GB2290857A

GB2290857A - Water saving device for domestic hot water system

Info

Publication number: GB2290857A
Application number: GB9412906A
Authority: GB
Inventors: Robin Twine
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-06-28
Filing date: 1994-06-28
Publication date: 1996-01-10
Anticipated expiration: 2014-06-28
Also published as: GB9412906D0; GB2290857B

Abstract

A domestic hot water system supplying a tap 12 is provided with a water saving device 14. When the hot tap is turned on, a valve 20 in the device closes so that cooled water in pipe 10 bypasses the tap and is recirculated through return pipe 16. When hot water reaches the device the valve 20 opens to supply the tap. The device comprises a pressure switch 22 which senses that the tap has been turned on and closes the valve 20 and starts a pump 24. A temperature sensor 26 in the pipe 10 opens the valve 20 and stops the pump when the water runs hot. The device may be used to supply a washing machine with hot water. <IMAGE>

Description

WATER CONTROLLER This invention relates to domestic hot water systems.

A common domestic hot water system has a hot water tank containing a heating element, the tank being maintained in a filled state by a header tank. Cold water from the mains supply in turn ensures the level in the header tank is substantially constant.

The hot water tank is held at a predetermined temperature, typically about 700C. When hot water is required at a particular outlet, it is drawn from the tank through often considerable lengths of piping to reach it. As domestic hot water needs are generally intermittent, the pipes are likely to be filled with water which has lost its heat whilst static within the pipes. Therefore, for a significant length of time, only cold water is supplied to the outlet.

If the outlet is a hot water tap, for example, this water is often allowed to run to waste whilst the user waits for warmer water. Alternatively, if the water is fed to an appliance such as a washing machine, then the machine cycle is prolonged as the cooled water must be re-heated until the desired temperature is reached. This results in increased energy consumption.

The present invention provides a water controller for use in a domestic hot water system comprising a control means, and a chamber having an inlet for water from the hot water system, a bypass outlet for returning water to the hot water system and at least one hot water supply outlet. In addition, a valve is provided for selectively closing the hot water supply outlet. When hot water is required from the hot water supply outlet, the control means closes the valve and causes water to be pumped from the inlet to the bypass outlet until the temperature of the water passing through the inlet is at or above a predetermined threshold, whereupon the control means stops the pumping, and opens the valve, to allow water to flow from the inlet to the hot water supply outlet.

In the preferred embodiment a pressure sensing device monitors the water pressure in the supply outlet.

A pressure drop is consistent with water being drawn from the outlet. It is also preferable that the temperature of the water flowing into the inlet is monitored using a temperature sensor in comparison with a reference temperature sensor. This reference sensor may be mounted on the hot water tank.

The water controller may be installed in the hot water system close to one or more outlets, and will only allow hot water to be supplied. In the event of hot water being required at an outlet, the water controller recirculates the cooled water from the pipes back to the header tank. This continues until the temperature of the water arriving at the controller reaches a predetermined threshold at which point the hot water is then directed to the outlet. Thus only water at or above a certain temperature is supplied.

The water controller will also save water, as rather than going to waste, the water which is not sufficiently hot is returned to the header tank. This process may save some of the heat energy carried by this water as it will raise the temperature of the water in the header tank to some extent.

Furthermore, with the invention installed in the hot water system, appliances such as washing machines receive a reliably hot supply of water. This is not otherwise possible, particularly when the outlet is some distance from the hot water tank. Therefore the energy consumption of the appliances is reduced as only the hot water held in the tank is used rather than cooled water from the pipes.

The invention will now be described by way of example and with reference to the accompanying schematic drawings wherein: Figure 1 shows diagrammatically the basic features of a common domestic hot water system, in combination with the invention; Figure 2 shows a perspective view of an embodiment of the invention.

In Figure 1, cold water from the mains supply maintains the water in the header tank 2 and the system pipes at a substantially constant level 3. The header tank in turn replaces water drawn from the hot water tank 4, via supply pipe 6. To remove the possibility of a pressure build-up in the hot water tank, a vent 8 is included to return any overflow to the header tank 2.

Water is supplied from the hot water tank along the pipe 10. In the example shown, there is for simplicity a single outlet, the tap 12. The pipe 10 is often of considerable length, resulting in a significant volume of water being allowed to cool when water is not being drawn from the hot water tank. A water controller 14 is shown situated close to the tap, with a bypass pipe 16 running from it to the header tank 2. When the tap 12 is turned on, this is sensed by the controller, which causes any cooled water from pipe 10 to be recirculated back to the header tank 2 along pipe 16. This continues until the water reaching the water controller 14 is at a temperature equal to or greater than a predetermined threshold. Only then is recirculation ceased, and the water supplied to the tap 12.

The operation of the water controller may be considered in more detail with reference to the embodiment shown in Figure 2. Water is fed from the hot water tank into the water controller 14 through the pipe 10. Hot water supply pipe 18 connects the controller to a particular outlet, the tap 12 for example. An electric valve 20 opens and closes this output and is normally open, that is, it is open when no current is supplied to it. A pressure switch 22 monitors the pressure in the hot water supply pipe 18. The height of the header tank 2 above the pipe determines this pressure. The pressure switch is adjusted so that when the tap 12 is closed and the pressure is at a maximum, the switch is deemed to be off. This pressure is typically about 10 P.S.I (70kPa).

The switch turns on when a drop in the pressure occurs, consistent with the tap being turned on. The pump unit 24 is used to recirculate water back through bypass pipe 16 to the header tank when necessary. A powerful pump unit is not required as effectively the only work it does is in recirculating water from the header tank back to the header tank, and the water need only be lifted a few centimetres above the general level 3 of the system in order to clear the side of the tank. This distance 17 is typically about 10 centimetres. A temperature sensor 26 monitors the temperature of the water in the pipe 10 close to the water controller. A second temperature sensor is located at the top of the hot water tank 4.

Each sensor produces a voltage proportional to their local temperature, and they are each connected to an input of a comparator. The comparator is in turn connected to a relay which is of the normally closed type, that is, when there is no power to it, the points are closed. This in conjunction with the pressure switch 22, operates the pump unit 24 and electric valve 20.

Normally the comparator output is low. Only when the output from the sensor in the pipe 10 exceeds a given threshold, related to the output from the sensor on the hot water tank, does the output go high, switching on the relay and opening its points.

When the tap 12 is turned on, the pressure in the supply pipe drops, turning on pressure switch 22. This in turn closes the electric valve 20 and activates the pump unit 24, via the relay. Water ceases to flow from the tap 12. Hence the pressure remains relatively low in the supply pipe 18, keeping the pressure switch on.

Water is drawn by the pump unit from the hot tank through pipe 10 and returned to the header tank along bypass pipe 16, until the output from the sensor 26 reaches the predetermined threshold, indicating that water is reaching the water controller at the required temperature. Hence the output on the comparator goes high, turning on the relay and so stopping the pump and opening the electric valve 20. Hot water then flows from the tap 12. When the tap is shut, pressure again builds up in the hot water supply pipe 18, turning off the pressure switch. If the tap is then opened again after only a short period of time, water will flow immediately if the temperature of the water in the pipe 10 at the sensor 26 is still above the threshold.

It is apparent that there will generally be a delay before water is supplied from the hot tap. Therefore, users requiring a small amount of water, perhaps to rinse something quickly, must become accustomed to using the cold water tap for such purposes. This is advantageous, as using the hot tap in these circumstances would only serve to draw water from the hot water tank into the pipes, where its heat is lost to the surroundings.

Claims

CLAIMS:

1. A water controller for use in a domestic hot water system comprising a control means; a chamber having an inlet for water from the hot water system, a bypass outlet for returning water to the hot water system, and at least one hot water supply outlet; and a valve for selectively closing the hot water supply outlet, such that when hot water is required from the hot water supply outlet, the control means closes the valve and causes water to be pumped from the inlet to the bypass outlet until the temperature of the water passing through the inlet is at or above a predetermined threshold, whereupon the control means stops the pumping, and opens the valve, to allow water to flow from the inlet to the hot water supply outlet.

2. A water controller according to Claim 1 comprising a pump unit for pumping water from the inlet to the hot water supply outlet.

3. A water controller according to Claim 1 or Claim 2 including a pressure sensing device for monitoring the water pressure in the at least one hot water supply outlet.

4. A water controller according to any preceding Claim including an input temperature sensor for monitoring the temperature of the water entering the inlet, and a reference temperature sensor for monitoring the temperature of the water at another position in the hot water system.

5. A water controller according to Claim 3 wherein the reference temperature sensor is mounted on a hot water tank in the hot water system.