Heating apparatus comprising a burner of the kind to which a substantially stoechiometric fuel/airmixture is supplied

Abstract

 Apparatus comprising a burner (2) of the type to which a substantially stoichiometric fuel/air mixture is supplied, a flow duct (3) accomodating said burner consisting of a feed duct (4) for combustion air and a discharge duct (5) for combustion gas, a gas line (7) opening out into said feed duct and provided with a gas valve (8), a mixing box for mixing gas from said gas line with combustion air and an ignition device (24) comprising a spark forming element. The burner comprises only a main burner. The spark forming element is positioned in the direct proximity of said main burner, for the purpose of ignition of same, and the gas valve comprises only one closable gas duct.

Description

[0001] The invention relates to a heating apparatus comprising a burner of the type to which a substantially stoichiometric fuel/air mixture is supplied, a flow duct accommodating the burner consisting of a feed duct for combustion air and a discharge duct for combustion gas, a gas line opening out into the feed duct and provided with a gas valve, a mixing box for mixing gas from the gas line with combustion air and an ignition comprising a spark forming element.

[0002] A burner of such a heating apparatus is also sometimes called a fully pre-mixed burner. This means that all the air necessary for combustion is mixed in one stage with the gas for combustion. Such a burner has a very small burn-out hei­ght, as a result of which a heat exchanger can be arranged at a small interval from the burner, which results in a limited total construction height. Known heating apparatuses of this type comprise a pilot burner to which a small part of the gas is fed and ignited using the spark-forming element. When the pilot burner is burning the quantity of gas corresponding to the full loading of the burner is supplied and the main burn­er is ignited using the pilot burner. Owing to the presence of the pilot burner, the separate gas supply for same and the extra gas tap that is required, this heating apparatus is comparatively complicated.

[0003] The invention has for its object to give a heating app­aratus of the type described in the preamble a simpler and more compact form. This is achieved in a heating apparatus according to the invention because the burner comprises only a main burner, because the spark forming element is position­ed in the direct proximity of the main burner, for the pur­pose of ignition of same, and the gas valve comprises only one closable gas duct. Very surprisingly, it has been found that, provided that the gas/combustion air ratio does not deviate too greatly from the optimum ratio, the burner can be ignited directly in very reliable manner, while the quantity of gas/air corresponding to a full load is supplied thereto. The ignition is reliable to the extent that direct ignition of a wholly pre-mixed burner at full load is permissible acc­ording to the invention, for example, for domestic heating installations.

[0004] In accordance with a further development of the invent­ion the flow duct comprises a fan and an adjustable restrict­ion. As a result an optimum gas/air volume flow can be adj­usted in the burner irrespective of the length and resistance of the total flow duct.

[0005] The invention will be further elucidated with reference to the annexed drawing. The figure shows a schematic view of a heating apparatus according to the invention.

[0006] The heating apparatus 1 in fig. 1 comprises a burner 2 which in this embodiment takes the form of a so-called fully pre-mixed burner. Burner 2 is accommodated in a flow duct 3 which consists of a combustion air feed duct 4 and a combust­ion gas discharge duct 5. Feed duct 4 and discharge duct 5 respectively lead from and to the outside.

[0007] Accommodated in feed duct 4 is a fan 9 which is driven by a motor 10. At the location of the fan 9 gas is carried into the duct 4 via gas supply 7. This supply at the location of the fan 9 results in a good mixing of gas and combustion air. The supply of gas is regulated using gas tap 8.

[0008] Located in the combustion gas discharge duct 5 is a heat exchanger 11. This also forms part of the water circuit 12 in which water is force circulated using pump 13. The water supplied with pump 13 is heated in the heat exchanger 11.

[0009] The burner 2 comprises a perforated plate 20 for dis­tribution of the supplied gas/air mixture and a ceramic bur­ner plate 21 placed beneath it having a large number of fine channels. The supplied combustible mixture is ignited using the ignition 24 on the underside of ceramic plate 21.

[0010] Heating apparatus 1 further comprises a control device 14. Connected to control device 14 are a control thermostat 15 and a maximum thermostat 16 which co-operate with feelers 17 protruding into the heating water. Also fitted is a flow switch 18 so that the control device 14 can detect whether the pump 13 is functioning. The gas tap 8, the fan motor 10 and pump 13 are controlled by control device 14. In order to check whether there is sufficient water present in the circ­uit and to see what the water temperature is, a generally known pressure/ temperature gauge is fitted.

[0011] Arranged for adjustment of the resistance corresponding with an optimum combustion air delivery in the whole of the flow duct 3 is an adjustable compensating valve 22. Adjust­ment can be controlled with the pressure sensor 23.

[0012] The gas tap 8 comprises only one closable gas duct. As soon as the burner must be ignited on the basis of the meas­urement data fed to the control device 14, the motor 10 of fan 9 is actuated, following which the gas tap 8 is placed from the closed to the opened position in one action. As a result gas flows via line 7 into the combustion air feed duct 4. A quantity of gas/air mixture corresponding to full load­ing of the burner is thus supplied to burner 2. At the same time as the gas tap 8 is opened the schematically shown ign­ition plug 24 is switched on, igniting the flame on the und­erside of the ceramic burner plate 21 as soon as the mixture containing gas arrives there. It is apparent that the entire gas control and ignition system according to the invention is exceptionally simple.

[0013] For regulation of the total resistance in flow duct 3, this total resistance being dependent on the length and res­istance of the combustion air feed and gas discharge ducts 4, 5, the adjustable restriction 22 in the form of a butterfly valve is placed in a suitable position. The suitable position is determined using a pressure difference sensor 23 which determines the difference in pressure on either side of a nozzle. This difference in pressure is proportional to the volume flow through the nozzle.

Claims

1. Heating apparatus comprising a burner of the type to which a substantially stoichiometric fuel/air mixture is sup­plied, a flow duct accommodating said burner consisting of a feed duct for combustion air and a discharge duct for combus­tion gas, a gas line opening out into said feed duct and pro­vided with a gas valve, a mixing box for mixing gas from said gas line with combustion air and an ignition comprising a spark forming element, characterized in that the burner com­prises only a main burner, that the spark forming element is positioned in the direct proximity of said main burner, for the purpose of ignition of same, and that the gas valve com­prises only one closable gas duct.

2. Apparatus as claimed in claim 1, characterized in that the flow duct comprises a fan and an adjustable restri­ction.

3. Apparatus as claimed in claim 1 or 2, characterized in that the burner is of the type with a substantially flat burner surface extending transversely of the gas flow gener­ated in the flow duct.

4. Apparatus as claimed in any of the foregoing claims, characterized in that at an interval from the burner surface and approximately at the burn-out height thereof is located a heat exchanger.

Drawing