GB2317944A - Electrical water heating appliance - Google Patents

Abstract

An electrical through-flow water heating appliance, comprising an inlet 27 for water from a supply; an electrically powered heater 15 through which water can flow from said inlet to a heater outlet 22; and valve means 39 operable to receive and mix water from said heater outlet and from said inlet and to deliver such mixed water to an appliance outlet 42, in a proportion determined by a means for sensing the temperature of water delivered from the valve means to said appliance outlet. Preferably a flow regulator 14 ensures constant flow rate of water through the heater, the temperature responsive means is a wax capsule, and the valve is thermostatically controlled and is vented. A pressure operated switch 33 may control the supply of electrical power to the heating elements of the heater.

Description

Title: ELECTRICAL WATER HEATING APPLIANCE Description of Invention This invention relates to an electrical water heating appliance of the through-flow (instantaneous) type, suitable for supplying heated water to a shower.

Through-flow electric water heating appliances are commonly used for supplying heated water to showers. They are readily installed at any position where a cold water supply and a mains electrical supply can be provided, and are compact and energy-efficient since they do not store a large quantity of water at an elevated temperature.

One problem associated with such appliances is that of maintaining a substantially constant temperature of water delivered to the shower. In known such appliances, the outlet temperature is determined by a flow control valve at the inlet to the heater which usually is pressure-regulated, so as to provide a more or less constant selected flow rate which should not be altered by changes in inlet pressure. If the flow rate of water through the heater is decreased then the outlet temperature increases, and vice versa. However, such flow control valves do not work particularly well and a drop in flow rate might be caused if there is a drop in water pressure in the system feeding the appliance, for example if a tap elsewhere in the system upstream of the appliance is turned on. Whilst a decrease in the temperature of water supply to a shower might cause some discomfort to a person using the shower, an increase in such temperature brings a risk of injury to the shower user through scalding, and must be avoided.

Further, such controls take no account of variations in the temperature of inlet water, nor of voltage variations in the power supply which cause the power of the heater to vary. There have been various further proposals for ways in which the outlet temperature of a shower heating appliance might be controlled, but some of such methods have been unsatisfactory and/or complex and expensive.

Accordingly it is the object of the present invention to provide a heating appliance wherein the above described problem is overcome or reduced.

According to the invention, I provide an electrical through-flow water heating appliance, comprising an inlet for water from a supply; an electrically powered heater through which water can flow from said inlet to a heater outlet; and valve means operable to receive and mix water from said heater outlet and from said inlet and to deliver such mixed water to an appliance outlet, in a proportion determined by a means for sensing the temperature of water delivered from the valve means to said appliance outlet.

Preferably there is means for regulating the flow rate of water through the heater to a substantially constant value.

In a heating appliance in accordance with the invention, the use of a valve means which mixes or blends water from the heater outlet and the inlet of the appliance in accordance with the temperature of water delivered to the appliance outlet, preferably in combination with a means for regulating the flow of rate of water through the heater, has the effect that accurate control of the temperature of water delivered to a shower can be achieved despite variations in water pressure at the inlet of the appliance. By virtue of the means for regulating flow through the heater, changes in water pressure at the inlet to the appliance do not cause a significant change to take place in the rate of flow through the heater and thus in the temperature of water at the heater outlet. The valve means is then able to provide water at the appliance outlet of a desired temperature, and does not have to respond to rapid changes in the temperature of water at the heater outlet. The outlet temperature is determined by measurement in the vicinity of the outlet, rather than by measurement at some other point.

The valve means may be thermostatically controlled by a mechanical device, e.g. one whose temperature responsive element is a wax capsule. Such a valve means might not respond rapidly enough to changes in water temperature at the heater outlet to ensure safety of a shower user if there were not the means for regulating the flow rate of water through the heater.

Preferably the valve means is vented as between the heater outlet and appliance outlet, i.e. does not completely close off communication therebetween.

The heater does not then have to be constructed as a pressure vessel, since its outlet theoretically can never be blocked.

However, as an alternative, a non-vented valve means could be used, in which case the heater could be constructed as a pressure vessel with a flow switch.

The power of the heater may be variable, e.g. the heater may comprise twO or more heating elements operable together or separately, and there may be means for determining which of such elements are to be energised when the heater is in use, in dependence on the water temperature at the inlet of the appliance. Alternatively a heater element (or elements) may have its power variable, e.g. by having its electrical current regulated by a thyristor chopper circuit or otherwise. The power of the heater may alternatively or in addition be determined by a user of the shower, e.g. by having a control which enables the appliance to be operated in an "economy" mode in which less than the full power of the heater is available.

Preferably the inlet of the appliance incorporates a main on-off control valve for flow of water through the appliance from said inlet. Conveniently this valve may be a solenoid-operated valve.

Preferably there is provided, between said main control valve and heater, a pressure-operated switch for controlling supply of electrical power to the heater.

These and other features of the invention will now be described by way of example with reference to the accompanying drawing, which is a diagrammatic view of the principal components disposed in relation to one another in a heating appliance in accordance with the invention.

Referring to the drawings, the appliance comprises a casing indicated generally at 10, which has a rear panel 11 adapted to be secured to a wall by fasteners extending through apertures 12 therein, and a front cover which has a peripheral wall 13 which fits to the rear panel 11 and conceals the components hereafter described. The appliance will normally be installed in the orientation in which it is illustrated.

Within the casing there is disposed a heater tank 15 which comprises two metal shell parts fixed together at a peripheral seam 16. Within the heater tank are disposed three immersion heater elements 17, 18, 19 of which are of helical configuration, the element 17 being of greater power than the elements 18, 19 and disposed to one side of the latter elements which are in line with one another. The elements extend outside the heater tank as indicated at 20 where they have suitable electrical connectors at their ends. The heater tank further has an inlet fitting 21 and an outlet 22, the latter having a stand pipe 23 extending upwardly therefrom, within the heater element 17.

The heater tank 15 is further provided with the usual components which are associated with such heater tanks in shower heating appliances, namely a pressure relief valve 24 and an overheat cut out sensor which is not shown but which would be disposed in a recess 25 above the top of the stand pipe 23.

Beneath the heater tank 15 there is disposed an inlet manifold 26 with ports 27, 28, 29. The manifold further has a side chamber 30 on which is mounted a pressure switch 31 including a diaphragm 32 to be operated by the pressure of water within the manifold 26 communicated through an aperture in the side chamber. Movement of the diaphragm 32 is communicated to a microswitch 33 via rocker lever 34 and a push rod.

The port 27 connects to the inlet fitting 21 of the heater tank 15. The port 28 has a valve 35 connected thereto, this being an on-off valve operated by a solenoid 36. An inlet elbow 37 connects to the inlet of the valve 35, and provides for connection to a mains water supply.

The port 29 of the manifold 27 connects to one inlet 38 of a thermostatically controlled blending valve 39. The other inlet 40 of the valve 39 connects to the heater outlet 22 by way of a fitting 41. The valve 39 has an outlet 42 for connection of a pipe, which may be flexible, leading to a shower head. The valve conveniently is of the thermostatic type controlled by a wax capsule responsive to the temperature of water delivered to its outlet 42 to control appropriate blending of water supplies from its two inlets 38, 40, and is controlled by a user-operable temperature selection control which extends through the front cover of the casing of the heating appliance. The valve is a vented type, i.e. it cannot completely shut off communication between its outlet and its inlet 40 so that the heater tank 15 theoretically cannot become a closed pressure vessel.

At the inlet fitting 21 of the heater tank there is disposed a flow regulator 14 which is an active device operable to ensure a substantially constant flow of water through the heater tank despite changes in water pressure in the manifold 27.

The controls available to a user of the appliance preferably comprise the temperature control aforesaid and an on-off switch which when switched on causes the solenoid 36 to be energised to open the valve 35 and cause water from the mains to be delivered to the manifold 27. From the manifold 27, water passes through the heater tank 15 and the heated water is blended by the valve 39 with cold water directly from the manifold to supply water to the shower at the required temperature. The heater elements are switched on by the microswitch 33 which responds to water pressure in the manifold 27, as detected by diaphragm 32. An inlet water temperature sensor (not shown) may be provided in association with the manifold 27, to control the total electrical input power of the heater. Such a sensor may determine which of the heater elements are energised, causing the electrical power supply to such elements to be switched by relays 44.

Thus the invention provides a water heating appliance for use with a shower, which in a simple manner provides accurate control of water temperature.

A further advantage of the invention is that, by virtue of providing two paths for flow of water through the appliance, there is less resistance to such flow than in the case of an appliance whose outlet temperature is determined by a flow control valve at the inlet of the appliance. Thus a greater shower flow may be obtained when the water inlet pressure is low.

It will be appreciated that modifications could be made from the construction above described without departing from the scope of the invention.

For example, instead of mechanically controlled blending valve 39 operated by a wax capsule, a water outlet temperature sensor could be provided which gives an electrical signal to a temperature control circuit which controls a suitable blending valve. Instead of switching two or more heater elements to control the total power of the heater, a heater element (or elements) could have its power controlled by a thyristor chopper circuit or otherwise.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (14)

1. An electrical through-flow water heating appliance, comprising an inlet for water from a supply; an electrically powered heater through which water can flow from said inlet to a heater outlet; and valve means operable to receive and mix water from said heater outlet and from said inlet and to deliver such mixed water to an appliance outlet, in a proportion determined by a means for sensing the temperature of water delivered from the valve means to said appliance outlet.

2. An appliance according to Claim 1 further comprising means for regulating the flow rate of water through the heater to a substantially constant value.

3. An appliance according to Claim 1 or Claim 2 wherein said valve means is thermostatically controlled by a mechanical device.

4. An appliance according to Claim 3 wherein said valve means is one whose temperature-responsive element is a wax capsule.

5. An appliance according to any one of the preceding claims wherein the valve means is vented as between the heater outlet and appliance outlet.

6. An appliance according to any one of the preceding claims wherein the power of the heater is variable.

7. An appliance according to Claim 6 comprising means for determining the power of the heater when in use, in dependence on the water temperature at the inlet of the appliance.

8. An appliance according to Claim 6 or Claim 7 comprising two or more heating elements operable together or separately to vary the power of the heater.

9. An appliance according to Claim 6 or Claim 7 comprising electronically controlled means for varying the power of the heater.

10. An appliance according to any one of the preceding claims comprising a main control valve for controlling flow of water through the appliance from said inlet.

11. An appliance according to Claim 10 wherein said valve is a solenoidoperated valve.

12. An appliance according to Claim 10 or 11 wherein there is provided, between said valve and heater, a pressure-operated switch for controlling supply of electrical power to the heater.

13. An appliance substantially as hereinbefore described with reference to the accompanying drawings.

14. Any novel feature or novel combination of features described herein and/or in the accompanying drawing.