GB2099559A - Warm water supply system - Google Patents

Abstract

In a warm water supply system including a mixing valve 2 blending relatively hot and cold water from lines 4 and 5 respectively to discharge warm water at a desired temperature means are provided to treat the "cold" water supplied to the mixing valve so as to minimise the risk of contamination by bacteria. These means comprise a conduit 13 taking a portion of the hot water being delivered to the mixing valve and including a cooler 14 to cool the hot water portion prior to supply to the cold inlet of the mixing valve. The cooling fluid for the cooler preferably comprises the cold feed to the systems main calorifier 11 and an efficient heat balance can be maintained in the system. The mixing valve can supply to a recirculatory circuit 17A-B and preferably temperature control is maintained in the recirculating water by use of a small secondary heat exchanger 31. <IMAGE>

Description

SPECIFICATION Warm water supply system The present invention relates to a warm water temperature control system for use with a mixing valve to enable the provision of warm water at a controlled temperature with the minimum risk of contamination by bacteria.

A mixing (or blending) valve takes delivery of relatively hot and cold water supplies and mixes these supplies to provide warm water at a controlled temperature. A particular form of warm water supply installation using such a mixing valve is described in the applicants U.K. Patent No.

1462187. In prior supply installations the hot water e.g. at 600C or higher was supplied to the valve from a calorifier or boiler while the cold feed to the valve e.g. at 20OC was simply taken from the cold supply tank e.g. break tank or watertower.

It is possible for bacteria to be present in the cold water in this tank, particularly if there are unfavourable environmental conditions and if the tank is poorly maintained. This tank may additionally supply cold feed to the boiler or calorifier, but when the water is heated to a temperature above 600C most of the bacteria is destroyed and the hot water will have a very low bacteria count. However, if cold water with bacteria present is fed to the mixing valve the raising of the temperature of the cold water to the mixing temperature could in fact cause the bacteria to grow. This is unsatisfactory, particularly if the warm water supply system is used in a hospital or other medical centre.

It is the main object of the present invention to provide a supply installation to enable the mixing valve to supply warm water economically substantially free of bacteria or with a very low bacteria count.

Broadly in the present invention the relatively cold water for the mixing valve is taken from a calorifier or boiler andcooled in a cooler prior to entry to the valve.

More particularly the present invention provides a water supply system for supplying relatively hot and cold water to a mixing valve comprising a heater for supplying hot water to the hot inlet of the mixing valve, a cold water feed to the heater, a branch for supplying a cooled portion of said hot water to the cold inlet of the mixing valve, said branch including a cooler wherein the hot water portion is cooled by cooling fluid.

Preferably the cooling fluid comprises cold feed to the heater, and all of this cooling fluid can be fed to the heater: by this arrangement there is no need for any secondary cold water supply and there need be no loss or dumping of water.

Thus the relatively cold water for the mixing valve is firstly heated to a suitable elevated temperature e.g. 600C and above to destroy bacteria, and the subsequent cooling step will not alter the substantially bacteria free nature of this water, so that the mixed warm water discharged from the mixing valve will be substantially bacteria free (or have a very low bacteria count). Since in the above inventive water supply system the heated water is proportioned for supply to the hot and cold inlets of the mixing valve i.e. only a portion is cooled, an effective heat balance can be attained in the system without the need for cold water dumping and consequently there is high thermal efficiency.

Further, no temperature control is necessary in the cooler, the fine temperature adjustment being achieved by the mixing valve, so that the cooler can be of simple and economic construction.

In a preferred embodiment for the supply of temperature controled water to draw-offs and the like, the mixing valve supplies temperature blended water to a relatively small secondary calorifierfrom which a fluid recirculating system draws water for delivery to draw-offs, said system returning water to said secondary calorifier, the blending valve being responsive to the temperature of fluid in the secondary calorifier, and additional means are provided to control the temperature of fluid in the secondary calorifier.

Embodiment of the present invention will now be described by way of example with reference to the accompanying Figs. 1 to 4 which show circuit diagrams of various water supply systems for supplying warm water to usage points.

Referring to Fig. 1, a temperature control system for supplying warm water comprises a central pre-assembled warm water supply unit 1 having a blending or mixing valve 2 carried by a small calorifier 30 and supplying blender water thereto all arranged to satisfy the fluid supply system described and claimed in the applicant's U.K. patent 1462187. The valve 2 includes hot inlet 4, cold inlet 5 and blended water discharge 6 discharging into the calorifier 30, and the unit additionally includes one-way valves and stop valves (not shown) appropriately located.

Additionally, the thermostat of the blending valve is responsive to the temperature of water in calorifier 30.

Hot water is supplied at a suitable temperature e.g. 650C from calorifier 11 to the hot inlet 4 of mixing valve 2 via line 12, and this water will be substantially bacteria free due to heating to the elevated temperature. In prior arrangements, the water to the cold inlet 5 was taken direct from the cold water supply tank (break tank or water tower) and it was very possible that this would not be bacteria free: in the present supply system therefore a portion of the hot water in line 12 is fed to cold inlet 5 via branch line 1 3 and a cooler 14 is intercalated in this branch 13, the hot water flowing through coil 1 5 in cooler 14.The cold water feed passing to calorifier 11 through line 1 6 from the supply tank is caused to pass through the cooler 14 to cool the hot water in coil 15, so that the cooler 14 serves additionally to pre-heat the feed water in line 16: there is no contract between the hot and cold water in cooler 14 and consequently the cooled hot water will remain substantially bacteria free.

It will be noted that only a portion of the hot water is cooled, so that the cooling (feed) water flow will be greater than the hot water flow in coil 1 5, and this flow characteristic enables a heat balance to be effectively achieved in the supply system so that a very high thermal efficiency can be obtained with low energy loss. In particular there is no need to dump any of the cooling water prior to supply to the calorifier. The temperature of the water in line 13 will be reduced to below the blended water temperature e.g. below 43 OC.

The mixing valve 2 can be adjusted to provide blended water at the desired temperature (e.g.

430 C) irrespective of variation of temperatures of the flows at inlets 4,5, and no control of temperature is really necessary at the cooler 1 4.

Consequently the cooler 1 4 can be of simple and relatively inexpensive construction.

Since all the water in the system has passed through the hot water calorifier 11 and, therefore, the bacteria in the cold feed water entering the system will be destroyed, the blended water discharged from valve 2 will be substantially free of bacteria.

The unit 1 is connected to a recirculating circuit 17 feeding to usage points i.e. draw-offs (not shown) via line 1 7A and including a return line 17B. The circuit 1 7 includes a circulating pump 18 which may be in the flow line 1 7A or as shown in the return line 17B. The recirculation water is fed back to the small calorifier 30 via line 1 7B as described in detail in U.K. patent 1462187, the calorifier30 including a heating coil 31 to make up heat losses in the recirculation circuit 1 7A, 1 7B and carries blending valve 2 which discharges into the calorifier 30. The inlets 4,5 have non-return valves incorporated therein. The heating capacity of the heating coil 31 will be low and the calorifier 30 would not be suitable for heating up water from cold but will be capable of making up the heat losses.Flow in the coil 31 is controlled by thermostatic valve 32. Hot water for coil 31 is taken from line 12 and is returned via discharge line 31 A to a hot water return line 1 2B delivering to the main boiler 11. In this arrangement, hot water from the boiler 11 will not pass through the cooler 14 when the draw-offs (e.g. taps) are closed in the recirculation circuit 1 7A, 1 7B and the blending valve 2 will not receive any supply flows. Line 1 2B includes a pump 33 and a nonreturn valve 34. The main boiler (calorifier) 11 supplies hot draw-offs such as kitchen taps via supply line 1 2A and the hot return 1 2B, the hot supply being for example at 60 to 650C, but it may not always be necessary to include the hot circuit 12A, 12B.

In some instances however, all the hot water from the calorifier 11 will be reduced in temperature by the blending valve 2 from 600C to 430C. In such a case, the hot water flow 12A, hot water return 12B and non-return valve 34 would not be fitted. In general it will always be necessary however to have cirulating pump 33 in the system. Where there is a hot water flow and return then pump 33 would have to be large enough to cope with the hot water circulation.

Where there is a hot water circuit 1 2A, 1 2B the pump 33 may be located in line 12 between the hot water calorifier 11 and the branch line 13 through the cooler as an alternative to being in line 12B. Where there is not hot water flow and return and pipes 1 2A and 1 2B are not being used, then pump 33 will be positioned as shown but can be small because only a small amount of hot water is taken from pipe 1 2 and passed through the heating coil 31 in the calorifier to make up the heat losses in pipes 1 7A and 17B.

Fig. 2 shows a warm water supply system to outlets 35 and in fact where there is no recirculating return.

Fig. 3 shows a warm water supply system including a recirculation return but without provision of temperature control to the returning water.

The pre-assembled unit 1 can be conveniently fitted at site to the fluid supply pipework 1 2, 13 and to the recirculation pipework 1 7A, 1 7B, 19.

Thus the above described system enables the efficient supply of blended water which is substantially free of bacteria or which has a very low bacteria count. The present invention will find particular application in hospitals and other medical centres, but could of course be used in other buildings, e.g. hotels.

Modifications are possible. For example, the cooling waterforthe cooler 14 could be cold water other than feed to calorifier 11, and indeed if there are multiple calorifiers (or boilers) present e.g. supplying various circuits then the heated water to be delivered to the mixing valve cold inlet could be taken from a source other than that supplying the hot inlet of the mixing valve. It will be appreciated that the cooler could be constructed differently; in particular it could be arranged that the cold water flows in the cooler coil with the hot water passing therearound.

In the embodiment of Fig. 4, a pre-assembled temperature control unit 1 A is provided and includes a blending valve 2 supplying to the recirculation circuit 17, and a small temperature control valve 3 receiving recirculated water via line 17B. When there is no draw-offs in circuit 1 7 the valve 3 controls the temperature of the recirculated water by delivering a small portion of the recirculated water to the main calorifier 11 as explained in detail in U.K. patent 1462187, the bulk of the recirculated water being returned to valve 2 via line 21. In the corresponding example described in U.K. patent 1462187, a small portion of hot water is fed directly to the hot inlet 4 of the blending valve 2 to make up heat losses when there is no draw-off in circuit 1 7. In contrast in the arrangement of present Fig. 4 there is a branch of the calorifier hot supply via line 13 to the cooler 14, and this may be disadvantageous with regard to maintaining an accurate setting of the blending valve 2. However, the control arrangement of present Fig. 1 avoids this possible disadvantage since in Fig. 1 temperature control of the recirculating water does not rely on a small portion of hot water flowing from the boiler (calorifier) 11 to the hot inlet 4 of blending valve 2, which is achieved in Fig. 4 by returning an equal portion of the recirculated water to the boiler 11.

Fig. 4 shows one way valves 7 and stop valves 8 appropriately located. 9 is a thermometer and 10 a flow indicator.

Claims (1)

1. A warm water supply including a mixing valve receiving and mixing relatively hot and cold water supplies to deliver water at a blended temperature, wherein the cold water supply for the mixing valve comprises hot water from a hot source cooled in a cooler prior to delivery to the mixing valve.

2. A water supply system for supplying relatively hot and cold water to a mixing valve comprising a heater for supplying hot water to the hot inlet of the mixing valve, a cold water feed to the heater, a brach for supplying a cooled portion of said hot water to the cold inlet of the mixing valve, said branch including a cooler wherein the hot water portion is cooled by cooling fluid.

2. A water supply system for supplying temperature controlled water to draw-offs and the like including a mixing valve supplying temperature blended water to a relatively small secondary calorifier from which a fluid recirculating system draws water for delivery to the draw-offs, said recirculating system returning water to said secondary calorifier, the mixing valve being responsive to the temperature of water in the secondary calorifier, means being provided to control the temperature of the water in the secondary calorifier, a heater for supplying relatively hot and cold water supplies to the mixing valve for temperature blending, and a cooler wherein a portion of hot water from the heater is cooled by cooling fluid, said cooled water portion serving as the relatively cold water for the mixing valve.

4. A water supply system as claimed in claim 2 or 3 wherein the cooling fluid comprises cold feed to the heater.

5. A water supply system as claimed in Claim 4, wherein substantially all of the cold feed to the heater comprises the cooling fluid for the cooler.

6. Water supply systems substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings.