GB2241569A

GB2241569A - Boilers

Info

Publication number: GB2241569A
Application number: GB9004765A
Authority: GB
Inventors: David Donkin
Original assignee: Creda Ltd
Current assignee: Creda Ltd
Priority date: 1990-03-02
Filing date: 1990-03-02
Publication date: 1991-09-04
Anticipated expiration: 2010-03-02
Also published as: GB2241569B; JPH0599510A; GB9004765D0

Abstract

In an electric boiler for use as part of a hot water heating system, the boiler includes a heat store so as to be capable of being heated by off-peak electricity. The heat store consists of identical bricks (28) having vertical semi-cylindrical recesses which can be loaded into the boiler from the front to closely surround the boiler tubes (24, 25). Insulation panels to the side of the heat store are removable to give the clearance necessary to insert the bricks at the side. The brick is preferably made from a clay or chemically bonded mineral mixture containing in excess of 95% magnesium oxide. <IMAGE>

Description

Boilers This invention relates to boilers, especially electrically powered boilers.

Boilers have been proposed in which boiler tubes extend through a heat store surrounded by insulating material and heated by electrical means. The heating of the boiler is usually carried out during periods of a daily cycle when electricity is available at a reduced cost.

Because of the weight of the boiler, it is usual to transport the heat store e.g. bricks and the cabinet separately and to assemble them on site. In one previous design, the heat store was top-loaded by threading apertured bricks over the tops of the boiler tubes, and then connecting a manifold to the tops of the boiler tubes.

The invention provides an electric boiler, comprising a heat store, electrical means for heating the heat store, heat insulating material surrounding the heat store, a plurality of boiler tubes extending through the heat store, the heat store including pairs of heat storage bricks having recesses which, when the bricks of each pair are placed together, surround the boiler tubes.

The use of such pairs of bricks enables the boiler to be loaded after both manifold connections have been made, while still maintaining good contact with the boiler tubes. Consequently, such manifold connections can be made in the factory rather than at the installation site, thereby easing assembly.

Advantageously, the heat store includes pairs of heat storage bricks having recesses which, when the bricks of each pair are placed together, surround the tubes. The boiler may be arranged to receive bricks from the front, the bricks being arranged so that each pair joins on a line extending from the front to the rear of the boiler, and the heat insulating material at a side of the boiler being withdrawable to facilitate assembly of the storage bricks.

Manifolds at both or either ends of the boiler tubes preferably include portions which communicate with the sides of the boiler tubes, the adjacent ends of the boiler tubes being closed and terminating inside the heat insulating material. The first and/or second manifold may communicate with the region outside the heat insulating material by means of portions which extend around the periphery of the insulating material adjacent the respective ends of the boiler tubes.

A domestic hot water system including an electric boiler, constructed in accordance with the invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of the hot water system; Figure 2 is a perspective view of the electric boiler in partially assembled state; Figure 3 is a perspective view illustrating the positions of the bricks when the boiler has been assembled; Figure 4 is a perspective view of the boiler tubes; Figure 5 is a perspective view of an alternative arrangement of boiler tubes; Figure 6 is a front view of the boiler tubes of Figure 7 positioned in the boiler; Figure 7 is a perspective view of the lower insulation for the tubes of Figure 7; and Figure 8 is a plan view of the top course of bricks.

Referring to Figure 1, the hot water system is powered by an electric boiler indicated generally by the reference numeral 17 which heats a primary water/steam circuit indicated generally by the reference numeral 18, which in turn heats a secondary hot water circuit indicated generally by the reference numeral 19 by means of a heat exchanger 20.

The boiler is intended to be powered by off-peak electricity which is available at certain periods during a 24 hour period from a separately metered power source at a reduced price.

A water pump 21 pumps the hot water in the secondary circuit around fan-assisted water pipe coils 22, 23. The secondary circuit could include hot water radiators or other heat dissipation means, positioned within the rooms to be warmed.

The primary water/steam circuit consists of four water/steam boiler tubes 24 - 27 arranged at the corners of the square (see Figure 4) and a heat store consisting of a stack of bricks 28. The heat store is surrounded by insulation in the form of a top panel 29, a bottom panel 30, side panels 31 and 32 and front and rear panels (not shown). The bricks are heated by means of heating coils 33.

When the bricks have been heated to a high temperature, water is allowed to pass from a reservoir tank 34 by means of a control valve 35 by gravity into the lower end of the boiler tubes, where the water is evaporated into super-heated steam. The steam gives up its heat in the heat exchanger 20 and condenses back to water which is collected in the reservoir tank 34. The control valve 35 enables the return condensed flow to be interrupted so that all the primary circuit water is retained in the reservoir 34 in order that the withdrawal of heat from the primary circuit can cease. Contraction and expansion of the primary water is allowed for by standpipe 36, but a closed flexible membrane or pressurised tank could be used instead if desired. The secondary water circuit is provided with a conventional header tank (not shown).

Referring to Figures 2, 3 and 4, the upper manifold consists of tubes 37, 38 which are welded to apertures in the sides of the boiler tubes 25 to 27, and intermediate section 39 and an outlet section 40. The lower manifold consists of tubes 41 to 44 which are welded to apertures in the sides of the boiler tubes, and an inlet pipe 45 into which the tubes 41 to 44 connect. All these tubes are welded at the factory and the boiler is delivered with the tube assembly in position. The upper and lower ends of the boiler tubes are closed.

The upper and lower insulation panels 29, 30 have recesses to locate the tube end portions. They also have peripheral recesses 29a, 30a, to allow inlet pipe 45 and outlet section 40 to communicate with the region outside the boiler to connect to the primary water circuit. The side insulation panels 31, 32 are shown partly removed in Figure 2.

It will be apparent that, because the boiler tubes and manifolds so not extend through apertures in the top and bottom insulation panels, the fitter does not have to assemble the manifolds on site.

The rest of the installation is as follows. With the panels 31, 32 completely removed, those bricks in the first course which lie to the left of the tubes 24, 25 are inserted into the cabinet. Because the thickness of the panel 31 is greater than the depth of the semi-cylindrical recesses which engage the tubes, there is sufficient room for the bricks to be inserted. They are then displaced sideways until their recesses engage the tubes 24, 25. Next, the bricks of the lower course that lie to the right of the tubes 24, 25 are inserted, and pushed adjacent to the ones already in the cabinet.

The same procedure is then applied for the bricks of the first course which surround the tubes 26, 27, which are not shown in Figure 3.

Having inserted the first course of bricks, the fitter then inserts the element 33, which lies in the four sections of the horizontally extending grove 46 which is formed in the upper surface of the bricks.

Since the bricks to the right of the tubes 24 and 25 and those to the left of the tubes 26 and 27 are in contact with each other when inserted, it follows that the bricks to the left of the tubes 26, 27 have to be held above the first course and with the recesses in engagement with the tubes 26, 27 and then lowered vertically to be installed. It will be apparent that this is not possible with the uppermost course of bricks since there is no room above the uppermost course for the bricks to the left of the tubes 26, 27 to be held. This situation is dealt with by providing just two bricks 47, 48 of reduced width in the direction from side to side of the boiler, the width reduction being greater than the depth of the recesses that engage the boiler tubes, so that these bricks 47, 48 can be inserted in a front to back direction level with the other bricks of the top course (Figure 8).The gap thus left is then filled with a pair of keying bricks 49.

As an alternative to the boiler tube assembly shown in Figure 4, the boiler tube assembly in Figure 5 may be adopted, in which the connections to an outlet pipe 50 are by means of individual tubes 51 to 54. To accommodate the tubes 51 to 54, the bottom insulation panel has recesses for the tubes (Figure 7), and this arrangement is also shown in Figure 6. The construction of Figure 5 has the advantage that there is a certain flexibility in the tubes 24 to 27, allowing greater tolerances to be provided in the recesses in the base insulation 29.

When all the bricks have been inserted, and are in contact with the tubes 24 to 27, the side insulation panels 31, 32 are inserted, and the inner faces thereof may be faced with stainless steel to assist this operation.

The heating coil end leads for each course are connected to the electrical supply terminals and the front slab of thermal insulation is mounted over the front face of the storage mass. An outer metal panel is mounted over the front insulation completing the construction of the outer casing.

Each brick has proportions roughly of length twice its width and three times its thickness. A clay or chemically bonded mineral mixture containing in excess of 95% magnesium oxide is used to make the brick, this material having particularly suitable storage properties of heat retention and thermal conductivity heat storage on the one hand and for the withdrawal of heat into the water/steam primary circuit on the other hand.

Of course, modifications may be made without departing from the scope of the invention. Thus, for example, the manifold arrangement for the bottom of the tubes shown in Figure 5 may be used for the tops of the tubes if desired. Equally, additional boiler tubes 24 to 27 may be provided if desired.

Claims

1. An electric boiler, comprising a heat store, electrical means for heating the heat store, heat insulating material surrounding the heat store, a plurality of boiler tubes extending through the heat store, the heat store including pairs of heat storage bricks having recesses which, when the bricks of each pair are placed together, surround the boiler tubes.

2. An electric boiler as claimed in claim 1, in which the boiler is arranged to receive bricks from the front, the bricks being arranged so that each pair joins on the line extending from front to rear of the boiler, and heat insulating material at a side of the boiler is withdrawable to facilitate assembly of the storage bricks.

3. An electric boiler as claimed in claim 2, in which the bricks of the store are arranged in a plurality of courses, at least some of the courses including two bricks arranged between upstanding boiler tubes, the recess engaging the boiler tubes and the opposed faces of the bricks being in contact with one another, at least one course including a brick of reduced width in the direction between the boiler tubes and a keying brick arranged between and in contact with the two bricks between the boiler tubes of that course.

4. An electric boiler as claimed in any one of claims 1 or 3, in which the upper faces of the bricks have open groves to accommodate a heating coil.

5. An electric boiler as claimed in claim 4, in which the recesses in the bricks are of semi-cylindrical shape.

6. An electric boiler as claimed in claim 4, in which the bricks are identical except for any of reduced width used in conjunction with a keying brick.

7. An electric boiler as claimed in one of claims 1 - 6 in which a first manifold includes portions which communicate with the sides of the boiler tubes, the adjacent ends of the boiler tubes being closed and terminating inside the heat insulating material.

8. An electric boiler as claimed in claim 7, in which a second manifold includes portions which communicate with the sides of the boiler tubes, and the adjacent ends of the boiler tubes are closed, and terminate inside the heat insulating material.

9. An electric boiler as claimed in claim 7 or claim 8, in which the first and/or second manifold and respective boiler tubes form a welded assembly.

10. A hot water system including an electric boiler as claimed in any one of claims 1 to 9.

10. An electric boiler substantially as hereinbefore described.

11. A hot water system including an electric boiler as claimed in any one of claims 1 to 10.

1. An electric boiler, comprising a heat store, electrical means for heating the heat store, heat insulating material surrounding the heat store, a plurality of boiler tubes extending through the heat store, the heat store including pairs of heat storage bricks having semi-cylindrical recesses which, when the bricks of each pair are placed together, closely surround the boiler tubes.

4. An electric boiler as claimed in any one of claims 1 or 3, in which the upper faces of the bricks have open grooves to accommodate a heating coil.

5. An electric boiler as claimed in any one of claims 1 to 4, in which the bricks are identical except for any of reduced width used in conjunction with a keying brick.

6. An electric boiler as claimed in any one of claims 1 to 5 in which a first manifold includes portions which communicate with the sides of the boiler tubes, the adjacent ends of the boiler tubes being closed and terminating inside the heat insulating material.

7. An electric boiler as claimed in claim 6, in which a second manifold includes portions which communicate with the sides of the boiler tubes, and the adjacent ends of the boiler tubes are closed, and terminate inside the heat insulating material.

8. An electric boiler as claimed in claim 6 or claim 7, in which the first and/or second manifold and respective boiler tubes form a welded assembly.

9. An electric boiler substantially as hereinbefore described.