IE920670A1 - Improvements to instantaneous water heaters - Google Patents

Abstract

An electrical instantaneous water heater comprises a pump 5 positioned in the water inlet supply to provide water at a substantially constant pressure to the heater elements contained in a heater can 6, and a flow control valve 2 for controlling the flow of water to the pump 5, the valve 2 incorporating a pair of apertured ceramic discs (16) and (17) (Fig. 2, not shown) which are rotatable relative to one another to control water flow through it and being disposed at the inlet to or outlet from the pump. The valve 2 may include a micro-switch controlled by cam 4 to activate the pump 5. The outlet water temperature may be varied by adjustment of the valve 2 and of the power input to the heater elements by a selector switch 8.

Description

IMPROVEMENTS TO INSTANTANEOUS WATER HEATERS The present invention relates to improvements in electrical instantaneous water heaters which incorporate a pump between the cold water supply and the heating elements.

At low water inlet pressures, for example in tank fed systems, it is frequently not possible to utilise standard electric instantaneous water heaters to provide hot water for showers, hand basins or other domestic uses. In such circumstances it has been found necessary to incorporate into the system a pump which draws water from the supply and forwards it to the heating elements at a pressure and at a flow rate suitable for use therewith. An example of such an instantaneous water heater system is the applicant’s Triton T90 instantaneous water heater system sold for use with showers.

The systems employing pumps, however, have the disadvantage that, in addition to a water inlet stop20 cock being required on the inlet to the pump, a flow control valve is also required on the heater outlet, the temperature of the water at the shower head being controlled partly by the rate of flow of water taken from the heater i.e. by the outlet flow control valve, and the power supplied to the heater, which power is normally selectable by the user. A major problem arises with this arrangement as a result of limescale affecting the outlet flow control valve, with the result that the flow of water may be reduced to unacceptably low levels. In addition some markets now require that, for safety reasons, instantaneous water heater systems should not incorporate water temperature control devices on the outlet side of the heater.

It has now been found that it is possible to 2. dispense with the outlet flow control device and to incorporate flow control into the on/off valve on the inlet side of the pump.

According to the present invention there is provided an electrical instantaneous water heater including a pump positioned in the water inlet supply to provide water at a substantially constant pressure to the heater elements and a valve to control the flow of water through said pump, wherein the said valve is a flow control valve incorporating ceramic components in the form of apertured discs rotatable relative to each other to control the flow of water therethrough.

Advantageously said flow control valve incorporates means, typically in the form of a micro15 switch, operable to activate the pump when the flow of water is turned on.

By such means an electrical instantaneous water heater is provided in which the output thereof is derived directly from said heater elements, thereby obviating the need for an outlet flow control device.

An exemplary embodiment of the invention will now be described reference being made to the accompanying drawings, in which: Fig. 1 depicts an electrical instantaneous water 25 heater in accordance with the present invention; and Fig. 2 is a partially exploded view of the flow control valve of Fig. 1.

In the drawing water from a tank supply (not shown) is fed via an inlet 1 to a flow control valve 2 incorporating a ceramic disc rotatable about an axis such that on turning a shaft 3 of the valve 2 the disc is driven through 270° and flow is increased from zero to maximum. (A suitable flow control valve is manufactured by CICE of France).

A micro-switch (not shown) is activated by means 3. of a cam 4 mounted on the shaft 3 of the flow control valve 2 as soon as the valve 2 is opened.

A pump 5 coupled to the flow control valve 2 draws water through the flow control valve 2 and forwards it to a plurality of heater elements contained within a heater can 6, the ends of four heater elements being shown at 7. The rate at which water is drawn through the valve 2 will depend upon the degree to which the valve 2 has been opened and therefore the flow of water to the heater can 6 is controllable.

The power supply to the heater elements is controlled by a selection switch 8 which typically comprises a rotatable shaft 9 which is engageable with a plurality of micro-switches (not shown) which enable the heater elements in the heater can 6 to be selectively energised e.g. at a rate of 3.3, 4.7 or 8 kilowatts per hour of electrical power to heat the water flowing in the heater can 6. Water from the heater can 6 flows directly, i.e. without the need for an outlet flow control device, via outlet 10 to a shower head (not shown). The temperature of the water issuing from the outlet 10 and thus from the shower head is controlled by controlling the flow of water to the pump 5 by the flow control valve 2 and/or by varying the power input into the heater can 6 by operation of selection switch 8.

Preferably, also, a pressure switch 11 is provided for sensing the water pressure in the heater can 6 via coupling 12, the pressure switch 11 being arranged to operate in conjunction with the micro-switches (not shown) of the selection switch 8 whereby when water at a predetermined pressure flows through the heater can 6 the heater elements thereof are activated, and when the water pressure falls below the predetermined level, the heater elements are de-activated. The heater can 6 may 4. also be provided with a pressure relief device 13 which is operable should the water pressure exceed a predetermined level.

In Fig. 2 of the drawings there is shown a 5 partially exploded view of the flow control valve 2 of Fig. 1. The valve 2 comprises a valve body 14 in which is rotatably mounted the shaft 3- Within the end 15 of the valve body 14 is mounted two ceramic discs 16 and 17, which are retained in the end 15 by means of a silicon compression gasket 18 which is itself secured in the end 15 by any suitable means.

The ceramic disc 16 is provided with a sector shaped cut-out 19 and is mounted on the shaft 3 of the flow control valve 2 so as to be rotatable with it.

The other ceramic disc 17 is provided with a shaped cut-out 20 and is fixedly mounted in the end 15 of the valve body 14 so that it remains stationary relative to the rotatable ceramic disc 16. Water flow through the valve 2 is upwards through the bottom of the valve 2, through an aperture 21 in the silicon compression gasket 18, through the shaped cut-out 20 in the fixed ceramic disc 17, through the sector shaped cut-out 19 in the rotatable ceramic disc 16 and out through a side outlet 22 which would be coupled to the pump 5 (Fig. 1). As will be clearly seen from Fig. 2, as the shaft 3 of the valve 2 is rotated counter-clockwise, the ceramic disc 16 is also rotated counter-clockwise to increase the overlapping relationship between the cut-outs 19 and 20 in the rotatable ceramic disc 16 and fixed ceramic disc 17, whereby the water flow through the valve 2 is increased from zero to maximum.

Although in the embodiment of the invention which has been described the flow control valve 2 is positioned before the pump 5 to control water flow therethrough, it should be appreciated that it could be . positioned after the pump 5 but before the heater can 6.

By providing the flow control valve 2 in the water inlet 1 to the pump 5 the requirement of a flow control valve in the water outlet is obviated, and because the valve 2 passes relatively cold water, the limescale build-up is much less than is normally the case when the flow control valve is provided in the water outlet, i.e. at a higher water temperature. In addition, the use of ceramic components in the flow control valve 2 also inhibits the build-up of limescale.

Claims (7)

1. An electrical instantaneous water heater including a pump positioned in the water inlet supply to provide water at a substantially constant pressure to the heater elements and a valve to control the flow of water through said pump, wherein the said valve is a flow control valve incorporating ceramic components in the form of apertured discs rotatable relative to each other to control the flow of water therethrough.

2. A water heater according to claim 1, wherein said flow control valve incorporates means operable to activate the pump when the flow of water is turned on.

3. A water heater according to claim 2, wherein the said means is a micro-switch.

4. A water heater as claimed in any preceding claim, in which said valve is positioned at the inlet of said pump.

5. A water heater as claimed in any of claims 1 to 3, in which said valve is positioned at the outlet of said pump before said heater elements.

6. A water heater as claimed in any preceding claim, in which the output thereof is derived directly from said heater elements.

7. An electrical instantaneous water heater substantially as hereinbefore described with reference to the accompanying drawings.