GB1591036A

GB1591036A - Combined convector and thermal storage space heater

Info

Publication number: GB1591036A
Application number: GB4774/77A
Authority: GB
Original assignee: PRL SOC
Current assignee: PRL SOC
Priority date: 1977-02-04
Filing date: 1977-02-04
Publication date: 1981-06-10
Also published as: FR2379773B1; DE2803388A1; FR2379773A1; DE2803388C2; DE7802324U1

Description

(54) COMBINED CONVECTOR AND THERMAL STORAGE SPACE HEATER (71) We, SOCIETE PRL, a French Societe Anonyme, of 32, rue du Landy - 93300 Aubervilliers, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a combined convector and thermal storage space heater.

Storage heaters operate by heating a heat store comprising a storage block of heat-absorbing material - usually concrete - by means of cheap-rate electricity at night.

During the day the electricity is cut off and heat is allowed to leak from the storage block to warm the environment.

A disadvantage of storage heaters is that they are difficult to regulate. If a high-capacity storage heater is used and much heat is stored during the night, the temperature of the heat store is high in the morning and a considerable amount of heat is given off. This can be uncomfortable, particularly if the ambient temperature is high. Conversely, if a low-capacity storage heater is used and less heat is stored during the night, the heating capacity of the heater in the afternoon may be insufficient.

In order to overcome this problem, it has been proposed to use a medium-capacity storage heater in combination with a convector heater. The convector heater is switched on, perhaps manually or automatically, only when necessary to boost the output from the storage heater.

It is convenient to mount the convector heater and the storage heater together. A prior proposal has been simply to mount a conventional storage heater cabinet in contact with a conventional convector heater cabinet to provide a combined unit. This arrangement has been found to be unsatisfactory in practice.

A conventional storage heater comprises the heat store in which heating elements are mounted, the cabinet, and a quantity of heat insulation packed between the heat store and the cabinet. Heat leaks through the insulation from the heat store to the cabinet. The cabinet warms the environment by radiation and convection. Thus, the cabinet can be relatively hot, particularly in the early morning. For safety reasons, the maximum temperature of a heater cabinet must not be allowed to rise above a certain maximum. The only way of reducing cabinet temperature for a given heat store in a conventional storage heater is to increase the amount of insulation.

It is similarly necessary to ensure that the temperature of a convector heater cabinet is not too high in operation. Thus, both storage heaters and convector heaters are designed so that under normal circumstances their cabinet temperatures do not exceed a predetermined maximum. It is found that a mere juxtaposition of a conventional storage heater with a conventional convector heater results in the cabinets heating each other. The resulting temperature distribution of the cabinets is uneven and local temperatures achieved can be very high indeed. This is unacceptable for general use since there is a danger of injury. One way of alleviating this problem is to provide more insulation in the storage heater.

However, this adversely affects the heating characteristics of the heater, as well as adding to the bulk and expense.

The present invention approaches the problem in a different way. Instead of filling the space between the heat store and the cabinet of the storage heater with insulation material, an air space is left. In addition, one or more convector heater elements are mounted in the same cabinet. Thus, air circulates around the heat store and, in passing up through the cabinet receives heat from the heat store. This is in contradistinction to conventional storage heaters, where the heat is extracted from the heat store by conduction through the insulation to the cabinet.

According to the invention, there is provided a space heater comprising a cabinet with an upper air outlet and a lower air inlet to allow the passage of convection air through the cabinet; a heat store within the cabinet comprising at least one heat storage block and electric heating elements mounted in the heat store; one or more electric convector heater elements mounted within the cabinet beneath the heat store; an air space around the heat store to allow the convection air to pass between the heat store and the cabinet; and a thermostat for sensing the temperature of the incoming air and for controlling the or each convector heater element.

Mounting the or each convector heater element beneath the heat store encourages the existing convection flow of air and assists in ensuring an even temperature distribution of the cabinet.

The arrangement described offers the further advantage that it is possible to achieve a required cabinet temperature simply by adjusting the overall size of the cabinet, for a given heat store. Thus, if the cabinet height is raised then the cabinet temperature will be lower.

Also, it is possible to mount, within the cabinet, a temperature cut-out to ensure that all power is switched off in the event of the temperature of the cabinet rising too high.

Preferably the heat store has a surrounding layer of thermal insulation.

The invention will further be described with reference to the accompanying drawings, of which: Figure 1 is a perspective view, broken in part, of a space heater in accordance with the invention; and Figure 2 is a schematic sectional elevation of the heater of Figure 1.

Referring to Figure 1, the heater comprises a sheet metal cabinet 1 in the form of a box.

The cabinet is intended to be free-standing and has a lower air inlet in the form of vents near its base at the front and rear. The front vents are shown at 2. Further, an upper air outlet in the form of upper outlet, vents is shown at the top of the cabinet at 3.

Within the cabinet is mounted a heat store. This comprises a stack of concrete storage blocks 5. There are four layers of blocks. Between the lower two layers of blocks is mounted a U-shaped electric heating element 6. Between the upper two layers of blocks is mounted a similar electric heating element 7. The heat store has a layer of thermally insulating material 8 surrounding the stack of blocks 5.

The arrangement described thus far is a storage heater. When cheap-rate electricity is available during the night, the elements 6 and 7 are connected to the electricity supply to heat the stack of blocks 5. The supply is cut off in the morning and the heated blpcks give heat to the air.

Beneath the heat store is mounted a pair of electric convector heater elements 9. These elements have V-shaped fins of the kind described in co-pending Patent Application No.

2764/76 Serial No. 1535561.

Figure 1 shows a thermostat 10 with a manual regulator 11 for sensing the temperature of incoming air and switching on the convector heater elements 9 when necessary. Also, there is a temperature cut-out 12 which senses the temperature of the top of the cabinet and switches off the electricity supply if there should be over-heating.

Figure 2 shows the manner in which air is heated. Air entering the vents 2 passes around both sides of the heat store 4 and is heated by the heat store to pass through the vents 3 and back to the room. If the temperature of the air as sensed by the thermostat 10 should fall too low, then the convector heater elements 9 are switched on and this adds heat to the incoming air. In being situated beneath the heat store, the elements 9, when switched on, assist in the existing convection flow of air around the store 4.

It will be seen that the air space 13 around heat store allows convection air to flow. In addition to efficiently heating the environment, the passage of convection air in this way insulates the cabinet 1 from the heat store so that for a given heating capacity, the cabinet temperature is relatively low. Also, with the arrangement described, the heat distribution around the cabinet is even. For example, the temperature of the blocks 5 may reach 300"C, but the cabinet temperature can be maintained at 900C or less.

The invention is not restricted to the details of the embodiment described above. For example, in some embodiments the insulation layer around the heat store may be dispensed with. There may be more heat storage blocks in the stack. For example, the arrangement shown is suitable for a 1000 watt heater, where each of the elements 6 and 7 are of 500 watt rating. An additional layer of blocks at the top of the stack would allow more heat to be stored and each element 6 and 7 could then be of 750 watt rating, for example. Greater ratings could be achieved by more stacks of blocks and more heating elements.

Claims

WHAT WE CLAIM IS:

1. A space heater comprising a cabinet with an upper air outlet and a lower air inlet to allow the passage of convection air through the cabinet; a heat store within the cabinet comprising at least one heat storage block and electric heating elements mounted in the heat store; one or more electric convector heater elements mounted within the cabinet beneath the heat store; an air space around the heat store to allow the convection air to pass between the heat store and the cabinet; and a thermostat for sensing the temperature of the incoming air and for controlling the or each convector heater element.

2. A space heater as claimed in Claim 1 wherein the heat store has a surrounding layer of insulation.

3. A space heater as claimed in any preceding claim including a cut-out responsive to temperature of the cabinet, for switching off all power to the elements in the event of the cabinet temperature rising too high.

4. A combined convector and thermal storage space heater substantially as hereinbefore described with reference to the accompanying drawings.