Note: Descriptions are shown in the official language in which they were submitted.
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WATER HEATER WITH FORCED DRAFT AIR INLET
[0001] This application claims priority under 35 U.S.C. 120 to U.S. Patent
Application No.
11/865,378 filed October 1, 2007, the entire contents of which are
incorporated herein by
reference.
BACKGROUND
[0002] The present invention relates to a water heater having a forced draft
air inlet.
SUMMARY
[0003] In one embodiment, the invention provides a water heater comprising: a
tank for
water to be heated; a powered anode extending into the tank and creating an
electrical current to
reduce corrosion of the tank; a combustion chamber; an exhaust structure; a
flue in the tank
communicating between the combustion chamber and the exhaust structure; a
burner in the
combustion chamber operable to burn a mixture of primary combustion air with
gaseous fuel in a
partially premixed but substantially diffusion flame having an envelope, such
that combustion of
the mixture is completed at the diffusion flame envelope in the presence of
secondary air to
produce products of combustion, the products of combustion flowing through the
flue to the
exhaust structure to heat the water in the tank; a centrifugal blower forcing
primary and
secondary air into the combustion chamber at pressure above atmospheric; a gas
valve for
controlling a supply of gaseous fuel to the burner; a user interface for
programming operating
parameters of the water heater; and a 24 V controller that provides power to
the user interface
and powered anode, and that controls operation of the blower and gas valve.
[0004] In some embodiments, the water heater may include a pressure sensor
operatively
interconnected with the 24 V controller; wherein the pressure sensor generates
a signal in
response to sensing that the pressure of air downstream of the blower is below
a minimum
threshold; and wherein the 24 V controller closes the gas valve in response to
receiving the
signal from the pressure sensor. In some embodiments, the water heater may
include a
flammable vapor sensor operatively interconnected with the 24 V controller;
wherein the
flammable vapor sensor generates a signal in response to sensing the presence
of flammable
vapors outside of the water heater in concentrations above a maximum
threshold; and wherein
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the 24 V controller closes the gas valve in response to receiving the signal
from the flammable
vapor sensor. In some embodiments, the water heater may include a pressure
sensor sensing the
pressure of air downstream of the blower; and a flammable vapor sensor sensing
the presence of
flammable vapors outside of the water heater; wherein the 24 V controller
closes the gas valve
upon the occurrence of any of the following: (a) conditions dictated by the
user interface, (b) the
pressure sensor sensing air pressure below a minimum threshold, and (c) the
flammable vapor
sensor sensing flammable vapors external to the water heater in concentrations
above a
maximum threshold.
[00051 In another embodiment, the invention provides a water heater
comprising: a tank for
water to be heated; a combustion chamber; an exhaust structure; a flue in the
tank
communicating between the combustion chamber and the exhaust structure; a
burner in the
combustion chamber operable to burn a mixture of primary combustion air with
gaseous fuel in a
partially premixed but substantially diffusion flame having an envelope, such
that combustion of
the mixture is completed at the diffusion flame envelope in the presence of
secondary air to
produce products of combustion, the products of combustion flowing through the
flue to the
exhaust structure to heat the water in the tank; an air intake assembly
including an air inlet above
the combustion chamber and a conduit communicating between the air inlet and
the combustion
chamber; a centrifugal blower within the air intake assembly operable to suck
air into the air
intake assembly through the air inlet and force primary and secondary air into
the combustion
chamber through the conduit at pressure above atmospheric; a gas valve for
controlling a supply
of gaseous fuel to the burner; a controller that controls operation of the
blower and gas valve;
and a flammable vapor sensor external of the combustion chamber and lower than
the air inlet,
the flammable vapor sensor being operatively interconnected with the
controller and operable to
generate a signal in response to sensing the presence of flammable vapors
outside of the water
heater in concentrations above a maximum threshold; wherein all primary and
secondary
combustion air supplied to the combustion chamber flows through the air inlet
and conduit; and
wherein the controller closes the gas valve in response to receiving the
signal from the
flammable vapor sensor. In some embodiments, the flammable vapor sensor is
lower than at least
one of the combustion chamber and burner.
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[00061 In another embodiment, the invention provides a water heater
comprising: a tank for
water to be heated; a combustion chamber; an exhaust structure; a flue in the
tank
communicating between the combustion chamber and the exhaust structure; a
burner in the
combustion chamber operable to burn a mixture of primary combustion air with
gaseous fuel in a
partially premixed but substantially diffusion flame having an envelope, such
that combustion of
the mixture is completed at the diffusion flame envelope in the presence of
secondary air to
produce products of combustion, the products of combustion flowing through the
flue to the
exhaust structure to heat the water in the tank; an air intake assembly
including an air inlet above
the combustion chamber and a conduit communicating between the air inlet and
the combustion
chamber; a centrifugal blower within the air intake assembly operable to suck
air into the air
intake assembly through the air inlet and force primary and secondary air into
the combustion
chamber through the conduit at pressure above atmospheric; a gas valve for
controlling a supply
of gaseous fuel to the burner; a controller that controls operation of the
blower and gas valve;
and a baffle in the flue that restricts flow sufficiently to reduce the
pressure of the products of
combustion to near atmospheric upon flowing out of the flue into the exhaust
structure. In some
embodiments, the blower is an axial-intake, centrifugal blower. In some
embodiments, the
exhaust structure is a category I vent structure.
[0007] In another embodiment, the invention provides a water heater
comprising: a tank for
water to be heated; a combustion chamber; an exhaust structure; a flue in the
tank
communicating between the combustion chamber and the exhaust structure; a
burner in the
combustion chamber operable to burn a mixture of primary combustion air with
gaseous fuel in a
partially premixed but substantially diffusion flame having an envelope, such
that combustion of
the mixture is completed at the diffusion flame envelope in the presence of
secondary air to
produce products of combustion, the products of combustion flowing through the
flue to the
exhaust structure to heat the water in the tank; an air intake assembly
including an air inlet above
the combustion chamber and a conduit communicating between the air inlet and
the combustion
chamber; a centrifugal blower within the air intake assembly operable to suck
air into the air
intake assembly through the air inlet and force primary and secondary air into
the combustion
chamber through the conduit at pressure above atmospheric; a gas valve for
controlling a supply
of gaseous fuel to the burner; and a controller that controls operation of the
blower and gas
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valve; wherein the air intake assembly includes an interior space, all primary
and secondary air
being provided to the combustion chamber flowing through the interior space;
and wherein the
blower is mounted within the interior space of the air intake assembly.
[0008] In some embodiments, the blower is an axial-intake, centrifugal blower.
In some
embodiments, the air intake assembly includes a longitudinal extent; and the
air intake assembly
includes a two-piece construction divided along the longitudinal extent of the
air intake
assembly. In some embodiments, the interior space of the.air intake assembly
is non-cylindrical
and has an equivalent hydraulic diameter of a four inch inner diameter tube.
In some
embodiments, at least a portion of the interior space of the air intake
assembly is non-cylindrical
to accommodate mounting the blower in the interior space; and the non-
cylindrical portion of the
interior space defines a minor dimension and a major dimension that is
perpendicular to the
minor dimension and at least twice the minor dimension. In some embodiments,
the air intake
assembly includes a partition that divides the interior space into an inlet
side communicating
with ambient air and an outlet side communicating with the combustion chamber,
the partition
including a window; and the blower is within the inlet side of the interior
space and forces
primary and secondary air into the outlet side of the interior space through
the window in the
partition. In some embodiments, the air intake assembly includes a louvered
opening
communicating between the inlet side and ambient air; and all air sucked into
the inlet side of the
interior space by the blower flows through the louvered opening. In some
embodiments, the
water heater further comprises a pressure sensor communicating with the
interior space, the
pressure sensor operable to disable the gas valve to cut off the supply of
gaseous fuel to the
burner when pressure within the interior space drops below a minimum
threshold. In some
embodiments, the air intake assembly includes an exterior surface, a sensor
mounting cavity in
the exterior surface and a wire routing channel in the exterior surface; the
air intake assembly
further includes a hole communicating between the sensor mounting cavity and
the interior
space; the pressure sensor is mounted within the sensor mounting cavity and
communicates with
the interior space through the hole; and the blower includes a power cord that
is received in the
wire routing channel.
[0009] In another embodiment, the invention provides a water heater
comprising: a tank for
water to be heated; a combustion chamber; an exhaust structure; a flue in the
tank
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communicating between the combustion chamber and the exhaust structure; a
burner in the
combustion chamber operable to burn a mixture of primary combustion air with
gaseous fuel in a
partially premixed but substantially diffusion flame having an envelope, such
that combustion of
the mixture is completed at the diffusion flame envelope in the presence of
secondary air to
produce products of combustion, the products of combustion flowing through the
flue to the
exhaust structure to heat the water in the tank; an air intake assembly
including an air inlet above
the combustion chamber and a conduit communicating between the air inlet and
the combustion
chamber; a centrifugal blower within the air intake assembly operable to suck
air into the air
intake assembly through the air inlet and force primary and secondary air into
the combustion
chamber through the conduit at pressure above atmospheric; a gas valve for
controlling a supply
of gaseous fuel to the burner; a controller that controls operation of the
blower and gas valve; an
air distributor plate having a generally horizontal top surface defining a
plurality of edges, and a
bottom surface at least partially defining a secondary air distribution space
and a primary air
plenum; wherein all primary and secondary air flows into the respective
primary air plenum and
secondary air distribution space; wherein the air distributor plate defines a
primary air opening
for the provision of primary air from the primary air plenum to the burner;
and wherein the air
distributor plate includes a plurality of secondary air openings for
substantially axisymmetric
distribution of secondary air around the air distributor plate.
[0010] In some embodiments, the air distributor plate has first, second,
third, fourth, fifth,
and sixth edges; wherein the air distributor plate has generally vertical
surfaces extending from
the first, second, third, fourth, and fifth edges to at least partially define
the secondary air
distribution space; wherein the generally vertical surfaces define the
secondary air openings; and
wherein the substantially axisymmetric distribution includes secondary air
flow rates through the
plurality secondary air openings with standard deviation less than 0.88 from
average secondary
air flow rate. In some embodiments, the standard deviation is less than 0.10.
In some
embodiments, the standard deviation is about 0.08. In some embodiments, the
water heater
further comprises an air diverter secured to an edge of the air distributor
plate to direct all
primary and secondary combustion air from an air intake to the respective
primary air plenum
and secondary air distribution space. In some embodiments, the water heater
further comprises a
plenum pan mounted to a bottom surface of air distributor plate to at least
partially define the
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primary air plenum. In some embodiments, the plenum pan includes a plurality
of tabs; the
distributor plate includes a plurality of slots through which tabs extend; and
the tabs are bent
against the top surface of distributor plate to secure the plenum pan to the
bottom surface of the
distributor plate. In some embodiments, the distributor plate includes an
integral first locating
member, an integral burner locating member, an integral manifold pocket, and
an integral
manifold clearance indentation; wherein a portion of the burner mates with the
burner locating
member; the water heater further comprising a gas manifold for the provision
of gaseous fuel
from the gas valve to the burner, the manifold extending into the manifold
clearance indentation
during installation, and the manifold extending into the manifold pocket when
installed; and a
condensation tray including a first mating portion that mates with the first
locating member, and
a second mating portion that extends around the manifold pocket. In some
embodiments, the
distributor plate includes first and second locating members; the water heater
further comprising
a condensation tray having first and second clocking points that mate with the
respective first
and second locating members; wherein the condensation tray is secured to the
distributor plate
with a single threaded fastener in combination with mating of the first and
second clocking
points with the first and second locating members. In some embodiments, the
water heater
further comprises a condensation tray mounted in the combustion chamber;
wherein the burner
includes a condensate drain that directs condensation to the condensation
tray. In some
embodiments, the condensation tray has a containment capacity at least equal
to the volume of
condensate predicted during heavy condensation cold start of the water heater.
In some
embodiments, the condensation tray is dimensioned to cause a sufficient
surface area of
condensate in the condensation tray to be exposed to heat in the combustion
chamber to result in
total evaporation of the condensate upon the water heater reaching steady-
state combustion and
normal operation.
[0011] Other aspects of the invention will become apparent by consideration of
the detailed
description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Fig. 1 is a perspective view of a water heater embodying the present
invention.
[0013] Fig. 2 is an exploded view of the water heater.
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[0014] Fig. 3 is a cross-section view of the water heater taken along line 3-3
in Fig. 1.
[0015] Fig. 4 is an illustration of the control system and wiring of the water
heater.
[0016] Fig. 5 an exploded view of an air intake assembly of the water heater
from a first
perspective.
[0017] Fig. 6 is an exploded view of the air intake assembly from a second
perspective.
[0018] Fig. 7 is a cross-section view of the air intake assembly.
[0019] Fig. 8 is an exploded view of the combustion chamber assembly of the
water heater.
[0020] Fig. 9 is an exploded view of the combustion chamber assembly from a
second
perspective.
[0021] Fig. 10 is a perspective view of a partially assembled combustion
chamber assembly
with arrows indicating the flow of primary and secondary air.
DETAILED DESCRIPTION
[0022] Before any embodiments of the invention are explained in detail, it is
to be
understood that the invention is not limited in its application to the details
of construction and the
arrangement of components set forth in the following description or
illustrated in the following
drawings. The invention is capable of other embodiments and of being practiced
or of being
carried out in various ways.
[0023] Figs. 1-3 illustrate a water heater 10 that includes a tank 15 in which
water is heated
and stored, a combustion chamber assembly 20 supporting the tank 15, an air
intake assembly 25
through which combustion air is provided to the combustion chamber assembly
20, high
temperature insulation 30 surrounding the combustion chamber assembly 20, a
foam dam 32
above the high temperature insulation 30, and a jacket 35 surrounding the tank
15, high
temperature insulation 30, and foam dam 32. Foamed-in-place insulation is
introduced into an
annual space defined between the jacket 35 and tank 15, above the foam dam 32.
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[00241 The tank 15 includes a flue 40, a baffle 45 in the flue 40, an inlet
spud 50, an outlet
spud 55, an anode spud 60 or anode hole, a temperature probe hole 65, a drain
valve 70, and a
T&P valve 75 (i.e., temperature and pressure valve 75). Hot products of
combustion created in
the combustion chamber assembly 20 flow up from the combustion assembly
through the flue
40. As the products of combustion flow through the flue 40, heat is
transferred from the products
of combustion to the flue 40 wall and then to the water surrounding the flue
40. The baffle 45
restricts the flow of products of combustion through the flue 40, which
increases the time during
which the products of combustion dwell within the flue 40. Generally speaking,
an increase in
the dwell time also increases the amount of heat transferred from the products
of combustion to
the water in the tank 15 through the flue 40 wall. Also, the pressure of the
products of
combustion drops as the products of combustion flow through the restricted
flow path of the flue
40 and baffle 45 assembly.
[00251 There are many types, styles and designs for baffles, and the baffle 45
may be
removable from the flue 40 or permanently fixed within the flue 40 (as with
metallurgical
bonding such as brazing or welding, or with mechanical fasteners). In other
embodiments, the
baffle 45 may be integrally formed with the flue 40 wall. As will be discussed
in more detail
below, the baffle 45 restricts the flow of products of combustion such that
the products of
combustion are at atmospheric pressure or near atmospheric pressure when they
flow out of the
flue 40. As used in this disclosure, "near atmospheric" means a pressure of
exhaust that is within
a range for which a natural draft (e.g., Category I) vent structure or exhaust
structure (as
illustrated at 77) is suitable, even if such pressure of exhaust is above
atmospheric pressure.
[00261 A cold water pipe 80 is threadedly interconnected to the inlet spud 50
and a hot water
pipe 85 is threadedly interconnected to the outlet spud 55. A dip tube 90 is
threaded or otherwise
fit within the inlet spud 50. As hot water is drawn from the tank 15 through
the hot water pipe
85, cold water flows into the bottom of the tank 15 through the cold water
pipe 80 and dip tube
90. A powered anode 95 (Fig. 4) is threaded or otherwise secured into the
anode spud 60. The
powered anode 95 generates current which reduces the rate of tank 15 corrosion
or eliminates
tank 15 corrosion altogether. The drain valve 70 permits draining of water
from the tank 15
during servicing, and the T&P valve 75 permits pressure to be released from
the tank 15 in the
event of high pressure within the tank 15 resulting from overheating of the
water.
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[0027] With additional reference to Fig. 4, the water heater 10 also has a
control system 100,
which includes a controller 105, a gas valve 115, a user interface 120, a
pressure sensor 125
having a pressure tap 126 (Fig. 5), a FV sensor 130 (i.e., a flammable vapor
sensor), a hot
surface igniter 135, and a flame sensor 140. The controller 105 in the
illustrated embodiment is a
24V controller 105 (i.e., 24 Volt controller) which is powered by a 24 Volt
power supply which
may be provided, for example, by a transformer 150 that is plugged into a
standard voltage
outlet. The controller 105 includes a processor for receiving inputs from the
sensors 125, 130,
140 and user interface 120, and monitoring and controlling operation of the
water heater 10.
[0028] A powered anode wire 160 interconnects the controller 105 and the
powered anode
95 for the provision of power to the powered anode 95. Power and/or
communications (as
necessary for functionality) between the controller 105 and the other control
system 100
components are provided by way of a user interface wire 165, a pressure sensor
wire 170, a FV
sensor wire 175, an igniter wire 180, and a flame sensor wire 185. Wireless
communication
between the controller 105 and one or more of these components is possible for
other
embodiments.
[0029] In the illustrated embodiment, the gas valve 115 and controller 105 are
integrated into
a single unit, but in other embodiments the gas valve 115 and controller 105
may be separate
units with a suitable wired and/or wireless connection. The gas valve 115
includes a temperature
probe 190 that extends into the water in the tank 15 through the probe hole
65. The gas valve 115
receives a supply of gaseous fuel (e.g., natural gas) from a source of gaseous
fuel, through a
hook-up line 200. A supply line 205 delivers the gaseous fuel from the gas
valve 115 to the
combustion chamber assembly 20 to create the products of combustion discussed
above. The
user interface 120 permits the operator or user of the water heater 10 to
program operating
parameters, such as target water temperature and vacation settings.
[0030] The air intake assembly 25 is illustrated in Figs. 5-7. The air intake
assembly 25
includes a shell 220 having a first piece 225, a second piece 230, a partition
235, and a blower
240. The first piece 225 includes a pressure sensor cavity 250 formed in its
exterior surface
(which faces the water heater 10). A central hole 251 in the pressure sensor
cavity 250
communicates between the sensor mounting cavity and the interior space of the
air intake
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assembly 25. The pressure tap 126 of the pressure sensor 125 extends through
the central hole
251. The first piece 225 also includes a power cord channel 255 or wire
routing channel in its
exterior surface. The first piece 225 also defines an elbow 260 which
interconnects to the
combustion chamber assembly 20. The first piece 225 also includes mounting
flanges 265 to
accommodate fasteners 270 that secure the air intake assembly 25 to the jacket
35. Mounted to
the second piece 230 is air inlet 280, which in the illustrated embodiment is
a plate with a
louvered window. In other embodiments, the air inlet 280 may be formed
integrally with the
second piece 230. All combustion air for the water heater 10 flows into the
water heater 10
through the air inlet 280.
[00311 To achieve a high quality, attractive shell 220, it is preferable to
form the first piece
225 and second piece 230 by injection molding, but the shell 220 may be
alternatively
constructed as a single, integrally-formed part through blow molding. The
first piece 225 and
second piece 230 are interconnected with adhesive or another suitable joining
process along a
joining line or interface extending generally along a longitudinal extent of
the air intake
assembly 25 (i.e., a vertical interface). A gasket 285 is captured between the
edges of the first
piece 225 and second piece 230 at the interface to create a substantially air
tight seal. The
surfaces of the first piece 225 and second piece 230 that face each other are
referred to as their
internal surfaces.
100321 The internal surfaces define an interior space 290 of the air intake
assembly 25.
Although the interior space 290 (or the shell 220 generally) is non-
cylindrical, the geometry of
the internal surfaces is designed to give the overall air intake assembly 25 a
hydraulic
functionality equivalent to a cylindrical conduit or tube of standard size
(e.g., the air intake
assembly 25, although non-cylindrical in shape, functions equivalently to a
standard 4 inch inner
diameter PVC conduit). Thus, the air intake assembly 25 achieves the same
hydraulic
performance as a standard cylindrical conduit, but with a more aesthetically
pleasing non-
cylindrical shape. The interior space 290 defines a minor dimension and a
major dimension (both
perpendicular to the longitudinal extent and each perpendicular to the other).
The major
dimension may be, for example, at least twice the minor dimension. It is
possible to construct the
intake assembly 25 such that only a portion of the interior space 290 is non-
cylindrical.
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(0033] The partition 235 is generally flat and includes a partition window
295. The partition
235 is mounted to one or both of the internal surfaces of the first piece 225
and second piece 230.
The partition 235 divides the interior space 290 of the air intake assembly 25
into an inlet side
297 and an outlet side 298. The inlet side 297 is above the partition 235 and
communicates with
ambient air (i.e., air surrounding the water heater 10) through the air inlet
280. The outlet side
298 is below the partition 235 and communicates with the combustion chamber
assembly 20
through the elbow 260. The partition 235 reduces or eliminates recycling of
air from the outlet
side 298 back into the blower 240.The blower 240 is mounted within the inlet
side 297 of the
interior space 290. The non-cylindrical shape of the inlet side 297
accommodates the shape and
size of the blower 240. In the illustrated embodiment, the blower 240 is an
axial inflow,
centrifugal blower. In the illustrated embodiment, the blower 240 is of
relatively small size,
producing less than about 15CFM ("cubic feet per minute") of airflow with a
maximum static
pressure head or pressure rating of less than 2 inches water column or in some
embodiments a
fraction of 1 inch of water column. This is in comparison to blowers for known
power burners
which are multiple times larger than blower 240. For example, in a known
residential 120,000
Btu/hr power burner application, the associated blower has a mid-range
operating airflow rate of
about 80CFM to 140CFM. Known power burner models of above 120,000 Btu/hr
employ a
blower that operates at 160CFM and above. Static pressure head of such power
burners (i.e., the
above-mentioned 120,000Btu/hr power burner and those above 120,000Btu/hr) is
on the order of
I 1 inches water column. Commercial water heater power burners have even
higher airflow rates
and static pressure ratings than the models described above.
100341 In other embodiments, the blower 240 could be an axial fan or other air
moving
device that achieves the basic functionality of sucking ambient air into the
inlet side 297 through
the air inlet 280 and forcing the air into the outlet side 298 and combustion
chamber assembly 20
at pressures above atmospheric pressure. The term "pressurized," as used
throughout this
disclosure means at a pressure higher than atmospheric pressure. The blades of
the blower 240
are of a known design referred to as a "squirrel cage," and the blower 240
includes a volute
casing 300. The pressure of the air rises as it is forced through the volute
casing 300. The blower
inlet communicates with the air inlet 280 and the blower outlet communicates
with the partition
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window 295. A blower wire 305 or power cord communicates between the pressure
sensor 125
and the blower 240 and is received in the power cord channel 255.
[0035] With reference to Figs. 3 and 7, the blower 240 sucks ambient air
through the air inlet
280 into the inlet side 297 at atmospheric pressure, raises the pressure of
the air above
atmospheric, and forces the pressurized air into the outlet side 298 through
the partition window
295. In this regard, the inlet side 297 may be referred to as the low pressure
side of the interior
space 290 and the outlet side 298 may be referred to as the high pressure
side. Also, the
illustrated water heater 10 may be termed a forced draft water heater because
combustion air is
pressurized in the combustion chamber, and products of combustion are forced
up the flue 40
under the influence of positive pressure at the air inlet assembly. This is
contrasted with an
induced draft water heater 10 in which a blower at the top of the flue 40
draws the products of
combustion up the flue 40 by creating a low pressure region at the top of the
flue 40 (i.e., at the
inlet to the blower) and a high pressure region at the outlet of the blower.
[0036] Turning now to Figs. 8-10, the combustion chamber assembly 20 includes
a stand
310, a bottom plate 315, a skirt 320, a burner-door assembly 325, an air
diverter 330, an air
distributor plate 335, a primary air pan 340, and a condensation tray or
condensation pan 345.
The bottom plate 315 rests on the stand 310 and is joined to the skirt 320 by
a folding or other
metal joining method. The skirt 320 extends upwardly from the bottom plate
315, and supports
the bottom of the water tank 15. A combustion chamber 347 (Fig. 10) is defined
by the bottom
plate 315, skirt 320, and bottom of the tank 15. In the illustrated
embodiment, the combustion
chamber 347 is below the water in the water tank 15, and is not a submerged
combustion
chamber which is surrounded by water. The stand 310 elevates the combustion
chamber
assembly 20 from the floor or surface on which the water heater 10 stands, to
reduce
temperatures to which the floor is exposed during operation of the water
heater 10.
[0037] The skirt 320 includes an opening 350 and an inlet fitting 352. An
inlet gasket 353
fits snuggly over the inlet fitting 352, and also fits snuggly within the
elbow 260 of the air intake
assembly 25. The inlet gasket 353 creates a substantially airtight seal
between the air intake
assembly 25 and the combustion chamber assembly 20 so that substantially all
high pressure air
flowing from the air intake assembly 25 is delivered to the combustion chamber
assembly 20 and
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does not leak to the surrounding environment. The air inlet 280 is above the
combustion chamber
347. The air intake assembly 25 functions as a conduit between the air inlet
280 and the
combustion chamber 347.
[0038] The burner-door assembly 325 includes a door 355 that fits over the
opening 350 in
the skirt 320. In the final assembly, a shield 357 (Fig. 1) is mounted to the
jacket 35 and covers
the portions of the burner-door assembly 325 that are exterior of the skirt
320. The burner-door
assembly 325 also includes a gas manifold 360 (Fig. 9) attached to the door
355 and
communicating with the gas supply line 205 through the door 355. The igniter
wire 180 and
flame sensor wire 185 pass through the door 355 and are surrounded by a
grommet 363 or the
like for a substantially air-tight seal between the wires and the door 355. In
other embodiments,
the burner-door assembly 325 may be of the type described and illustrated in
U.S. Patent
Application No. 12/431,525 filed April 28, 2009, the entire contents of which
is incorporated
into this disclosure by reference.
[0039] The burner-door assembly 325 also includes an air duct 365 supported by
the gas
manifold 360, a burner 370 supported by the air duct 365, and a mounting
bracket 375 on the gas
manifold 360. Gaseous fuel from the gas manifold 360 is mixed with primary air
in the air duct
365 to form a partially premixed combustible mixture, and the combustible
mixture is burned by
the burner 370, as will be discussed in more detail below. The mounting
bracket 375 supports the
hot surface igniter 135 and flame sensor 140 near the burner 370 so that the
combustible mixture
can be ignited and monitored.
[0040] The burner 370 includes a condensation drain hole 380. Condensate that
pools on the
burner 370 drains through the condensate drain hole 380 to the condensation
pan 345. This can
occur, for example, during a cold start of the water heater 10. Condensation
that collects in the
condensation pan 345 evaporates and is exhausted through the flue 40 with
products of
combustion when the water heater 10 is operating at steady state. More
specifically, the
condensation pan 345 is dimensioned to cause a sufficient surface area of
condensate in the
condensation pan 345 to be exposed to heat in the combustion chamber 347 to
result in total
evaporation of the condensate upon the water heater reaching steady-steate
combustion and
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normal operation. The condensation pan 345 should be of a size sufficient to
pass heavy
condensation tests.
[0041] The air distributor plate 335 is designed to evenly distribute
secondary air in the
combustion chamber 347 to promote even combustion at the burner 370. The air
distributor plate
335 includes a top surface 410 and a bottom surface 415 that are generally
planar and horizontal.
In the illustrated embodiment, the air distributor plate 335 includes a first
edge 421, a second
edge 422, a third edge 423, a fourth edge 424, a fifth edge 425, and a sixth
edge 426, all of equal
length and at equal angles, and in this regard may be termed a "hex plate" due
to its hexagonal
shape. Depending from the first edge 421, second edge 422, third edge. 423,
fourth edge 424,
fifth edge 425, and sixth edge 426 is a respective first side wall 431, second
side wall 432, third
side wall 433, fourth side wall 434, fifth side wall 435, and sixth side wall
436. These side walls
431-436 define generally vertical surfaces. Formed in these respective side
walls are a first
opening 441, second opening 442, third opening 443, fourth opening 444, fifth
opening 445, and
sixth opening 446. The first-fifth openings 441-445 may collectively be
referred to as "secondary
air openings" and are at least partially defined by the generally vertical
surfaces.
[0042] The first side wall 431 includes a portion that extends from the first
edge 421 to the
bottom plate 315, and another portion that extends only partially (e.g.,
halfway) from the first
edge 421 toward the bottom plate 315. The first side wall 431 does not extend
the entire length
of the first edge 421. Consequently, the first opening 441 includes a portion
that extends fully
between the first edge 421 to the bottom plate 315, and another portion that
extends only
partially from the bottom plate 315 toward the first edge 421 (i.e., the space
between the bottom
plate 315 and the short portion of the first side wall 431).
[0043] The third side wall 433 is actually divided into roughly equal portions
on either side
of the third opening 443, such that the third opening 443 is roughly centered
with respect to the
third edge 423. The fifth opening 445 is defined at opposite ends of the fifth
side wall 435. The
sixth side wall 436 is actually two relatively small wall portions or tabs at
opposite ends of the
sixth edge 426, such that the sixth opening 446 is relatively large and
centered with respect to the
sixth edge 426.
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[0044] The air diverter 330 includes a lip 450 and feet 455. The feet 455 sit
on and are
mounted with fasteners to the bottom plate 315, and the lip 450 extends along
the top surface 410
of the air distributor plate 335 along the sixth edge 426 over the sixth
opening 446. Side walls of
the air diverter 330 extending from opposite ends of the lip 450 down to the
feet 455 are
positioned along the sixth side wall 436 portions at opposite ends of the
sixth opening 446.
Consequently, the air diverter 330 surrounds the sixth opening 446, and places
the inlet fitting
352 and sixth opening 446 in communication. Substantially all combustion air
flowing at
elevated pressure from the air intake assembly 25 is diverted downwardly by
the air diverter 330,
through the sixth opening 446 and under the air distributor plate 335.
[0045] Formed in the air distributor plate 335 are a three slots 460 that
accept three tabs 465
of the primary air pan 340. The tabs 465 are extended up through the slots 460
and bent over to
secure the primary air pan 340 to the bottom surface 415 of the air
distributor plate 335. The air
distributor plate 335 is mounted to the bottom plate 315 with three fasteners
470. A primary air
plenum is defined between the primary air pan 340 and the bottom surface 415
of the air
distributor plate 335, and a secondary air plenum or secondary air
distribution space is defined
by the space that surrounds the primary air pan 340 between the bottom surface
415 of the air
distributor plate 335 and the bottom plate 315.
[0046] The air distributor plate 335 also includes an integral first locating
member 485, an
integral burner locating member 490, an integral manifold pocket 495, and an
integral manifold
clearance indentation 500. The first locating member 485 is in the form of a
concave bump or
boss in the top surface 410 of the air distributor plate 335. The first
locating member 485 and
integral manifold pocket 495 define two clocking points for mounting the
condensation pan 345
to the air distributor plate 335. More specifically, the condensation pan 345
includes a first
mating portion and a second mating portion that receive the respective first
locating member 485
and the integral manifold pocket 495. This ensures that the condensation pan
345 is positioned
properly to receive condensation that drains from the burner 370. With the
first locating member
and integral manifold pocket 495 received in indentations in the condensation
pan 345, a single
threaded fastener 510 may be used to secure the condensation pan 345 to the
air distributor plate
335.
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[0047] The burner locating member 490 is in the form of a raised trapezoidal
base in the top
surface 410 and a primary air hole 515. The a primary air opening or primary
air hole 515
communicates with the primary air plenum. The air duct 365 of the burner-door
assembly 325
fits snuggly around the raised trapezoidal base of the burner 370 locating
member, such that
substantially all primary air flowing through the primary air hole 515 from
the primary air
plenum flows into the air duct 365 for eventual delivery to the burner 370. In
other embodiments,
the base of the burner locating member 490 can be other shapes, but it
preferably will snuggly
receive the bottom edge of the air duct 365 to ensure that the air duct 365
receives substantially
all primary air flowing out of the primary air plenum and primary air hole
515.
[0048] The manifold pocket 495 is a convex (with respect to the top surface
410)
deformation with an opening 520 at one end. The manifold pocket 495 receives a
distal end of
the gas manifold 360 to secure the manifold with respect to the combustion
chamber 347. The
manifold clearance indentation 500 is a concave (with respect to the top
surface 410)
deformation that permits the burner-door assembly 325 to be inserted into the
opening 350 in the
skirt 320 at an angle and then tilted into the operable position without the
gas manifold 360
bumping into the top surface 410 of the air distributor plate 335.
[0049] In operation, the controller 105 monitors water temperature with the
temperature
probe 190 and controls the temperature of water within the tank 15 based on
the settings input by
an operator through the user interface 120. When water temperature drops below
a low-end set
point (e.g., due to standby heat loss or during a draw of hot water from the
tank 15 and the
resultant introduction of cold water into the tank 15 through the dip tube
90), the controller 105
engages the blower 240. When operating properly, the blower 240 creates high
pressure in the
outlet side 298 of the air intake assembly 25. The high pressure is sensed by
the pressure sensor
125 through the pressure tap 126, and a signal is sent to the controller 105
confirming that the
blower 240 is operating properly.
[0050] The high pressure air from the air intake assembly 25 is forced into
the combustion
assembly through the inlet fitting 3352 on the skirt 320. The air diverter 330
directs the high
pressure air into the primary air plenum and secondary air plenum under the
air distributor plate
335. The flow of high pressure air into the primary air plenum is subsonic,
which results in
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feedback waves through the air particles to the air diverter 330. The feedback
waves result in a
balance of high pressure air flowing into the primary air plenum and secondary
air plenum, and
avoid an undesirable amount of high pressure air flowing into the primary air
plenum at the
expense of air supply to the secondary air plenum. The pressurized primary air
flows from the
primary air plenum up through the primary air hole 515, and into the air duct
365 of the burner-
door assembly 325.
[00511 Once the controller 105 has confirmed that the blower 240 is operating
properly, the
controller 105 provides power (i.e., electrical current) to the hot surface
igniter 135, to cause the
hot surface igniter 135 to achieve a temperature sufficient to ignite a fuel-
air mixture. The
controller 105 determines that the hot surface igniter 135 has achieved such
temperature by
known means, or assumes that the hot surface igniter 135 has achieved such
temperature after the
passage of sufficient time.
[00521 Once the controller 105 has confirmed that the blower 240 is operating
properly and
the hot surface igniter 135 is at an appropriate temperature to ignite a fuel-
air mixture, the
controller 105 opens the gas valve 115 to permit gaseous fuel to flow from the
gas hook-up line
200, through the gas valve 115, to the gas supply line 205, and to the gas
manifold 360. The
gaseous fuel flows out of the gas manifold 360 into the air duct 365, where it
mixes with
pressurized primary air to create a pressurized (above atmospheric pressure)
partially premixed
fuel-air mixture. The fuel-air mixture flows from the air duct 365 into the
burner 370.
[00531 The illustrated burner 370 is a pancake style burner 370 having burner
orifices around
its perimeter. The illustrated burner 370 is in the combustion chamber 347 and
is below the water
tank 15, and may be termed an "upwardly firing" burner because products of
combustion rise
upwardly from the burner 370. The fuel-air mixture flows out of the burner
orifices and is ignited
by the hot surface igniter 135 to create a ring of flame around the burner
370. The flame sensor
140 confirms to the controller 105 that the flame is present on the burner
370. The flame created
by the burner 370 combusting the primary air and fuel mixture is a partially
premixed but
substantially diffusion flame having an envelope. Combustion of the diffusion
flame is
completed within the diffusion flame envelope in the presence of secondary
air.
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[0054] The partially premixed, diffusion flame produced by the burner 370 in
the present
invention includes a fuel-rich core that is surrounded by a flame envelope
into which secondary
air is diffused to complete combustion and lower NOx emissions. The core
region includes
insufficient air to complete combustion of the fuel, which is why the
diffusion flame is referred
to as "partially" premixed. The diffusion flame front consequently propagates
from the flame
envelope inward to complete the combustion of the core region with the help of
the secondary
air. The majority of air required for complete combustion and reduced NOx is
added at the flame
envelope in the form of secondary air.
[0055] The partially premixed diffusion flame of the present invention is
distinguished from
the flame created by fully premixed power burners. Fully premixed power
burners include
sufficient air in the air/fuel premixture to support full combusion of the
fuel and low NOx
emissions. Indeed, in most power burner applications, the blower that is part
of the power burner
is pushing more air than is required for complete combustion because the
blower is also required
to force the products of combustion out the flue at elevated pressure for the
purpose of direct
venting or utilization of the products of combustion for another purpose
(e.g., space heating)
downstream of the water heater. The blower in a power burner is typically much
larger than the
blower contemplated by the present invention, in terms of airflow (measured in
CFM) and static
pressure head (measured in inches of water column) as discussed above.
[0056] Secondary air collects in the secondary air plenum under the air
distributor plate 335.
The secondary air is pressurized (i.e., above atmospheric pressure) and flows
out of the
secondary air plenum through the first opening 441, second opening 442, third
opening 443,
fourth opening 444, and fifth opening 445. The openings 441-445 are sized and
spaced to create
substantially axisymmetric distribution of secondary air flowing out of the
secondary air plenum
and into the combustion chamber 347 around the burner 370. The air distributor
plate 335 and
openings 441-445 create a substantially uniform supply of secondary air to the
combustion
chamber 347. Uniform airflow out of the secondary air plenum reduces potential
surface/floor
temperature issues and also gives rise to improved combustion. A design that
minimizes standard
deviation of air flow rates from the average secondary air flow rate for the
openings 441-445 is
desirable for improving combustion. The combined size and geometry of the
primary plenum
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and air distributor plate 335 can achieve standard deviations of less than
1.35, with standard
deviations reaching 0.88 and as low as 0.08 in some embodiments.
[0057] To summarize the air flow and combustion process, pressurized
combustion air flows
under the air distributor plate 335 from the air diverter 330 through the
sixth opening 446 at one
side of the air distributor plate 335. The pressurized combustion air is
divided into primary air,
which flows into the primary air plenum, and secondary air, which flows into
the secondary air
plenum. Both the primary air and secondary air are pressurized due to the
blower 240 forcing the
air into the combustion chamber 347. The primary air is mixed with gaseous
fuel and is ignited at
the perimeter of the burner 370 to create a diffusion flame. The secondary
air, despite entering
the secondary air plenum from the sixth side of the air distributor plate 335,
is substantially
evenly distributed through the first through fifth openings 441-445 due to the
size, shape, and
position of the openings 441-445. The high pressure secondary air flows around
the sides of the
air distributor plate 335 and completes combustion of the fuel-air mixture
within the envelope of
the diffusion flame.
[0058] Combustion of the fuel-air mixture at the diffusion flame creates
products of
combustion. The blower 240 pressurizes the entire combustion chamber 347 to a
pressure higher
than atmospheric, and the products of combustion also have natural buoyancy
owing to their
high temperature. As a result, the products of combustion rise and are forced
into the flue 40.
The products of combustion transfer heat to the baffle 45 and flue 40, which
in turn transfer heat
to the water. The burner 370 continues to generate products of combustion as
discussed above,
until the temperature probe 190 senses that the water temperature has reached
the desired set
point or high-end set point (as programmed at the user interface 120).
[0059] The flow of the products of combustion is restricted as they flow up
through the flue
40 by the restricted flow path caused by the baffle 45. The products of
combustion lose pressure
as they flow from the flue inlet end (lower end of the flue 40 communicating
with the
combustion chamber 347) to the flue outlet end (upper end of the flue 40
communicating with
the venting structure 77). The blower 240 is sized to create a known pressure
(also called head
pressure or head) in the combustion chamber 347. Given the known pressure in
the combustion
chamber 347, the flue 40 and baffle 45 are designed to reduce pressure in the
products of
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combustion to near atmospheric at the flue outlet to permit the water heater
10 to benefit from a
pressurized diffusion flame in the combustion chamber 347, a restricted flow
flue 40 and baffle
45 assembly to increase dwell time of the products of combustion, and a
Category I atmospheric
venting configuration.
[0060] The FV sensor 130 is positioned external of the combustion chamber
assembly 20,
relatively low or close to ground level because flammable vapors tend to be
heavier than air and
would typically collect close to ground level. The FV sensor 130 is lower than
the air inlet 280,
and in the illustrated embodiment is lower than the burner 370 and combustion
chamber 347. If
during the operation of the water heater 10, the FV sensor 130 senses the
presence of flammable
vapors outside of the water heater 10 in concentrations above a maximum
threshold, the FV
sensor 130 generates a signal to the controller 105 and the controller 105 can
shut down
operation of the water heater 10 by closing the gas valve 115. Elevating the
air inlet with respect
to the FV sensor 130 increases the likelihood that the FV sensor 130 will
sense the presence of
the flammable vapors and the controller 105 will shut down the gas valve 115
prior to the
flammable vapors being entrained in the incoming combustion air and reaching
the burner 370.
In view of the FV sensor 130 and the functionality described above, the water
heater 10 of the
present invention is deemed a flammable vapor ignition resistant ("FVIR")
water heater.
[0061] Similarly, if the pressure sensor 125 senses that the pressure of air
downstream of the
blower 240 (i.e., in the outlet side 298) is below a minimum threshold, the
pressure sensor 125
generates a signal to the controller 105 and the controller 105 can shut down
operation of the
water heater 10 by closing the gas valve 115. Likewise, if the flame sensor
140 fails to sense the
presence of a flame at the burner 370, the flame sensor 140 generates a signal
to the controller
105 to shut down operation of the water heater 10. In all cases, the
generation of a signal can
include the cessation of a signal or the changing of a signal.
[0062] Thus, the invention provides, among other things, a water heater
including a 24 volt
controller to control various powered aspects of the water heater, a water
heater, a sealed
combustion chamber water heater with a FV sensor lower than the air inlet for
the combustion
chamber; a forced-draft water heater having a blower in the air inlet and a
baffle in the flue such
that combustion occurs at elevated pressure but pressure of products of
combustion drop to near
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atmospheric at the outlet end of the flue; a water heater having an air intake
assembly having an
internally-mounted blower mounted inside; and a water heater having an air
distributor plate for
substantially axisymmetric distribution of secondary air in the combustion
chamber. Various
features and advantages of the invention are set forth in the following
claims.
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