GB2356698A

GB2356698A - Heating appliance having a downdraught arrangement

Info

Publication number: GB2356698A
Application number: GB9919719A
Authority: GB
Inventors: Alan Pryke
Original assignee: Focal Point Fires PLC
Current assignee: Focal Point Fires PLC
Priority date: 1999-08-20
Filing date: 1999-08-20
Publication date: 2001-05-30
Anticipated expiration: 2019-08-20
Also published as: GB9919719D0; GB2356698B

Description

2356698 IMPROVEMENTS IN RELATION TO HEATING APPAPATUS The present

apparatus relates to heating apparatus, - and S more particularly to an open flued heatingapparatus.

Whilst the specific embodiment described relates to a gas fire, the present invention is equally applicable to other fuel types, such as a coal or oil fired heating appliance.

A conventional gas fire comprises.a combustion chamber, or fire box, in which combustion of the fuel takes place. Air for combustion enters the combustion chamber through an inlet, generally located below the chamber from the room in which the apparatus is situated, by the action of natural is draught. An outlet is provided towards the top of the combustion chamber, for the combustion products to escape, and be vented through the chimney or flue provided for this purpose.

In the event of a flue blockage, or down draught conditions (in which the air travels back down the chimney or flue, due, for example, to the external weather conditions), the combustion gases cannot escape through its usual route. If the heating apparatus is open-fronted, with an open 2S combustion chamber, such as a coal fire, or an open-fronted "living flame" gas fire, then the combustion gases can escape out of the front of the appliance.

However, in a close-fronted fire, if the flue becomes blocked, or in down draught conditions, the combustion gases tend to build up in the region of the combustion chamber.

A down draught acting on an unprotected firebox can force 3S flames down through the burner of the appliance causing damage to the controls and other components located below the burner. In such conditions, the user's safety may also be at risk, if they happen to be in proximity to the fire.

Heating apparatus thus disturbed by flame reversal is also highly likely to produce excessive CO (carbon monoxide) gas, thereby giving rise to an additional hazard.

A down draught diverter is therefore provided, particularly on an open flued closed-fronted gas fire, to protect the burner and combustion chamber from the damaging effects of intermittent draught reversal in a chimney or flue. In addition, in the event of flue blockage, the appliance may also function without degradation of the combustion is products, so that the build up of toxic by-products, such as CO gas is not excessive.

Various designs of down draught diverter are known. Traditionally, a down draught diverter is either built vertically on the back of outset, or hearth standing, fires, as illustrated in Figures 1A and 1B of the accompanying drawings, or horizontally on the top of inset type fires, as illustrated in Figures 2A and 2B of the accompanying drawings.

The down draught diverters are provided with a baffle, such that in normal use, the combustion gasses pass around the baffle, before passing up the flue. In down draught conditions, when the flow of air in the flue is reversed, the baffle provides a barrier to disturb air flow, and prevent, as far as possible, the hot combustion gases from re-entering the combustion chamber.

As can be seen from the drawings, existing diverters, are canopy constructions which are relatively large and bulky, having regard to their function, such that they do not easily lend themselves to small shallow inset fires.

It is therefore an object of the present invention to provide improvements in relation to one or more of the matters discussed above, and/or to provide improvements generally.

According to the present invention there is provided heating apparatus comprising a combustion chamber having an outlet for egress of combustion gases from the chamber to the flue; an air inlet for the supply of air to the combustion chamber, and optionally to provide a convection current of air; an aperture to allow ingress and egress of fluid between the apparatus and the room in which the apparatus is located; and a baffle member to direct the flow of fluid between the combustion chamber and the flue; wherein the aperture is located above the combustion chamber in proximity to the baffle, and in communication with the flue.

The baffle member serves as a down draught diverter. Under normal flue conditions, the hot gasses from the combustion chamber are drawn into the flue, around the baffle, and are evacuated up the flue by the natural draught mechanisms of hot air rising. Air from the room is also drawn into the flue through the aperture.

Under down draught conditions, the flow of fluid in the flue is reversed, and gases from the flue pass over the top of the baffle. In these conditions, the combustion gases are unable to pass out of the flue. However, the apparatus of the present invention provides an alternative route for the fluid, because both the combustion gases and the down draught may evacuated into the room via the aperture.

Evacuation of the combustion chamber in this way prevents hazardous pressurisation of the combustion chamber.

In an embodiment, the configuration of the baffle member S and/or housing is such that the fluid egressing from the combustion chamber is forced to pass through a restriction, prior to passing the air inlet.

In this way, under down draught conditions, the flow of air passes through the throat portion area, and its frictional contact with the gases from the combustion chamber underneath, and an increase in cross-sectional area of the passage causes a venturi effect, which enhances the evacuation of the combustion chamber gases.

The throat area can easily be designed to suit a number of different product types and sizes, to thereby create a negative pressure in the firebox under the required conditions.

In an embodiment, the baffle member is located on a mounting attachable to the main body of the apparatus, and may be formed as an integral part of the mounting. In this form, there are no internal baffles to be fitted to the 2S down draught diverter, thereby making the apparatus more straightforward to assemble.

The mounting may be in the general form of an open box member, located over the back face of the main body of the apparatus so that the baffle element _Js located close to the air input aperture.

In an embodiment, one end face of the mounting, preferably the top most end face, may serve as a debris deflector, to prevent dust and other debris from blocking the outlet to the f lue, or entering the appliance. The mounting may also serve to provide a duct to direct the combustion gases from the combustion chamber, passed the baf f le.

The shape and dimensions of the baffle/cover panel, and thus the throat dimensions may vary, according to the size and shape of the heating apparatus. The cover panel may be shaped to conform to the shape of the existing fire back, if required. Using the apparatus of the present invention, the appliance does not have to be significantly deeper or taller, than an equivalent appliance which does not incorporate a down draught diverter, and the flame picture area may be maintained.

A useful further advantage is that the usual test to show that all the combustion gases are travelling up the flue, known as the spillage test can be done at the top of the fire through the throat area of the draught diverter. This test entails visualising the airflow into the flue using a trail of smoke produced from a smoke match. In conventional fires, this must be done at the rear of the fire, or at the bottom of the glass panel, which is often difficult to get to. The arrangement of the present invention provides enhanced accessibility.

In an embodiment, the apparatus comprises a further flow directing element/s, such that in use, room air entering from the lower air inlet which supplies the combustion chamber forms a convention current which passes by the combustion chamber to be heated by the hot combustion gases. The heated air then passes out of the apparatus, by convection, and is directed back into the room. In this way the efficiency of the heating appliance is increased. The combustion gases are typically at a temperature of approximately 500"C to 8000C, such that the convected air is -6heated by approximately 3500C.

The combustion gases may pass through a heat exchanger located at the outlet of the combustion chamber, before escaping passed the baffle and out of the flue. In such an arrangement, the convected air passes around the heat exchanger.

The heated convected air may be directed out of the apparatus through an outlet in the front of the fire, which is covered by a hood element in order to direct the flow.

An advantage of the design of the present invention, which results from placement of the diverter aperture at the top end of the fire, and above the convection flow outlet is that the temperature around the top cross member of a convector fire is reduced.

In conventionally designed convector fires, the convection outlet is at the top of the appliance. In such apparatus, the hot air from the convection current outlet tends to heat up the appliance. The aperture provided in the present invention serves as both an air inlet and outlet, so that cool air flows around the convector outlet, to reduce the temperature of the appliance and its surroundings. This enhances the safety of the apparatus, and reduces technical difficulties relating to high temperatures in respect of both the fire itself, and its surroundings.

A further advantage of the present invention is that the flow of convected air out of the appliance may be separated from the air flow through the diverter aperture into the flue. The heated convector air flow may be directed away from the diverter aperture, such that the heated air may be used to heat the room, and does not escape up the f lue via the aperture. This increases the efficiency of the appliance, and is often a drawback of conventional designs of inset fires.

S Whilst it is intended that the present invention may be used in conjunction with open fronted fires, in which the combustion chamber is open to the room in which the apparatus is located, the efficiency of the apparatus may be further improved by providing a closed chamber. If desired, the front of the combustion chamber may take the form of a glass panel, such that combustion of the fuel may be visible to the user.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figures 1A, 1B and 2A, 2B which illustrate prior art systems described in the preamble;

Figure 3 is a sectional view of apparatus according to the present invention, in use under normal conditions; and Figure 4 is a sectional view of the apparatus of Figure 3, in down draught conditions.

As can be seen in Figures 3 and 4, a heating appli-ance 10 in the form of an open flue gas fire, is located partially within a flue 11. The appliance 10 comprises a combustion chamber 12, in which combustion of the gas (supply not shown) takes place. The combustion chamber 12 is of the ",closed" type, and the front of the chamber 12 is provided with a glass front 14, in order that the fuel bed is visible.

An outer fire box 16 provides an inlet for air to enter the appliance to form a convection current. This air supply also provides the air required for combustion in the chamber 12.

The combustion chamber 12 includes an outlet 18 through which the combustion gases may escape in order to reach the flue 11, after passing through a heat exchanger 20. The convection air current entering through the lower air inlet passes through the heat exchanger 20, where it is heated by the hot combustion gases, and passes out into the room in which the appliance 10 is situated, through outlet 22. The direction of the flow is controlled by the provision of a hood 24.

is The appliance 10 also includes a further aperture 26 located towards the top of the appliance. The aperture 26 is in communication with the flue 11, and in normal operation, as illustrated in Figure 3, room air enters the aperture 26, and is drawn up into the flue 11. This serves to cool the top of the appliance 10, which might otherwise reach a high temperature, heated by the hot convection air current.

A structure 28 which takes the general form of an open box is mounted on the back of the outer fire box 16, to provide a down draught diverter 30 for the appliance 10. The back face 32 of the structure 28 is shaped to form a baffle 34, and to provide an outlet 36 for the combustion gases leaving the heat exchanger 20. The top end face 34 forms a debris deflector.

Under normal flue conditions, illustrated in Figure 3, the hot gasses from the combustion chamber 12 are drawn into the flue 11, around the baffle 32, and are evacuated up the flue by the natural draught mechanisms of hot air rising. Air from the room is also drawn into the flue through the diverter aperture 26.

Under down draught conditions, shown in Figure 4, the flow of fluid in the flue 11 is reversed, and gases from the flue 11 pass over the top of the baffle 32. In these conditions, the combustion gases are unable to pass out of the flue 11. However, both the combustion gases and the 10 down draught may evacuated into the room via the aperture 26. Evacuation of the combustion chamber in this way prevents hazardous pressurisation of the combustion chamber.

Claims

1. Heating apparatus comprising a combustion chamber having an outlet for egress of combustion gases from the chamber to the flue; an air inlet for the supply of air to the combustion chamber, and optionally to provide a convection current of air; an aperture to allow ingress and egress of fluid between the apparatus and the room in which the apparatus is located; and a baffle member to direct the flow of fluid between the combustion chamber and the flue: wherein the aperture is located above the combustion chamber in proximity to the baffle, and in communication with the flue.

2. Apparatus according to claim 1 wherein the configuration of the baffle member and/or housing is such that the fluid egressing from the combustion chamber is forced to pass through a restriction, prior to passing through the air inlet.

3. Apparatus according to claim 1 or claim 2 wherein the baffle member is located on a mounting attachable to the main body of the apparatus.

4. Apparatus according to claim 3 wherein the baffle member is formed as an integral part of the mounting.

5. Apparatus according to claim 3 or claim 4 wherein the mounting is in the general form of an open box member, located over the back face of the main body of the apparatus so that the baffle element is located close to the air input aperture.

6. Apparatus according to any one of claims 3 to wherein one end face of the mounting serves as a debris deflector.

7. Apparatus according to any one of claims 3 to 6 wherein the mounting serves to provide a duct to direct the combustion gases from the combustion chamber, passed the baffle.

8. Apparatus according to any one of the preceding claims comprising a further flow directing element/s, such that in use, room air entering from the lower air inlet forms a convention current which passes by the combustion chamber to be heated by the hot combustion gases.

9. Apparatus according to claim 8 wherein combustion gases are caused to pass through a heat exchanger located at the outlet of the combustion chamber, before escaping past the baffle and out of the flue.

10. Apparatus according to any one of the preceding claims wherein heated convected air directed out of the apparatus through an outlet in the front of the fire, which is covered by a hood element in order to direct the flow.

11. Heating apparatus substantially as hereinbefore described with reference to the accompanying drawings.