System and apparatus for venting water heater

A direct venting system for an indoor domestic type water heater vents the combustion chamber of the water heater directly with the outdoor atmosphere by means of natural convection both to supply incoming combustion air and to expel flue gases. A conduit assembly extends from an indoor end associated with the water heater to an outdoor end in communication with the outdoor atmosphere, and provides continuous combustion air inlet and flue gas outlet plenums to isolate the combustion chamber of the water heater from the indoor room air.

SYSTEM AND APATUS FOR VENTING WATER HEATER 
The present invention pertains to the art of gas water heaters, and 
particularly to a closer system for venting an indoor domestic type gas 
water heater to the outdoor atmosphere under the force of natural 
convection. 
BACKGROUND OF THE INVENTION 
Water heaters for use in the home, apartments, or other relatively small 
building units having comparable demands for heated water often employ 
natural gas as the source of heat. Such water heaters usually comprise a 
cylindrical body including a tank for storage of water to be heated, a 
cold water inlet, a hot water outlet, and an apparatus for applying heat 
to the stored water including a natural gas inlet, control valves and 
associated thermostat mechanisms, and a combustion chamber in which the 
natural gas is burned and which is adapted to conduct or otherwise convey 
the heat of combustion to the quantity of stored water. 
The lower region of the cylindrical body includes a combustion air inlet 
opening communicating the combustion chamber with the room air. A vertical 
flue pipe extends from the combustion chamber through the tank to an open 
end at the top of the water heater body. A draft hood is provided at the 
top of the water heater body to make a connection between the open end of 
the flue pipe and a conduit leading to a chimney or other existing passage 
to a roof top opening. The draft hood is generally conical, with a wider 
lower end mounted on brackets in a position raised above the top of the 
water heater and concentric with the top end of the flue pipe. The 
narrower upper end of the draft hood is sealed to the chimney conduit. The 
draft hood thus reaches down from the chimney conduit as a skirt around 
the end of the flue pipe to define an open annular space therebetween. 
Operation of the water heater is usually vented by the force of convection 
currents caused by the the heat of combustion. Room air is drawn into the 
combustion chamber through the combustion air inlet opening, and flue 
gases rise out of the combustion chamber through the flue pipe to the 
chimney connection. Convective flow of the flue gases out through the 
chimney is aided by a draft of room air entering the chimney conduit 
directly through the open skirt arrangement of the draft hood. 
Such conventional water heaters have several disadvantages. A particular 
disadvantage is caused by the use of room air as combustion air for the 
water. Energy expended to heat, cool, or humidify room air is wasted when 
that air is drawn into the water heater and driven out through the 
chimney. Room air continues to exit through the chimney when the heater 
rests between intermittent heating operations since the heat contained in 
the tank of water tends to induce a residual convective flow through the 
heater. In addition to wasting the energy of heating or air conditioning, 
this continued loss of room air carries with it the heat stored in the 
tank of water. Furthermore, an outward draft of room air tends to induce 
an inward draft of outdoor air through door and window frame spaces, which 
is undesirable in both winter and summer. 
Another cause of loss of room air is the open arrangement of the draft hood 
as a skirt around the top end of the flue pipe. This opening allows a flow 
of air from the interior of a house out through the chimney. 
Another disadvantage is that conventional water heaters can be installed 
only in locations where a chimney connection can be made. Construction of 
a chimney to accommodate a water heater in an existing building is likely 
to be impractical if not impossible and installation in a building which 
does have a chimney is limited to locations adjacent the chimney which may 
not be practical for plumbing and/or electrical requirements. It also may 
not be desirable to design the location and clearance around a chimney in 
a new building, particularly a home, to accommodate placement of a water 
heater. 
Known domestic type indoor water heaters and associated venting systems 
thus fail to provide a means for heating water without wasting valuable 
energy used to heat or otherwise condition indoor room air, and are not 
readily adaptable to installation in convenient locations in new or 
existing building structures. 
SUMMARY OF THE INVENTION 
The present invention overcomes the above referred to disadvantages and 
others and provides a water heater and direct venting system for venting 
the combustion chamber of the water heater by natural convection directly 
with outdoor atmospheric air in isolation from indoor room air. 
In accordance with a principal feature of the invention there is provided 
an indoor domestic type water heater which is vented directly to the 
outdoor atmosphere by means of natural convective air flow. The water 
heater includes a combustion chamber with a combustion air inlet opening 
and a flue gas outlet opening, and a flue pipe rising from the combustion 
chamber outlet opening to an open end atop the heater. A conduit assembly 
extends from the heater to an outdoor end in communication with the 
atmosphere. The conduit assembly includes a first conduit extending from 
the outdoor end to an indoor position adjacent the open end of the flue 
pipe, and a closure member making an airtight sealed connection between 
the first conduit and the flue pipe. A second conduit extends 
telescopically over the first conduit to define an air flow space between 
the two conduits, and is joined at the indoor position by duct work which 
communicates the air flow space between the conduits with the combustion 
chamber inlet opening of the water heater. The combustion chamber is 
thereby vented directly to the outdoor atmosphere through a continuous 
airtight flue plenum defined by the flue pipe, the closure member, and the 
first conduit; and through a continuous airtight combustion air inlet 
plenum defined by the second conduit received over the first conduit, and 
the connective duct work between the second conduit and the combustion 
chamber. 
In accordance with a more specific feature of the invention, the closure 
member is provided in the form of a closed vent hood which is generally 
conical. A wide lower end of the closed vent hood is received over the 
open upper end of the flue pipe and is connected to the top of the water 
heater with an airtight seal. The narrow upper end of the conical closed 
vent hood is sealed to the indoor end of the first conduit to make an 
airtight connection for convective flow between the flue pipe and the 
first conduit. 
In accordance with another specific feature of the invention, the first and 
second conduits are circular in cross-section and substantially coaxial 
such that the air flow space therebetween is annular in cross-section. 
Thus telescopic relationship of the two conduits increases efficiency of 
the venting system by providing a heat exchanger to preheat the incoming 
combustion air by conduction from the outgoing flue gases in the first 
conduit. 
A further specific feature of :he invention includes the provision of 
baffles within the water heater adjacent the combustion air inlet opening 
which restrict the residual convective flow during inoperative periods of 
the water heater to reduce heat loss from the tank of water. 
Yet another specific feature of the invention is that the conduit assembly 
may extend from the water heater either vertically to an exposed roof or 
horizontally to an exterior building wall. The invention is thus adaptable 
for installation independently of a chimney in basements, garages, or 
other locations not associated with a chimney. 
In accordance with another principal feature of the invention there is 
provided a direct venting system for venting a domestic indoor water 
heater directly to the outdoor atmosphere by means of natural convection. 
The venting system comprises a conduit assembly having an indoor end 
associated with the water heater and an outdoor end communicating with the 
outdoor atmosphere. The conduit assembly includes a continuous combustion 
air inlet plenum extending from the outdoor end to the combustion air 
inlet opening of the water heater, and a continuous flue gas outlet plenum 
extending from the open upper end of the water heater flue pipe to the 
outdoor end of the conduit assembly through a conduit which extends 
through and within the combustion air inlet plenum. The inlet and outlet 
plenums are thus telescopically coextensive between the indoor and outdoor 
ends of the conduit assembly so that a direct venting connection can 
conveniently be made between a water heater and the outdoor atmosphere by 
a closed unitary member of the venting system reaching from any indoor 
location to an exterior building wall or an exposed roof. 
In accordance with a more specific feature of the invention, duct work is 
provided to complete a section of the continuous combustion air inlet 
plenum at the indoor end of the conduit assembly between the telescopic 
conduits and the combustion chamber of the water heater. The duct work is 
adapted to provide air to the combustion chamber in a wide, slow flow as 
compared to the rapid flow of fluid gases being driven out by the heat of 
combustion. This advantageously insures that natural convection alone will 
provide a sufficient volume of combustion air adjacent the inlet opening. 
In accordance with yet another principal feature of the invention, the 
natural convection direct venting system for an indoor water heater is 
comprised of a conduit assembly and a cap assembly. The conduit assembly 
includes a first conduit extending within a second conduit to define an 
outer air plenum between the two conduits and an inner air plenum within 
the first conduit. The cap assembly is associated with the outdoor end of 
the conduit assembly, and is adapted to separately communicate the inner 
and outer air plenums with outdoor atmosphere. 
Another specific feature of the invention is an arrangement wherein the 
inlet plenum has a cross-sectional area at the telescopic section of the 
conduit assembly which is substantially greater than the cross-sectional 
area of the corresponding section of the outlet plenum. This arrangement 
reduces resistance to the convective inlet flow and promotes preheating of 
the combustion air. 
In accordance with another specific feature of the invention, the first 
conduit extends beyond the second conduit, and the cap assembly includes a 
shield disposed about the periphery of the extended portion of the first 
conduit to block air flow directly between the two air plenums. The two 
air plenums are thereby separately open to the outdoor atmosphere. 
In accordance with another specific feature of the invention, the cap 
assembly includes a first screen cover extending from the shield 
longitudinally towards the extended portion of the first conduit in the 
form of a sleeve received over that portion of the first conduit, and a 
second screen cover extending longitudinally from the shield toward the 
second conduit. The screen covers may be perforated to permit air flow 
directly between the associated plenums and the outdoor atmosphere, or in 
an alternate embodiment may be solid in the form of a skirt or a wind band 
to permit only indirect air flow through the sleeve interiors between the 
associated plenums and the outdoor atmosphere. In either embodiment the 
screen covers serve to prevent foreign objects and wind gusts from 
entering the venting system. Preferably, the conduits and screen covers 
are coaxial and circular in cross-section. 
The principal object of the present invention is to provide a domestic type 
indoor water heater and associated venting system which directly vent the 
combustion chamber of the water heater with outdoor atmosphere by means of 
natural convection both to supply incoming combustion air and to expel 
flue gases. 
Another object of the invention is to provide a natural convection direct 
venting system for a domestic indoor water heater which vents the heater 
to the outdoor atmosphere in isolation from room air, and which is readily 
adaptable for installation with a conventional water heater. 
A further object of the invention is to provide a natural convection direct 
venting system for an indoor domestic water heater which is readily 
adaptable for installation to communicate the water heater with the 
outdoor atmosphere from indoor locations not associated with a chimney, 
such as in garages, workshops, or other buildings not having a chimney. 
Another object of the inventor is to provide a cap assembly for the outdoor 
end of the venting system which enables separate communication of the 
inlet and outlet openings of the water heater combustion chamber with 
outdoor atmosphere.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now to the drawings wherein the showings are for the purpose of 
illustrating a preferred embodiment of the invention only and not for the 
purpose of limiting same, in FIG. 1 there is shown a partially sectional 
view of an indoor domestic type water heater adapted in accordance with 
the present invention. The water heater 10 is comprised of conventional 
components including a cylindrical body 12 containing a tank 14 adapted to 
hold a quantity of water to be heated. Associated with the tank 14 is a 
cold water inlet 16 and a hot water outlet 18. Disposed beneath the tank 
14 is a combustion chamber 20 housing a burner 22 which is connected to a 
source of natural gas fuel by a fuel line 24. Associated with the fuel 
line 24 at the exterior of the water heater body 12 is a gas control valve 
apparatus 26 which is operatively connected with a water temperature 
responsive thermostat means, which may be of conventional construction and 
is not shown in the drawings. 
In accordance with the invention the water heater 10 is provided with a 
direct vent system communicating the combustion chamber 20 with the 
outdoor atmosphere A. The direct vent system comprises a combustion air 
inlet opening 28 at a position vertically below the burner 22, and a flue 
gas outlet opening 30 at a position vertically above the burner 22. 
Baffles 32 are disposed between the combustion air inlet opening 28 and 
the burner 22. A flue pipe 34 extends vertically from the combustion 
chamber outlet opening 30 through the tank 14 to reach an open upper end 
36 at the top of the water heater body 12. The flue pipe 34 may also 
include baffles 38 to conduct heat to the water in the tank 14. 
The direct vent system further comprises a conduit assembly 40 having an 
inner end 4Z associated with the water heater 10, and an outer end 44 at 
the exterior of building B. A closure member in the form of a vent hood 46 
is positioned substantially concentrically over the open upper end 36 of 
the flue pipe 34. The vent hood 46 is generally conical and has a wider 
lower end 48 attached to the upper surface of the water heater body 12 
with an airtight seal. A first conduit 50 is joined to the narrower upper 
end 52 of the closed vent hood 46 with an airtight seal, and extends 
therefrom to the outdoor end 44 of the conduit assembly 40 at the exterior 
of the building B. The vent hood 46 thus joins the flue pipe 34 and the 
first conduit 50 in an airtight sealed relationship whereby a continuous 
flue plenum 54 is defined to extend from the combustion chamber outlet 
opening 30 through the flue pipe 34 and the first conduit 50 to the 
outdoor atmosphere A. 
A second conduit 56 is received substantially concentrically over the first 
conduit 50 and extends from a position adjacent the closed vent hood 56 
along the length of the first conduit 50 to the outdoor end 44 of the 
conduit assembly 40 to define an annular plenum 58 between the first 
conduit 50 and the second conduit 56. An upper connecting duct 60 
communicates the annular plenum 58 with a third conduit 62. The third 
conduit 62 extends from the upper connecting duct 60 to a lower connecting 
duct 64 which communicates the third conduit 62 with the combustion 
chamber inlet opening 28. Airtight seals are provided at the connections 
between the conduits and the associated connecting ducts whereby a 
continuous combustion air inlet plenum 66 is defined to extend from the 
outdoor atmosphere A through the annular plenum 58 to the upper connecting 
duct 60, and further from the upper connecting duct 60 through the third 
conduit 62 and the lower connecting duct 64 to the combustion chamber 
inlet opening 28. 
Associated with the outdoor end 44 of the conduit assembly 40 is a cap 
assembly 70. The first conduit 50 extends beyond the end of the second 
conduit 56 at the outdoor end 44 of the conduit assembly 40 and thereby 
extends into the cap assembly 70. The cap assembly 70 includes a shield 72 
mounted on the extended portion 70 of the first conduit 50, a first screen 
cover 76 on one side of the shield 72, and a second screen cover 78 on the 
other side of the shield 72. 
One embodiment of the cap assembly 70 is shown in FIG. 2. The first and 
second conduits 50, 54 are circular in cross-section and are coaxial with 
respect to a central axis X. The first and second screen covers 76 and 78 
are also circular in cross-section and coaxial with respect to the central 
axis X, with the first screen cover 76 being disposed radially inwardly of 
the second screen cover 78. An end piece 80 is provided to close the open 
end of the first screen cover 76, and perforations 82 are provided to 
permit air flow between the flue plenum 54 and the outdoor atmosphere A as 
indicated by the arrows shown in FIG. 2. The second screen cover 78 
extends between a first support flange 84 and a second support flange 86. 
The support flanges 84, 86 serve to rigidify the second screen cover 78, 
with the first support flange 84 further acting as an extension of the 
shield 72 to block air flow directly from the first screen cover 76 to the 
second screen cover 78 in the general direction of the axis X. The second 
screen cover 78 is provided with additional perforations 88 to permit air 
flow directly between the outdoor atmosphere A and the combustion air 
inlet plenum 66 as indicated by the arrows shown in FIG. 2. A mounting 
bracket 90 [s adapted to register with the second support flange 86 and to 
enable mounting of the cap assembly 70 onto the outdoor end 44 of the 
conduit assembly 40 at the end of the second conduit 56 as shown. 
Another embodiment of the cap assembly 70 is shown in FIGS. 3 and 4. In 
that embodiment the first conduit 50 and the second conduit 56 are 
circular in cross-section and coaxial about the central axis X. The first 
and second screen covers 76, 78 are also circular in cross-section, are 
equally spaced radially with respect to the central axis X, and are joined 
axially by the shield 72. The first screen cover 76 is provided with an 
end closure member 92 and with apertures 94 adapted to permit air flow 
between the flue plenum 54 and the outdoor atmosphere A, as indicated by 
the arrows shown in FIG. 4. The second screen cover 78 is formed as a 
continuous skirt around the second conduit 56 and is open in an axial 
direction away from the shield 72 to permit air flow between the outdoor 
atmosphere A and the combustion air inlet plenum 66, as indicated in the 
figure. A wind hood is comprised of a cap piece 96, and a shroud piece 98 
spaced radially outwardly from the first and second screen covers 76 and 
78 to protect the air flow paths shown in the figure from wind gusts and 
foreign objects. The cap assembly may be mounted on the second conduit 56 
by brackets 100. 
Operation of the water heater and direct vent system in accordance with the 
invention proceeds with a convective flow of air directly between the 
combustion chamber 20 and the outdoor atmosphere A completely in isolation 
from the indoor room air. Ignition and combustion of the natural gas fuel 
at the burner 22 causes a draft of the air within the combustion chamber 
20 and of the flue gases produced by combustion at the burner 22 upwardly 
through the combustion chamber outlet opening 30 and into the flue pipe 
34. Air is thereby drawn upwardly through the combustion chamber inlet 
opening 28 from the lower connecting duct 64. Isolation of the combustion 
chamber 20 from the surrounding room air causes an initial inlet draft in 
the lower connecting duct 64 corresponding to the outlet draft initially 
developed in the flue pipe 34. As combustion proceeds, the draft through 
the combustion chamber 20 draws a convective venting flow inwardly from 
the outdoor atmosphere A through the continuous air tight combustion air 
inlet plenum 66, and drives it outwardly to the outdoor atmosphere A 
through the continuous airtight flue plenum 54. The shield 72 at the cap 
assembly 70 prevents the flue gases exiting from the outdoor end of the 
flue plenum 54 from returning directly into the combustion air inlet 
plenum 66 with the incoming atmospheric combustion air. 
Efficiency of the convective venting in accordance with the invention is 
found to be enhanced by providing the combustion air inlet plenum 66 with 
a rear cross-sectional area than the flue plenum 54. Since the lower wall 
15 of the tank 14, the flue pipe 34, and the flue baffles 38 all become 
heated during operation of the burner 22, the flue gases rising through 
the flue pipe 34 are caused to expand and be further driven convectively 
by the heat present in those components as well as by the convective force 
developed by the burning fuel in the combustion chamber 20. The flue gases 
are thus driven out of the water heater at a high flow rate. Provision of 
a relatively wide combustion air inlet plenum at the combustion chamber 
inlet opening 28 enables a corresponding volume of combustion air to 
immediately enter the combustion chamber 20 at a relatively lower flow 
rate. A more restricted inlet flow through a narrower combustion air inlet 
plenum could fail to provide the volume required to match the forcefully 
driven outlet flow of flue gases. 
A relatively slower flow rate through the combustion air inlet plenum 66 
further enhances efficiency of the invention where the conduit assembly 40 
includes the first and second conduits 50 and 56 in a coaxial heat 
exchanging relationship. A slower flow rate through the annular plenum 58 
enables the incoming combustion air to remain in a heat conducting 
relationship with the outgoing flue gases in the first conduit 50 long 
enough for the combustion air to become somewhat preheated whereby heat 
loss through the flue plenum 54 to the outdoor atmosphere A is reduced and 
combustion efficiency in the combustion chamber Z0 is increased. Effective 
preheating and convective low rates are found to be obtained with a 
structural relationship of relative first and second conduit diameters in 
the ratio of 5:3, for example 5 inches and 3 inches, whereby the annular 
plenum 58 has a cross-sectional area nearly twice the area of the first 
conduit 50. 
Wben the burner 22 is not in operation, the heat retained by the tank 14 
and associated heated components may cause a residual convective flow to 
continue through the system, although not at the driven rate obtained when 
the burner 22 is operating. The baffles 32 serve to restrict such a 
residual convective flow rate through the combustion chamber 20 and 
thereby reduce any consequent heat losses. 
Installation of the invention can be made with a water heater particularly 
adapted with a direct vent system as shown in the Figures, or as an 
adaptation to an existing conventional water heater In either case, the 
indoor location of a water heater can be selected without regard to the 
location or existence of a chimney and without the need of a powered 
blower. As shown in FIG. 1, the conduit assembly 40 may be turned to 
extend horizontally towards a building side wall which will require only a 
simple opening 102 to permit passage of the conduit assembly 40 to an 
outdoor venting position. This installation arrangement is especially 
convenient when a water heater must be installed in a basement or other 
location remote from either a chimney or the roof of the building. 
Alternately, the conduit assembly 40 may extend vertically to the roof of 
a building such as a garage or workshop which would not have a chimney. 
A conventional water heater may be adapted in accordance with the invention 
in order to replace an existing open room air tyPe venting system with a 
closed atmospheric direct vent system. Removal of a conventional draft 
hood should ordinarily provide clearance at the top of a water heater for 
placement of a closure member such as the closed vent hood 46. The first 
and second conduits 50, 56 would be installed as described above to 
complete the flue plenum 54 and to provide the combustion air inlet plenum 
66 to the extent of the annular plenum 58. The balance of the continuous 
combustion air inlet plenum 66 could either be provided by the upper and 
lower connecting ducts 60, 64 and the third conduit 62 as described above, 
or in any other configuration of duct work and/or conduits whereby a 
continuous airtight extension to the annular plenum 58 is constructed with 
sufficiently low resistance to air flow to provide the required volume of 
combustion air at the combustion air inlet opening of the water heater. 
The invention has been described with reference to the preferred 
embodiment. Obviously, modifications and alterations will occur to others 
upon the reading and understanding of the specification. It is intended to 
include all such modifications insofar as they come within the scope of 
the appended claims or the equivalence thereof.