US20030221686A1

US20030221686A1 - Variable high intensity infrared heater

Info

Publication number: US20030221686A1
Application number: US10/157,685
Authority: US
Inventors: Farshid Ahmady
Original assignee: Solaronics Inc
Current assignee: Solaronics Inc
Priority date: 2002-05-29
Filing date: 2002-05-29
Publication date: 2003-12-04
Also published as: CA2428563A1

Abstract

A radiant heating system having a housing for holding a plurality of gas burners with a ceramic burner element that emits infrared rays after becoming hot. A controller is used for selectively controlling at least one valve to restrict the gas flow to the individual burners. A method is shown for radiating heat from a gas burner in response to a thermostat by controlling the gas flow to individual burners with electronic valves located in a gas supply line and selectively shutting off the gas flow to each burner.

Description

FIELD OF THE INVENTION

This invention relates to an apparatus and method for heating an enclosed space with a variable high intensity infrared heater.

BACKGROUND OF THE INVENTION

High intensity gas-fired infrared heaters are typically used in large commercial or industrial settings. A gas heater burns natural gas, propane or other similar combustible gases to heat a porous ceramic plate. The ceramic plate turns red hot and emits infrared energy waves. Such heaters often include reflectors to broadly reflect the energy waves. Such high intensity infrared heaters generally operate at full capacity when not in an off condition. This operating condition results in the burner constantly cycling between its on condition and its off condition thus making it difficult to control heating levels.

SUMMARY OF THE INVENTION

A radiant heating system having a housing for holding a plurality of gas burners. The fuel used in these burners is typically natural gas or propane gas. The gas burners each have a plenum for mixing the gas with combustion air, a ceramic burner element that emits infrared rays after becoming hot, a controller for selectively controlling the gas burners, a common rail gas line for supplying the gas from an inlet line to the plurality of burners, and at least one valve positioned in the common rail gas line to prevent gas from flowing to burners located downstream from the valve. The valves for controlling the gas flow to the individual burners are positioned downstream of the first burner and prior to the inlet of each succeeding burner so that the downstream burners can be individually turned on and off by the controller. A controller for the gas heater provides a room temperature set by a thermostat. The controller controls the temperature between a lower threshold temperature and an upper threshold temperature by controlling the numbers of individual gas burners operating. A control algorithm is designed to heat up a space as quickly as possible by turning all the burners on, while minimizing the overshoot and undershoot of the set point temperature by selectively reducing the number of burners operating as the room temperature fluctuates between the lower threshold and the set point temperature. The gas burner has a 100 percent safety shut-off feature and is powered by a 24-volt electrical source. Direct spark ignition with a spark electrode is used to ignite the fuel. The burner does not require a pilot to be lit continually for operation. The burner uses a flame sensing electrode for determining if the burner is operational.

A method for radiating heat comprising operating a gas burner in response to a thermostat, controlling the gas flow to individual burners with electronic valves located in a gas supply line by selectively shutting off the gas flow delivered to individual burners, generating infrared rays from a hot ceramic burner surface, and reflecting the radiated infrared rays from a reflector in a desired direction.

Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: [0006]
FIG. 1 shows a front view of a variable high intensity infrared heater; [0007]
FIG. 2 shows a rear view of the variable high intensity infrared heater; [0008]
FIG. 3 is a control diagram of the variable intensity infrared heater; and [0009]
FIG. 4 is a graph of temperature versus time showing less wasted energy with a multi-stage system than with a single stage system. [0010]

DESCRIPTION OF THE PREFERRED EMBODIMENT

High intensity gas-fired infrared heaters are typically either controlled in the on or off position so that the burner elements are either all firing or all off. An improvement to the heater allows one or more burner elements to be selectively shut off so that a set point temperature can be controlled more precisely by minimizing overshoot and undershoot of the desired temperature. [0011]
With reference to FIGS. 1 and 2, there is shown a high-intensity [0012] radiant heating system 10 having a housing 12 for holding a first burner 16 and a second burner 18. This preferred embodiment shows two burners, but it should be understood that there is no limit as to the maximum number of burners in this apparatus, e.g., 3, 4, 5, 6, . . . Ceramic burner elements 17, 19 are heated until they are red hot so that infrared energy waves are generated therefrom. A reflector 14 reflects the infrared rays emitted from burners 16, 18 in a desired direction to provide heat. A spark electrode ignitor 27 is used to initiate combustion of the fuel. A combination power supply and controller 28 includes logic for ignition detection control and operational control over the various components on the heating system 10. After power is applied to an ignition detection controller (IDC) 31, a delay of preferably fifteen seconds occurs before a spark is developed at the electrode 27 and a gas regulator valve 22 opens allowing gas to flow to the burners 16, 18. A flame sensing electrode 29 is used to determine when combustion has begun and to signal the IDC 31 to power down the spark electrode ignitor 27. The flame sensing electrode 29 will signal the IDC 31 to power up the spark electrode ignitor 27 when a flameout condition is detected. The spark electrode ignitor 27 generally begins firing within 0.8 seconds of a flameout condition.
[0013] Heater 10 has a gas inlet line 20 for providing gas from an external source to the burners 16,18. Gas, preferably natural gas or propane, passes through a regulator valve 22. Regulator valve 22 is capable of shutting off the gas flow to burners 16, 18 and providing a fixed amount of gas to burners 16 and 18. After passing through regulator valve 22, the gas enters a common rail gas line 24 for distribution to individual burners 16, 18. A trunk line 30 tees into common rail 24 to deliver gas to burner 16 while a second trunk line 32 provides gas from common rail 24 to burner 18. It is understood that if more than two burners are provided, each would be provided gas by a trunk line connected to the common rail 24. A solenoid valve 26 can be installed in common rail 24 or in trunk line 32 downstream of burner 16. Solenoid valve 26 prevents gas from traveling downstream therefrom thus preventing gas from flowing to burner 18.
[0014] Spark electrode ignitor 27 provides a spark to start combustion in burner 16 which, if gas is flowing to burner 18, causes burner 18 to ignite by a flame transfer from burner 16. A combination power supply and controller 28 controls power to the solenoid valve 26, spark ignitor electrode 27, regulator valve 22, and the flame sensing electrode 29. Solenoid valve 26 is operable to selectively prevent gas from flowing downstream to burner 18 thus selectively allowing only burner 16 to operate.
Referring now to FIG. 3, a schematic diagram illustrates a method for controlling the variable high intensity [0015] infrared heater 10. The control sequence starts with determining if the thermostat set point temperature is below a first (lowest) threshold in query 52. If the answer to query 52 is yes, then the controller turns all the burners on in 54. Power is applied to the IDC 31 and, fifteen seconds after power is applied, a spark is developed at the spark electrode ignitor 27 and the regulator valve 22 opens allowing gas to flow to the burners 16, 18. The spark electrode ignitor 27 begins ignition and an electrical current begins flowing from the flame sensing electrode 29 through the flame to a ground to determine when to shut off the spark. The IDC 31 senses the current and turns off the spark once the flame has taken hold and the gas continues to flow through the regulator valve 22. If the burners 16, 18 have a flame outage detected by the flame sensing electrode 29, the IDC 31 responds by initiating sparking within preferably 0.8 seconds. A preferred fifteen second ignition period initiates the attempt to relight the burners 16, 18. If the flame is reestablished, then normal operation resumes. If the burners 16, 18 do not light after the first try, an interpurge sequence preferably occurs between trials before attempting to relight the burners 16, 18. If the burners 16, 18 fail to light after the third trial, the IDC 31 will de-energize the regulator valve 22 and go into lock-out mode. Lock-out recovery requires the thermostat 40 to be reset below ambient temperature or the electrical power supply to be shut off for five seconds. If the answer to query 52 is no, then the controller checks the thermostat to see if the temperature is below a second (lower) threshold in query 56. If the answer to query 56 is yes, then the controller 28 turns one burner on in 58. If the answer to query 56 is no, then the controller loops back to 50 and turns all the burners off. The controller loops back to query 52 after turning all burners on in 54 or turning one burner on in 58 to determine if the temperature is below a first (lowest) threshold. The controller 28 will continue looping through the algorithm until heater 10 is manually turned off.
The [0016] controller 28 allows the heater 10 to operate with a variable number of burners to control the room temperature within a second (lower) threshold temperature and the set point temperature while minimizing the on and off fluctuations of the heater system 10. The control system is designed to heat a location as quickly as possible while minimizing overshoot and undershoot of the set point temperature by varying the number of burners firing. For example, starting in the query 52, if set point temperature is 72° F., the first (lowest) threshold could be 60° F., and a room temperature is 50° F., then all the burners will be turned on at 54. As the room temperature begins to warm up, the controller 28 continues to measure the room temperature via the thermostat 40 to determine if the temperature is below the first threshold temperature. If the answer is no, then the controller will check whether the temperature is below a second (lower) threshold in 56, for example 70° F. If the room temperature is above 70° F. in query 56, then all of the burners are turned off in 50. If the room temperature in query 56 is less than 70° F., but greater than 60° F., then the controller will turn one burner on in 58. If the room temperature falls below the first threshold 60° F. in query 52 then all of the burners are turned on in 54. The control algorithm will continue to loop through this method until the heating system 10 is manually shut off.
Referring now to FIG. 4, a [0017] plot 80 of temperature versus time is shown comparing a single stage system 82 with a multi-stage system 84. The plot 80 shows that with the multi-stage system 84 the overshoot and undershoot of the temperature set point is greatly reduced compared with that of the single stage system 82. Overshoot peaks 86 show the amount of wasted energy that the single stage system 82 produces relative to the multi-stage system 84. The multi-stage system 84 not only saves on energy usage, but, since the undershoot and overshoot of the temperature set point is minimized, the comfort level is improved for occupants in the room.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law. [0018]

Claims

What is claimed is:

1. A radiant heating system comprising:

a housing for holding a plurality of gas burners, the burners having a plenum for mixing gas with air prior to combustion of the gas and air mixture;

a gas line having a first end and a second end for supplying gas to the burners; and

at least one valve positioned in the line to selectively prevent gas from flowing to burners located downstream from the valve.

2. The radiant heating system of claim 1, wherein the gas line is a common rail.

3. The radiant heating system of claim 1 further comprising:

a reflector attached to the housing and positioned around the burners for reflecting the infrared rays in a desired direction.

4. The radiant heating system of claim 1, wherein the valve is a solenoid valve.

5. The radiant heating system of claim 1 further comprising:

a gas regulator valve connected between the gas inlet line and the gas common rail line for providing a fixed amount of the gas flow to the common rail.

6. The radiant heating system of claim 1 further comprising:

an ignitor located on at least one of the burners for igniting the air and gas mixture.

7. The radiant heating system of claim 6 further comprising:

a power supply for supplying power to the controller, the solenoid valve, the ignitor, and the regulator valve.

8. The radiant heating system of claim 1 wherein the burner element is made of ceramic material.

9. The radiant heating system of claim 1 further comprising:

a thermostat for signaling the controller to start and stop individual burners when heat is required.

10. A radiant heating system comprising:

a controller for a gas heater to provide a set point room temperature within a lower threshold and an upper threshold by controlling gas flow to individual burners based on a control algorithm;

the control algorithm being designed to heat a location as quickly as possible while minimizing overshoot and undershoot of the set point temperature by firing all the burners in a cold condition and selectively reducing the number of burners operating once the room temperature is within a predetermined temperature of the set point temperature;

the control algorithm being designed to selectively fire the individual burners to keep the temperature between the lower threshold and the set point temperature.

11. A method for radiating heat comprising:

operating a gas burner in response to a thermostat;

controlling gas flow to individual burners with electronic valves located in a gas supply line by selectively shutting off the gas flow delivered to the individual burners;

generating infrared rays from a hot ceramic burner surface; and

reflecting the radiated infrared rays from a reflector in a desired direction.

12. The method claim 11 further comprising:

regulating gas flow entering into a common rail line.

13. The method claim 11 further comprising:

igniting a gas and air mixture in a plenum of at least one of the burners for generating heated combustion products.

14. The method claim 11 further comprising:

supplying power to the controller, the solenoid valve, the ignitor, and the regulator valve for operation of the gas burner.

15. The method claim 11 further comprising:

signaling the controller with a thermostat to start and stop individual burners for providing a desired amount of heat.

16. An apparatus for radiating heat comprising:

means for operating a gas burner in response to a thermostat;

means for controlling gas flow to individual burners with electronic valves located in a gas supply line by selectively shutting off the gas flow delivered to each burner;

means for generating infrared rays from a hot ceramic burner surface; and

means for reflecting the radiated infrared rays from a reflector in a desired direction.

17. The apparatus claim 16 further comprising:

means for regulating gas flow entering into a common rail line.

18. The apparatus claim 16 further comprising:

means for igniting a gas and air mixture in a plenum of at least one of the burners for generating heated combustion products.

19. The apparatus claim 16 further comprising:

means for supplying power to the controller, the solenoid valve, the ignitor, and the regulator valve required for operation of the gas burner.

20. The apparatus claim 16 further comprising: