GB2242508A - Caravan water heater - Google Patents

Abstract

A gas-fired water heater for a caravan comprises a gas/air mixing tube 14 and a heat exchanger 17 with a pre-mix burner element 19, preferably a perforated ceramic burner adapted to produce a short flame, disposed therebetween. The gas burner input is preferably of the order of 8 kilowatts. A fan-powered exhaust 20 is associated with the water heater for extraction of combustion products and exhaustion thereof outside of the caravan via a multi-directional flue. <IMAGE>

Description

CARAVAN WATER HEATER This invention relates to water heaters particularly for use in caravans, mobile homes or other dwellings having a relatively restricted living space (hereinafter and in the claims for convenience simply referred to as "caravans").

When a caravan is driven on to site and the occupant requires hot water the usual procedure is to obtain a supply of water in a drum or similar from a mains water supply, connect same by a pipe incorporating a pump to a gas-fired water storage heater in the caravan, and wait until the water is heated sufficiently for use. This waiting time, with existing gas-fired water heaters, is usually of the order of thirty minutes or thereabouts.

It is an object of the present invention to provide a gasfired water heater which will provide virtually instantaneously an adequate supply of hot water for the caravan occupant.

According to the present invention there is provided a water heater, particularly for a caravan, comprising a gas/air mixing tube and a heat exchanger between which is disposed a pre-mix burner element, and a fan-powered exhaust chamber or duct.

The water heater is preferably of extremely compact bulk so that it can be located within any convenient location within a caravan, for example under a bed bunk spaced, say, 250mm, above the caravan floor without occupying the full width of the bed bunk thereby leaving storage space lengthwise and widthwise under the bed bunk.

Preferably, the pre-mix burner element is a perforated ceramic plate adapted to produce a short flame, for example 4mm high.

The pre-mix burner element may alternatively be formed of metal.

The fan-powered exhaust chamber or duct preferably includes a fan chamber housing a suction fan driven by a motor and located external of the fan chamber or duct for cooling purposes.

Preferably, the exhaust gas outlet flue from the fan chamber, which is normally disposed outside the caravan can be directed in any convenient direction. For example, the exhaust gases may be directed sideways out of a wall of the caravan, or underfloor, or out of a chimney if the water heater is disposed within a cupboard in the caravan for example.

The flue is preferably a small rectangular pipe or duct.

The gas supply is preferably bottled L.P. (low pressure) gas connected to a gas injector of the mixing tube.

The gas supply, water supply and ignition are preferably electronically controlled and are preferably powered by a 12 volt or a 24 volt battery.

Ignition is preferably effected by a non-permanent pilot flame.

The gas burner input is preferably of the order of eight kilowatts.

The water inlet to the water heater is preferably fitted with a water flow switch which is operatively associated with the gas controls such that there is no gas supply to the burner element, and consequently no ignition, until there is a sufficient flow of water to the water heater.

A suitable water volume in the water heater for gas supply/ignition start up is approximately 1.5 litres.

The water outlet from the water heater is preferably fitted with a thermostat to ensure that the water temperature does not exceed a predetermined maximum value.

A suitable maximum water temperature value is approximately 70 C.

The water heater controls preferably include a pressure switch operatively associated with the gas controls, which pressure switch immobilises gas supply and ignition if the suction from the fan is adequate.

The water heater is preferably enclosed in a room-sealed casing.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing in which: Fig. 1 is a diagrammatic side view of a caravan water heater according to the invention; Figs. 2 and 3 are respectively diagrammatic a side view and a sectional end view of the caravan water heater to an enlarged scale; Fig. 4 is a diagrammatic view of the fan chamber illustrating alternative dispositions of flue egress; and Fig. 5 is a front elevation of the caravan water heater with its insulated casing removed.

The gas-fired water heater generally indicated at 10 is disposed in a caravan generally indicated at 11 under a bunk bed 12 for example. It is enclosed in a room sealed casing (not shown).

The gas-fired water heater 10 comprises a gas/air mixing chamber 13 housing a mixing tube 14 through which LP gas is fed from a tank or cylinder 15 to a gas injector 16.

A heat exchanger 17 is spaced from the mixing chamber 13 and mixing tube 14 and includes heat exchange tubes 18 (see Figs. 2 and 3) disposed in parallel and through which water is passed, the water being heated by combustion gases generated at a pre-mix burner element 19 which is constituted by a ceramic body pierced by a multiplicity of holes.

This pre-mix burner element 19 creates a short (4mm) blue flame to heat the water flowing through the heat exchanger tubes 18.

Water heating is thus achieved by convection heating generated from the pre-mix burner element 19.

The gas-fired water heater 10 is negatively fan-powered by a suction fan 20 housed in a casing 21 having a flue outlet 22 of rectangular cross-section.

The exhaust fan 20 is driven by a motor 23 which may be disposed externally of the housing 21 for cooling purposes (see for example Figs. 2 and 3).

The gas-fired water heater 10 has electronic control means including gas supply and ignition controls operated from a 12 volt or 24 volt battery (not shown) which also supplies power to the motor 23.

The input of the gas burner (injector) 16 is of the order of 8 kilowatts which provides extremely fast water heating, say, of the order of one minute to provide a sufficient supply for a shower or domestic washing.

In the embodiments shown in Figs. 1, 2, 3 the exhaust from the gas-fired water heater 10 is under the floor 24 of the caravan and combustion air for the gas burner element 19 is through an opening 25 in the floor closed by a perforated grill 26, the combustion air entering the gas burner injector 16 as indicated by arrows A.

The water supply for the gas-fired water heater 10 is provided, as is customary, by a container 27 filled with water from a mains supply and delivering water to the heat exchanger tubes 18 via a pipe 28 connected to a pump 29 disposed in the container 27.

The exhaust fan system can be arranged so that the exhaust flue 22 is directed in any convenient direction (see Fig. 4).

The water-fired gas heater 10 according to the present invention can be disposed in such a way that there is upward exhaust of combustion products from the gas-fired water heater through a vertical chimney extending out of the roof of the caravan.

The combustion air inlet may be concentric with the exhaust flue 22 or in a wall of the caravan.

The gas supply and ignition controls and other water heater controls are electronically controlled.

The gas supply pipe 30 connecting the gas cylinder 15 to the gas injector 16 is fitted with a governor 31 and a pressure switch 32 controlling a solenoid valve 33.

The pressure switch 32 is operatively coupled to the power supply and maintains the solenoid valve 33 closed, i.e. no gas supply or ignition, until the motor 23 and consequently the fan 20 are operating adequately, i.e. adequate suction present.

Ignition of the gas at the burner element 19 is effected by a pilot flame ignition device 34 which is supplied with gas from a branch pipe (not shown) extending from the supply pipe 30 to the ignition device 34.

Controls are also provided for the water supply.

A flow switch 35 is operatively associated with the water supply pipe 28 and with the solenoid valve 33 and serves to ensure that the latter remains closed, i.e. no gas supply or ignition, until there is sufficient water in the heat exchanger 17, say, for example, 1.5 litres.

The hot water outflow pipe 36 of the heat exchanger 37 is fitted with an overheat switch or thermostat which ensures that the hot water does not exceed a predetermined temperature level, say, for example 700C.

Finally, fail-safe sensing probes (or one probe) are provided in the gas supply/ignition controls to detect ignition and maintenance thereof otherwise the solenoid valve 31 is caused to close.

The various controls described above are housed in a convenient control box (not shown) mounted on the water heater casing and readily accessible to an occupant of the caravan.

Claims (16)

1. A water heater, particularly for a caravan, comprising a gas/air mixing tube and a heat exchanger between which is disposed a pre-mix burner element, and a fan-powered exhaust chamber or duct.

2. A water heater as claimed in claim 1, in which the pre-mix burner element is a perforated ceramic plate adapted to produce a short flame, for example 4mm high.

3. A water heater as claimed in claim 1 or 2, in which the fanpowered exhaust chamber or duct includes a fan chamber housing a suction fan drive.. by a motor.

4. A water heater as claimed in claim 3, in which the motor is located external of the fan chamber or duct for cooling purposes.

5. A water heater as claimed in any one of claims 1 to 4 comprising an exhaust gas outlet flue from the fan chamber and which is adapted to be directed in any convenient direction externally of a caravan within which the water heater is fitted.

6. A water heater as claimed in claim 5 in which the outlet flue is of rectangular cross-section.

7. A water heater as claimed in any one of claims 1 to 6, having a gas supply constituted by bottled L.P. gas connected to a gas injector of the mixing tube.

8. A water heater as claimed in any one of claims 1 to 7, connected to a water supply container, preferably mains fed, by a water supply pipe.

9. A water heater as claimed in any one of claims 1 to 8, comprising battery-powered electronic control means including gas supply and ignition controls.

10. A water heater as claimed in claim 9, in which the fan motor is also battery powered.

11. A water heater as claimed in claim 9 or 10, in which the gas and ignition controls include a pilot flame ignition device.

12. A water heater as claimed in any one of claims 9 to 11, in which the control means includes a water flow switch which is operatively associated with the gas controls such that there is no gas supply to the burner element, and consequently no ignition, until there is a sufficient flow of water to the water heater.

13. A water heater as claimed in any one of claims 9 to 12, in which the control means includes a thermostat fitted to a water outlet of the heat exchanger to ensure that the water temperature does not exceed a predetermined maximum value

14. A water heater as claimed in any one of claims 9 to 13, in which the control means includes a pressure switch operatively associated with the gas controls, which pressure switch immobilises gas supply and ignition if the suction fan is inoperative or providing inadequate suction.

15. A water heater as claimed in any one of claims 1 to 14, enclosed in a room-sealed casing.

16. A water heater, particularly for a caravan, substantially as hereinbefore described with reference to the accompanying drawings.