Gas-fired heating apparatus

Abstract

 The apparatus comprises a furnace which is provided on one side, preferably at the bottom, with one or more burners (6) which can be ignited by a pilot light (22), and at the top with a heat exchanger (1) covered by a top wall (12) connecting a flue (14). A self-acting valve (16) is mounted in the flue, which valve is opened when a fan (30) arranged in the air supply duct or the flue rotates at a high speed, and closed, for instance by means of a weight (18) or a spring, when said fan rotates at a low speed. An air passage (31) may be provided in the flue downstream of the self-acting valve to create a by-pass effect.

Description

[0001] The invention relates to a gas-fired heating apparatus, comprising a furnace which is bounded on one side, preferably at the bottom, by one or more burners which can be ignited by a pilot light, and at the top comprises a heat exchanger covered by a top wall comprising a flue.

[0002] The invention aims to improve such an apparatus known from applicant's Dutch patent application 88.00649 in respect of the operation of the pilot light.

[0003] Now, it is known to switch off the fan when only the pilot light is burning. With certain flue constructions and wind conditions, the pilot light may be choked or condensation of the flue gases may occur in the flue. To avoid the problems described above, it is required that when the pilot light is burning the fan continues to rotate, but slowly. In that case, however, the displacement of air in the boiler should not be excessive, because then the heat exchanger would cool off too much, due to which it would take too much time for any hot water to be supplied when required. Fans that qualify for this type of boiler, however, cannot be adjusted to as low a speed as is desirable and thus cause the heat exchanger to cool off too much.

[0004] The invention aims to overcome the drawbacks mentioned.

[0005] To that effect an apparatus of the type described in the preamble is characterized according to the invention by a self-acting valve mounted in the air supply duct or the flue, which valve is opened when the fan rotates at a high speed, and closed when the fan rotates at a low speed, for instance by means of a weight or a spring. When the fan rotates at a low speed, the valve will be closed, but nevertheless there will be a minor degree of air circulation within the furnace, which also contains the pilot light, so that the water of the boiler will not cool off completely, and at the same time the pilot light will not choke. When, on the other hand, heat is required, the fan will be switched to the normal mains voltage, which causes the fan to rotate at high speed, which in turn increases the difference in pressure across the valve and, accordingly, the valve will be completely opened.

[0006] To effect the intended action of the valve, the shaft on which the valve is mounted may be mounted rotatably and asymmetrically in the flue.

[0007] To ensure the proper operation of the valve, it may comprise an "additional" weight, mounted on the long side of the asymetrically arranged valve.

[0008] Preferably, the centre of gravity of the valve and the weight together is above the horizontal plane containing the shaft. Thus a proper unstable valve action is effected in response to the small differences in pressure which occur. There are not any intermediate positions, but only end positions.

[0009] In a further elaboration of the invention, by forming a bend in the valve it is ensured that also when the flue is completely cleared, the valve is still under the influence of the flue gas passing by. The bend may be formed in the "long" side of the valve.

[0010] To ensure the valve will assume a proper closed position, a valve support may be mounted in the flue.

[0011] In a further elaboration of the invention a stop may be mounted in the flue so as to ensure the valve will assume a proper "open" position.

[0012] In a further elaboration of the invention, when the fan is arranged in the air supply duct, an air passage may be provided in the flue downstream of the self-acting valve, which creates a "by-pass" effect. The fan may be arranged in the flue downstream of the self-acting valve and the air passage may be arranged upstream of the fan. This permits the use of a reduced pressure throughout the system, so that problems of leakage will be avoided.

[0013] The self-acting valve and the air passage referred to may be of such construction that when the valve is opened the air passage is completely or partly shut off. Thus the advantage is obtained that a smaller fan will suffice since during the burning process the valve will be open and the by-­pass will be shut off.

[0014] To explain the invention one embodiment of the wall boiler will now be described, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic longitudinal sectional view of a wall boiler;

Fig. 2 is an enlarged view of the valve arranged in the flue;

Fig. 3 is a plan view of the valve according to Fig. 2;

Fig. 4 is a view similar to Fig. 1 of another embodiment; and

Fig. 5 is a view according to Fig. 1 of yet another embodiment.

[0015] According to the drawings a heating apparatus as known from Dutch patent application 8800649 comprises a heat exchanger 1 with fins 2 and a water compartment 3. To the water compartment 3 connect an inlet 4 and, diametrically opposite, an outlet 5, both omitted for the sake of clarity.

[0016] Arranged upstream of a burner 6 are injectors 7, a manifold 8 and a gas supply duct 9. The injectors 7 and the burner 6 are arranged in a body 10 whose inner wall has an insulating lining 11 applied to it. In the vicinity of the burner a pilot light 22 is provided.

[0017] The top of the heat exchanger 1 is closed with a hood 12 in which an opening is provided above which a fan 13 is arranged whose outlet connects to a flue 14 for burnt gases.

[0018] The whole arrangement is accommodated in a housing or box 15 in which an air supply opening is provided (not shown).

[0019] In the flue 14 a valve 16 is mounted. As further shown in Fig. 1, the furnace is closed at the top with a drum provided with an insulating cover 20. In this connection reference is made to EP-A-89200666.9.

[0020] With reference to Figs 2 and 3, the operation of the valve 16 will be described. The valve 16 is mounted on a shaft 17 rotatably mounted in the wall of the flue 14. The shaft 17 is mounted asymmetrically in the flue 14. As further shown in the drawing, a weight 18 is mounted on the upper side of the valve, causing the valve to close when no heat is required and the burner is off. The end of the valve 16 that is remote from the shaft 17 has a bend 19. The end portion 19 thus formed, when the valve is in the closed position, rests on a support 20 fixedly attached to the wall of the flue 14. The bent portion 19 ensures that the flue gas flow continues to bring a force to bear on the valve when it is in the fully opened position.

[0021] When the valve is closed, the fan 13 operates at a lower voltage, for instance of 70 volts, which ensures the burner space is ventilated. This last is of particular importance when there is a pilot light in the burner space. Furthermore, it is thus ensured that the water in the heat exchanger 1 is maintained at a reasonable temperature (for example 70°C), so that upon tapping one need not wait long for hot water to be supplied. However, when heat is required by the central heating system or there is a demand for hot tap water, the fan will be adjusted to a voltage of 220 volts, which causes the valve 16 to move automatically into the open position under the influence of the difference in pressure. In order to keep the valve in the proper open position, a stop 21 is mounted on the wall of the flue 14 for the weight to engage when the valve is opened.

[0022] The means for switching the motor of the fan from the lower to the higher voltage and vice versa have been omitted for the sake of clarity since such means are well known in the art, for instance from Dutch laid-open patent application 79,04582.

[0023] It will be clear that within the framework of the invention modifications are conceivable. Thus, the valve has flat edges at its lower and upper side as shown in Fig. 3, which ensures the valve is open widely when in the opened position.

[0024] In the embodiments shown in Figs 4 and 5 like parts are designated by like reference numerals. A difference between the apparatus according to Fig. 4 and the apparatus according to Fig. 1 resides in the fact that in the embodiment according to Fig. 4 a fan 30 is provided which is arranged in the air supply duct. The direction of flow is indicated with an arrow

[0025] Further, in the flue 14, just above the valve 16 a tubular opening 31 is provided, which creates a by-pass effect in that in such an arrangement a large part of the air supply will be directly discharged via the flue and will thus be prevented from withdrawing any substantial heat from the burner space. Of course, sufficient air, i.e. oxygen, must be supplied to ensure the pilot light will not choke.

[0026] The end of the tubular opening 31 terminating in the flue is indicated at 32 and can be shut off by coaction with the top of the weight 18.

[0027] Fig. 5 shows a variant of the apparatus according to Fig. 4, in which a fan 35 is arranged in the flue 14 again. The valve 16 and the tubular "by-pass" opening 31 are identical to those shown in Fig. 4 and will therefore not be further described here.

[0028] The constructions described not only have the advantage that any loss sustained when the burner is inoperative will be small, but also that the dew point of the air/burnt-gas mixture in the flue is lowered, which prevents condensation in the flue.

Claims

1. Gas-fired heating apparatus, comprising a furnace which is bounded on one side, preferably at the bottom, by one or more burners which can be ignited by a pilot light, and at the top comprises a heat exchanger covered by a top wall comprising a flue, characterized by a self-acting valve mounted in the air supply duct or the flue, which valve is opened when a fan arranged in the air supply duct or the flue rotates at a high speed, and closed, for instance by means of a weight or a spring, when said fan rotates at a low speed

2. Apparatus according to claim 1, characterized in that the valve is rotatably mounted by means of a shaft which is asymmetrically mounted relatively to the flue and the valve.

3. Apparatus according to claim 2, characterized in that the weight is arranged on the "long" side of the asymmetrically arranged valve and the centre of gravity of the valve and the weight together is above the horizontal plane containing the shaft.

4. Apparatus according to one or more of the preceding claims, characterized in that the valve has a bend or curve.

5. Apparatus according to claim 4, characterized in that the bend or curve is formed on the "long" side of the valve.

6. Apparatus according to claim 5, characterized in that a valve support or valve seat is mounted in the flue.

7. Apparatus according to one or more of the preceding claims, characterized in that a stop for the weight of the valve is mounted in the flue.

8. Gas-fired heating apparatus according to claim 1, in which the fan is mounted in the air supply duct, characterized in that an air passage is provided in the flue downstream of the self-acting valve.

9. Gas-fired heating apparatus according to claim 1, in which the fan is mounted in the flue, characterized in that the fan is mounted in the flue downstream of the self-acting valve and a passage is provided upstream of the fan.

10. Apparatus according to claim 8 or 9, characterized in that said passage comprises adjustable closing means.

11. Gas-fired heating apparatus according to claim 8, 9 or 10, characterized in that the self-acting valve and the air passage are of such construction that the air passage is partly or completely closed when the valve is opened.

Drawing