GB2152652A

GB2152652A - An electric storage heater

Info

Publication number: GB2152652A
Application number: GB08400379A
Authority: GB
Inventors: Anthony Crispin Fells
Original assignee: POWRAMTIC Ltd
Current assignee: POWRAMTIC Ltd
Priority date: 1984-01-09
Filing date: 1984-01-09
Publication date: 1985-08-07
Also published as: GB8400379D0

Abstract

An electric storage heater comprises a plurality of heat storage elements 16 assembled in a stack to constitute a heat storage body 14. Each heat storage element 16 has a recess (46, Fig. 12) the recesses defining elongate air flow passages through the heat storage body (14) which receive heating elements (60) (Fig. 15) comprising two limbs (64, 66). The heating elements (60) can be removed from the heat storage body 14 without disturbing the other heating elements (60) or the heat storage elements 16. Air is driven through the heat storage body 14 by a fan 18 such that air passes through a lower group of the air flow passages in one direction and through an upper group of air flow passages in the other direction. A damper is provided for allowing air heated by flow through the heat storage body 14 to be mixed with cool air, so as to provide air at the required temperature. Air flows through outlet elements 6 which can be swivelled relatively to the casing of the heating to direct warm air to selected locations. <IMAGE>

Description

SPECIFICATION Electric storage heaters This invention relates to electric storage heaters.

According to one aspect of the present invention, there is provided an electric storage heater comprising a heat storage body assembled from a plurality of heat storage elements which abut one another and are provided with recesses defining air flow ducts through the heat storage body, the heater further comprising heating elements each having two parallel limbs which are interconnected at one end of the heating element, each heating element being accommodated in a respective one of the ducts with the free end of each limb projecting from the duct and being releasably connected to current supply means, wherebyeach heating element can be withdrawn from the heat storage body independently of the other heating elements, after disconnecting the heating element to be removed from the current supply means.

Preferably, the limbs of each heating element are interconnected at the said one end by a bend in the heating element. In a preferred embodiment of an electric storage heater in accordance with this aspect of the invention, means is provided for connecting the heating elements to a three-phase electricity supply, in which case the heating elements may be divided into three groups; one limb of each heating element in each group is connected to a respective live phase of the supply, while the other limb of each element is connected to the neutral phase. The groups of heating elements may be disposed one above another.The electricity supply to the heating elements may take place through a busbar assembly comprising a neutral conductor assembly which electrically interconnects the said other limbs of the heating elements, and three lie conductor assemblies connected, respectively, to the said one limbs of each group. The live conductor assemblies each have a terminal connected to the respective live phase of the supply and the neutral conductor assembly has a terminal connected to the neutral phase.

According to a second aspect of the present invention, there is provided an electric storage heater comprising a heat storage body provided with a plurality of horizontal air flow passages arranged in first and second groups disposed one above the other, ducting being provided for constraining air to flow from an inlet through the passages of the first group in one direction, and then through the passages of the second group in the opposite direction to an outlet.

Preferably, the first group of air flow passages is below the second group. The inlet and/or the outlet may be provided in the upper region of the heater.

In a preferred embodiment, a fan is provided for driving air through the air flow passages. The fan is preferably provided between the second group of passages and the outlet. The ducting may comprise an inlet duct extending between the inlet and the first group of air flow passages, a transfer duct interconnecting the first group and second group of air flow passages, and an outlet duct extending between the second group of air flow passages and the outlet. The inlet and outlet ducts may be separated from each other by a wall in which there is a closable bypass aperture which, when open, allows air to flow from the inlet duct to the outlet duct without passing through the heat storage body.Means may be provided for closing the inlet and outlet ducts as the by-pass aperture is opened, and in a preferred embodiment a single closure member is provided which is movable between a first position, in which the by-pass aperture is closed and the inlet and outlet ducts are opened, and a second position in which the by-pass aperture is opened an the inlet and outlet ducts are closed.

According to a third aspect of the present invention, there is provided an electric storage heater comprising a heat storage body and inlet and outlet ducts for conveying air, respectively, to and from the heat storage body, a by-pass aperture being provided between the inlet and outlet ducts, and a power-driven closure member being provided which is movable between a first position. in which it closes the inlet and outlet ducts and leaves open the by-pass aperture, and a second position in which it closes the by-pass aperture and leaves open the inlet and outlet ducts.

The damper may be controlled by means which is responsive to the outlet air temperature of the heater. The control means may be adapted to close the inlet and outlet ducts under power when no heat is required from the heater, and as a fail-safe measure, for example if the outlet air temperature rises above a predetermined level.

Where the fan and the by-pass aperture are provided, the fan is preferably downstream of the aperture in order to promote mixing of cold air with warm air which has passed through the heat storage body.

In a preferred embodiment, there is a temperature sensor disposed downstream of the damper so as to be responsive to the temperature of air issuing from the heater. Where the fan is provided, the temperature sensor is preferably downstream of the fan.

According to a fourth aspect of the present invention, there is provided an electric storage heater comprising a heat storage body and a fan for driving air through the heat storage body to an outlet, the outlet comprising an adjustable outlet element whereby the direc tion in which air issues from the outlet is controllable.

In a preferred embodiment, the outlet element is rotatably mounted on a casing of the heater, for example for rotation about a vertical axis. The outlet aperture of the outlet element may be provided with louvres. Preferably, two or more outlet elements, which are adjustable independently of each other, are provided in order that air may be directed to different parts of the space in which the heater is situated.

The heater may comprise an outlet plenum into which air is discharged by the fan, in which case the outlet elements communicate, independently of each other, with the outlet plenum. The throughput of the fan is preferably sufficiently great to create a blast of air from the outlet aperture or apertures.

According to a fifth aspect of the present invention there is provided a heat storage element for use in a heat storage body, the element comprising two substantially rectangular major faces disposed opposite each other, and two side faces and two end faces which extend between respective edges of the major faces, one of the major faces having a recess which extends across that major face from one side face to the other and is bounded adjacent to the end faces by shoulder portions of that major face, the edges at which each side face meets each end face being chamfered.

The present invention also provides a heat storage body comprising an assembly of heat storage elements as defined in the preceding paragraph, the recesses of adjacent elements defining elongate passages through the heat storage body, and the chamfered edges defining narrower passages at each junction of four elements.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the acompanying drawings, in which: Figure 1 is a rear view of an electric storage heater; Figure 2 is a side view of the heater of Fig.

1; Figure 3 is a front view of the heater of Figs. 1 and 2; Figure 4 is a plan view of the heater of Figs. 1 to 3; Figures 5 to 7 show the heater of Figs. 1 to 4 in three different operative conditions; Figure 8 is a side view of a heat storage body of the heater of Figs. 1 to 4; Figure 9 is a front view of the heat storage body of Fig. 8; Figure 10 is a plan view of the heat storage body of Figs. 8 and 9; Figure 11 is a view, on a larger scale, of a portion marked "A" in Fig. 10; Figure 12 is a front view of a heat storage element of the heat storage body of Figs. 8 to 11:: Figure 13 is an end view of the heat storage element of Fig. 12; Figure 14 is a plan view of the heat storage element of Figs. 1 2 and 13; Figure 15 is a heating element of the heater of Figs. 1 to 4; Figure 16 is a front view of the heat storage body and current supply means; Figure 1 7 is a side view of the heat storage body and the current supply means of Fig.

16; and Figure 18 is a circuit diagram representing the control and power circuitry of the heater.

Refering first to Figs. 1 to 4, the electric storage heater comprises a casing 2 which is provided with inlet louvres 4 and outlet elements 6, each of which has a louvred outlet aperture 8. The outlet apertures 8 are rectangular and are inclined slightly to the vertical so that a line normal to the plane of each outlet aperture slopes upwardly away from the aperture. Control means 10 is provided on the front of the casing. The outlet elements 6 can be swivelled relatively to the casing 2 about vertical axes in order to direct air to selected parts of the premises in which the heater is situated.

As shown in Figs. 5 to 7, the interior of the casing is divided into upper and lower compartments by a partition 1 2. The lower compartment accommodates a heat storage body 1 4 which is constituted by a stack of heat storage elements 1 6 in the form of bricks made from a refractory brick material such as Feolite (E256), which is a form of bonded magnetite.

The uper compartment accommodates a fan 1 8 which is mounted to deliver air into an output plenum 20 of the upper compartment.

The capacity of the fan is sufficient to deliver a strong blast of air from each of the outlet apertures 8.

A partition 22 is provided in both the upper and lower compartments to define inlet and outlet ducts 24 and 26 respectively. It will be appreciated from Figs. 5 to 7 that, on the side away from the partition 22, the heat storage body 14 is spaced from the front wall of the casing 2, to provide a transfer duct 28.

The partition 1 2 has an aperture 30 and the partition 22 has an aperture 32. A damper 34 is mounted pivotally for movement between a first position (Fig. 5) in which the aperture 32 is closed, but the aperture 30 is open, and a second position (Fig. 7) in which the aperture 32 is open and the aperture 30 is closed. The damper 34 may also assume any position between the first and second positions, as shown in Fig. 6. The damper 34 is operated by an actuator 36. The actuator 36 is controlled by circuitry which will be described later in this description, but at this stage it is sufficient to say that the actuator 36 is responsive to the tenlpeEature c,f tsEe air passing through the plenum 20.

Assuming that the heat storage body 14 is hot (and the way in which the body 14 is heated will be discussed later in this description), the operation of the heater when delivering heat is as follows, referring first to Fig. 5.

Air is drawn by the fan through the inlet louvres 4 and the inlet duct 24 to pass through the lower portion of the heat storage body 14, the transfer duct 28, the upper portion of the heat storage body 14, through the outlet duct 26 and the outlet apertures 8 to be discharged into the space which is to be heated. As shown in Fig. 5, all of the air emitted from the outlet apertures 8 has passed twice through the heat storage body 14, once in one direction and once in the other.

A temperature sensor in the outlet plenum 20 is set to provide a desired temperature of the air issuing from the outlet apertures 8.

This temperature may be, for example, 65"C.

If the temperature of the air passing through the plenum chamber 20 exceeds the predetermined temperature, the actuator 36 is operated to pivot the damper 32 in the anticlockwise direction, so partly opening the bypass aperture 32 and partly closing the aperture 30. This condition is shown in Fig. 6, and it will be observed that, although some air still passes through the heat storage body 14, a certain amount of air passes directly from the inlet louvres 4 through the by-pass aperture 32 into the outlet duct 26, to be mixed with the heated air which has passed through the heat storage body 14. The two streams of air will be intimately mixed by the fan 1 8 before passing into the plenum chamber 20 and through the outlet apertures 8.

Thus, by controlling the position of the damper 34 in response to the temperature of the air passing through the plenum chamber 20, the desired temperature for the air issuing from the outlet apertures 8 can be maintained, even as the heat storage body 14 cools down. If the air temperature of the space to be heated exceeds the predetermined temperature, the damper 34 will be moved by the ram 36 into the position shown in Fig. 7, in which the by-pass aperture 32 is left fully open, and the aperture 30 is completely closed, thus isolating the heat storage body 14 from the air flow through the heater. In this condition, the heater will operate merely to circulate the air without heating it.It is important to note that, when no heat is required from the heater, the damper 34 is automatically moved into the position in which the lower compartment, containing the heat storage body 14, is completely closed.

The heat storage body is shown in greater detail in Figs. 8 to 11, from which it will be appreciated that the body 14 is build up from a large number of bricks which are shown in Figs. 1 2 to 1 4. Eech brick has substantially rectangular major faces 38 and 40 which are on opposite sides of the brick. Side walls 42 and end walls 44 extend between respective edges of the major faces 38 and 40. The major face 40 (the lower face in Figs. 1 2 to 14) has a recess 46 which extends across the whole of the face 40 between the side faces 42. The recess 46 has a flat base 48 and the side walls 50 which are inclined at 45 to the plane of the base 48. Shoulder faces 52 are provided between the side walls 50 and the respective end faces 44.Each side face 42 meets the adjacent end faces 44 at chamfered edges 54. The dimensions of the illustrated brick 1 6 are 250mm X 1 25mm X 65mm. The shoulders 52 are 40mm wide and the recess 46 is 20mm deep.

When the bricks 1 6 are assembled to form the heat storage body 14 (Figs. 8 to 10), each brick is disposed so that its recess 46 faces the recess 46 of another brick, so as to define horizontal air flow passages 56 (Fig. 9).

As shown in Fig. 10, the chamfered edges 54 define vertical passages 58 at the places where four bricks meet. The size of the passages is indicated by the half-diagonal measurement x in Fig. 11; x may be, for example, 4.5 millimetres.

The flow through the heat storage mass 14 as indicated in Figs. 5 to 7 takes place through the air flow passages 56. In each passage 56 there is a heating element 60 (Fig. 17) which extends over substantially the full length of the respective passage 56. A single heating element 60 is shown in Fig.

15, in which the front face of the heat storage body is indicated by a chain-dotted line 62.

The element 60 comprises two parallel limbs 64 and 66, the limb 66 being longer than the limb 64. The two limbs 64, 66 are interconnected at one end by a bend 68, and at the other end they are provided with screw threaded terminal portions 70. As shown in Fig. 16, the terminals 70 are connected to a busbar assembly 72. The busbar assembly 72 comprises three sets of conductors 74, 76 and 78 each having a respective terminal 74', 76' and 78' for connection to individual live phases of a three phase supply. The busbar assembly 72 also comprises a set of neutral conductors 80 which have a terminal 80' for connection to the neutral phase of the supply.

It will be appreciated from Fig. 1 6 that the sets of conductors 74, 76 and 78 are disposed one above the other and each extend over six layers of bricks 1 6 (In Fig. 16, the heat storage body 1 4 is shown divided, by chain-dotted lines, into blocks which each represent a pair of bricks 1 6 defining between them an air flow passage 56).

The longer limb 66 of each element 60 is connected, by means of its terminal portion 70, to a respective one of the sets of conductors 74, 76 and 78. The shorter limb 64 of each element 60 is connected, by its terminal portion 70, to the set of neutral conductors 80.

The supply and control circuitry for a heater is represented by the circuit diagram of Fig.

18. It will be appreciated that the storage heater operates by drawing electric power during the night (when the cost per unit is relatively low), to heat up the heat storage body 14, the heat then being released as required during the day. The heater thus requires two separate supplies, namely an unrestricted supply, which provides power for the various control components of the heater, and a restricted supply, which supplies the heating elements 60 for heating the heat storage body. The restricted supply is, as mentioned above, a three-phase supply, and passes through a manual isolator A to a trip B and thence to a main contactor C which supplies the heating elements 60, which are indicated by the letter D in Fig. 1 8.

The control circuitry includes a charge controller M which receives input signals from an outside temperature sensor responsive to outside air temperature, from a core thermocouple M1, from a storage time clock G, and from a core temperature limit thermostat P having a core thermocouple P,. The thermocouples M and P1 are accommodated in two of the vertical passages 58 defined by the chamfered edges 54. The charge controller M operates the main contactor C to supply power to the heating elements 60 to heat the heat storage body 1 4. The overall charging time is limited to the period of restricted supply by the storage time clock G.However, the charge controller is also responsive to the outside temperature sensor and the core thermocouple M1, with the result that the charging time is dependent on the outside air temperature jwhich provides a guide to the likely air temperature the following day when heat is required) and the core temperature, i.e. the temperature of the heat storage body 14. Thus, for example, the higher the outside air temperature and the residual temperature of the heat storage body 14, the later will be the beginning of the charging cycle.The function of the thermostat P is to cut off the supply of current to the elements 60 if the temperature of the heat storage body 14 rises above a predetermined limit, for example 600"C. The discharge cycle of the heater is under the overall control of a time clock H which controls the supply of current through a relay L and a fan car:ract.or F to the motor of the fan 1 8. The actuator 36 for the damper 34 is controlled in response to an outlet air temperature sensor R, disposed in the plenum chamber 20 and a room thermostat responsive to the temperature in the space to be heated. Thus the damper is controlled as described with reference to Figs. 5 to 7. An outlet air high temperature limit thermostat R automatically causes the damper to move under power to the position shown in Fig. 7 if the outlet air temperature rises above a predetermined level.

A summer/winter switch S is provided for enabling the heater to be operated merely to circulate air, without heating it. Thus, when the switch S is closed, the damper 34 is moved to the position shown in Fig. 7, and the main contactor C is not operated during the night to supply power to the heating elements 60.

The heater described herein is particularly suitable for use in industry, where heat needs to be supplied to large-volume premises. The outlet elements 6 can be swivelled relatively to the casing 2 in order to direct air to selected parts of the premises. For this purpose, the capacity of the fan is sufficient to create a strong blast of air from the apertures 8.

Claims

1. An electric storage heater comprising a heat storage body assembled from a plurality of heat storage elements which abut one another and are provided with recesses defining air flow ducts through the heat storage body, the heater further comprising heating elements each having two parallel limbs which are interconnected at one end of the heating element, each heating element being accommodated in a respective one of the ducts with the free end of each limb projecting from the duct and being releasably connected to current supply means, whereby each heating element can be withdrawn from the heat storage body independently of the other heating elements, after disconnecting the heating element to be removed from the current supply means.

2. An electric storage heater as claimed in claim 1, in which the limbs of each heating element are interconnected at a bend.

3. An electric storage heater as claimed in claim 1 or 2, which is adapted to be connected to a three-phase electrical supply, the elements being arranged in three groups, one limb of each element being connected to the neutral phase of the supply and the other limb of each element in each group being connected to a respective one of the live phases.

4. An electric storage heater as claimed in claim 3, in which the groups of elements are disposed one above another.

5. An electric storage heater as claimed in claim 3 or 4, in which a busbar assembly is provided comprising four sets of conductors, one set being connected to said one limb of each heating element, and ther other sets being connected respectively to the other limbs of the heating elements in the respective groups of elements, each set of conductors being provided with a terminal for connection to the respective live and neutral phases of the three-phase supply.

6. An electric storage heater comprising a heat storage body provided with a plurality of horizontal air flow passages arranged in first and second groups disposed one above the other, ducting being provided for constraining air to flow from an inlet through the passages of the first group in one direction, and then through the passages of the second group in the opposite direction to an outlet.

7. An electric storage heater as claimed in claim 6, in which a fan is provided for driving air through the ducting and the air flow passages.

8. An electric storage heater as claimed in claim 7, in which the fan is disposed in the air flow path between the second group of air flow passages and the outlet.

9. An electric storage heater as claimed in any one of claims 6 to 8, in which the ducting comprises an inlet duct extending between the inlet and the first group of air flow passages, a transfer duct extending between the first group and the second group of air flow passages, and an outlet duct extending between the second group of air flow passages and the outlet.

10. An electric storage heater as claimed in claim 9, in which the inlet and outlet ducts are separated from each other by a partition provided with a closable aperture which, when open, permits air to flow from the inlet duct to the outlet duct without passing through the heat storage body.

11. An electric storage heater as claimed in claim 10, in which closure means is provided for closing the inlet and outlet ducts.

1 2. An electric storage heater as claimed in claim 11, in which the by-pass aperture and the inlet and outlet ducts are closable by a common damper,which is movable between a first position in which the inlet and outlet ducts are open and the by-pass aperture is closed, and a second position, in which the inlet and outlet ducts are closed and the bypass aperture is open.

1 3. An electric storage heater as claimed in claim 12, in which the damper is responsive to the temperature of air passing through the outlet.

14. An electric storage heater as claimed in claim 12 or 13, in which the damper is moved under power to close the inlet and outlet ducts when no heat is required.

1 5. An electric storage heater as claimed in any one of claims 11 to 1 4 when appendant to claim 7, in which the fan is disposed downstream of the by-pass aperture whereby the fan promotes mixing of air from the bypass aperture and from the heat storage body.

16. An electric storage heater as claimed in any one of claims 6 to 15, in which the first group of air flow passages is disposed beneath the second group.

1 7. An electric storage heater as claimed in any one of claims 6 to 16, in which the inlet is provided in the upper region of the heater.

1 8. An electric storage heater as claimed in any one of claims 6 to 17, in which the outlet is provided in the upper region of the heater.

1 9. An electric storage heater comprising a heat storage body and inlet and outlet ducts for conveying air, respectively, to and from the heat storage body, a by-pass aperture being provided between the inlet and outlet ducts, and a power-driven closure member being provided which is movable between a first position, in which it closes the inlet and outlet ducts and leaves open the by-pass aperture, and a second position in which it closes the by-pass aperture and leaves open the inlet and outlet ducts.

20. An electric storage heater as claimed in claim 19, in which the position of the damper is dependent on the temperature of air flowing through the outlet duct.

21. An electric storage heater as claimed in claim 20, in which the damper is responsive to a temperature sensor provided in the outlet duct.

22. An electric storage heater as claimed in claim 21, in which a fan is provided for driving air through the heater, the temperature sensor being disposed downwstream of the fan.

23. An electric storage heater as claimed in any one of claims 19 to 21, in which the damper is closed under power when no heat is required.

24. An electric storage heater comprising a heat storage body and a fan for driving air through the heat storage body to an outlet, the outlet comprising an adjustable outlet element whereby the direction in which air issues from the outlet is controllable.

25. An electric storage heater as claimed in claim 24, in which the outlet element is mounted rotatably on a casing of the heater.

26. An electric storage heater as claimed in claim 25, in which the outlet element is rotatable about a vertical axis.

27. An electric storage heater as claimed in any one of claims 24 to 26, in which the outlet element has an outlet aperture provided with louvres.

28. An electric storage heater as claimed in any one of claims 24 to 27, in which two or more of the outlet elements are provided, which are adjustable independently of one another.

29. An electric storage heater as claimed in claim 28, in which a plenum chamber is provided into which the fan discharges, the outlet elements communicating with the plenum chamber independently of each other.

30. An electric storage heater as claimed in any one of claims 24 to 29, in which the throughput of the fan is sufficient to create a blast of air issuing from the outlet element or elements.

31. A heat storage element for use in a heat storage body, the element comprising two substantially rectangular major faces disposed opposite each other, and two side faces and two end faces which extend between respective edges of the major faces, one of the major faces having a recess which extends across that major face from one side face to the other and is bounded adjacent to the end faces by shoulder portions of that major face, the edges at which each side face meets each end face being chamfered.

32. A heat storage body comprising an assembly of heat storage elements as claimed in claim 31, the recesses of adjacent elements defining elongate passages through the heat storage body, and the chamfered edge defining narrower passages at each junction of four elements.

33. A heat storage body as claimed n claim 32, in which the larger elongate passages are substantially horizontal and the narrower passages are substantially vertical.

34. An electric storage heater substantially as described herein with reference to, and as shown in, the accompanying drawings.

35. A heat storage element substantially as described herein with reference to, and as shown in, Figs. 8 to 14.