GB2597655A - Electricity-saving shower unit - Google Patents

Abstract

A shower unit 1 comprises a hot water inlet 2, a cold water inlet 3, at least one temperature sensor 4, 5 to monitor the temperature of water flowing through the unit, and means for controlling the ratio of maxing of the hot and cold water from the inlets, such as positive displacement pumps 9, 10, adjustable valves or a three-way valve. An electric, variable-power, instantaneous water heater 13 is controlled to increase the temperature of the water as it flows through the unit when water from the hot water inlet is below a desired output temperature. An extended passage 11 or chamber may be provided between the hot water temperature sensor and the mixing of the hot and cold water. In an alternative mode of operation, only water from the cold water inlet is drawn into the unit, and is heated by the heater. The unit may be used along with a typical shower head 16 and hose 15.

Description

Electricity-Saving Shower Unit This invention relates to a device to provide a flow of warm water for showering.

Contemporary shower units typically provide warm water for showering either by mixing hot water with cold water or by heating cold water as it flows through the unit. However, present designs suffer from a variety of problems including high electricity consumption; inefficient use of hot water; showers that may run cold part-way through; risk of scalding; and non-intuitive controls.

To address these problems, the current invention proposes a shower unit comprising a hot water inlet; a cold water inlet; at least one sensor arranged to monitor the temperature of the water flowing through the unit; a means for controlling the ratio of water coming from the hot water inlet to water coming from the cold water inlet; a variable power heater arranged to increase the temperature of the water flowing through the unit to the desired output temperature whenever water coming from the hot water inlet is below the desired output temperature; and electronic control circuitry.

The variable-power instantaneous water heater preferably includes multiple heating elements, with one of the elements having continuously variable power output.

Pumps, preferably of the "positive displacement" type, may be used to provide increased water pressure and to control the volumes of water coming from the hot water inlet and cold water inlet, respectively. Alternatively, one or more adjustable valves may be used to control water flow rates through the apparatus.

A solenoid valve may be included at each inlet to ensure no water leaks through the apparatus while it is not being used.

Preferably, a passage or chamber may be included through which water must flow after it has passed the temperature sensor. This allows more time for the system to respond to sudden changes in water temperature, particularly from the hot water inlet.

A thermostatic cut-off switch and/or over-pressure relief valve may also be included for increased safety.

The shower unit may optionally include a mode of operation where only water from the cold feed is drawn into the unit. This allows for the conservation of stored hot water. This mode of operation may optionally be automatically activated during periods of low electricity prices, for example while night-rate tariffs are in effect The invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 shows the preferred embodiment of the shower unit, with the cover removed.

Figure 2 shows an embodiment of the shower unit with the cover in place and illustrates a possible design for the user interface.

Figure 3 shows a cross-section of the suggested construction of the variable-power instantaneous water heater.

Figure 4 shows a conceptual schematic of the invention.

Figure 5 shows an alternative embodiment of the shower unit, with the cover removed.

Figure 6 shows a further alternative embodiment of the shower unit, also with the cover removed.

In Figure 1, shower unit 1 includes hot water inlet 2 and cold water inlet 3. The hot water inlet is to be connected to a hot water supply system. However, it should be understood that the incoming water may in reality sometimes be lukewarm or even cold. Temperature sensors 4 and 5 monitor incoming water temperatures and relay data to the electronic control circuitry (not shown). When the apparatus is turned on, solenoid valves 6 and 7 open to allow water to flow through the internal plumbing 8 of the unit. Variable-speed pumps 9 and 10, which are preferably of the positive displacement variety, urge water through the unit. These pumps are also used to control water flow rates from the hot water inlet and the cold water inlet, respectively. Extended passage 11 is preferably included on the hot water line in order to increase the time delay from the moment when hot water passes the temperature sensor to the moment it mixes with cold water at joint 12. This allows more time for sensors to detect sudden changes in the incoming water temperatures and for the unit to adjust water flow rates and/or heating power accordingly. When sufficiently hot water is available, the shower unit will mix hot and cold water together at joint 12 to achieve the desired output temperature. If incoming water from the hot water inlet is not sufficiently warm, variable-power instantaneous water heater 13 increases the water temperature to the desired degree before it flows through outlet 14, flexible hose 15, and shower head 16. Electrical components are contained within housing 17.

An over-pressure relief valve (not shown) may also be included as a safety feature. Furthermore, a thermostat (not shown) may be included for redundant safety. Preferably, the thermostat may be arranged to cut off the power supply to the water heater, pumps, and solenoid valves in the unlikely event that dangerously hot water is about to escape from outlet 14.

In Figure 2, an alternative view of shower unit 1 is shown. User interface 201 includes power button 202, temperature decrement button 203 and temperature increment button 204. Display 205 shows the selected temperature. Optionally, the user interface may also allow the user to select a mode of operation whereby water is drawn in from the cold water inlet only and/or to program other features of the microcontroller. A cover 206 for the shower unit is also shown. It is envisaged that controls may also be included to vary the flow rate of water through the unit and to choose between alternate modes of operation.

Figure 3 shows a preferred embodiment of variable-power instantaneous water heater 13. Water enters at inlet 301 and is contained by external walls 302. Internal walls 303 ensure the water flows over all of the Ohmic heating elements 304 before exiting through outlet 305. Variable power may be achieved, for example, by use of a TRIAC. Consider for example a heater comprising 3 heating elements, each with a maximum power output rating of 3 kW. In such a case, variable power from 0 kW to 9 kW may be achieved by varying the power delivered to one of the heating elements and switching the other two elements on and off. The precise construction of the variable-power instantaneous water heater is immaterial to the invention; it is even possible that the single variable-power instantaneous water heater may be replaced by a number of smaller units.

Figure 4 shows a conceptual diagram of the shower unit, in its preferred embodiment. Micro- controller 401 receives inputs from user interface 201 and temperature sensors 4,5. The micro-controller executes an algorithm to determine the correct water flow rates and heating power to achieve the desired output water temperature. There are four specific scenarios which may arise: 1) The incoming hot water is already exactly at the desired output temperature: In this case, the output flow should be made up entirely of water from the hot feed and no extra heating is required. Therefore, pump 10 should be activated, while pump 9 and instantaneous electric water heater 13 should remain inactive.

2) The incoming hot water is above the desired output temperature: In this case, hot water and cold water should be blended together and no extra heating is required. Pumps 9 and 10 should both be activated and operated at the correct speed to provide the appropriate flow rates of hot and cold water, respectively. The appropriate hot water flow rate can be calculated according to Formula (1): ( (1) Hot Water Flow Rate =Total Flow Rate x '''''' Lula T -T) T hat -T wid Where: is the desired output water temperature Tram is the temperature of water coming from the cold water inlet Thot is the temperature of water coming from the hot water inlet The cold water flow rate is then given by Formula (2): Cold Water Flow Rate = Total Flow Rate -Hot Water Flow Rate (2) 3) The incoming hot water is below the desired output temperature: In this case, the entire flow should come from the hot water inlet and the variable-power heater should be used to boost the temperature of the water. Pump 10 should be operated while pump 9 should remain inactive. The power to instantaneous water heater 13 may be calculated to an acceptable degree of accuracy according to Formula (3): P=F 1T0 -TX 70 (3) Where: P is the power, in Watts, to be delivered to the heater F is the flow rate through the unit, in litres per minute Tou,,,ut is the desired output temperature Th,,is the temperature of water coming from the hot feed 4) In an alternative mode of operation, the shower unit may draw water from the cold feed only in order to conserve stored hot water. In this case, pump 9 should be operated while pump 10 remains inactive. Power to be delivered to instantaneous water heater 13 may be calculated to an acceptable degree of accuracy according to Formula (4): P=F x11'0",p", -T coldRC 70 (4) Where: P is the power, in Watts, to be delivered to the heater F is the flow rate through the unit, in litres per minute To","", is the desired output temperature 11,0 is the temperature of water coming from the cold feed Based on these calculations, the microcontroller sends the appropriate signals to pumps 9, 10 and variable-power instantaneous water heater 13.

It is envisioned that the device may be given Internet of things functionality to allow for remote control and/or monitoring. Furthermore, it is envisioned that the device may respond to fluctuations in electricity prices for customers with varying electricity tariffs. Specifically, the device may be programmed to consume only cold water during periods of low electricity prices or when a surplus of locally generated renewable electricity is available. This results in stored hot water being saved at the expense of higher electricity consumption.

It is further envisioned that the device may include a visual data display. In this case, data on energy use, water use, incoming water temperatures, etc. may preferably be relayed from the microcontroller to the user via a liquid crystal or light emitting diode display.

Figure 5 shows an alternative embodiment which uses adjustable valves 501 instead of variable-speed pumps to regulate water flows. These valves may also serve to prevent water leaking through the apparatus while it is turned off. An impeller type pump 502 is preferably used to urge water through the system and a hall effect sensor 503 may be used to monitor the flow rate. Temperature sensor 504 is preferably included to monitor the temperature of the mixed water.

Figure 6 shows a further alternative embodiment in which a single adjustable three-way valve 601 is used to regulate the ratio of water from the cold inlet to water from the hot inlet.

Claims (6)

1. Claims 1. A shower unit comprising a hot water inlet; a cold water inlet; at least one sensor arranged to monitor the temperature of water flowing through the unit; a means for controlling the ratio of water coming from the hot water inlet to water coming from the cold water inlet; a variable power heater arranged to increase the temperature of the water flowing through the unit to the desired output temperature, whenever water coming from the hot water inlet is below the desired output temperature; and electronic control circuitry.
2. 2. A shower unit according to claim 1, in which positive displacement pumps are used to control the flow rates of water from the cold water inlet and water from the hot water inlet, respectively.
3. 3. A shower unit according to claim 1, in which adjustable valves are used to control the flow rate of water coming from the hot water inlet and water coming from the cold water inlet, respectively.
4. 4. A shower unit according to claim 1, in which a three-way valve is used to control the ratio of water coming from the hot water inlet to water coming from the cold water inlet.
5. 5. A shower unit according to any of the previous claims, in which water must flow through an extended passage or chamber between the point where its temperature is first measured and the point where it is mixed with the other stream of water.
6. 6. A shower unit according to any of the previous claims, having also an alternative mode of operation in which only water from the cold water inlet is drawn into the unit.