Note: Descriptions are shown in the official language in which they were submitted.
~2;~S9~
FLUE PIPE coi~NEcTIorl
- This invention relates to ~ue~-fired appliances and
in particular to the dxaining of condensate which may form in
the flue gas conduits of appliances such as household gas-fired
furnaces. More specifically the invention relates to a special
connection or joint between flue gas conduit sections which
permits downwardly moving condensate to be drained away while
permitting flue gases to pass upwardly through the connection.
BACKGROUND
In recent years the heating efficiency of fuel-fired
appliances such as household furnaces has been increased by ex-
tracting additional heat from the combustion gases before passing
those gases into a flue external of the appliance. In the case of
a gas-fired, forced-air furnace, for example, the combustion
gases after passing through the usual heat exchanger cell, which
also serves as part of a combustion chamber, are passed through one
or more additional but non-fired heat exchanger cells and then
into an external 41ue. Room air is forced past the exterior of
all the exchangers so that heat exchange takes place through the
metal walls of the exchangers. This heat exchange will typically
reduce the temperature of the flue gases in the non-fired heat
exchanger or recuperative cell to a level, for example 200F, at
which some of the water vapor in the flue gases will condense on the
inner surface of the recuperative cell. A drain connection is
provided in the recuperative cell to allow the condensate to pass
to a permanent drain. A recuperative furnace of this type is
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disclosed in United States Patent 4,261,326.
SUMMARY OF T~E INVE~TI0~
The present invention relates to the removal of
condensate from flue gas ronduits at a point d~wnstream of the
heat-extraction means of a fuel-fired appliance. For example,
in a recuperative gas-fired furnace of the kind summarized above
there is likely to be additional condensation in the external flue
pipe leading from the furnace, this flue pipe being connected at
its inlet end to the outlet end of an internal flue conduit
section leading from the recuperative cell. As such condensate
is acidic and corrosive as a result of impurities in the fuel,
it is desirable to prevent the condensate from passing through
a connection from which it might leak thereby damaging the
appliance or the building structure.
According to the principles of the present invention,
there is provided a sp~cial joint between upper and lower flue
gas conduit sections which freely passes flue gases from the lower
section to the upper section and which includes means for draining
away condensate moving down the interior surfaces of the upper
conduit section. The special joint may be formed by the ends of
the conduit sections or it may include one or more components fitted
to the ends of the conduit sections. In any case the draining
means includes a generally annular wall cooperating with the
inner surface of at least one of the conduit sections (usually
the upper conduit section) to form a generally annular trough
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which is l~cated to receive any condensate formed on and flowlng
down the inner surface of the upper conduit section, the trough
including at least one drain passage for draining condensate by
gravity from the trough in a generally radially outward direction
to a location external of the conduit sections. The joint may
include one or mDre cQnnecting components which cooperate with the
ends of both conduit sections. The connecting component or assembly
includes the draining means so that the condensate drains away
before reaching the lower conduit section thus isolating the sea~
between that conduit section and the collar and avoiding leakage
of condensate at this location. The drained-away condensate can
be disposed ~f in any suitable way.
In a recuperative gas-fired furnace of the type described
th~ special joint has particular utility when provided between the
flue conduit inside the furnace (i.e. a lower condl~it section) and
the external flue pipe (i.e. an upper conduit section). In this
case the condensate which drains away from the joint is desirably
merged by means of a conduit with condensate draining from the
recuperative cell of the furnace. The reason for this is that a
furnace of this kind includes a blower in the internal flue gas
conduit for producing a negative pressure in the heat exchanger
cells and a positive pressure upstream of the blower. The connection
between the internal flue conduit and the external flue pipe is thus
at positive flue gas pressure. Consequently the drain opening in
the special connection of the present invention is at positive flue
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gas pressur~ and flue gas is likely to accompany condensate drain-
ing from the connection. By connecting the drain opening in the
connection to the recuperative cell or to the condensate drain
from that cell flue gas will be prevented from escaping to the
surrounding atmosphere.
In a preferred form of joint there is a collar structure
having an upper or outlet aperture connectable to an upper flue
conduit section, a lower or inlet aperture connectable to a lower
flue conduit section and an annular upwardly-facing trough between
the inlet and outlet apertures for receiving condensate from the
upper conduit section and for isolating such condensate from the
joint or seal between the collar and the lower conduit section. A
drain opening is provided in the trough and a hose or other
conduit is connected to the drain opening for carrying away the
condensate. The flue gas outlet aperture is formed by a cylindrical
socket-like recess into which the lower end of the external flue
pipe is inserted, the side wall of the socket being tapered d~wn-
wardly and inwardly so as to provide a friction fit with the external
flue pipe. The flue gas inlet aperture is formed by the lcwer end
of a short vertical length of pipe of smaller diameter than the
socket, the pipe projecting upwardly into and spaced f~ m the side
wall of the socket. The trough is formed by the outer surface of
the upper portion of the pipe, the surface of the side wall of the
socket and an annular bottom wall extending generally radially
between these two surfaces. The drain opening is provided in this
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annular bottom wall. A peripheral radially, extending flange
may be included as a means for att~ching the collar to the
horizontal upper wall of the appliance.
The collar can thus be vi~wed as being constructed of
an outer pipe section having an open upper end for receiving the
external flue pipe, an inner pipe section having an open upper
end and a lower open end connectable to the internal fluid conduit,
an annular wall joining the outer pipe section to the exterior of
the inner pipe section at a location between the ends of the latter
so as to form an annular condensate collection chamber around the
inner pipe section and a drain opening placing the interior of the
collection chamber in communication with the outside of the collar.
Conveniently the entire collar is cast as an integral one-piece
structure, although it can be constructed of separate parts joined
together.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a vertical sectional view of a joint formed
by a condensate drain collar embodying the principles of the
present invention;
Figure 2 is a plan view of the drain collar of Figure l;
Figure 3 is an elevational view of the drain collar of
Pigure l;
Figure 4 is a schematic fragmentary view of a household
gas-fired furnace having an internal flue conduit joined to an
external flue pipe by the drain collar illustrated in Figure 1, and
l~æ3s~
Figure 5 is a schem~tic view of an existing household
gas-fired furnace which has been retrofitted with the drain
- collar of Fiyure 1.
DETAILED DESCRIPTION
Figure 1 illustrates a joint between an upper flue
conduit section 10 and a lower flue conduit section 12 formed
by a connecting collar 14 embodying the principles of the
present invention. The collar 14 includes an outer pipe section
15 having an upwardly facing recess or socket which receives the
l~wer end of the upper conduit section. The side wall 16 of the
soc~et is frustoconical in that it inclines slightly downwardly
and inwardly so as to form a snug fit around the upper conduit
section 10. The upper end of the lQwer flue conduit section 12
fits over the tapered lower end of an inner pipe section 18 which
is part of the collar 14. The upper end of the inner pipe 18
resides in the socket and is spaced from the socket side wall 16.
A generally radial annular wall 20 connects the socket side wall
16 and the exterior of inner pipe 18 at a location between the
ends of the latter. There is thus formed an annular condensate
collection chamher or trough 22 between the socket side wall 16
and the exterior of the inner pipe 18, with the radial wall 20
defining the bottom wall of the trough 22.
Any condensate formed in the upper flue conduit section
10 and moving down the inner surface of that section will pass
into this trough 22 and will then drain by gravity through a drain
9~
spening 24 in the bottom wall 20 of the trough 22. The drain
opening 24 could alternatively be provided in the wall of the
outer pipe section 15. In the illustrated embodiment the drain
opening 24 is the upper end of a vertical pipe stub 26 and a
flexible hose 28 is releasably connected to the lower end of the
stub 26 to carry the condensate to a suitable location for
disposal. The bottom wall 20 of the condensate trough 22 is
inclined toward the drain opening 24 to facilitate flow of con-
densate out of the trough 22. As the upper end of the flue gas
inlet pipe 18 is well above the bottom wall 20 of the condensate
trough 22 and is radially spaced from the lower end of the upper
flue section 10, flue gases passing upwardly through the joint
are isolated from contact with the condensate. In addition, the
seal between the upper flue section 10 and the collar 14, i.e. the
contact area between flue section 10 and the trough side wall 16,
is isolated from the condensate so that no leakage of condensate
from the collar 14 will occur.
The collar 14 also includes a peripheral radial mount-
ing flange 30, provided with bolt holes 32, to facilitate attach-
ment of the collar 14 to a support structure such as the top wall
34 of a fuel-fired appliance. Radial holes 36 through the side
wall 16 of the socket are provided to receive screws or bolts
which aid in attaching the upper flue section 10 to the collar 14.
As illustrated in the drawings the collar 14 is a
unitary cast structure. It may, if preferred, be constructed of
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its several parts connected together in a suitable manner.
Figure 4 illustrates schematically a household gas-
fired furnace 40 of the recuperative type described previously,
with the condensate drain collar 14 of Figure 1 installed betw~en
an internal flue gas conduit 42 and an external flue pipe 44. The
conduit 42 and pipe 44 are connected.to the collar 14 in Lhe
same manner as the conduit sections 10 and 12 in Figure 1. The
collar 14 is attached to the horizontal top wall 46 of the furnace
casing 47 by bolts (not shown) passing through the collar flange
36. The furnace 40 includes two heat exchanger/combustion cells
48,50 each provided with a gas burner 52 which injects gas and
air into the respective cell in the usual way. Combustion gases
generated in the cells 48,50 pass upwardly into a plenum 54 and
then downwardly through a non-fired recuperative heat exchanger
cell 56. From the bottom of the cell 56 the gases pass upwardly
through a blower 58 and into the internal flue gas conduit 42.
A main blower 60 draws in household air and passes it over the
outside of the cells 48,50 and 56 so as to be heated. The thus-
heated air is then distributed to the rooms of the house by ducts
tnot shown). As explained previously heat exchange ~etween flue
gas in the recuperative heat exchanger cell 56 and the household
air may reduce the temperature of the flue gas to a level such
that water vapor will condense on the inner surfaces of the
recuperative cell 56. It is conventional to connect a condensate
drain tu~e 62 to the lower end of the recuperative cell 56 for
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draining away the condensate to a household drain.
As the temperature of the flue gas will drop still
further in the external flue pipe 44, additional condensate
may be formed in the latter. This additional condensate flows
downwardly into the condensate trough 22 in the drain collar
14 and then out through the pipe stub 26 as described previously.
In the embodiment of Figure 4 a conduit such as a flexible hose
64 connects the pipe stub 26 with the interior of the recuperative
heat exchanger cell 56 near the lower end thereof. Condensate
draining through the drain hose 62 is thus a combination of
condensa~e from the recuperative cell 56 and condensate from the
external flue pipe 44.
Figure 5 illustrates schematically an existing recuperative
furnace 14a which has been retrofitted with the condensate drain
collar 14 of Figure 1 installed between the external flue pipe 44a
and the internal flue conduit 42a. In this embodiment a conduit
66, containing a U-shaped trap portion 67, connects with the drain
pipe 26 of the collar 14 and extends to the outside of the furnace
casing 47a where it connects with the upper end of an external
conduit 68 by means of a conventional fittin~ 70. The recuperative
cell condensate line 62a passes to the outside of the furnace
casing 47a where it connects via a tee 72 with a main drain hose
74. The upper end of the tee 72 is open to the atmosphere. The
lower end of the flue pipe condensate hose 68 connects with the
main drain hose 74 by means of a tee 76.
