HVAC system with environmental contaminant protection

Abstract

A heating, ventilating and air conditioning system providing enhanced protection from environmental contaminants such as chemical, biological or radioactive contaminants by maintaining a positive pressure inside the evaporator compartment thereby reducing the possibility of contaminant entry from the lower pressure ambient environment. The system also increases air flow over the evaporator coil by using a radial fan that provides an improved and efficient diffused air flow over the evaporator coil and enables use of a smaller and lighter evaporator compartment.

We claim:  
     
         1 . A HVAC system for reducing contaminant entry, said system having an evaporator compartment comprised of: 
 a compartment housing;    a supply air duct and a return air duct coupled to said housing;    an evaporator coil disposed within said housing;    a fan assembly disposed within said housing, said fan assembly having a fan motor and an impeller attached to said fan motor wherein said impeller is a radial fan impeller.    
     
     
         2 . The HVAC system described in  claim 1  wherein said radial fan impeller is disposed perpendicular to said evaporator coil.  
     
     
         3 . The HVAC system described in  claim 1  wherein said radial fan impeller is disposed adjacent to said return air duct.  
     
     
         4 . The HVAC system described in  claim 1  wherein said radial fan impeller is comprised of at least one of the materials from the following group: plastic, ceramic, metal alloy or fiber compositions.