Push and Pull Premix Combustion System With Blocked Vent Safety Shutoff

Abstract

A furnace with a push and pull combustion system is disclosed. The furnace may include a cabinet housing a burner box, a gas valve assembly, a premix chamber, a heat exchanger, a blower, an induced-draft blower, and a flue pipe. The gas valve assembly may meter gas into the premix chamber, while the blower may draw air into the premix chamber, wherein air and gas may mix to produce a lean gas/air mixture. The blower may also push the lean gas/air mixture into the burner box. The burner box may ignite the lean gas/air mixture to produce combustion products. A blocked vent safety shutoff switch may be mounted over an opening of the burner box to ensure negative pressure by detecting any leakage of combustion products. The induced-draft blower may pull the combustion products through the heat exchanger, the flue pipe, and out into the atmosphere.

1 ) A push and pull combustion system for a furnace, comprising:
 a premix chamber capable of mixing gas and air to produce a lean gas/air mixture;   a gas valve assembly coupled to the premix chamber and capable of metering gas into the premix chamber;   a burner box downstream of the premix chamber;   a blower coupled to the premix chamber and capable of drawing air into the premix chamber, and pushing the lean gas/air mixture into the burner box;   an igniter associated with the burner box capable of igniting the lean gas/air mixture to produce combustion products; and   an induced-draft blower capable of pulling the combustion products out of the burner box.   
     
     
         2 ) The push and pull combustion system of  claim 1 , wherein the burner box includes an opening and a blocked vent safety shutoff switch is mounted over the opening, the blocked vent safety shutoff switch adapted to make thermal contact with fluid flowing out of the opening, and sense leakage of combustion products out of the burner box. 
     
     
         3 ) The push and pull combustion system of  claim 2 , wherein the blocked vent safety shutoff switch is a thermal switch. 
     
     
         4 ) The push and pull combustion system of  claim 1 , wherein the blower creates an upstream path of positive pressure in the burner box, while the induced-draft blower creates a downstream path of negative pressure in the burner box, and wherein the burner box includes an opening for decoupling the upstream path from the downstream path by maintaining atmospheric pressure in the burner box. 
     
     
         5 ) The push and pull combustion system of  claim 4 , wherein the opening is sized relative to the volume of the burner box to determine the effectiveness of the decoupling. 
     
     
         6 ) The push and pull combustion system of  claim 1 , wherein the gas valve assembly meters gas into a premix blower and a premix motor draws air into the premix blower, the air and gas mixing in the premix blower to produce the lean gas/air mixture, the premix blower pushing the lean gas/air mixture into the burner box. 
     
     
         7 ) The push and pull combustion system of  claim 1 , wherein the gas valve assembly meters gas into a burner mixing tube and an air blower draws air into the burner mixing tube, the air and gas mixing in the burner mixing tube to produce the lean gas/air mixture, the air blower pushing the lean gas/air mixture into the burner box. 
     
     
         8 ) A furnace with a push and pull combustion system, comprising:
 a premix chamber capable of mixing gas and air to produce a lean gas/air mixture;   a gas valve assembly coupled to the premix chamber and capable of metering gas into the premix chamber;   a burner box downstream of the premix chamber;   an igniter associated with the burner box and adapted to ignite the lean gas/air mixture to produce combustion products;   a blower coupled to the premix chamber and adapted to draw air into the premix chamber, wherein air and gas mix to produce a lean gas/air mixture, the blower then pushing the lean gas/air mixture into the burner box;   a heat exchanger downstream of the burner box;   a flue pipe downstream of the heat exchanger;   an induced-draft blower coupled in-between the flue pipe and the heat exchanger and adapted to pull the combustion products through the heat exchanger, the flue pipe, and out into the atmosphere; and   a cabinet housing therein the burner box, the gas valve assembly, the premix chamber, the heat exchanger, the blower, the induced-draft blower, and the flue pipe.   
     
     
         9 ) The furnace of  claim 8 , wherein the burner box includes an opening and a blocked vent safety shutoff switch is mounted over the opening, the blocked vent safety shutoff switch adapted to make thermal contact with fluid flowing out of the opening and sense leakage of combustion products out of the burner box. 
     
     
         10 ) The furnace of  claim 9 , wherein the blocked vent safety shutoff switch is a thermal switch. 
     
     
         11 ) The furnace of  claim 8 , wherein the blower creates an upstream path of positive pressure in the burner box, while the induced-draft blower creates a downstream path of negative pressure in the burner box, and wherein the burner box includes an opening for decoupling the upstream path from the downstream path by maintaining atmospheric pressure in the burner box. 
     
     
         12 ) The furnace of  claim 8 , wherein the gas valve assembly meters gas into a premix blower and a premix motor draws air into the premix blower, the air and gas mixing to produce the lean gas/air mixture, and the premix blower pushing the lean gas/air mixture into the burner box. 
     
     
         13 ) The furnace of  claim 8 , wherein the gas valve assembly meters gas into a burner mixing tube and an air blower draws air into the burner mixing tube, the air and gas mixing to produce the lean gas/air mixture, and the air blower pushing the lean gas/air mixture into the burner box. 
     
     
         14 ) A method for controlling combustion emission for a furnace, comprising the steps of:
 metering gas into a premix chamber;   drawing air into the premix chamber;   mixing gas and air within the premix chamber to produce a lean gas/air mixture;   pushing the lean gas/air mixture into a burner box;   igniting the lean gas/air mixture within the burner box to produce combustion products; and   pulling the combustion products out of the burner box.   
     
     
         15 ) The method of  claim 14 , wherein the air is drawn by a premix motor into a premix blower and gas is metered by a gas valve assembly into the premix blower, the air and gas mixing in the premix blower to produce the lean gas/air mixture, the lean gas/air mixture being pushed by the premix blower into the burner box. 
     
     
         16 ) The method of  claim 14 , wherein air is drawn by an air blower into a burner mixing tube and gas is metered by a gas valve assembly into the burner mixing tube, the air and gas mixing in the burner mixing tube to produce the lean gas/air mixture, the lean gas/air mixture being pushed by the air blower into the burner box. 
     
     
         17 ) The method of  claim 14 , wherein the combustion products are pulled out of the burner box by an induced-draft blower. 
     
     
         18 ) The method of  claim 14 , wherein the lean gas/air mixture is pushed into the burner box by a blower. 
     
     
         19 ) The method of  claim 14 , further comprising the step of ensuring negative pressure in the burner box by mounting a blocked vent safety shutoff switch relative to an opening of the burner box, the blocked vent safety shutoff switch detecting leakage of combustion products out of the burner box. 
     
     
         20 ) The method of  claim 14 , wherein pushing the lean gas/air mixture into the burner box creates an upstream path of positive pressure in the burner box and pulling the combustion productions out of the burner box creates a downstream path of negative pressure in the burner box, and wherein the burner box further includes an opening for maintaining atmospheric pressure in the burner box and decoupling the upstream path from the downstream path.