U.S. patent application number 12/545582 was filed with the patent office on 2009-12-17 for water heater with forced draft air inlet.
Invention is credited to Emadeddin Y. Tanbour.
Application Number | 20090308332 12/545582 |
Document ID | / |
Family ID | 41413601 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090308332 |
Kind Code |
A1 |
Tanbour; Emadeddin Y. |
December 17, 2009 |
WATER HEATER WITH FORCED DRAFT AIR INLET
Abstract
A water heater includes an air intake assembly that includes a
blower for providing primary and secondary air to a combustion
chamber at pressures above atmospheric pressure. The primary air is
mixed with gaseous fuel and the mixture is combusted at a burner in
a partially premixed but substantially diffusion flame having an
envelope. Combustion of the mixture is completed within the
envelope in the presence of secondary air at elevated pressure. A
24 V controller provides power to a user interface and a powered
anode in the tank. The controller receives input from a pressure
sensor in the air intake assembly, a flame sensor in the combustion
chamber, and a flammable vapor sensor outside the water heater. The
controller controls operation of the blower and a gas valve. A flue
and baffle arrangement in the tank causes products of combustion
from the burner to lose pressure and vent at near atmospheric
pressure at the top of the flue. An air distributor plate creates a
substantially uniform distribution of pressurized secondary air
within the combustion chamber.
Inventors: |
Tanbour; Emadeddin Y.;
(Johnson City, TN) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
100 E WISCONSIN AVENUE, Suite 3300
MILWAUKEE
WI
53202
US
|
Family ID: |
41413601 |
Appl. No.: |
12/545582 |
Filed: |
August 21, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11865378 |
Oct 1, 2007 |
|
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12545582 |
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Current U.S.
Class: |
122/14.2 ;
122/19.2 |
Current CPC
Class: |
F24H 1/205 20130101;
F24H 9/14 20130101; F24H 9/148 20130101; F23C 7/02 20130101; F24H
9/0026 20130101 |
Class at
Publication: |
122/14.2 ;
122/19.2 |
International
Class: |
F24H 9/20 20060101
F24H009/20; F24H 9/02 20060101 F24H009/02 |
Claims
1. 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.
2. The water heater of claim 1, further comprising 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.
3. The water heater of claim 1, further comprising 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 the
24 V controller closes the gas valve in response to receiving the
signal from the flammable vapor sensor.
4. The water heater of claim 1, further comprising 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.
5. 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.
6. The water heater of claim 5, wherein the flammable vapor sensor
is lower than at least one of the combustion chamber and
burner.
7. 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.
8. The water heater of claim 7, wherein the blower is an
axial-intake, centrifugal blower.
9. The water heater of claim 7, wherein the exhaust structure is a
category I vent structure.
10. 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 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.
11. The water heater of claim 10, wherein the blower is an
axial-intake, centrifugal blower.
12. The water heater of claim 10, wherein the air intake assembly
includes a longitudinal extent; and wherein the air intake assembly
includes a two-piece construction divided along the longitudinal
extent of the air intake assembly.
13. The water heater of claim 10, wherein the interior space of the
air intake assembly is non-cylindrical and has an equivalent
hydraulic diameter of a four inch inner diameter tube.
14. The water heater of claim 10, wherein 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 wherein
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.
15. The water heater of claim 10, wherein 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 wherein 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.
16. The water heater of claim 15, wherein the air intake assembly
includes a louvered opening communicating between the inlet side
and ambient air; and wherein all air sucked into the inlet side of
the interior space by the blower flows through the louvered
opening.
17. The water heater of claim 10, further comprising 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.
18. The water heater of claim 17, wherein 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; wherein the air intake assembly further includes a hole
communicating between the sensor mounting cavity and the interior
space; wherein the pressure sensor is mounted within the sensor
mounting cavity and communicates with the interior space through
the hole; and wherein the blower includes a power cord that is
received in the wire routing channel.
19. 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; 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.
20. The water heater of claim 19, wherein 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.
21. The water heater of claim 20, wherein the standard deviation is
less than 0.10.
22. The water heater of claim 20, wherein the standard deviation is
about 0.08.
23. The water heater of claim 19, further comprising 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.
24. The water heater of claim 19, further comprising a plenum pan
mounted to a bottom surface of air distributor plate to at least
partially define the primary air plenum.
25. The water heater of claim 24, wherein the plenum pan includes a
plurality of tabs; wherein the distributor plate includes a
plurality of slots through which tabs extend; and wherein the tabs
are bent against the top surface of distributor plate to secure the
plenum pan to the bottom surface of the distributor plate.
26. The water heater of claim 19, wherein 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.
27. The water heater of claim 19, wherein 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.
28. The water heater of claim 19, further comprising a condensation
tray mounted in the combustion chamber; wherein the burner includes
a condensate drain that directs condensation to the condensation
tray.
29. The water heater of claim 28, wherein 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.
30. The water heater of claim 28, wherein 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.
Description
[0001] This application claims priority under 35 U.S.C. 120 to U.S.
patent application Ser. No. 11/865,378 filed Oct. 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 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.
[0005] 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.
[0006] 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 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 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 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.
[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.
[0024] 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.
[0025] 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.
[0026] 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.
[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
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.
[0031] 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.
[0032] 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.
[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 15 CFM ("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 80 CFM to 140 CFM. Known power burner models
of above 120,000 Btu/hr employ a blower that operates at 160 CFM
and above. Static pressure head of such power burners (i.e., the
above-mentioned 120,000 Btu/hr power burner and those above 120,000
Btu/hr) is on the order of 11 inches water column. Commercial water
heater power burners have even higher airflow rates and static
pressure ratings than the models described above.
[0034] 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 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 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 Ser. No.
12/431,525 filed Apr. 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 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.
[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.
[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 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.
[0051] 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.
[0052] 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.
[0053] 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.
[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 combustion 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
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
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 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.
* * * * *