Rooftop Exhaust System for Exhausting Air from a Building

Abstract

The present invention entails a rooftop exhaust system for a building. The exhaust system includes a motor that is configured to directly drive a fan. The fan during the course of operation generates a negative pressure on the upstream side of the fan. This negative pressure is utilized to induce outside cooling air into a shroud that partially encloses the motor. Cooling air passing through the shroud contacts the motor and heat associated with the motor is transferred to the cooling air after which the cooling air exits the shroud.

What is claimed is: 
     
         1 . A method of exhausting air from a building with a rooftop exhaust system comprising a housing, a motor, a shroud at least partially encompassing the motor, and a fan directly driven by the motor and wherein the motor, shroud and fan are generally disposed in the housing, the method comprising:
 driving the fan and inducing exhaust air to move from the building through the housing and out an outlet of the rooftop exhaust system;   generating a negative pressure in a zone that lies on an upstream side of the fan and adjacent an opening provided in the shroud;   wherein the negative pressure induces outside cooling air to enter one or more air cooling inlets formed in the housing;   directing the cooling air from the air cooling inlet in the housing to one or more conduits extending through the housing and between the air cooling inlet in the housing and one or more air cooling inlets formed in the shroud;   directing the cooling air from the air cooling conduit through the air cooling inlet of the shroud and into and through the shroud;   cooling the motor within the shroud by contacting the motor with the cooling air passing through the shroud;   discharging the cooling air from the shroud through the opening; and   after discharging the cooling air from the shroud, mixing the cooling air with the exhaust air.   
     
     
         2 . The method of  claim 1  wherein the shroud includes a side wall structure that extends around the motor and a bottom that lies underneath the motor; and wherein the opening is formed in the top of the shroud and faces the fan. 
     
     
         3 . The method of  claim 1  wherein the exhaust air passes around and outside of the shroud and wherein substantially no exhaust air directly contacts the motor. 
     
     
         4 . A rooftop exhaust system for exhausting exhaust air from a building comprising:
 a housing having one or more side walls and configured to be mounted on the roof of the building;   a motor mounted in the housing;   a direct drive fan operatively connected to the motor for inducing the exhaust air to flow into an inlet end of the housing and through the housing;   a shroud disposed in the housing and extending at least partially around the motor and configured to generally isolate the motor from exhaust air passing from the building through the housing;   the shroud is generally enclosed except for an open top that faces the fan;   one or more air cooling inlets formed in the shroud;   one or more air cooling inlets formed in the side wall of the housing;   one or more air cooling conduits connected between the air cooling inlet formed in the shroud and the air cooling inlet formed in the housing;   wherein the fan is configured to generate a negative pressure zone on an upstream side of the fan and by virtue of the negative pressure zone, the fan is configured to induce cooling air to flow from outside of the building into the air cooling inlet in the housing, through the air cooling conduit and into and through the shroud where the cooling air cools the motor; and   wherein the rooftop exhaust system is configured to discharge the cooling air from the open top of the shroud where the cooling air mixes with the exhaust air.   
     
     
         5 . A method of exhausting smoke from a building fire with a rooftop exhaust system comprising a housing, a motor, a shroud at least partially encompassing the motor, and a fan directly driven by the motor and wherein the motor, shroud and fan are generally disposed in the housing, the method comprising:
 driving the fan and inducing smoke to move from the burning building through the housing and out an outlet in the rooftop exhaust system;   as the building burns, running the motor continuously when the motor is exposed to a temperature of up to 572° F. and running the motor for a period of four hours or less when the motor is exposed to a temperature of 573° F. to 1000° F., wherein running the motor under said temperature conditions and during a building fire include:
 generating a negative pressure in a zone that lies on an upstream side of the fan and adjacent an opening provided in the shroud; 
 wherein the negative pressure induces outside cooling air to enter one or more air cooling inlets formed in the housing; 
 directing the cooling air from the cooling air inlet in the housing to one or more cooling conduits extending through the housing and between the air cooling inlet in the housing and one or more air cooling inlets formed in the shroud; 
 directing the cooling air from the air cooling conduit through the air cooling inlet of the shroud and into and through the shroud; 
 cooling the motor within the shroud by contacting the motor with the cooling air passing through the shroud; 
 discharging the cooling air from the shroud through the opening in the shroud; and 
 wherein the discharged cooling air from the shroud mixes with the smoke being exhausted by the exhaust system.