GB2147980A

GB2147980A - Water heaters

Info

Publication number: GB2147980A
Application number: GB08426916A
Authority: GB
Inventors: Alan James Currall
Original assignee: Redring Electric Ltd
Current assignee: Redring Electric Ltd
Priority date: 1982-02-10
Filing date: 1984-10-24
Publication date: 1985-05-22
Also published as: GB2147980B; GB8426916D0

Abstract

An instantaneous electric water heater has a low voltage manual control panel separate from the main body of the heater thereby enabling the main body of the heater in the case of a shower unit to be located outside the shower area, the separate control panel being accessible from within the shower area. <IMAGE>

Description

SPECIFICATION Water heaters This invention relates to so-called instantaneous electric water heaters, that is to say heaters of the kind incorporating electric heating means, commonly in the form of one or more sheathed or open coil wire electric heating elements, designed to heat the water as it is flowing through the heater, and is primarily, though not exclusively, concerned with such water heaters designed for use as shower units.

In accordance with the invention an instantaneous electric water heater incorporates a main body containing electrical heating means for heating the water and an electrically operable valve for controlling the flow of water through the heater, with the power supplied to the heater and valve controlled by respective controlled semiconductor devices, the heater incorporating also a microprocessor for controlling the operation of the semiconductor devices, and a low voltage manual control panel separate from the main body of the heater for feeding control signals to the microprocessor.

Preferably the water heater is incorporated into a shower unit with the main body arranged to be located outside the shower area, and the separate manual control panel being accessible from within the shower area.

Thus the present invention, by enabling the body of the heater to be mounted outside the shower area avoids the need for mains electrical supplies to enter the area and thus provides advantageous safety feature.

According, therefore, to another aspect of the invention a shower unit comprises an instantaneous electric water heating having a main body located outside the shower area and incorporating an electric heating means and an electrically operable valve for controlling the flow of water through the heater, a microprocessor for controlling the operation of the heating means and valve, and a low voltage manual control panel separate from the main body of the heater and located within the shower area for controlling the operation of the microprocessor.

The microprocessor is preferably arranged to maintain the temperature of the water at the set value for different flow rate settings.

The control panel may include a visual display device which gives an indication of the temperature of the water leaving the heater.

The display device may, for example, incorporate a series of LED's arranged to light up in sequence, under the control of the microprocessor, as the water temperature increases.

The LED's are conveniently disposed in line and are arranged to be progressively illuminated from one end, giving a readily understandable indication of the water temperature.

Preferably the body of the heater includes a temperature sensitive device and control means responsive thereto operative to close the valve and de-energise the electric heating means should the sensed temperature of the water downstream of the heating means exceed a predetermined value.

By shutting off the flow of water, as well as de-energising the heating means, when the sensed water temperature attains a value considered to be unsafe, for example 56"C, the danger of a user being accidentally scalded is effectively avoided.

The control means may be operable normally to open the valve and initiate the operation of the heater by actuation of a manual control, and preferably includes an inhibiter circuit which becomes effective to prevent opening of the valve in the event of the valve having been closed in response to the water from the heater reaching an excessively high temperature, unless a second manual control is also actuated.

This will prevent inadvertent starting of the heater by a user once the valve has closed under such conditions, at least until the temperature of the heating means has fallen to a suitably low value.

Preferably the heater also includes an audible and/or visual warning device, which becomes operative when the temperature of the water approaches a predetermined unsafe value.

The or each controlled semiconductor device is conveniently mounted on a thermally conductive member in close thermal contact with a pipe through which cold water is introduced into the heater, this serving to cool the device in use of the heater.

The invention will now be described by way of example with reference to Figs. 1 and 2 of the accompanying schematic drawings of which Figure 1 shows a shower unit incorporating a water heater in accordance with the invention; and Figure 2 shows a water heater in accordance with the invention.

Fig. 1 shows a shower unit incorporating an instantaneous electric water heater having a main body 1 mounted on a wall outside the shower cubicle 2, and connected to an inlet water pipe 3 and to an electric mains supply cable 4. An outlet pipe 5 extends through the wall of the shower enclosure to a spray head 6. Although the latter is shown as fixed, it could be connected to the outlet pipe 5 of the heater by a flexible pipe in known manner.

The heater comprises, as shown in diagrammatic form and not to scale in Fig. 2, two 4 kW electric heating elements 7A, 7B (Fig. 2) arranged, either individually or together, to heat the water passing through the heater.

The rate of flow of water is controlled by a manual control 8 within the shower cubicle 2.

A solenoid on-off valve 9 controls the passage of water through the heater, and operation of the valve 9 and the heating elements 7A, 7B is controlled by a microprocessor 10 through triacs 11. The triacs controlling the heating elements are mounted on a metal plate 12 in close thermal contact with the inlet pipe 3. A temperature sensor 13, in thermal contact with the outlet pipe 5, provides one of the inputs to the microprocessor 10.

A control panel C is separate from the main body 1 of the heater and is mounted on a wall, within the shower area itself. The control panel C which may be in the form of a small flat box similar in size, for example to a bathroom tile, is wires to the body 1 of the heater unit by means of a thin ribbon type cable 24, and has a series of touch button controls 1 6 to 1 9 which provide further inputs to the microprocessor 10 for starting the flow of water through the heater and energising the heating elements 7A, 7B, for stopping the operation of the heater, and for increasing or decreasing the water temperature respectively.

Also on the control panel C is an indicator 14, comprising a series of, for example ten, LED's 15 connected to outputs of the microprocessor, to provide a visual indication of the temperature of water leaving the heater.

On first switching on, the sixth LED, which represents a preset temperature, will light up to indicate that the heater is operative and as the temperature of the water rises the sequence of LED's will commence to light up progressively from one end in the manner of a thermometer until the water reaches the temperature selected, therefore giving the user a ready indication of the water temperature at any moment.

The microprocessor controls the heater triacs through interface circuits 22 and 23 maintaining the temperature of water leaving the water heater at the set value within normal flow rate limits, but should the flow rate be set at a value which is too low to enable the microprocessor to provide the required temperature control, such that the temperature of the water rises, the solenoid valve is actuated to cut-off the flow of water and the heating elements are switched off when a predetermined maximum 'safe' temperature is attained, for example 56"C.

If this should occur the heater cannot be restarted simply by depressing the "start" button 16, but requires the simultaneous depression of both buttons 1 6 and 1 9. This prevents the inadvertent re-starting of the heater by a user while the water temperature is above an unsafe value.

When switching-off the heater by depressing the "stop" button 17, the water will continue to flow until the monitored temperature has fallen sufficiently to carry away excess, residual heat of the heating elements, so as to ensure that the temperature of the water emerging from the heater when it is next switched on is below the "safe" value.

The microprocessor is designed to ensure that, when the shower unit is switched on, the water is heated to a preset comfortable temperature, thereby avoiding the need to re-set the water temperature each time the unit is used.

With the control panel separate from the main body of the heater the latter, with its mains electrical supplies, can be mounted outside the shower area, whilst enabling the water temperature and flow rate to be controlled from within the shower area.

In a modification of the heater described.

the water flow-rate could be set at a value say of three litres per minute, or alternatively it could be controlled electrically by the addition of one or more further touch buttons on the control panel in association with a suitable flow valve with electrical activation.

Claims

1. An instantaneous electric water heater incorporating a main body containing electrical heating means for heating the water and an electrically operable valve for controlling the flow of water through the heater, with the power supplied to the heater and valve controlled by respective controlled semiconductor devices, the heater incorporating also a microprocessor for controlling the operation of the semiconductor devices. and a low voltage manual control panel separate from the main body of the heater for feeding control signals to the microprocessor.

2. A water heater according to Claim 1 comprising a shower unit with the main body of the heater arranged to be located outside the shower area, with the separate manual control panel being accessible from within the shower area.

3. A shower unit comprising an instantaneous electric water heater having a main body located outside the shower area and incorporating an electric heating means and an electrically operable valve for controlling the flow of water through the heater, a microprocessor for controlling the operation of the heating means and valve, and a low voltage manual control panel separate from the main body of the heater and located within the shower area for controlling the operation of the microprocessor.

4. A shower unit according to Claim 3 wherein the microprocessor is arranged to maintain the temperature of the water at a set value for different flow rate settings.

5. A shower unit according to Claim 3 or 4 wherein the control panel includes a visual display device which gives an indication of the temperature of the water leaving the heater.

6. A shower unit according to Claim 5 wherein the display device incorporates a series of LED's arranged to light up in sequence, under the control of the microprocessor, as the water temperature increases.

7. A shower unit according to Claim 6 wherein the LED's are disposed in line and are arranged to be progressively illuminated from one end.

8. A shower unit according to Claim 3 wherein the control panel is provided with an audible or visual warning device which becomes operative when the temperature of water from the shower approaches a predetermined unsafe value.