Multiple stage modulating gas fired heat exchanger

Patent metadata

Field	Value
Publication number	US-10174967-B2
Application number	US-201514976354-A
Country	US
Kind code	B2
Filing date	Dec 21, 2015
Priority date	Dec 21, 2015
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

A modulating heating system includes a tube heat exchanger having a plurality of burners, a combustion air blower (CAB) having an exhaust vent connected with the plurality of burners, the CAB operable at a first speed and a second speed, a first valve connecting a fuel source to a first subset of the plurality of burners, and a second valve connecting a fuel source to a second subset of the plurality of burners, wherein the first and second valves each have a low fire rate and a high fire rate. The heat exchanger is operable through multiple heat stages at a constant fuel-air mixture.

First claim

What is claimed is:

1. A heating system, comprising:
a heat exchanger comprising burners configured to burn a combustible fuel-air mixture;
a combustion air blower (CAB) operable at a low speed and a high speed to supply air to the burners;
a first subset of the burners connected to a fuel source through a first valve;
a second subset of the burners connected to the fuel source through a second valve,
wherein the first valve and the second valve each have an off position, a low fire rate, and a high fire rate; and

wherein the burners are configured to operate in a low fire mode at the low speed and the low fire rate and operated in a high fire mode at the high speed and the high fire rate and the heat exchanger is operable through multiple heat stages.

2. The system of claim 1 , wherein the heat exchanger is operable at about a nineteen percent fuel input rate at one of the multiple heat stages.

3. The system of claim 1 , wherein the multiple heat stages achieve a turndown ratio of about 3:1 or greater.

4. The system of claim 1 , wherein the multiple heat stages achieve a turndown ratio of about 5:1 or greater.

5. The system of claim 1 , wherein the multiple heat stages achieve a turndown ratio of about 7.5:1 or greater.

6. The system of claim 1 , wherein the fuel-air mixture ratio is maintained constant through the multiple heat stages.

7. The system of claim 1 , wherein the CAB comprises a vent common to the burners and the fuel-air mixture ratio is maintained constant through the multiple heat stages.

8. The system of claim 1 , wherein the first valve comprises a low fire gas valve and a high fire gas valve, wherein at the low fire rate only the low fire gas valve is open and at the high fire rate the low fire gas valve and the high fire gas valve are open; and
the second valve comprises a low fire gas valve and a high fire gas valve, wherein at the low fire rate only the low fire gas valve is open and at the high fire rate the low fire gas valve and the high fire gas valve are open.

9. The system of claim 1 , comprising a single ignition controller in operational connection with a single flame ignitor and a single flame sensor for all of the burners.

10. The system of claim 1 , wherein the first subset of burners comprise a first flame ignitor and a first flame sensor and the second subset of burners comprise a second flame ignitor and a second flame sensor.

11. The system of claim 1 , wherein the burners comprise five burners and the multiple heat stages achieve a turndown ratio of about 3:1 or greater.

12. The system of claim 1 , wherein the burners comprise seven burners and the multiple heat stages achieve a turndown ratio of about 5:1 or greater.

13. The system of claim 1 , wherein the burners comprise eleven burners and the multiple heat stages achieve a turndown ratio of about 5:1 or greater.

14. A heating system, comprising:
a tube heat exchanger comprising a plurality of burners;
a combustion air blower (CAB) having an exhaust vent connected with the plurality of burners, the CAB operable at a first speed and a second speed;
a first valve connecting a fuel source to a first subset of the plurality of burners;
a second valve connecting a fuel source to a second subset of the plurality of burners,
wherein the first and second valves each have a low fire rate and a high fire rate; and
an electronic controller in connection with the CAB, the first valve and the second valve, the electronic controller configured to operate the heat exchanger through multiple heat stages at constant fuel-air mixture.

15. The system of claim 14 , wherein the heat exchanger is operable at about a nineteen percent fuel input rate at one of the multiple heat stages.

16. The system of claim 14 , wherein the multiple heat stages achieve a turndown ratio of about 3:1 or greater.

17. The system of claim 14 , wherein the multiple heat stages achieve a turndown ratio of about 5:1 or greater.

18. The system of claim 14 , wherein the multiple heat stages achieve a turndown ratio of about 7.5:1 or greater.

19. A method, comprising:
modulating a gas-fired heat exchanger of a heating system through multiple heat stages while maintaining a constant gas-air ratio, wherein the heating system comprises: the heat exchanger having burners;
a combustion air blower (CAB) having an exhaust vent connected with the burners, the CAB operable at a first speed and a second speed; a first valve connecting a fuel source to a first subset of the burners; and
a second valve connecting a fuel source to a second subset of the burners, wherein the first and second valves each have a low fire rate and a high fire rate.

20. The method of claim 19 , wherein the modulating the gas-fired heat exchanger comprises operating the heat exchanger at about a nineteen percent fuel input rate at one of the multiple heat stages.

21. The method of claim 19 , wherein the multiple heat stages comprise a turndown ratio of about 3:1 or greater.

22. The method of claim 19 , wherein the multiple heat stages comprise a turndown ratio of about 5:1 or greater.

23. The method of claim 19 , wherein the multiple heat stages comprise a turndown ratio of about 7.5:1 or greater.

24. The method of claim 19 , comprising an ignition procedure comprising proving a flame by energizing all of the burners, igniting at a first end of the burners and confirming a flame at a flame sensor at a second end of the burners.

25. The method of claim 19 , wherein the plurality burners are operated in a low fire mode at the low speed and the low fire rate and operated in a high fire mode at the high speed and the high fire rate and wherein the multiple heat stages comprises four or more of the heat stages selected from the group of:
a first stage wherein the burners in the first subset are in the low fire mode and the burners in the second subset are off;
a second stage wherein the burners in the first subset are in the high fire mode and the burners in the second subset are off;
a third stage wherein the burners in the first subset are off and the burners in the second subset are in the low fire mode;
a fourth stage wherein the burners in the first subset are off and the burners in the second subset are in the high fire mode;
a fifth stage wherein the burners in the first subset are in the low fire mode and the burners in the second subset are in the low fire mode; and
a sixth stage wherein the burners in the first subset are in the high fire mode and the burners in the second subset are in the high fire mode.

26. The method of claim 25 , staging back to a lowest available gas input stage after a two-stage thermostat demand goes from a high heat demand to a low heat demand thereby maintaining the burners on to instantly satisfy a future thermostat heating demand.

27. The system of claim 25 , wherein the multiple heat stages achieve a turndown ratio of about 3:1 or greater.

28. The method of claim 25 , wherein the multiple heat stages comprise a turndown ratio of about 5:1 or greater.

29. The method of claim 25 , wherein the multiple heat stages comprise a turndown ratio of about 7.5:1 or greater.

Assignees

• Lennox Ind Inc

Inventors

• Schneider Steven
• Perez Eric
• Smith Bryan
• Tran John

Classifications

• F23N2237/02

  two or more burners · CPC title

• F23N1/00 Primary

  Regulating fuel supply · CPC title

• F24H3/065

  using fluid fuel · CPC title

• F24D5/02

  operating with discharge of hot air into the space or area to be heated · CPC title

• F24H3/087 Primary

  using fluid fuel · CPC title