GB2332737A - Organisation of water heating systems - Google Patents

Abstract

A water heating system, especially a thermal storage water heating system, comprises three water storage tanks 10,12,13 arranged in a narrow, elongated upright casing. These tanks are hydraulically inter-linked so as in effect to form one storage volume, but they are arranged at the comers of the casing, which is square in cross section, so as to leave a corner space 90, for the location of ancillary equipment which is needed for the system. In an alternative arrangement the heating system comprises two side by side storage tanks with one tank shorter than the other so that the ancillary equipment can be located above the shorter tank.

Description

Improvements Relating to Water Heating Apparatus This invention relates to water heating apparatus, and in particular concerns water heating apparatus usable mainly in connection with the heating of water for domestic dwellings. As the explanation of the invention proceeds, it will be appreciated that the invention may be adapted for the heating of water in other buildings such as small offices and workshops, but as clearly the main application of the invention is for domestic water heating, references hereinafter will be limited to this application.

The methods of heating water in domestic dwellings have changed over the last fifteen years. Thus, prior to 1980 in the United Kingdom, water heating systems comprised a boiler and a water storage tank. The boiler served to heat the water in the storage tank by heat exchange, and the water in the tank could be drawn off at outlets such as taps in the dwelling for washing purposes. The water in the tank was referred to as secondary water, and was distinguished from what was referred to as the primary water which was contained in the central heating system connected directly to the boiler. Such systems are still in use today in the United Kingdom, but more and more domestic hot water systems are based upon what is known as thermal storage.

In thermal storage systems, again a storage tank has water contained therein which is heated by the boiler or electric immersion heating means, but the boiler or electric immersion heating means operates to maintain the water in the tank at a pre-set level, for example in the order of 76 to 80"C and when there is a demand for heat or hot water, a draw is made on the store which may or may not result in the boiler being fired or the electric heating means being switched on depending upon the demand. The boiler or electric heating means reacts in relation to the temperature of the store, in order to add heat to the store when required. This may take place at times when the demand has terminated, and the thermal store therefore acts in a similar manner to the well-known electric thermal storage heaters. Thermal storage has been found to be a more economical system for the management and supply of hot water to a domestic dwelling.

As a development of thermal storage there has been introduced what is known as "integrated thermal storage" wherein the storage tank contains primary water which is circulated through the domestic dwelling central heating system and in addition the primary hot water is utilised by being passed through heat exchange means in order to heat mains pressure secondary water to meet the demand for hot water at the outlet taps.

As a competitor to thermal storage systems there has been developed the "combi" boiler system which is basically a hot water boiler arranged to supply heated water, but at mains pressure, directly to outlet taps, or to circulate hot water around a central heating system connected to the boiler. With such a combi boiler system, there is no separate storage tank for water, the arrangement being that the boiler includes a burner heat exchanger through which the primary water for the central heating system is pumped in the event of a demand for space heating, or through which mains water is pumped in the event that there is a demand for hot water at the outlet taps. The system is prioritised insofar as if there is a demand for hot water at the taps, that demand takes priority over a demand for space heating which in practise does not create any problems because demands for hot water at taps are usually prevalent only for a relatively short time and the diversion of the heat from the heating system to the secondary hot water demand is unlikely to have any significant effect on the heating system.

The problem with combi boilers however is that they are limited in terms of providing sufficient quantities of hot secondary water for example when hot water is required for baths, because they cannot provide sufficient output flow rates at sufficiently high temperatures to achieve the running of a bath in a reasonable time.

To overcome this difficulty, combi boilers have more recently been combined with storage tanks to provide a volume of hot secondary water which can be drawn on demand, resulting in a unit which is a combi and also a thermal storage system.

All systems require certain ancillary equipment such as heat exchangers, pumps piping and so on, and that equipment is located outside the storage tank. There is there for a design function to be accommodated.

In the case of the combi boiler and storage tank arrangement, the boiler and tank are located side by side with the ancillary equipment located as best as possible, and everything is housed in a casing which typically is fitted into the domestic dwelling kitchen under the sink and is a fairly large, cumbersome unit.

The outlet flue from the boiler is invariably taken from the combi unit through the domestic dwelling wall so that the flue gases can be discharged into the atmosphere.

It has also been known to provide combined boiler/thermal storage tank units for fitting in cupboards, so that small bore flue pipes connected to the boiler can be directed from the cupboards which may be centrally located in the dwelling, through the dwelling structure and out of the dwelling through the wall thereof. Such small bore arrangements require the use of a fan assisted flue in order to achieve sufficient discharge of the flue gases to the atmosphere outside the dwelling.

In thermal storage, there is usually a single cylindrical tank and the ancillary equipment is fitted around the tank, again as best as possible.

There is a demand in relation to each system, to provide more storage capacity, and this has created problems as concern design of the tank and boiler arrangement.

The present invention provides a solution which provides an increase in the stored volume and enables the economic use of space for accommodating the tank and ancillary equipment.

In accordance with the present invention there is provided a water heating system having storage tank means and ancillary equipment, such as heat exchangers, piping, pumps and so on, wherein the tank means is arranged either as two side by side cylinders with their axes upright and parallel, but of which one is shorter than the other so that the ancillary equipment can be located, above the shorter cylinder, or as three cylinders arranged side by side with their axes parallel, but lying at three corners of a rectangle, so that the ancillary equipment can be fitted into the space forming the fourth corner, whereby, in either case the system can be fitted neatly into 9 rectangular casing.

The casing is preferably of a size to fit into a standard domestic airing cupboard. For example, the casing size may be 590mm x 590mm x 1900mm.

The arrangement of three cylinders is preferred as this provides for an increase in the storage capacity in a minimum of space, whilst still providing generous space for the ancillary equipment, as there will be created inside the casing a long corner space for the location of such ancillary equipment. When the casing is opened, being provided with a door for this purpose, this corner space will be readily accessible, so that the ancillary equipment can easily be serviced, repaired adjusted and replaced.

As to the increase in storage of water, the three cylinders can be such as to contain nearly 300 litres of water in a casing of a size acceptable for domestic use.

The cylinders preferably are of the same dimensions and of course they will be hydraulically inter-linked to provide a single body of water. The use of three smaller cylinders, as opposed to a single large cylinder of the same capacity, provides the advantage that the assembly can be more easily and more neatly accommodated in a domestic dwelling. Also, using three smaller cylinders, rather than one, provides that the metal which is used for the cylinders can be of reduced gauge, representing a saving in cost and in volume.

In the preferred form the system is embodied in an integrated thermal storage system.

The present invention in a simple and effective manner provides an arrangement wherein considerable advantages can be achieved, and at least in the preferred form, some of the disadvantages mentioned above can be overcome.

The storage tanks preferably are of the sealed type, so that the conventional feed and expansion tank as used in domestic hot water systems can be eliminated, and where such a sealed system requires an expansion unit, that expansion unit preferably is located under the storage tanks.

The heat exchanger for the secondary hot water may be a plate heat exchanger located in the said space.

The invention is particularly useful when the heating of the water is by an electric immersion heater or heaters, as with a large stored volume of water, more energy can be supplied at an off peak tariff. It is to be noted that the invention can however be used when the heating source is a gas fired or other boiler.

A particularly compact and novel arrangement therefore results.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein: Fig. 1 shows diagrammatically the elements of a unit according to the invention and of which the water is heated by a single electric immersion heater, and the hydraulic connections of the unit, and Figs 2, 3 and 4 show in front, side and plan views respectively, the unit of Fig. 1.

Referring to the drawings, Fig. 1 the hydraulic circuit couplings in relation to the storage tank means which in this example is made up of three storage tanks 10, 12 and 13 which are of identical elongate configuration as shown. Three storage tanks are used, coupled in parallel, in order to enable the unit to be encased neatly compared to one in which a single tank is used.

In the production unit, the hydraulic connections of Fig. 1 will be embodied in casing of the apparatus, shown in the other three figures.

Reverting to Fig. 1, the three elongate tanks 10, 12 and 13 are disposed upright and side by side, and shown as entering tank 13 is an electric immersion heater 14, which is of the flow tube type. Also shown is a heat exchanger 16. In Fig. 1 the tanks are shown as being hydraulically connected at 20, 21, the connection 20 being connected to a system filling point 23, which also serves as a point for connection to an expansion vessel, whilst connection 21 is also connected to a system pressure relief valve 25. In fact, in modern water heating systems, expansion tanks are no longer compulsory, and it is to be mentioned that the provision of such a tank is not necessary to the present invention.

The heating of the water is achieved by operation of the immersion heater 14, coupled with the pumping of water from the heater 14 by pump 16A through line 18 into the tanks 10, 12 and 13. The pump 14 draws water from tank 13 by means of pump 16 a, and line 18 has a non return valve 22 and an isolating valve 24.

Coupling lines 30 and 21 couple the tanks 10, 12 and 13 in parallel and the pump 27 draws water from the tanks 10, 12 and 13 through line 21 and line 26 and then, when hot water is being supplied, through the heat exchanger 16.

The water which has given up its heat is delivered through line 28 and is charged into the tanks 10, 12 and 13 through the parallel branch 30.

The tanks 10, 12 and 13 which are of the sealed variety are initially filled from the mains by means of a mains coupling and when filling has been completed, the coupling is removed as it is a regulation that sealed water tanks have to be uncoupled from the mains after filling.

The water in tanks 10, 12 and 13 is primary water and is therefore used for the central heating system of the dwelling.

Fig. 1 also shows the hydraulic arrangement for the supply of the central heating system. The tanks 10, 12 and 13 are shown, and also shown are two further parallel coupling lines 50 and 52 which respectively connect to the central heating system. The pump 27 also serves the central heating system. When the central heating system calls for heating either by a timer device or a thermostatic device or both, water is circulated from the tanks 10, 12 and 13 by pump 27 through three way port diverter 36 and line 50, the central heating radiators, and returns by line 52.

In the third hydraulic circuit shown in Fig. 1, hot water is circulated through heat exchanger 16 by pump 27. The heat exchanger is a high efficiency plate heat exchanger of which the other couplings are connected to a cold water mains inlet line 72, and a hot domestic secondary water outlet line 74 which supplies water to for example the domestic dwelling outlet such as taps. Line 72 contains a flow switch 78 which is operated when for example a tap is opened demanding hot water. This causes the water to flow through the line 72, plate heat exchanger 16 and line 74 to the tap, and the flow switch 78 is actuated. When this switch is actuated, pump 27 is actuated, if not already running, diverter valve 36 to set to cause circulation of hot water through the heat exchanger 16 and heat exchange between the flowing secondary water and the circulating primary water so that the secondary water is heated before it reaches the tap. The flow of the secondary water through the heat exchanger is by virtue of mains pressure.

Other components, which are self explanatory and which are shown in Fig. 1 are as follows; 1 Automatic air vent and anti-vacuum valve 2 Isolating valve 3 Modulating three way valve 5 Non return valve 6 RAV sensor 7 Bottom store thermostat 8 Top store thermostat Figs. 2, 3 and 4 show the assembled unit 80 and the spacing layout of the major components. It will be seen that the tanks 10, 12 and 13 are located upright and side by side, with their axes on three corners of a rectangle, in this case a square, so as to create a corner space 90 in which the ancillary equipment 2, 3, 27, 5, 6, 36, 16, 22, 16A, 14 is located. The ancillary equipment can include other components, such as at least some of the piping described herein, and if a side of the system casing 92 adjacent the space 92, is or has a door which can be opened, then all such ancillary equipment can be accessed for servicing and repair and the like, making a particularly convenient arrangement, without requiring a single large cylinder. Smaller cylinders furthermore have better hoop strength characteristics than large cylinders. The cylinders may be lagged with heat insulation material.

Claims (11)

CLAIMS.

1. A water heating system having storage tank means and ancillary equipment, such as heat exchangers, piping, pumps and so on, wherein the tank means is arranged either as two side by side cylinders with their axes upright and parallel, but of which one is shorter than the other so that the ancillary equipment can be located above the shorter cylinder, or as three cylinders arranged side by side with their axes parallel, but lying at three corners of a rectangle, so that the ancillary equipment can be fitted into the space forming the fourth corner, whereby, in either case the system can be fitted neatly into a rectangular casing.

2. A system according to claim 1, including the casing.

3. A system according to claim 2, wherein the casing is of a size to fit into a standard domestic airing cupboard.

4. A system according to claim 2 or 3, wherein the arrangement of three cylinders is provided and there is created inside the casing a long corner space for the location of the ancillary equipment, the casing being provided with a door for this purpose, enabling the corner space to be readily accessible, so that the ancillary equipment can easily be serviced, repaired, adjusted and replaced.

5. A system according to any one of the preceding claims, wherein when there are three cylinders they are of the same dimensions.

6. A system according to any one of the preceding claims, wherein the system is embodied in an integrated thermal storage system.

7. A system according to any one of the preceding claims, wherein the storage tanks are of the sealed type.

8. A system according to claim 7, including an expansion unit for accommodating expansion of the water in the tanks.

9. A system according to claim 8, wherein the expansion unit is located under the storage tanks.

10. A system according to any preceding claim including as heat exchanger for secondary hot water, said the heat exchanger being a plate heat exchanger located in the said space.

11. A water heating system according to any embodiment substantially as hereinbefore described with reference to the accompanying drawings