Conventional fan heaters and convector heaters rely upon an electric element or coil as their heat source. It is the present applicant's contention that an electric coil is an inefficient converter of electrical energy to heat.

It is an object of the present invention to provide a domestic heater device which operates more efficiently in terms of the electrical energy consumed for a given heat output than conventional fan heaters and convectors using electric elements or coils.

According to the present invention there is provided a domestic heater device comprising-a housing, a heat source including a tungsten halogen bulb and a heat exchanger in thermal contact with the'heat source.

In a preferred embodiment of the present invention the tungsten halogen bulb is mounted within an enclosure to which the heat exchanger is physically connected so as to transfer heat from the bulb to the heat exchanger. Conveniently, the enclosure comprises a copper box. Under normal operating circumstances the tungsten halogen bulb operates at a temperature of 150° Celsius. This heat output is transferred to the enclosure and thence to the heat exchanger. Preferably, the heat exchanger forms a closed circuit through which fluid is pimped, and includes a pipe which is physically connected to the heat source to ensure the effective transfer of heat to the fluid circulating therethrough and heat radiating means.

It has been found by the present applicant that a tungsten halogen bulb operating at 395 Watts will produce approximately the same heat output as a kilowatt fan heater.

It is, therefore, approximately 3 times more heat efficient.

In one embodiment of the present invention the domestic heater device takes the form of a fan heater and comprises an internal fan which circulates ambient air through the said housing over the said heat radiating means to warm the said air before returning it to the space to be heated.

In a second embodiment of the present invention the said heat radiating means convects heat into the space to be heated. To this end it may take the shape and form of a radiator.

Preferably, the domestic heater device further comprises a first thermal switch associated with the tungsten halogen bulb which operates to turn the bulb off when the temperature thereof reaches a predetermined maximum. An auxiliary-fan may be provided to assist in maintaining the temperature of the bulb at or below the said predetermined maximum by blowing ambient air over it. Ambient air circulated past the bulb may be directed onto the heat exchanger.

Preferably, the domestic heater device further comprises a second thermal switch associated with the heat exchanger which operates to shut the domestic heater device down when the temperature thereof exceeds a predetermined maximum.

In the domestic heater device in accordance with the first embodiment of the present invention the temperature of the air blown therefrom is proportional to the speed of the fan circulating air past the heat exchanger. This may be taken advantage of to

control the heat output of the domestic heater device; temperature sensing means may be provided in the output from the domestic heater device which is linked to control means regulating the speed of the air circulating fan.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a domestic heating device in accordance with the present invention in the form of a fan heater; and Fig. 2 shows a domestic heating device in accordance with the present invention in the form of a convector heater.

Conventional electric heaters that can currently be purchased use an electric element or coil as their heat source. The domestic heater device in accordance with the present invention uses a tungsten halogen bulb as its heat source as these have been found to be far more efficient in the way they use energy. Under normal circumstances the external operating temperature of a tungsten halogen bulb is approximately 150° Celsius.

By constructing a copper box and soldering it to a copper pipe in an enclosed situation, heat can be transferred from the bulb into the copper pipe and thereafter into fluid circulating through the pipe.

Referring to Fig. 1 there is shown a fan heater embodying the present invention comprising a heat source 1 consisting of a copper box enclosing a tungsten halogen bulb (not visible). A copper pipe 2 passes through the copper box and is in close thermal contact therewith. The pipe 2 is connected to a pump 3 and thence to one side of a radiator 4. At the other side of the radiator 4 a further section of pipe 5 leads back to the

heat source 1. The pipe 2, the pump 3, the radiator 4 and the further section of pipe 5 form a closed circuit through which fluid is circulated by the pump 3. It will be understood that the heat source 1 heats the fluid in the pipe 2. The heated fluid then passes through the radiator 4 from which heat is radiated.

A fan 6 draws air into a housing 7 in the front of which is mounted the radiator 4 and directs this air over the radiator 4. The effect of this is to cause the air to be warmed. This warmed air blown out into the space occupied by the fan heater warms the space.

Conveniently a thermal switch (not shown) is mounted on the heat source 1 which cuts out on the bulb when the temperature thereof reaches or exceeds 125° Celsius. This prevents damage to the bulb and ensures a reasonable working life. A further thermal switch (not shown) on the pipe 5 also ensures that the system shuts down should this reach or exceed 70° Celsius.

When the fan 6 is operating at full speed the temperature of the air blown from the heat exchanger is at its minimum, because of the cooling effect exerted by the air, but the space to be heated will be warmed quickly. By slowing the fan 6 the temperature of the air blown from the heat exchanger will be increased, but it will circulate through the space more slowly. This may be taken advantage of to regulate the temperature at the output of the fan heater. In this regard, a temperature detector in the output of the fan heater may be employed to provide control feedback to control means regulating the speed of the fan 6.

A further fan 10 is installed adjacent to the heat source 1 to cool this and prevent

it from overheating.

Referring to Fig. 2 there is shown a convector heater embodying the present invention comprising a heat source 11 and a heat exchanger consisting of a pipe 12 in close thermal contact with the heat source 11 connected at each end to a radiator 13, via a pump 14. The pump 14 circulates fluid through the pipe 12 and the radiator 13, thereby ensuring that heat generated by the heat source is conveyed to the radiator 13, where it warms the air around it by convection. Once again, the heat source 11 comprises a tungsten halogen bulb mounted within a box or enclosure.

A small auxiliary fan 15 serves to cool the heat source 11 and prevent this from overheating. A thermal switch (not shown) has been installed on the enclosure to prevent the temperature thereof reaching or exceeding 125° Celsius. A further thermal switch on the pipe 12 limits the temperature of the fluid circulating therein to 70° Celsius.

The applicant has found that the domestic heating devices described hereinbefore and making use of tungsten halogen bulb as their heat source are capable of heating a room to the same temperature as a 1 kilowatt electrical heating coil, yet operate at a mere 3 95 Watts.