GB2317219A

GB2317219A - Waterheaters

Info

Publication number: GB2317219A
Application number: GB9619322A
Authority: GB
Inventors: Hugo William Maule
Original assignee: IMI WATERHEATING Ltd
Current assignee: IMI WATERHEATING Ltd
Priority date: 1996-09-13
Filing date: 1996-09-13
Publication date: 1998-03-18
Also published as: GB9619322D0

Abstract

An instantaneous electric waterheater, for example a shower heater, includes a spiral passageway (7) of rectangular cross-section within and along which one or more heating elements (18, 18') extend. In use, mains cold water flows along the passageway (7) in close proximity to the heating elements (18, 18') whereby it becomes instantaneously heated and issues from a hot water outlet (9). One of the walls of the passageway (7) is defined by the internal surface of a rear, planar wall (2) of a decorative, outer plastics casing (1). The metal can conventionally used in such waterheaters is thereby dispensed with, thus affording a more compact and cost-effective construction. The usual controls are provided on the front cover.

Description

WATERHEARS This invention relates to waterheaters and more particularly to so-called instantaneous electric waterheaters of the type used, for example, in instantaneous shower units.

Conventionally, instantaneous electric waterheaters include a small, generally cylindrical container, made for example of copper, containing one or more convoluted heating elements, typically rated at between 5 and 8 KW and having an inlet for cold water, usually mains cold water, and an outlet for hot water which is connectable to a point of use, such as a shower head. Upon demand, cold water flows into the container, via an on/off solenoid valve and a variable flow regulator or a valve combining both functions, wherein it is instantaneously heated by the heating element(s) and whence it flows, via the outlet, to the point of use. The flow regulator controls the volume of water passing over the element(s) per unit time and hence the temperature of the hot water issuing from the outlet. Operation is controlled by electrical switches and/or electronic circuitry and the heater further includes a number of safety devices such as a thermal cut-out device. All of the aforesaid components and the necessary electrical wiring are enclosed in a casing, typically a plastics moulding designed to be externally attractive to the eye.

Whilst such conventional instantaneous waterheaters function quite adequately and are widely used, they are relatively bulky because of the need for a relatively large diameter cylindrical container for the heating element(s). In addition, the container (commonly referred to as a "can")/heating element assembly is susceptible to localised overheating and, therefore, to excessive scaling especially where the heater is used in hard water areas.

It is an object of the present invention to provide an instantaneous electric waterheater of more compact, cost effective construction and which, in a preferred embodiment, mitigates the problem of localised overheating.

According to the present invention, there is provided an instantaneous electric waterheater including an external casing having a substantially planar rear portion for mounting against a wall, an inlet for cold water, an outlet for hot water and, located within the external casing, a passageway interconnecting the inlet and the outlet and having one or more electric heating elements located therein for heating the cold water during its passage between the inlet and the outlet via the passageway, the waterheater further including means to control the flow of water through said passageway and means to control energisation of the heating element(s), characterised in that at least one wall of said passageway is defined by an internal surface of the said rear portion of the external casing.

Preferably said passageway is elongate and the or each heating element is elongate and extends substantially centrally along the passageway in proximal, generally parallel relationship with the wall(s) thereof whereby all of the water is constrained by the passageway to flow progressively therealong and over the entire length of the element(s) in close proximity thereto.

The invention, together with preferred features thereof, will now be illustrated, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a front elevation (with its decorative front cover removed) of an instantaneous electric waterheater constructed in accordance with the invention; Fig.2 is a similar view to that of Fig. I but revealing the electric heating elements; Fig.3 is a view on the line III - III of Fig.l but with the decorative front cover in place; Fig.4 is a view on the line IV - W of Fig.l; and Fig.5 is a similar view to that of Fig.2 showing an alternative example of a waterheater constructed in accordance with the invention.

Referring to the drawings, the waterheater comprises a main outer casing 1 moulded in one piece in plastics material. The casing 1, which is substantially rectangular, consists of a rear wall 2, opposed side walls 3, 3' and opposed top and bottom walls 4, 4'. Moulded integrally with, and extending perpendicularly from, the rear wall 2 is a generally spiral wall member 5 which, together with the internal surface of the rear wall 2, defines a generally spiral channel which is closed by a separately formed, flat cover 6 so as to form a spiral passageway 7 of rectangular cross-section.

The cover 6 has formed in it an aperture 8 which serves as an inlet for mains cold water into the central end of the passageway 7 as is described in more detail below. The outermost lower end of the passageway 7 terminates in a threaded hot water outlet connector 9 secured to bottom wall 4' of the casing 1.

Secured into the inlet aperture 8 is a vertically extending pipe 10 which is connected to the outlet side of a user-operable flow/temperature regulator 11. The inlet side of the regulator 11 is connected to a threaded, mains cold water, connector 12, also secured to the bottom wall 4', via an on/off solenoid valve 13.

Located in the pipe 10 is a moving magnet/reed switch assembly 14. A thermal cut-out device 15 is mounted on the front face of the cover 6, as is a printed circuit board 16 carrying the usual components necessary to control operation of the waterheater. A front, decorative cover 17 is secured to the casing 1.

Heating of the mains cold water is effected by a pair of heating elements 18, 18' that extend side-by-side, in substantially spiral fashion, centrally along most of the length of the passageway 7, as can be seen in Figs. 2 and 3. The ends of each element 18, 18' are connected to, respectively, the live and neutral (designated + and - in Figs. 1 and 2) of a mains AC power source via the circuit board 16.

As will be appreciated, many of the components referred to above are conventionally used in instantaneous electric waterheaters and their function will be apparent to those skilled in the art. Indeed, the way in which the waterheater functions is identical to that of conventional instantaneous electric waterheaters. Nevertheless, its mode of operation will now be briefly described in the context of a shower unit, the hot water outlet connector 9 being coupled in the usual way to a shower head by means of flexible hose (not shown).

In order to operate the shower, the user manually switches on an electric switch (not shown) which causes the solenoid valve 13 to open whereupon mains cold water flows into the regulator 11 and thence into the pipe 10. Water flowing in the pipe 10 actuates the moving magnet/reed switch assembly 14, the switch closing and thus transmitting a control signal to a high power solid state switch, such as a triac, whereupon the elements 18, 18' become energised. Cold water then flows up the pipe 10 and, via the aperture 8 in the cover 6, into the spiral passageway 7 along which it flows, at the same time being rapidly heated by the elements 18, 18'. Heated water then flows from the heater to the shower head. The regulator 11 controls the volume of water passing over the elements 18, 18' per unit time and thus the temperature of the hot water generated by the heater. The temperature may be varied by the user by adjusting the position of the regulator 11, increasing the flow in order to reduce the temperature or, conversely, decreasing it in order to increase the temperature. The thermal cut-out device 15 is usually set at approximately 57"C and causes de-energisation of the elements 18, 18' in the event that the heated water exceeds that set temperature.

An additional safety device, in the form of a pressure relief valve (not shown), may be provided, as is conventional. This prevents an excessive build up of pressure within the passageway should abnormal operating conditions arise. Further, and again as is conventional, the regulator may incorporate a stabiliser which ensures that fluctuations in the mains cold water pressure are compensated for so that the heated water is continuously maintained at the desired temperature.

In the drawings, the necessary wiring has been omitted for clarity, but as will be appreciated, this would again be conventional.

The waterheater described above is, as already noted, conventional in terms of its mode of operation and control. However, the design of the "can", and the arrangement of the heating elements therein, in which the water is instantaneously heated, represent a radical departure from conventional designs. More particularly, the "can", in the form of the passageway 7, provides a much longer flow/heating path for the water and consequently the path may be of relatively small cross-section. By way of example, the passageway 7 may have cross-sectional dimensions of about 27 x 22mm and a length of about 900mm, the diameter of each heating element being about 6mm and, as can be seen in Fig. 2, extending along most of the length of the passageway 7. This, together with the fact that the passageway 7 is defined in part by the rear wall 2 of the casing 1, means, in particular, that the waterheater may have a slimmer, more aesthetically pleasing profile in side elevation. Further, because the water is constrained to flow evenly along the entire length of the elements 18, 18' the likelihood of overheating and scale formation is significantly reduced. The rear wall 2 of the casing 1, the walls 3, 3', 4 and 4' and the wall member 5 may comprise a single moulding in, for example, an injection moulded thermoplastic material.

Whilst the passageway 7 of the embodiment described above is generally spiral in fonn, it is to be understood that it could take any one of a number of alternative forms. By way of example, it would have a zig-zag, preferably rectangular cross-section, configuration. In that case, the heating elements would be of corresponding zig-zag configuration.

Fig. 5 shows a waterheater of the invention in which the passageway and the heating elements have a generally zig-zag configuration. Otherwise, the heater is similar to those shown in Figs.

1to4.

The drawing is a similar view to that of Fig. 2 and corresponding parts bear the same reference numerals. Here, it can be seen that there are a number of walls 5 that, together with the intemal surface of the rear wall 2 and a cover (not shown but corresponding to item 6 in Figs. 1, 3 and 4) define a zig-zag passageway 7 along which extend a pair of adjacent sinusoidal heating elements 18, 18'. The passageway 7, at its uppermost point, defines a weir 19, where the elements 18, 18' terminate, and which ensures that the elements are always fully immersed in water so avoiding the possibility of their running dry and burning out. The threaded outlet 9 is located adjacent to the weir 19. The embodiment shown in Figs. 1 to 4 may comprise a similar arrangement.

Claims

1. An instantaneous electric waterheater including an external casing having a substantially planar rear portion for mounting against a wall, an inlet for cold water, an outlet for hot water and, located within the external casing, a passageway interconnecting the inlet and the outlet and having one or more electric heating elements located therein for heating the cold water during its passage between the inlet and the outlet via the passageway, the waterheater further including means to control the flow of water through said passageway and means to control energisation of the heating element(s), characterised in that at least one wall of said passageway is defined by an internal surface of the said rear portion of the external casing.

2. A waterheater according to claim 1 wherein said passageway is of elongate, convoluted form, the or each heating element extending substantially centrally therealong in proximal, generally parallel relationship with wall(s) thereof whereby all of the water is constrained by the passageway to flow progressively therealong and over the entire length of the heating element(s) in close proximity thereto.

3. A waterheater according to claim 1 or claim 2 wherein the passageway is of generally spiral form.

4. A waterheater according to claim 1 or claim 2 wherein the passageway is of generally zig-zag form.

5. A waterheater according to any one of claims 1 to 4 wherein the passageway is of substantially rectangular cross-section.

6. A waterheater according to any one of claims 1 to 5 wherein said external casing comprising a plastics moulding.

7. A waterheater according to any one of claims 1 to 6 wherein there is a pair of heating elements extending in side-by-side relationship along the passageway.

8. An instantaneous electric waterheater substantially as hereinbefore described with reference to, and as illustrated in, Figs 1 to 4 of the accompanying drawings.

9. An instantaneous electric waterheater substantially as hereinbefore described with reference to, and as illustrated in, Figs 1 to 4, as modified by Fig 5, of the accompanying drawings.