Pressure Sensitive Bypass Defrost System

Abstract

A heat recovery ventilator defrost system utilizing a bypass section which supplies warm air in both channels of the heat exchanger to accelerate defrost, continue some ventilation of stale warm air, and recirculate a portion of the stale air flow, so as to warm incoming cold fresh air. When the system is in defrost mode, warm exhaust air to be expelled enters an exhaust inlet port and into an exhaust plenum. Because the air being exhausted (by way of the exhaust fan) through the exhaust plenum is under a positive pressure, the stale air will still be sucked out through exhaust passageway into discharge plenum, but also through the passive non-motorized bypass section into inlet plenum. Further, because fresh air continues to be drawn into inlet plenum, due to the positive pressure, the warm stale air which has passed through the bypass section (flap) into inlet plenum is then drawn through the heat exchanger along the inlet passageway into supply plenum, and out through supply port into the enclosure or dwelling. In this way, the heat recovery ventilators defrost system of the present invention supplies warm air in both channels of the heat exchanger.

1 . A heat recovery ventilator comprising: 
 a heat exchanger having discrete inlet and exhaust passageways extending therethrough for providing heat transfer and flow between respective fluids flowing along said inlet and said exhaust passageways, said inlet passageway providing fluid communication between an inlet plenum and a supply plenum, said exhaust passageway providing fluid communication between an exhaust plenum and an exhaust discharge plenum; and    a bypass section positioned between said inlet plenum and said exhaust plenum, the bypass section being movable between a venting configuration, in which the bypass section is in a closed position for allowing fluid communication between the exhaust plenum and the exhaust discharge plenum, and a defrost configuration, in which the bypass section is in an open position and permits fluid communication between said inlet plenum and said exhaust plenum, in addition to allowing fluid communication between the exhaust plenum and the exhaust discharge plenum.    
   
   
       2 . The heat recovery ventilator of  claim 1 , wherein the inlet plenum further comprises an inlet port for admitting supply air into said inlet plenum.  
   
   
       3 . The heat recovery ventilator of  claim 1 , wherein the supply plenum further comprises a supply port for discharging supply air from the supply plenum.  
   
   
       4 . The heat recovery ventilator of  claim 1 , wherein the exhaust plenum further comprises an exhaust inlet port for admitting exhaust air into the exhaust plenum.  
   
   
       5 . The heat recovery ventilator of  claim 1 , wherein the exhaust discharge plenum further comprises an exhaust port for discharging exhaust air from the exhaust discharge plenum.  
   
   
       6 . A heat recovery ventilator comprising a heat exchanger having discrete inlet and exhaust passageways extending therethrough for providing heat transfer and flow between respective fluids flowing along said inlet and said exhaust passageways, said inlet passageway providing fluid communication between an inlet plenum having an inlet port for admitting supply air into said inlet plenum and a supply plenum having a supply port for discharging supply air, said exhaust passageway providing fluid communication between an exhaust plenum having an exhaust inlet port and an exhaust discharge plenum, said exhaust discharge plenum having an exhaust port for discharging exhaust air from said exhaust discharge plenum; and 
 a bypass section positioned between said inlet plenum and said exhaust plenum, the bypass section being movable between a venting configuration, in which the bypass section is in a closed position for allowing fluid communication between the exhaust plenum and the exhaust discharge plenum, and a defrost configuration, in which the bypass section is in an open position and permits fluid communication between said inlet plenum and said exhaust plenum, in addition to allowing fluid communication between the exhaust plenum and the exhaust discharge plenum.    
   
   
       7 . A heat recovery ventilator of  claim 6 , wherein any of the said inlet passageway and exhaust passageway includes a plurality of individual adjacent passageways.  
   
   
       8 . A heat recovery ventilator of  claim 6 , wherein the supply inlet plenum, the supply discharge plenum, the exhaust inlet plenum and the exhaust discharge plenum are at least partially defined by a housing containing the heat exchanger.  
   
   
       9 . A heat recovery ventilator of  claim 6 , wherein either the fluid flow along the exhaust passageway is augmented by an exhaust fan mounted within one of the exhaust plenum and the exhaust discharge plenum or the fluid flow along said inlet passageway is augmented by a supply fan mounted within the inlet plenum.  
   
   
       10 . A heat recovery ventilator of claims  6 , wherein both the fluid flow along the exhaust passageway is augmented by an exhaust fan mounted within one of the exhaust plenum and the exhaust discharge plenum and the fluid flow along said inlet passageway is augmented by a supply fan mounted within the inlet plenum.  
   
   
       11 . A heat recovery ventilator of  claim 10 , wherein the exhaust fan and the supply fan are of similar capacity.  
   
   
       12 . A heat recovery ventilator as claimed in  claim 11 , wherein the exhaust fan and the supply fan share a common fan motor.  
   
   
       13 . A heat recovery ventilator comprising: 
 a heat exchanger having discrete inlet and exhaust passageways extending therethrough for providing heat transfer and flow between respective fluids flowing along said inlet and said exhaust passageways, said inlet passageway providing fluid communication between an inlet plenum having an inlet port for admitting supply air into said inlet plenum and a supply plenum having a supply port for discharging supply air, said exhaust passageway providing fluid communication between an exhaust plenum having an exhaust inlet port and an exhaust discharge plenum, said exhaust discharge plenum having an exhaust port for discharging exhaust air from said exhaust discharge plenum;    a supply fan mounted within the inlet plenum for augmenting fluid flow along said inlet passageway;    an exhaust fan mounted within one of the exhaust plenum and the exhaust discharge plenum for augmenting fluid flow along the exhaust passageway; and    a bypass section positioned between said inlet plenum and said exhaust plenum, the bypass section being movable between a venting configuration, in which the supply fan is turned on and the bypass section assumes a closed position for allowing fluid communication between the exhaust plenum and the exhaust discharge plenum, and a defrost configuration, in which the supply fan is turned off and the bypass section assumes an open position and permits fluid communication between said inlet plenum and said exhaust plenum, in addition to allowing fluid communication between the exhaust plenum and the exhaust discharge plenum.    
   
   
       14 . The heat recovery ventilator as claimed in  claim 13 , wherein, when the supply fan is turned off during the defrost configuration, the exhaust air being exhausted through the exhaust plenum is under a positive pressure, and, as a result of the positive pressure, the exhaust air continues to be drawn out while supply air continues to be drawn in to the inlet plenum.  
   
   
       15 . The heat recovery ventilator as claimed in  claim 14 , wherein, when the supply fan is turned on during the venting configuration, static pressure is created by supply air moving through the inlet passageway in the heat exchanger, and the static pressure creates a greater pressure drop than static pressure created by exhaust air moving through the exhaust passageway in the heat exchanger, which moves the bypass section to assume the closed position.  
   
   
       16 . The heat recovery ventilator as claimed in  claim 14 , wherein the bypass section is a passive, non-motorized damper.