the side and back panels of the enclosure and across a heat exchanger positioned within the interior of the enclosure,   a discharge hood mounted on the top of the enclosure over the condenser fan, the discharge hood including a discharge outlet, and   a damper mounted adjacent the outlet of the discharge hood and configured to adjust the opening of the outlet as a function of outside ambient air temperature.   
     
     
         2 . The outdoor heat pump unit of  claim 1  wherein the damper is spring biased to an open position. 
     
     
         3 . The outdoor heat pump unit of  claim 1  wherein the damper includes one or more blades rotatably coupled to the enclosure. 
     
     
         4 . The outdoor heat pump unit of  claim 3  wherein the damper blades are rotatable between a fully opened position to a closed position. 
     
     
         5 . The outdoor heat pump unit of  claim 4  wherein the damper blades are in a fully opened position for outside temperatures at or above 23° F. and are rotatable to a closed position as outside air temperatures fall below 23° F. 
     
     
         6 . The outdoor heat pump unit of  claim 4  wherein the closed position corresponds to the damper blades rotated to an angle position of about 85° from the fully opened position. 
     
     
         7 . The outdoor heat pump unit of  claim 2  further comprising a control unit having a damper actuator coupled to the damper. 
     
     
         8 . The outdoor heat pump unit of  claim 7 , wherein the control unit further comprises a circuit board coupled to the damper actuator and a thermister coupled to the circuit board. 
     
     
         9 . The outdoor heat pump unit of  claim 8 , wherein the circuit board is configured to convert a resistance value of the thermister corresponding to an outside temperature to a control voltage within a control voltage range having lower and upper control voltage thresholds. 
     
     
         10 . The outdoor heat pump unit of  claim 9 , wherein the control voltage range is 2-10 volts DC. 
     
     
         11 . The outdoor heat pump unit of  claim 9 , wherein the lower control voltage threshold corresponds to the fully opened position and the upper control voltage threshold corresponds to the closed position. 
     
     
         12 . The outdoor heat pump unit of  claim 11 , wherein the closed position corresponds to the damper blades rotating about 85° from the fully opened position in response to a control voltage that is less than the upper threshold control voltage. 
     
     
         13 . The outdoor heat pump unit of  claim 1  further comprising a plurality of wind deflectors positioned over the openings in the side and back panels of the enclosure and having air curtains adjacent air passage openings formed by the wind deflectors and the enclosure. 
     
     
         14 . A discharge hood for an outdoor heat pump unit comprising
 an enclosure mountable to a top of an outdoor heat pump enclosure over a condenser fan of the outdoor heat pump,   a discharge outlet formed in one of the side, front or rear panels of the enclosure, and   a damper mounted adjacent the discharge outlet and configured to adjust the opening of the outlet as a function of outside ambient air temperature.   
     
     
         15 . The discharge hood of  claim 14  wherein the damper is spring biased to an open position. 
     
     
         16 . The discharge hood of  claim 15  wherein the damper includes one or more blades rotatably coupled to the enclosure. 
     
     
         17 . The discharge hood of  claim 16  wherein the damper blades are rotatable between a fully opened position and a closed position. 
     
     
         18 . The discharge hood of  claim 17  wherein the damper blades are in a fully opened position for outside temperatures at or above 23° F. and movable to a closed position as outside air temperatures fall below 23° F. 
     
     
         19 . The discharge hood of  claim 16  wherein damper blades are rotable between 0° and 85°. 
     
     
         20 . The discharge hood of  claim 16  further comprising a control unit having a damper actuator coupled to the damper blades, a circuit board coupled to the damper actuator and a thermister coupled to the circuit board. 
     
     
         21 . The discharge hood of  claim 20 , wherein the circuit board is configured to convert a resistance value of the thermister corresponding to an outside temperature to a control voltage within a control voltage range having lower and upper control voltage thresholds. 
     
     
         22 . A kit comprising the discharge hood of  claim 14  and one or more wind deflectors positionable over condenser coil openings in an enclosure of an outdoor heat pump unit. 
     
     
         23 . The outdoor heat pump unit of  claim 4  wherein the damper blades are in a fully opened position for outside temperatures at or above a low outside temperature threshold and are rotatable to a closed position as outside air temperatures fall below the low outside temperature threshold. 
     
     
         24 . The discharge hood of  claim 17  wherein the damper blades are in a fully opened position for outside temperatures at or above a low outside temperature threshold and movable to a closed position as outside air temperatures fall below the low outside temperature threshold.