High efficiency, high turndown furnace system

Abstract

A condensing furnace assembly and method includes a primary heat exchanger having a first zone and a second zone, and a secondary heat exchanger having a first zone and a second zone. A manifold assembly includes a first set and a second set of burners. The primary and secondary heat exchanger assemblies may include a plurality of aligned tubes. The plurality of tubes may include a first zone and a plurality of the tubes include a second zone. A first air device is in communication with the first zone portions of the primary and secondary heat exchanger and the first set of burners. A second air device is in communication with the second zone of the primary and secondary heat exchangers and the second set of burners. The assembly provides for high efficiency operation (90%+ efficiency) and high turndown operation (10:1 or 10% of a maximum firing rate).

Having thus described the invention, we claim: 
     
         1 . A dual zone condensing furnace assembly comprising:
 a primary heat exchanger assembly having a plurality of tubes wherein a portion of the plurality of tubes make up a first zone portion and a portion of the plurality of tubes make up a second zone portion, and   a secondary heat exchanger assembly having a plurality of tubes wherein a portion of the plurality of tubes make up a first zone portion and a portion of the plurality of tubes make up a second zone portion.   
     
     
         2 . The dual zone condensing furnace assembly of  claim 1 , further comprising a burner manifold assembly having a first set of burners and a second set of burners. 
     
     
         3 . The dual zone condensing furnace assembly of  claim 1 , wherein the plurality of tubes of the primary heat exchanger assembly are a plurality of aligned multiple pass tubular heat exchanger tubes having a first straight, a first turn, a second straight, a second turn, and a third straight. 
     
     
         4 . The dual zone condensing furnace assembly of  claim 1 , wherein the tubes of the primary heat exchanger assembly each include an input in communication with a burner manifold assembly and an output in communication with a first coupler box. 
     
     
         5 . The dual zone condensing furnace assembly of  claim 1 , wherein the plurality of tubes of the secondary heat exchanger assembly are a plurality of aligned single-pass tubular heat exchange tubes made from a corrosion-resistant material. 
     
     
         6 . The dual zone condensing furnace assembly of  claim 5 , wherein the secondary heat exchanger assembly includes a plurality of fins. 
     
     
         7 . The dual zone condensing furnace assembly of  claim 5 , wherein each of the tubes of the secondary heat exchanger assembly includes an inlet in communication with a first coupler box and an outlet in communication with a second coupler box. 
     
     
         8 . The dual zone condensing furnace assembly of  claim 1 , wherein combustion gases within the first zone portions do not communicate with the second zone portions and combustion gases within the second zone portions do not communicate with the first zone portions. 
     
     
         9 . The dual zone condensing furnace assembly of  claim 1 , wherein a first coupler box and a second coupler box are in communication with the primary and secondary heat exchanger assemblies wherein each box includes a dual zone divider that separates the boxes into a first zone cavity and a second zone cavity. 
     
     
         10 . The dual zone condensing furnace assembly of  claim 9 , wherein the first zone cavities communicate with the first zone portion of the tubes of the primary and secondary heat exchanger assemblies and the second zone cavities communicate with the second zone portions of the tubes of the primary and secondary heat exchanger assemblies. 
     
     
         11 . The dual zone condensing furnace assembly of  claim 2 , further comprising a first combustion air device in communication with the first zone portions of the primary and secondary heat exchanger tubes and the first set of burners. 
     
     
         12 . The dual zone condensing furnace assembly of  claim 11 , further comprising a second combustion air device in communication with the second zone portions of the primary and secondary heat exchanger assemblies and the second set of burners. 
     
     
         13 . The dual zone condensing furnace assembly of  claim 3 , wherein the condensing furnace assembly is configured such that airflow traverses over the first straight of the primary heat exchanger tubes then traverses over the second straight, and third straight before traversing over the secondary heat exchanger assembly. 
     
     
         14 . The dual zone condensing furnace assembly of  claim 2 , wherein the first set of burners and the second set of burners can be modulated to provide combustion gas to the first zone portions or the second zone portions such that a risk of condensation freezing within the primary and secondary heat exchange assemblies is reduced. 
     
     
         15 . The dual zone condensing furnace assembly of  claim 1 , wherein the condensing furnace assembly exhibits an efficiency of 90% or greater, a turndown operation of 10:1, or a combination thereof. 
     
     
         16 . A dual zone condensing furnace system comprising:
 a primary heat exchanger assembly having a plurality of aligned multiple pass tubular heat exchanger tubes having a first straight, a first turn, a second straight, a second turn, and a third straight wherein a portion of the plurality of tubes make up a first zone portion and a portion of the plurality of tubes make up a second zone portion,   a secondary heat exchanger assembly having a plurality of aligned single-pass tubular heat exchange tubes made from a corrosion-resistant material wherein a portion of the plurality of tubes make up a first zone portion and a portion of the plurality of tubes make up a second zone portion,   wherein combustion gases within the first zone portions do not communicate with the second zone portions and combustion gases within the second zone portions do not communicate with the first zone portions, and   wherein the condensing furnace assembly exhibits an efficiency of 90% or greater, a turndown operation of 10:1, or a combination thereof.   
     
     
         17 . The dual zone condensing furnace system of  claim 16 , further comprising a burner manifold assembly having a first set of burners and a second set of burners wherein the first set of burners and the second set of burners can be modulated to combust the first zone portions or the second zone portions such that a risk of condensation freezing within the primary and secondary heat exchange assemblies is reduced. 
     
     
         18 . The dual zone condensing furnace system of  claim 16  further comprising:
 a first coupler box and a second coupler box in communication with the primary and secondary heat exchanger assemblies, wherein each box includes a dual zone divider that separates the boxes into a first zone cavity and a second zone cavity wherein, the first zone cavities communicate with the first zone portion of the tubes of the primary and secondary heat exchanger assemblies, and the second zone cavities communicate with the second zone portions of the tubes of the primary and secondary heat exchanger assemblies. 
 
     
     
         19 . A method for operating a dual zone condensing furnace system, the steps comprising:
 providing a primary heat exchanger assembly having a plurality of aligned multiple pass tubular heat exchanger tubes wherein a portion of the plurality of tubes make up a first zone portion and a portion of the plurality of tubes make up a second zone portion;   providing a secondary heat exchanger assembly having a plurality of aligned tubes wherein a portion of the plurality of tubes make up a first zone portion and a portion of the plurality of tubes make up a second zone portion;   traversing an airflow over the primary and secondary heat exchanger assemblies; and   modulating a burner manifold assembly to provide combustion gas into at least one of the first zone portion and the second zone portion of the primary heat exchanger assembly such that the condensing furnace system exhibits an efficiency of 90% or greater, a turndown operation of 10:1, or a combination thereof.   
     
     
         20 . A method for operating a dual zone condensing furnace system of  claim 19  further comprises modulating the burner manifold assembly to provide combustion gas into only one of the first zone portion and the second zone portion of the primary heat exchanger assembly.