GB2029555A - Domestic hot water supply system - Google Patents

Abstract

A hot water system includes an auxiliary circuit for supplying hot water at mains pressure. Cold water at mains pressure is fed through a heat exchanger 18 in heat-exchange relationship with the heated water contained within the conventional secondary storage tank 8 and through a heat exchanger 20 in heat exchange with hot water contained within the conventional primary circuit heat exchanger 10. A chamber 26 which fills with cold mains water discharges to and mixes with the hot water in the outlet 24 when a tap is turned on. <IMAGE>

Description

SPECIFICATION Improvements in or relating to hot water systems This invention relates to hot water systems and has particular application to such systems for providing hot water for domestic use.

It is often desirable to have a supply of hot water at a relatively high level within a domestic residence, for example at taps or showers in bath moms. If, however, the hot water storage tank is located at a level not substantially above said taps or showers, the pressure in the hot water system may not be sufficient to provide an adequate flow to said outlets at said relatively high level.

In the case of showers, therefore, it has become common practice to install instantaneous electric water heaters in bathrooms which are fed with cold water at mains pressure. However such heaters suffer from certain disadvantages in that the power thereof is not often sufficient to provide an adequate heated output therefrom while the close promimity of electricity and water is clearly not desirable.

According to the present invention there is provided a hot water supply system comprising a primary hot water circuit and a secondary circuit including a storage tank for storing therein secondary water fed from a cold water supply tank and heated by hot water in said primary circuit, the system further comprising an auxiliary circuit supplied with cold water at mains pressure, said auxiliary cold water being fed in heat-exchange relationship with the heated stored water in the storage tank and with the hot primary water.

Conveniently the auxiliary circuit includes an auxiliary heat exchanger located within said storage tank, while the primary circuit includes a primary heat exchanger, preferably located within said storage tank, the auxiliary circuit including an extent passing through said primary heat exchanger.

The auxiliary circuit may further include means for supplying to an outlet from said circuit a predetermined volume of cold water to mix with the heated water from said outlet on initial demand from the auxiliary circuit. Said means may comprise a container located between a cold water inlet to the auxiliary circuit and the heated water outlet therefrom, said container including therein a flow control member so arranged that, in use ofthe system and on initial demand at the outlet from the auxiliary circuit, said predetermined volume of cold water is supplied from the container to said outlet to mix with the heated water from the auxiliary circuit.

By way of example only, an embodiment of the invention will now be described in greater detail with reference to the accompanying drawing which shows part of a domestic hot water supply system according to the invention.

Referring to the drawing, the illustrated system includes a cold water feed cistern 2 supplying, by way of a feed pipe 4, cold water to a secondary heated water storage tank 8. The tank 8 has located therein a primary heat exchanger 10 forming part of a primary hot water circuit and fed with hot water from an associated boiler, the inlet to and outlet from said exchanger being indicated at 12, 14 respectively. Thus secondary cold water supplied to the tank 8 is heated in the conventional manner by heat exchange with the primary hot water.

It will be appreciated that heated water drawn from an outlet 16 from the tank 8 will be at relatively low pressure, the precise pressure depending upon the level of the point of demand - i.e. taps or the like relative to the tank 8.

The illustrated system further includes an auxiliary circuit supplied with cold water at mains pressure, said circuit comprising an auxiliary heat exchanger 18 located within the heated water in the tank 8 and further comprising an extent 20 passing through the primary heat exchanger 10. Thus it will be appreciated that cold water fed into said circuit at an inlet 22 can flow under mains pressure through the heat exchanger 18 to be heated by the stored water in the tank 8, thence through the heat exchanger 10 to be further heated by the primary hot water and to an outlet 24 from said auxiliary circuit. Said outlet 24 may be connected to one or more taps or to a shower whereby heated water at mains pressure is supplied thereto.

On initial demand from the auxiliary circuit of such a system, the water flowing to the outlet 24 will have been stored in the exchangers 10 and 18 and will be very hot. The auxiliary circuit therefore includes means for supplying an initial volume of cold water to mix with this very hot water to prevent scalding.

Said means comprises a cylindrical container or reservoir 26 connected across the auxiliary circuit between the inlet 22 and outlet 24 by inlet and outlet pipes 28, 30 respectively. Housed within the reservoir 26 is a flow control member 32 in the form of a floating ball of material just lighter than water, for example polypropelene, said ball being of diameter just less than that of the reservoir.

On initial supply of cold waterto the auxiliary circuit with the outlet 24 closed, said circuit, including the reservoir 26, is filled with cold water. As the reservoir 26 fills, the ball 32 rises to a normal rest position shown in the drawing and closing the inlet pipe 28. In this static conditon, fluid pressure is equal throughout the auxiliary circuit.

On demand from the outlet 24, water flows through the auxiliary circuit and the water pressure at the top of the reservoir 26 is greater than that at the bottom. Thus said ball 32 is forced down the reservoir 26 by incoming cold water, while the cold water previously housed within the reservoir is force through the outlet pipe 30 to mix with the heated water from the auxiliary circuit.

Once the ball 32 reaches the bottom of the reservoir, it is held there by the pressure of the water flowing in the auxiliary circuit, thus preventing further flow of cold water from the reservoir.

As soon as flow in the auxiliary circuit ceases, pressures equalise and the ball 32 floats back to its rest position at the top of the reservoir, said reservoir thus containing a further supply of cold water available when next a demand for heated water is made at the outlet 24.

As mentioned above, it is preferred that the ball 32 is of a material just lighter than water - the lighter the material, the greater the water pressure required to force it to the bottom of the reservoir.

The water of the auxiliary circuit may flow through the heat exchangers 10, 18 in any order, while said exchanger 10, although shown within the tank 8, could be located outside said tank. Other modifications from the illustrated arrangement will be apparent to those skilled in the art.

Claims (8)

1. A hot water supply system comprising a primary hot water circuit and a secondary circuit including a storage tank for storing therein secondary water fed from a cold water supply tank and heated by hot water in said primary circuit, the system further comprising an auxiliary circuit supplied with cold water at mains pressure, said auxiliary cold water being fed in heat-exchange relationship with the heated stored water in the storage tank and with the hot primary water.

2. A hot water supply system as claimed in claim 1 in which the auxiliary circuit includes an auxiliary heat exchanger located within the storage tank and the primary circuit includes a primary heat exchanger, the auxiliary circuit including an extent passing through said primary heat exchanger.

3. A hot water supply system as claimed in claim 2 in which the primary heat exchanger is located within the storage tank.

4. A hot water supply system as claimed in any one of claims 1 to 3 in which the auxiliary circuit further includes means for supplying to an outlet from said circuit a predetermined volume of cold water to mix with the heated water from said outlet on initial demand for the auxiliary circuit.

5. A hot water supply system as claimed in claim 4 in which said means comprise a container located between a cold water inlet to the auxiliary circuit and the heated water outlet therefrom, said container including therein a flow control member so arranged that, in use of the system and on initial demand at the outlet from the auxiliary circuit, a predetermined volume of cold water is supplied from the container to said outlet to mix with the heated water from the auxiliary circuit.

6. A hot water supply system as claimed in claim 5 in which the container comprises a vertical cylinder and the flow control member comprises a spherical float the diameter of which is just less than that of the container.

7. A hot water supply system as claimed in claim 6 in which the spherical float is of polypropelene.

8. A hot water supply system substantially as described with reference to and as illustrated by the accompanying drawing.