Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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VARIABLE HIGH INTENSITY INFRARED HEATER
FIELD OF THE INVENTION
[0001 ] This invention relates to an apparatus and method for heating an
enclosed space with a variable high intensity infrared heater.
BACKGROUND OF THE INVENTION
[0002] 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
[0003] 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 offby 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
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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.
[0004] 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 offthe 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.
[0005] 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
[0006] The description herein makes reference to the accompanying drawings
wherein like reference numerals refer to like parts throughout the several
views, and
wherein:
[0007] Fig. 1 shows a front view of a variable high intensity infrared heater;
[0008] Fig. 2 shows a rear view of the variable high intensity infrared
heater;
[0009] Fig. 3 is a control diagram of the variable intensity infrared heater;
and
[0010] Fig. 4 is a graph of temperature versus time showing less wasted energy
with a multi-stage system than with a single stage system.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011 ] 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.
[0012] With reference to Figures l and 2, there is shown a high-intensity
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 I6, 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 2$ 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) 3 l, 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 LDC 31 to power down the spark electrode ignitor 27. The flame sensing
electrode 29 will signal the IDC 3 I 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
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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 I6. 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 I6
to
operate.
[0015] Refernng now to Fig. 3, a schematic diagram illustrates a method for
controlling the variable high intensity 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
offthe
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 I6, I8 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, I 8. 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 I 6, 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
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temperature or the electrical power supply to be shut offfor 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.
[0016] The 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
S0. 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 ofthe burners are turned on
in 54. The
control algorithm will continue to loop through this method until the heating
system
is manually shut off.
[0017] Referring now to Fig. 4, a plot 80 of temperature versus time is shown
comparing a single stage system 82 with a mufti-stage system 84. The plot 80
shows
that with the mufti-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
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82 produces relative to the mufti-stage system 84. The mufti-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.
[0018] 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.
