Information
-
Patent Grant
-
6390028
-
Patent Number
6,390,028
-
Date Filed
Monday, March 12, 200123 years ago
-
Date Issued
Tuesday, May 21, 200222 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 122 1301
- 122 1431
- 122 142
- 122 1421
- 122 504
-
International Classifications
-
Abstract
A fuel-fired heating appliance, representatively a gas-fired water heater, has a combustion chamber in a lower end portion thereof, and fuel burner apparatus having main and pilot burner portions is operatively disposed in the combustion chamber. During operation of the water heater combustion air is supplied to the burner apparatus only via a duct structure having an inlet elevated relative to the floor or other horizontal support surface upon which the water heater rests. A flammable vapor sensor is mounted on the lower end portion of the water heater, externally of the combustion air supply duct structure and at an elevation lower than that of its elevated inlet, and is operatively connected to burner control circuitry which, in turn, is coupled to the burner apparatus. In the event flammable vapors are generated near the floor adjacent the water heater, the vapor sensor operates to detect such vapors and responsively disables the burner apparatus via the control circuitry. The difference in elevation between the vapor sensor and the elevated combustion air inlet gives the sensor additional time to detect and respond to flammable vapors before they upwardly reach the elevated combustion air inlet.
Description
BACKGROUND OF THE INVENTION
The present invention generally relates to fuel-fired heating appliances, such as water heaters and, in a preferred embodiment thereof, more particularly relates to a gas-fired water heater having incorporated therein a specially designed flammable vapor sensor-based burner shut-off system.
Gas-fired residential and commercial water heaters are generally formed to include a vertical cylindrical water storage tank with a gas burner structure, typically comprising a main burner and an associated pilot burner, disposed in a combustion chamber below the tank. The burner is supplied with a fuel gas through a gas supply line, and combustion air through one or more air inlet passages providing communication between ambient air and the interior of the combustion chamber.
Water heaters of this general type are extremely safe in operation. However, when gasoline or other flammable liquids are stored or used improperly in proximity to the water heater, there may exist a possibility of flammable vapors becoming entrained in the air intake of the water heater. It is theorized that such vapors might cause secondary combustion to occur within the confines of the water heater combustion chamber. It is accordingly possible for the resulting flame to propagate out of the combustion chamber into the ambient environment around the water heater as a result of following the intake path of the flammable vapor.
In view of this, various modern gas-fired water heater designs, as well as the designs of other types of fuel-fired heating appliances, focus upon the inhibition and/or control of the entrance of flammable vapors into a combustion chamber of the appliance. It is to this design goal that the present invention is directed.
SUMMARY OF THE INVENTION
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, fuel-fired heating apparatus, representatively a gas-fired water heater, is provided with a specially designed flammable vapor sensor-based burner shutoff system.
A gas-fired water heater illustratively embodying principles of the present invention may be either a power vented or natural draft type and is restable on a horizontal support surface such as a floor. In a representative preferred embodiment thereof, the gas-fired water heater includes a tank adapted to hold a quantity of water, a combustion chamber disposed beneath the tank, and a flue communicated with the interior of the combustion chamber and extending upwardly through the interior of the tank. A gas burner and an associated pilot device are disposed within the combustion chamber, with the burner being operable to receive gas from a source thereof and combust a gas/air mixture within the combustion chamber. A control system is provided and is operable to disable the burner and associated pilot device in response to receipt of a shutdown signal.
A combustion air inlet passage is provided and is operative to deliver combustion air to the combustion chamber. The combustion air inlet passage has an inlet portion exposed to ambient air adjacent the gas fired water heater, and combustion air is deliverable to the combustion chamber only via such inlet portion and through the combustion air inlet passage.
Also incorporated in the gas-fired water heater is a flammable vapor sensor which is disposed externally of the combustion air inlet passage, at an elevation lower than that of its inlet portion, and being operative to sense flammable vapor, illustratively hydrocarbon fumes, and responsively transmit the shutdown signal to the control system which, in turn, operates to disable the burner and associated pilot device.
The elevation of the combustion air passage inlet portion relative to the flammable vapor sensor uniquely creates a time delay between the time at which the sensor is exposed to flammable vapor created at floor level by, for example a spill of flammable liquid adjacent the water heater, and the time at which flammable vapor reaches the elevated combustion air passage inlet portion to enable the flammable vapor to traverse the combustion air passage and enter the combustion chamber. This time delay gives the sensor, and the associated burner control system, additional time to sense the flammable vapor and disable the burner and pilot device before a combustible concentration of flammable vapors enters the combustion chamber.
Illustratively, the combustion chamber has a perforated bottom side wall portion with openings therein through which combustion air may enter the combustion chamber. The openings are preferably spaced and configured to (1) allow combustion air to flow upwardly through the openings with a pressure drop which is sufficiently low so as to not materially impede the combustion process of the water heater, and (2) act as flame arresting passages that hinder a downward flow of flames through the openings in the event that flammable vapor passes upwardly through the openings into the combustion chamber are ignited within the combustion chamber.
In an illustrated preferred embodiment of the gas-fired water heater, the combustion air passage is at least partially defined by an external wall structure having a vertical portion in which the elevated combustion air passage inlet portion is formed, and a horizontal portion extending beneath the combustion chamber and having an interior communicated with the interior of the combustion chamber. As will be readily appreciated by those of skill in this particular art, however, a variety of other techniques could alternatively be employed to elevate the water heater's combustion air intake location relative to the flammable vapor sensor to provide a time delay between the sensor's exposure to flammable vapors and potential entry of such flammable vapors into the combustion chamber.
While principles of the present invention are illustrated herein as being representatively incorporated in a fuel-fired water heater, it will be readily appreciated by those of ordinary skill in this particular art that such principles are not limited to a water heater, but could be alternatively incorporated to advantage in a variety of other types of fuel-fired heating appliances including, but not limited to, boilers and air heating furnaces.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a simplified, somewhat schematic cross-sectional view, partly in elevation, through a bottom end portion of a gas-fired water heater incorporating therein a specially designed burner shut-off system embodying principles of the present invention; and
FIG. 2
is an enlarged cross-sectional detail view of the circled area “
2
” in FIG.
1
.
DETAILED DESCRIPTION
Cross-sectionally illustrated in simplified form in
FIG. 1
is a lower end portion of a specially designed fuel-fired water heater
10
embodying principles of the present invention. Illustratively, the fuel-fired water heater
10
is a gas-fired water heater, utilizing natural or liquefied petroleum gas, but could alternatively be an oil-fired water heater. Water heater
10
has a vertically oriented cylindrical metal water storage tank
12
in which a quantity of heated water
14
is stored, the tank
12
having an upwardly domed bottom head portion
16
that defines the upper wall of a combustion chamber
18
which communicates with the open lower end of a combustion flue tube
20
that centrally extends upwardly through the interior of the tank
12
. An annular outer side wall portion of the combustion chamber
18
is defined by an annular lower end portion
12
a
of the tank which extends downwardly past the periphery of the bottom head portion
16
. In a conventional manner suitable outlet and inlet pipes (not shown) are connected to the tank
12
to respectively flow heated water out of the tank and flow water to be heated into the tank.
The open lower end portion
12
a
of the tank
12
is partially closed by an annular bottom wall structure
22
which is sealingly received and suitably anchored within a peripheral section of the bottom tank end portion
12
a
. Circumferentially spaced support legs
24
extend downwardly from the annular bottom wall
22
and are restable on a horizontal support surface, such as the illustrated floor
26
, to position the bottom wall
22
in an elevated relationship with the floor
26
.
Outwardly circumscribing the tank
12
is a cylindrical insulating jacket structure
28
having an annular outer metal jacket portion
30
which is coaxial with the tank
12
and spaced outwardly therefrom. A suitable insulation material, such as foam insulation
32
, is disposed within the annular space between the metal jacket portion
30
and the tank
12
.
A circular perforated plate structure
34
is sealingly placed atop the annular bottom wall
22
at the bottom side of the combustion chamber and extends across and covers the circular central opening
36
in the bottom wall
22
. Representatively, the plate structure
34
is formed from a stacked plurality of disc-shaped metal plates
38
(representatively four in number as illustrated in FIG.
2
), with the perforations in the individual plates
38
being in registry with one another to combinatively define a spaced series Of vertical combustion chamber air intake openings
40
vertically extending from the bottom side of the plate structure
34
to its top side. The illustrated openings have circular cross-sections along their lengths, but could alternatively have other cross-sectional configurations. While the plate structure
34
is representatively formed from a stacked plurality Of representatively four individual perforated metal plates, it will be appreciated that if desired it could be alternatively formed from a greater or lesser number of plates, including a single plate.
The water heater
10
is representatively of a power vented type in which a conventional draft inducer fan (not shown) is operatively associated with the flue tube
20
to collect and propel to the outdoors combustion products passing upwardly through the flue tube during firing of the water heater
10
as later described herein. Alternatively, however, the water heater
10
could be a natural draft water heater which is operable without such a draft inducer fan.
Fuel burning apparatus
42
is operatively supported within the interior of the combustion chamber
18
and includes a main gas burner
44
and an associated intermittent pilot device, representatively a schematically depicted spark ignition device
46
. A thermostatic gas supply valve
48
, which monitors the temperature of the stored water
14
and correspondingly controls the firing of the burner
44
, to maintain a predetermined tank water temperature, is externally mounted on the outer side of the jacket structure
28
on the left side of the water heater
10
as viewed in FIG.
1
. Schematically depicted burner system control circuitry
50
is operatively associated with the thermostatic gas supply valve
48
and functions as subsequently described herein. Thermostatic valve
48
receives a supply of gaseous fuel through a gas pipe
52
and is coupled to the main burner
44
by a gas supply pipe
54
. The pilot device
46
is electrically coupled to the control circuitry
50
via lead
56
.
A combustion air intake duct structure
58
is associated with the balance of the water heater
10
, to supply combustion air
60
to the combustion chamber
18
as later described herein, and representatively includes a vertically oriented duct section
62
disposed externally adjacent the water heater jacket structure
28
and having an open upper inlet end
64
elevated relative to the floor
26
by a vertical distance X which representatively may range from about 6 inches to about 20 inches, but may be a greater or lesser dimension if necessary or desired.
At its lower end the vertical duct section
62
is connected to a horizontal duct section
66
that, from its juncture with the bottom end of the vertical duct section
62
, extends leftwardly beneath the annular bottom wall structure
22
. The overall duct structure
58
also includes a circular plenum structure
68
, having a bottom wall
70
and an open top side, which is sealingly disposed within the central opening
36
of the annular bottom wall structure
22
, with the interior of the plenum structure
68
being communicated with the interior of a left end portion of the horizontal duct section
66
by, for example, a connecting duct structure
72
interconnecting the bottom plenum wall
70
and the horizontal duct section
66
.
Upon a call from the thermostatic valve
48
for heat to be added to the water
14
stored in the tank
12
, fuel is supplied to the burner
44
, mixed with ambient combustion air
60
delivered to the combustion chamber
18
as later described herein, and (in response to operation of the pilot device
46
) combusted by the burner
44
to form hot combustion products
74
which travel upwardly through the flue tube
20
. During firing of the water heater
10
, ambient combustion air
60
is drawn into the combustion chamber
18
sequentially via the open upper duct inlet end
64
, the ducts
62
,
66
,
72
, the plenum
68
, and the air intake openings
40
in the perforated plate structure
34
. It is important to note that this path is the sole flow path for combustion air
60
entering the combustion chamber
18
. In other words, all combustion air
60
delivered to the combustion chamber
18
must initially enter the elevated inlet opening
64
.
The water heater
10
also includes a flammable vapor sensor
76
externally mounted on a lower end portion of the jacket structure
28
and operatively coupled to the burner system control circuitry
50
via an electrical lead
78
. Sensor
76
is of a conventional type operative to detect flammable vapor
80
created at the floor
26
by, for example, a spill of a flammable liquid near the water heater
10
, and responsively output a signal indicative of the sensing of such flammable vapor. Representatively, the sensor
76
is operative to sense hydrocarbon vapors and is of a type manufactured and marketed by Adsistor Technology, Inc. of Seattle, Wash.
As indicated in
FIG. 1
, the flammable vapor sensor
76
is supported at a distance Y above the floor
26
which is less than the vertical distance X between the floor
26
and the elevated open inlet end
64
of the vertical combustion air intake duct
62
. In the event that flammable vapor
80
is caused to emanate from floor level adjacent the water heater
10
, a portion of the flammable vapor
80
will contact the sensor
76
and activate it. Activation of the sensor
76
will, in turn, generate a burner system shutdown signal which is transmitted to the burner system control circuitry
50
via the lead
78
. upon receiving this sensor-generated shutdown signal, the circuitry
50
automatically functions to disable both the main burner
44
and its associated pilot device
46
. If the burner
44
is operating when the shutdown signal is generated by the sensor
76
, the thermostatic valve
48
is caused to terminate gas flow to the burner
44
via the gas supply pipe
54
, and the pilot device
46
is electrically disabled. If, on the other hand, the water heater
10
is in a standby mode when the shutdown signal is generated by the sensor
76
, subsequent burner gas delivery via the pipe
54
, and subsequent sparking of the pilot device
46
, are prevented by the burner system control circuitry
50
.
According to a key aspect of the present invention, the schematically illustrated difference in height between the higher combustion air duct inlet opening
64
and the lower flammable vapor sensor
76
uniquely creates a built-in time delay between (1) the time that flammable vapor
80
emanating from the floor
26
adjacent the water heater
10
and comes into contact with the sensor
76
, and (2) the time when the vapor
80
enters the combustion chamber
18
by sequentially rising to the level of the elevated combustion air intake opening
64
, traversing the intake ductwork system
62
,
66
,
72
,
68
and passing upwardly through the perforated plate structure openings
40
. This sensor/intake height differential thus desirably gives the above described flammable vapor sensor-based burner shutoff system more time to react to the presence of flammable vapors
80
near floor level adjacent the water heater
10
.
While a single flammable vapor sensor
76
has been illustrated, it will readily be appreciated that more than one sensor
76
could be utilized in the described burner shutoff system if desired. For example, a series of sensors
76
could be circumferentially spaced around the water heater near floor level. Additionally, the illustrated sensor
76
(and additional sensors, if used) could be vertically positioned somewhat lower or higher than the illustrated sensor
76
if desired.
Although the illustrated water heater
10
has been described as being a power vented water heater, it will be readily appreciated by those of skill in this particular art that a natural draft water heater could also be advantageously provided with the described burner shutoff system. In this case, the natural draft water heater might have a standing flame pilot device (instead of the illustrated intermittent spark type pilot device
46
) which was supplied with gas via a pilot gas supply line operatively coupled to the thermostatic gas valve
48
. If flammable vapor
80
was detected by the sensor
76
, the burner system control circuitry
50
could be utilized to responsively disable both the main burner and pilot burner by causing the thermostatic valve
48
to preclude further gas flow thereto.
Preferably, the previously described perforated plate structure
34
extending along the bottom side of the combustion chamber
18
is similar in construction to the perforated combustion chamber plate structure
48
illustrated and described in U.S. Pat. No. 5,941,202, which is hereby incorporated herein by reference, in that the spacing and configuration of the vertical plate structure openings
40
are selected to cause the openings
40
to (1) allow the combustion air
60
to flow upwardly through the openings
40
with a pressure drop which is sufficiently low so as to not materially impede the normal combustion process of the fuel-fired water heater
10
, while at the same time (2) act as flame arresting passages that hinder a downward flow of flames through the openings
40
in the event that flammable vapor
80
passing upwardly through the openings
40
are ignited within the combustion chamber
18
.
To provide the combustion air inlet openings
40
, which representatively have circular cross-sections, with these two characteristics, their hydraulic or effective diameters and their passage lengths are selected in a manner such that upward air inlet flow through the openings
40
can occur with minimal pressure drop, but the openings
40
act to decrease downward flame propagation velocity therethrough in a manner extracting sufficient heat from such downwardly directed flames to quench them before they downwardly exit the openings
40
. In this manner, downward flame outflow through the bottom ends of the openings
40
, caused by ignition within the combustion chamber
18
of flammable vapor
80
upwardly entering the combustion chamber through the openings
40
, is hindered to thereby reduce the possibility of such ignition being spread to flammable vapor
80
externally adjacent the water heater
10
. Further details relating to the operation and representative sizing and spacing of the plate openings
40
may be found in the aforementioned U.S. Pat. No. 5,941,200 incorporated by reference herein.
While the flammable vapor sensor-based burner shutoff system of the present invention has been representatively illustrated and described herein as being incorporated in a fuel-fired water heater, it will be readily appreciated that it could alternatively be incorporated in a variety of other fuel-fired heating appliances, including but not limited to boilers and other fuel-fired heating devices such as fuel-fired heating furnaces, as well without departing from the principles of the present invention.
Additionally, while the water heater
10
has been representatively illustrated as being provided with the elevated external combustion air intake duct structure
58
to provide a time delay between the exposure of the sensor
76
to flammable vapor
80
and the potential entry of flammable vapor
80
into the combustion chamber
18
, those of skill in this particular art will appreciate that other techniques could be employed to elevate the water heater's combustion air intake location by the representative distance of from about six inches to about twenty inches relative to the flammable vapor sensor. For example, the external ductwork structure
58
could be eliminated, the sensor
76
could be disposed closely adjacent the floor
26
, and the support legs
24
vertically lengthened to elevate the plate structure
34
above the floor by the representative distance of from about six inches to about twenty inches.
The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.
Claims
- 1. Fuel-fired liquid heating apparatus comprising:a storage tank adapted to hold liquid to be heated and having a bottom portion; a combustion chamber positioned beneath said bottom portion; fuel burning apparatus operative to combust fuel and combustion air supplied thereto from sources thereof and create hot combustion products within said combustion chamber; a control system operative to shut down said fuel burning apparatus in response to receipt of a shutdown signal; a flue extending through the interior of said storage tank and communicating with the interior of said combustion chamber; a combustion air inlet passage for delivering combustion air to said fuel burning apparatus and having an inlet portion exposed to ambient air adjacent said fuel-fired liquid heating apparatus, combustion air being deliverable to said fuel burning apparatus only via said inlet portion and through said combustion air inlet passage; and a sensor disposed externally of said combustion air inlet passage, at an elevation lower than that of said inlet portion, and being operative to sense flammable vapor and responsively transmit said shutdown signal to said control system.
- 2. The fuel-fired liquid heating apparatus of claim 1 wherein said fuel-fired liquid heating apparatus is a fuel-fired water heater.
- 3. The fuel-fired liquid heating apparatus of claim 2 wherein said water heater is a gas-fired water heater.
- 4. The fuel-fired liquid heating apparatus of claim 2 wherein said fuel-fired water heater is a power vented water heater.
- 5. The fuel-fired liquid heating apparatus of claim 2 wherein said fuel-fired water heater is a natural draft water heater.
- 6. The fuel-fired liquid heating apparatus of claim 1 wherein said sensor is operative to sense hydrocarbon vapors.
- 7. The fuel-fired liquid heating apparatus of claim 1 wherein said combustion chamber has a perforated bottom side wall portion with openings therein through which combustion air may enter said combustion chamber.
- 8. The fuel-fired liquid heating apparatus of claim 7 wherein said openings are spaced and configured to (1) allow combustion air to flow upwardly through the openings with a pressure drop which is sufficiently low so as to not materially impede the combustion process of the fuel-fired liquid heating apparatus, and (2) act as flame arresting passages that hinder a downward flow of flames through the openings in the event that flammable vapor passing upwardly through the openings into the combustion chamber are ignited within the combustion chamber.
- 9. The fuel-fired liquid heating apparatus of claim 1 wherein said combustion air inlet passage is at least partially defined by an external wall structure having a vertical portion in which said inlet portion is disposed, and a horizontal portion extending beneath said combustion chamber and having an interior communicated with the interior of said combustion chamber.
- 10. The fuel-fired liquid heating apparatus of claim 9 wherein:said fuel-fired liquid heating apparatus has a lower end portion, said sensor is mounted on said lower end portion, and said inlet portion is elevated relative to said sensor.
- 11. A gas-fired water heater comprising:a tank adapted to hold a quantity of water; a combustion chamber disposed beneath said tank; a flue communicated with the interior of said combustion chamber and extending upwardly through the interior of said tank; a gas burner disposed within said combustion chamber and operable to receive gas from a source thereof and combust a gas/air mixture within said combustion chamber; a pilot device disposed within said combustion chamber and operatively associated with said gas burner; a control system operative to disable said gas burner and said pilot device in response to receipt of a shutdown signal; a combustion air inlet passage operative to deliver combustion air to said combustion chamber and having an inlet portion exposed to ambient air adjacent said gas-fired water heater, combustion air being deliverable to said combustion chamber only via said inlet portion and through said combustion air inlet passage; and a flammable vapor sensor disposed externally of said combustion air inlet passage, at an elevation lower than that of said inlet portion, and being operative to sense flammable vapor and responsively transmit said shutdown signal to said control system.
- 12. The gas-fired water heater of claim 11 wherein said gas-fired water heater is a power vented gas-fired water heater.
- 13. The gas-fired water heater of claim 11 wherein said gas-fired water heater is a natural draft gas-fired water heater.
- 14. The gas-fired water heater of claim 11 wherein said flammable vapor sensor is operative to sense hydrocarbon vapors.
- 15. The gas-fired water heater of claim 11 wherein said combustion chamber has a perforated bottom side wall portion with openings therein through which combustion air may enter said combustion chamber.
- 16. The gas-fired water heater of claim 15 wherein said openings are spaced and configured to (1) allow combustion air to flow upwardly through the openings with a pressure drop which is sufficiently low so as to not materially impede the combustion process of the gas-fired water heater, and (2) act as flame arresting passages that hinder a downward flow of flames through the openings in the event that flammable vapor passing upwardly through the openings into the combustion chamber are ignited within the combustion chamber.
- 17. The gas-fired water heater of claim 11 wherein said combustion air inlet passage is at least partially defined by an external wall structure having a vertical portion in which said inlet portion is disposed, and a horizontal portion extending beneath said combustion chamber and having an interior communicated with the interior of said combustion chamber.
- 18. The gas-fired water heater of claim 17 wherein:said fuel-fired liquid heating apparatus has a lower end portion, said flammable vapor sensor is mounted on said lower end portion, and said inlet portion is elevated relative to said flammable vapor sensor.
- 19. For use in conjunction with a fuel-fired heating device having a combustion chamber to which combustion air may be supplied, and fuel burning apparatus operative to combust fuel and combustion air supplied thereto from sources thereof and create hot combustion products in said combustion chamber, a method of inhibiting entry of flammable vapor into said combustion chamber, said method comprising the steps of:permitting delivery of combustion air to said combustion chamber only via a flow path having an inlet portion; disposing a flammable vapor sensor adjacent the device, said flammable vapor sensor being external to said flow path and useable to disable operation of said fuel burning apparatus in response to being exposed to flammable vapor; and creating a time delay between the detection of flammable vapor by said sensor and entry of flammable vapor into said flow path by elevating said inlet portion relative to said flammable vapor sensor.
- 20. The method of claim 19 wherein said disposing step is performed using a flammable vapor sensor operative to detect hydrocarbon vapor.
- 21. For use in conjunction with a fuel-fired heating device having a combustion chamber positioned at a lower portion thereof, and fuel burning apparatus operative to combust fuel and combustion air supplied thereto from sources thereof and create hot combustion products within said combustion chamber, a method of inhibiting entry of flammable vapor into said combustion chamber, said method comprising the steps of:supporting said fuel-fired heating device on a horizontal surface with said combustion chamber being elevated relative to the horizontal surface by a distance in the range of from about six inches to about twenty inches; and disposing a flammable vapor sensor exteriorly adjacent said heating device and substantially at the level of the horizontal surface, the sensor being operative to detect flammable vapor and responsively terminate operation of said fuel burning apparatus.
- 22. The method of claim 21 wherein said supporting step is performed in a manner such that said combustion chamber is elevated relative to the horizontal surface by a distance of about eighteen inches.
- 23. Fuel-fired heating apparatus comprising:a combustion chamber; fuel burning apparatus operative to combust fuel and combustion air supplied thereto from sources thereof and create hot combustion products within said combustion chamber; a control system operative to shut down said fuel burning apparatus in response to receipt of a shutdown signal; a combustion air inlet passage for delivering combustion air to said fuel burning apparatus and having an inlet portion exposed to a source of combustion air, combustion air being deliverable to said fuel burning apparatus only via said inlet portion and through said combustion air inlet passage; and a sensor disposed externally of said combustion air inlet passage, at an elevation lower than that of said inlet portion, and being operative to sense flammable vapor and responsively transmit said shutdown signal to said control system.
- 24. The fuel-fired heating apparatus of claim 23 wherein said fuel-fired heating apparatus is a fuel-fired water heater.
- 25. The fuel-fired heating apparatus of claim 24 wherein said water heater is a gas-fired water heater.
- 26. The fuel-fired heating apparatus of claim 24 wherein said fuel-fired water heater is a power vented water heater.
- 27. The fuel-fired heating apparatus of claim 24 wherein said fuel-fired water heater is a natural draft water heater.
- 28. The fuel-fired heating apparatus of claim 23 wherein said sensor is operative to sense hydrocarbon vapors.
- 29. The fuel-fired heating apparatus of claim 23 wherein said combustion chamber has a perforated bottom side wall portion with openings therein through which combustion air may enter said combustion chamber.
- 30. The fuel-fired heating apparatus of claim 29 wherein said openings are spaced and configured to (1) allow combustion air to flow upwardly through the openings with a pressure drop which is sufficiently low so as to not materially impede the combustion process of the fuel-fired liquid heating apparatus, and (2) act as flame arresting passages that hinder a downward flow of flames through the openings in the event that flammable vapor passing upwardly through the openings into the combustion chamber are ignited within the combustion chamber.
- 31. The fuel-fired heating apparatus of claim 23 wherein said combustion air inlet passage is at least partially defined by an external wall structure having a vertical portion in which inlet portion is disposed, and a horizontal portion extending beneath said combustion chamber and having an interior communicated with the interior of said combustion chamber.
- 32. The fuel-fired heating apparatus of claim 31 wherein:said fuel-fired heating apparatus has a lower end portion, said sensor is mounted on said lower end portion, and said inlet portion is elevated relative to said sensor.
- 33. Fuel-fired heating apparatus comprising:a fuel-fired heating appliance having a lower portion in which a combustion chamber is disposed, said combustion chamber having fuel burning apparatus operatively associated therewith, and a combustion air inlet opening; and an unenclosed flammable vapor sensor disposed substantially at said horizontal surface, coupled to said fuel-fired heating appliance, and operative to shut off said fuel burner apparatus in response to detecting flammable vapor, said combustion air inlet opening being spaced upwardly apart from said flammable vapor sensor.
- 34. The fuel-fired heating apparatus of claim 33 wherein said combustion air inlet opening is spaced upwardly apart from said flammable vapor sensor by a distance of from about six inches to about twenty inches.
- 35. The fuel-fired heating appliance of claim 34 wherein said combustion air inlet opening is spaced upwardly apart from said flammable vapor sensor by a distance of approximately eighteen inches.
- 36. The fuel-fired heating apparatus of claim 33 wherein said fuel-fired heating appliance is a fuel-fired water heater.
- 37. The fuel-fired heating appliance of claim 36 wherein said fuel-fired water heater is a gas-fired water heater.
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A |
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B1 |
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