[0001] The present invention relates to an external compact gas-fired heater and particularly,
but not exclusively, incorporating a natural gas heater for heating a water/glycol
fluid and wherein the heater is provided within a housing which precludes unauthorized
access thereto and still further wherein the heater is easy to repair or replace.
BACKGROUND ART
[0002] Heating devices for heating homes or small buildings having heating capacities of
from about 20,500 Watt to about 44,000 Watt are usually mounted internally of such
buildings and such have inherent disadvantages. For example, the furnace or heater
occupies interior space in the building and often a specific furnace room has to be
provided for security. It is also necessary to have a fresh air duct connected to
such furnace and this often results in excessive cold air intrusion within the building,
as the air duct must penetrate the outside wall of the building. These heaters or
furnaces also generate noise and release gas or oil scent within the building. It
is also necessary to construct a chimney to evacuate the combustion products from
the furnace, and if there are leaks in the piping which connects the furnace to the
chimney, then this could cause serious health problems to the occupants of the building.
[0003] Another problem with some of these furnaces is that they consume electricity, which
is a high-cost commodity, as compared to natural gas. The efficiency of some of these
known furnaces can also be inferior to 80%. Furthermore, some of these furnaces are
unsightly, and thus the need to locate them in a special furnace room. They are sometimes
accessible to children, and this also poses a hazard.
[0004] Otherwise, US-A-4,893,609 discloses an outdoor gas-fired heater for heating a fluid
for use as a heat exchange medium. The heater has an inlet opening for air, a channel
for guiding air to a burner disposed in the heater and an exhaust opening for flue
products. But, such a furnace is often difficult to repair or replace.
SUMMARY OF INVENTION
[0005] It is a feature of the present invention to provide an external gas-fired heater
which substantially overcomes the above-mentioned disadvantages noted with some prior
art heaters or furnaces.
[0006] Another feature of the present invention is to provide an external gas-fired heater
which is secured externally of a building to be heated and which is easy to service,
repair and replace.
[0007] Another feature of the present invention is to provide an external gas-fired heater
which has an efficiency superior to 83% and a low NO
X emission inferior to 30 ppm at 3% of O
2.
[0008] Another feature of the present invention is to provide an external gas-fired heater
which is easy to use and which has an esthetically pleasing design.
[0009] Another feature of the present invention is to provide an external gas-fired heater
which is safe for children and access to which is provided only to authorized people.
[0010] Another feature of the present invention is to provide an external natural gas-fired
heater for heating a water/glycol fluid to produce a heat exchange medium to feed
heat exchange devices located inside a building to be heated by the heater.
[0011] According to the above features, from a broad aspect, the present invention provides
an external gas-fired heater for heating a fluid for use as a heat exchange medium.
The heater comprises a housing securable outside a building to which heated fluid
is to be supplied for heat exchange in heating devices contained within said building.
A heating coil is supported in the housing and through which is convected the fluid.
A combustion chamber contains the heating coil. A cylindrical gas burner is disposed
inside the coil to heat the coil and the fluid. An air/gas mixing blower is connected
to the gas burner to feed a combustible air/gas mixture thereto. Exhaust means is
provided to evacuate flue gases from the combustion chamber to atmosphere. An ignitor
is provided to ignite the air/gas mixture at the gas burner. A flame detector is provided
to detect a flame at the gas burner. The housing has an access panel to permit access
to the interior of the housing. Lock means secures the panel to the housing. Convection
means provides air circulation inside the housing. Coupling means permit use of installation
and removal of the housing or equipment therein.
BRIEF DESCRIPTION OF DRAWINGS
[0012] A preferred embodiment of the present invention will now be described with reference
to the accompanying drawings in which:
FIG. 1 is a perspective view of the external gas-fired heater housing of the present
invention secured to a wall of a building;
FIG. 2 is a fragmented front view of the external gas-fired heater of the present
invention;
FIG. 3 is a fragmented side view of Fig. 2;
FIG. 4 is a sectional top view of Fig. 2;
FIG. 5 is an exploded view showing the basic component parts of the external gas-fired
heater;
FIG. 6 is a fragmented perspective view showing a modification of the exhaust conduit
secured to the top end of the combustion chamber;
FIG. 7 is an exploded perspective view showing the construction of the housing; and
FIG. 8 is a simplified schematic view showing the external gas-fired heater utilized
on a roof unit for buildings.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] Referring now to the drawings, and more particularly to Fig. 1, there is shown generally
at 10 the external natural gas-fired heater of the present invention housed within
a housing 11 which is secured to the wall 12 of a building or roof unit. As herein
shown, the housing 11 is a rectangular housing provided with a detachable cover 13
which forms the front wall 13' and top wall 13" of the housing whereby to provide
access to the component parts of the heater and to provide security. Feed pipe 14
supplies the natural gas to the internal burner, as will be described later, and pipes
15 provide circulation of a heated liquid to the building for heat exchange with heaters
(not shown) provided therein.
[0014] Referring now to Figs. 2 to 7, there will be described a construction of the external
gas-fired heater 10 of the present invention. As herein shown, a thermally insulated
combustion chamber 16 is secured in an upper portion of the housing 11 and has a heating
coil 17 mounted therein. In this particular embodiment the heating coil is comprised
of two concentrically disposed spiral coils 17' and 17" of heat conductive material,
and which are serially connected to one another, and have an inlet 18 and an outlet
19 through which a water/glycol mixture is circulated by a pump 20. A temperature
and pressure gauge 21 monitors the glycol solution at the outlet of the coil.
[0015] A cylindrical natural gas burner nozzle 22 is supported concentrically at the center
of the heating coil 17 and is supplied a natural gas/air mixture by the mixing blower
23 to heat the spiral coil 17', 17", and hence the water/glycol liquid solution circulated
therethrough. Ideally, this solution is a 50/50 mixture. Of course, other suitable
solutions may be used, but it has been found that the particular glycol/water mixture
provides for the mixture to be operational from about -40°C to about 82°C making it
ideal for harsh northern climates. An ignitor 24 ignites the cylindrical burner 22
and a flame is detected by a flame detecting probe 25 mounted adjacent the burner
22. Controls for these are provided on a control panel 45.
[0016] As better seen in Fig. 5, the combustion chamber 16 is delimited by a thermally insulated
cylindrical metal container 26 having a bottom wall and on which is disposed a bottom
circular refractory disc 27. A top refractory disc 28 is disposed over the heating
coil 17 to reduce heat loss from the container and to increase the exchange efficiency
of the heater. A top wall 29 is secured over the top end 26' of the cylindrical container
26. The refractory disc 28 is a solid disc to force the flue gas through the heating
coil spirals and up above the disc 28 periphery and then through the evacuating portion
of the wall 29.
[0017] The flue gases which are convected through the port 29' is directed into an exhaust
duct which, as shown in Fig. 5, is constituted by an intake pipe 30 which interconnects
the port 29' to an exhaust conduit 31 which extends through the housing 11 from a
top end to a bottom wall 11' of the housing. The outlet end 32 of the exhaust pipe
31 communicates the flue gases to atmosphere through an orifice 33 provided in the
bottom wall 11'. This exhaust pipe 31 also pre-heats air within the housing to feed
warm air to the mixing blower 23 to increase the efficiency of the combustion mixture
thereof.
[0018] Fig. 6 illustrates an alternative embodiment of the exhaust conduit for use in less
cold climatic regions and, as herein shown, it may be provided by an intake pipe 34
secured about the port 29' of the top wall 29 of the combustion chamber, and having
diametrically opposed exhaust ducts 35 to release the combustion products from the
opposed sides of the top wall 13" of the cover 13. As herein shown, the top wall has
notches 36 on opposed side walls 37 thereof to accommodate the ducts 35.
[0019] As is better shown in Fig. 5, the various component parts of the heater are individually
removably secured within the housing 11 by individual attachment brackets, such as
bracket 38 and quick connectors 39, to permit the entire housing and its component
parts and wiring to be removed in a very short period of time for replacement and/or
for servicing elsewhere than on site if need be. These quick connectors connect the
gas pipes and heating fluid pipes. As shown in Fig. 5, the gas pipe feeds a gas valve
40 and an interchangeable orifice plate 41 regulates the amount of gas which is fed
to the blower 23 for admixture with air. The gas supply and orifice plate are connected
to blower 23 by an orifice plate 41'. A pressure control switch 42 and a temperature
limiting probe 43 are secured to the heated fluid pipes 15, 15'. An air/gas mixture
control 47 is provided on the control panel 45, and this control panel is mounted
internally of the housing 11 and is accessible only to authorized personnel who have
access to the key lock 50.
[0020] As previously described and as better shown in Fig. 7, the housing 11 is a rectangular
housing having an L-shaped removably detachable cover 13. Lock means in the form of
a key operated lock cylinder 52 capable of actuating a locking element 51, when a
key is positioned and operated in the key hole secures the cover 13 to the rectangular
housing 11. The front wall 13' of the cover 13, in a lower inner section thereof,
is provided with a spaced internal metal wall 53 to form a narrow convection passage
54 to feed air internally of said housing adjacent the top end of the cover, as shown
in Fig. 1. Access holes 56 are punched in the bottom wall 11' of the housing to accommodate
the necessary piping and wiring.
[0021] The heater, as above described, has a heating capacity from about 8'8 to 58'6 kw
(30,000 to 200,000 Btu/h) and is easily adjustable by interchanging the orifice plate
41 to deliver the required heat capacity within that range. The housing 11 is also
mounted on an exterior wall of a building to which the hot water/glycol solution is
to be fed.
[0022] Fig. 8 shows a typical embodiment wherein the heater 10 is mounted on the roof of
a building. The feed line 15 of the water/glycol solution is fed to a heat exchange
device 60 located inside the duct work 61 and through which air is circulated to heat
the air. An expansion valve 63, as is well known in the art, is connected in the line
15. A mixing valve 64 is also secured to the fluid pipe 15 to prevent passage of cold
water/glycol solution. The hot glycol solution is circulated through the heat exchange
coil 60 where it cools and is then returned to the heating coil 17 through the return
pipe 15'. As can be noted, the advantage of the heater being mounted externally of
the housing results in a saving of space within the building and the air supply for
the heater is taken directly from the outside air. Accordingly, there is no intrusion
of air within the building by convection ducts. Furthermore, the noise generated by
the heater is located outside the building and the gases are evacuated directly to
the atmosphere, thus avoiding the necessity of building a chimney. Such a heater can
also be utilized to replace existing electric heaters by natural gas heaters. The
heater is also easy to operate and provides of ease of maintenance.
[0023] It has been found that the efficiency of the heater of this invention is superior
to 83% and that the NO
x emission is inferior to 30 ppm at 3% O
2. The construction of the heater housing is also aesthetically pleasing to the eye
and provides added safety by locking the heater components inside a housing which
is accessible to authorized persons only. Because the housing is wall-mounted, such
as on support brackets 11" as shown in Fig. 3, it can be secured at a convenient height
for maintenance and above the snow line to provide ease of service in winter. The
heater of the present invention also results in a reduction in cost of operation as
compared to electricity. It also provides a more compact housing than competitive
heaters. It may also be used to heat water or swimming pools, radiant floors, radiators
and a multitude of other devices or may have other uses. It is pointed out that tests
have shown that the external gas-fired heater of the present invention has a jacket
heat loss of only about 2%. It is also feasible to utilize the gas-fired heater for
applications in buildings having three rooms only or to triplex-type buildings where
there may be 15 to 20 rooms. The units can also be fabricated in different sizes to
supply from about 8.8 kw to 58.6 kw or from 11.7 kw to about 58.6 kw.
1. An external compact gas-fired heater (10) for heating a fluid for use as a heat exchange
medium, said heat exchange medium operating within a temperature range of from about
-40°C to about 82°C to provide a heating capacity of from about 8,800 Watt to about
58,600 Watt, said heater comprising:
- a rectangular housing (11) securable outside a building (12) to which a fluid to
be heated is supplied, heated and fed as a heat source to heating devices (60) contained
within a building; said housing having :
• an access panel to permit complete access to the interior of said housing (11),
• lock means (50) for ease of securement and removal of said access panel to said
housing (11), and
• convection means (54) to provide air circulation inside said housing (11),
- coupling means to permit ease of installation and removal of said external compact
gas-fired heater (10),
- component parts comprising:
• a heating coil (17) supported in said housing (11) through which is convected said
fluid,
• a thermally insulated cylindrical container (26) having a top (29) and bottom circular
refractory walls and comprising a cylindrical combustion chamber (16), said combustion
chamber (16) containing said heating coil (17),
• a cylindrical gas burner (22) disposed inside said coil (17) to heat said coil (17)
and said fluid,
• an air/gas mixing blower (23) connected to said gas burner to feed a combustible
air/gas mixture thereto to maintain a stable flame in the presence of ambient climatic
conditions,
• an exhaust secured to said top wall (29) of said container (26) and provided with
exhaust outlet means (31 ; 35) to evacuate said flue gases from said combustion chamber
(16) to atmosphere outside said housing (11),
• an ignitor (24) to ignite said air/gas mixture at said gas burner,
• a flame detector (25) to detect a flame at said gas burner,
wherein :
said access panel is a cover (13) for said housing (11) and constitutes a front (13')
and top (13") wall of said housing (11), and
the external compact gas-fired heater (10) further comprises fasteners (38, 39) accessible
from a front and top portions (13', 13") of said housing (11) when said cover (13)
is removed,
said fasteners (38, 39) removably securing said component parts within said housing
(11).
2. An external gas-fired heater as claimed in claim 1 wherein said heat exchange medium
is a water and glycol liquid solution.
3. An external gas-fired heater as claimed in claim 2 wherein said water and glycol liquid
solution is substantially a 50/50 mixture of water and glycol.
4. An external gas-fired heater as claimed in one of the preceding claims, wherein said
lock means (50) is a key operated lock cylinder (52) actuating a locking element (51)
to secure said access panel to said housing (11).
5. An external gas-fired heater as claimed in one of the preceding claims, wherein said
exhaust outlet means comprises an exhaust conduit (31) having an intake end secured
at a top end (29') of said container (26) and an outlet end secured to a wall (11')
of said housing to evacuate said flue gases to atmosphere outside said housing (11),
said exhaust conduit (31) extending inside said housing (11) for heating air in said
housing (11) at least in the area of said mixing blower (23) and thereby providing
pre-heated air to said mixing blower (23) to enhance combustion of said air/gas mixture.
6. An external gas-fired heater as claimed in one of the preceding claims, wherein said
heating coil (17) is a spiral coil having a plurality of spirals (17', 17"), said
coil having an inlet end (18) and an outlet end (19), said coupling means including
a rapid-type connector secured at said inlet and outlet ends(18,19).
7. An external gas-fired heater as claimed in claim 6 wherein said heating coil (17)
is comprised of two (17', 17") concentrically disposed ones of said spiral coils connected
in series with one another.
8. An external gas-fired heater as claimed in one of the preceding claims, wherein said
convection means (54) is provided by a section of said panel being formed as a convection
channel by two spaced apart metal sheets (13' ; 53) formed in a lower front end portion
of said panel.
9. An external gas-fired heater as claimed in claim 8 wherein said convection means (54)
is formed with said front wall (13') of said cover.
10. An external gas-fired heater as claimed in one of the preceding claims, wherein said
gas burner is a natural gas burner, said flue gases emitting less than about 30 ppm
NOX at 3% of O2.
1. Außen befindlicher, kompakter gasbeheizter Erhitzer (10) zum Erwärmen eines Fluids
für die Verwendung als ein Wärmeaustauschmittel, wobei das Wärmeaustauschmittel innerhalb
eines Temperaturberelchs von etwa -40°C bis etwa 82°C arbeitet, um eine Wärmeleistung
von etwa 8800 Watt bis etwa 58600 Watt zu schaffen, wobei der Erhitzer aufweist:
- ein rechteckiges Gehäuse (11), das außerhalb eines Gebäudes (12) anbringbar ist,
welchem ein zu erwärmendes Fluid zugeführt wird, das als eine Warmequelle für Wärmevorrichtungen
(60) erwärmt und zugeführt wird, welche innerhalb eines Gebäudes enthalten sind; wobei
das Gehäuseaufweist:
• eine Zugangspanele, um den vollständigen Zugang zum Inneren des Gehäuses (11) zu
erlauben,
• Verschlußmittel (50) zum leichten Befestigen und Entfernen der Zugangspanele an/von
dem Gehäuse (11), und
• Konvektionsmittel (54), um Luftzirkulation innerhalb des Gehäuses (11) zu schaffen,
- Kupplungsmittel, um das leichte Installieren und Entfernen des außen befindlichen,
kompakten gasbeheizten Erhitzers (10) zu erlauben,
- Komponententeile mit:
• einer Heizspule (17), die in dem Gehäuse (11) gestützt ist, durch welche das Fluid
geleltet wird,
• einem thermisch isolierten, zylindrischen Behälter (26), der eine obere (29) und
eine untere kreisrunde feuerfeste Wand hat, und eine zylindrische Verbrennungskammer
(16) aufweist, wobei die Verbrennungskammer (16) die Heizspule (17) enthält,
• einem zylindrischen Gasbrenner (22), der innerhalb der Spule (17) angeordnet ist,
um die Spule (17) und das Fluid zu erwärmen,
• einem Luft/Gas-Mischgebläse (23), das mit dem Gasbrenner verbunden ist, um diesem
ein brennbares Luft/Gas-Gemisch zuzuführen, um eine stabile Flamme in der Gegenwart
von klimatischen Umgebungsbedingungen aufrecht zu erhalten,
• einem Abzug, der an der oberen Wand (29) des Behälters (26) befestigt und mit Abzugsauslaßmitteln
(31; 35) versehen ist, um die Abgase aus der Verbrennungskammer (16) in die Atmosphäre
außerhalb des Gehäuses (11) zu entleeren,
• einer Zündeinrichtung (24), um das Luft/Gas-Gemisch an dem Gasbrenner zu zünden,
• einem Flammendetektor (25), um eine Flamme an dem Gasbrenner zu erfassen, wobei:
die Zugangspanele eine Abdeckung (13) für das Gehäuse (11) ist und eine vordere (13')
und
eine obere (13") Wand des Gehäuses (11) bildet, und
der außen befindliche, kompakte gasbeheizte Erhitzer (10) ferner Befestigungseinrichtungen
(38, 39) aufweist, die von einem vorderen und einem oberen Abschnitt (13', 13") des
Gehäuses (11) zugänglich sind, wenn die Abdeckung (13) entfernt wird, wobei die Befestigungseinrichtungen
(38, 39) die Komponententeile innerhalb des Gehäuses (11) abnehmbar befestigen.
2. Außen befindlicher, gasbeheizter Erhitzer nach Anspruch 1, wobei das Wärmeaustauschmittel
eine flüssige Wasser- und Glykollösung ist.
3. Außen befindlicher, gasbeheizter Erhitzer nach Anspruch 2, wobei die flüssige Wasser-
und Glykollösung im wesentlichen eine 50/50-Mischung aus Wasser und Glykol ist.
4. Außen befindlicher gasbeheizter Erhitzer nach einem der vorhergehenden Ansprüche,
wobei das Verschlußmittel (50) ein mit einem Schlüssel betätigbarer Sperrzylinder
(52) ist, der ein Sperrelement (51) betätigt, um die Zugangspanele an dem Gehäuse
(11) zu befestigen.
5. Außen befindlicher, gasbeheizter Erhitzer nach einem der vorhergehenden Ansprüche,
wobei das Abzugsauslaßmittel eine Abzugsleitung (31) aufweist, die ein Einlaßende
hat, das an einem oberen Ende (29') des Behälters (26) befestigt ist, und ein Auslaßende,
das an einer Wand (11') des Gehäuses befestigt ist, um die Abgase in die Atmosphäre
außerhalb des Gehäuses (11) zu entleeren, wobei sich die Abzugsleitung (31) innerhalb
des Gehäuses (11) erstreckt, um Luft in dem Gehäuse (11) mindestens in dem Bereich
des Mischgebläses (23) zu erwärmen und dadurch vorgewärmte Luft für das Mischgebläse
(23) zu schaffen, um die Verbrennung des Luft/Gas-Gemisches zu steigern.
6. Außen befindlicher, gasbeheizter Erhitzer nach einem der vorhergehenden Ansprüche,
wobei die Heizspule (17) eine Spiralspule ist, die eine Vielzahl von Spiralen (17',
17") hat, wobei die Spule ein Einlaßende (18) und ein Auslaßende (19) hat und das
Kupplungsmittel einen Schnell-Verbinder aufweist, der an dem Einlaß- und Auslaßende
(18, 19) befestigt ist.
7. Außen befindlicher, gasbeheizter Erhitzer nach Anspruch 6, wobei die Heizspule (17)
aus zwei (17', 17") der konzentrisch angeordneten Spiralspulen besteht, die in Reihe
miteinander verbunden sind.
8. Außen befindlicher, gasbeheizter Erhitzer nach einem der vorhergehenden Ansprüche,
wobei das Konvektionsmittel (54) durch einen Abschnitt der Panele geschaffen ist,
der als ein Konvektionskanal durch zwei im Abstand gehaltene Blechtafeln (13'; 53)
gebildet ist, die in einem unteren vorderen Endabschnitt der Panele gebildet sind.
9. Außen befindlicher, gasbeheizter Erhitzer nach Anspruch 8, wobei das Konvektionsmittel
(54) mit einer vorderen Wand (13') der Abdeckung gebildet ist.
10. Außen befindlicher, gasbeheizter Erhitzer nach einem der vorhergehenden Ansprüche,
wobei der Gasbrenner ein Erdgasbrenner ist und die Abgase weniger als etwa 30 ppm
NOx bei 3% O2 emittieren.
1. Appareil extérieur de chauffage au gaz compact (10), pour chauffer un fluide destiné
à servir de milieu d'échange de chaleur, ledit milieu d'échange de chaleur opérant
dans une gamme de températures comprise entre environ -40°C et environ 82°C pour fournir
une puissance de chauffe comprise entre environ 8 800 Watt et environ 58 600 Watt,
ledit appareil de chauffage comprenant:
- un logement rectangulaire (11) fixable à l'extérieur d'un immeuble (12) auquel un
fluide à chauffer est distribué, chauffé et alimenté en tant que source de chaleur
de dispositifs de chauffage (60) contenus à l'intérieur de l'immeuble ; ledit logement
présentant :
• une trappe d'accès pour permettre un accès complet à l'intérieur dudit logement
(11),
• des moyens de verrouillage (50) pour faciliter le maintien et le retrait de ladite
trappe d'accès audit logement (11), et
• des moyens de convection (54) pour générer une circulation d'air à l'intérieur dudit
logement (11),
- des moyens d'attache pour permettre une mise en place et un retrait aisés dudit
appareil extérieur de chauffage au gaz compact (10),
- des composants comprenant :
• un enroulement de chauffage (17) supporté dans ledit logement (11) à travers lequel
ledit fluide circule,
• un boîtier cylindrique (26) thermiquement isolé présentant des parois circulaires
supérieure (29) et inférieure en matériau réfractaire et comprenant une chambre de
combustion cylindrique (16), ladite chambre de combustion (16) contenant ledit enroulement
de chauffage (17),
• un brûleur (22) cylindrique à gaz disposé à l'intérieur dudit enroulement (17) pour
chauffer ledit enroulement (17) et ledit fluide,
• un ventilateur (23) pour souffler un mélange air/gaz relié audit brûleur à gaz pour
l'alimenter en mélange combustible air/gaz, afin de maintenir une flamme stable en
présence de conditions climatiques ambiantes,
• un échappement maintenu sur la paroi supérieure (29) dudit boîtier (26) et muni
de moyens d'échappement (31 ; 35) pour évacuer lesdites fumées de ladite chambre de
combustion (16) vers l'atmosphère à l'extérieur dudit logement (11),
• des moyens d'allumage (24) pour enflammer ledit mélange air/gaz à l'endroit dudit
brûleur à gaz,
• un détecteur de flamme (25) pour détecter une flamme à l'endroit du brûleur à gaz,
dans lequel :
ladite trappe d'accès forme un couvercle (13) pour ledit logement (13) et constitue
des parois frontale (13') et supérieure (13") dudit logement (11), et l'appareil extérieur
de chauffage au gaz compact (10) comprend en outre des moyens de fixation (38, 39)
accessibles depuis des zones frontale et supérieure (13', 13") dudit logement (11)
quand ladite trappe (13) est retirée, lesdits moyens de fixation (38, 39) maintenant
de manière amovible lesdits composants à l'intérieur dudit logement (11).
2. Appareil extérieur de chauffage au gaz selon la revendication 1, dans lequel ledit
milieu d'échange de chaleur est une solution liquide d'eau et de glycol.
3. Appareil extérieur de chauffage au gaz selon la revendication 2, dans lequel ladite
solution liquide d'eau et de glycol est un mélange à sensiblement 50/50 d'eau et de
glycol.
4. Appareil extérieur de chauffage au gaz selon l'une quelconque des revendications précédentes,
dans lequel lesdits moyens de verrouillage (50) sont un cylindre de verrouillage à
clé (52) agissant sur un élément de verrouillage (51) pour maintenir ladite trappe
d'accès par rapport audit logement (11).
5. Appareil extérieur de chauffage au gaz selon l'une quelconque des revendications précédentes,
dans lequel lesdits moyens d'échappement comprennent un conduit d'échappement (31)
ayant une extrémité d'entrée maintenue sur la paroi supérieure (29') dudit boîtier
(26) et une extrémité de sortie maintenue sur une paroi (11') dudit logement pour
évacuer lesdites fumées dans l'atmosphère à l'extérieur dudit logement (11), ledit
conduit d'échappement (31) s'étendant à l'intérieur dudit conduit (11) pour chauffer
l'air à l'intérieur dudit logement (11) au moins dans la zone dudit ventilateur de
mélange (23) et ainsi alimenter le ventilateur de mixage (23) en air préchaufé pour
favoriser la combustion dudit mélange air /gaz.
6. Appareil de chauffage à gaz selon l'une quelconque des revendications précédentes,
dans lequel ledit enroulement de chauffage (17) est un enroulement hélicoïdal présentant
une pluralité d'hélices (17', 17"), ledit enroulement présentant une extrémité d'entrée
(18) et une extrémité de sortie (19), lesdits moyens d'attache comprenant un connecteur
de type attache rapide maintenu auxdites extrémités d'entrée et de sortie (18, 19).
7. Appareil de chauffage à gaz selon la revendication 6, dans lequel ledit enroulement
de chauffage (17) comprend deux enroulements hélicoïdaux (17', 17") disposés concentriquement
et connectés en série.
8. Appareil de chauffage à gaz selon l'une quelconque des revendications précédentes,
dans lequel lesdits moyens de convection (54) sont constituées par une section de
la trappe, deux tôles métalliques (13' ; 53) formant canal de convection dans une
partie frontale inférieure de ladite trappe.
9. Appareil de chauffage à gaz selon la revendication 8, dans lequel lesdits moyens de
convection (54) sont formés par ladite paroi frontale (13') de ladite trappe.
10. Appareil de chauffage à gaz selon l'une quelconque des revendications précédentes,
dans lequel le brûleur à gaz est un brûleur de gaz naturel, lesdites fumées émettant
moins d'environ 30 ppm de NOx à 3% de O2.