GB2365102A

GB2365102A - Water heater with insulated cold water tank

Info

Publication number: GB2365102A
Application number: GB0022884A
Authority: GB
Inventors: John Edward Vallis
Original assignee: ZIP HEATERS
Current assignee: ZIP HEATERS
Priority date: 2000-07-18
Filing date: 2000-09-19
Publication date: 2002-02-13
Anticipated expiration: 2020-09-19
Also published as: GB0022884D0; GB0017453D0; GB2365102B

Abstract

In a water heater comprising a lower reservoir 10 for heated water and an upper cold water feed/expansion reservoir 12 which are interconnected by a cold water supply pipe 14 and a hot water expansion pipe 16, the expansion pipe 16 is insulated from the water in the cold water reservoir 12. This prevents heat from the expansion pipe 16 warming up the cold water in the reservoir sufficiently to allow harmful bacteria to develop. The expansion pipe 16 may be insulated by means of a sleeve of thermally insulating material surrounding and in contact with the pipe. Alternatively, the sleeve 18 is of copper and surrounds the pipe 16 with an air gap. The end of the pipe 16 has a U-bend. The reservoirs are separated by an air gap or by thermally insulating material 42 and the pipes 14, 16 are made of material which is resistant to the flow of heat through it, or fastened by insulated collars (26, 28, Fig 2). The cold water reservoir 12 has a temperature sensor 48 which generates an alarm signal if the temperature exceeds 39{C. This reduces the risk of bacterial growth which can cause legionnaires disease. The alarm signal may produce an audible and/or visible alarm, either immediately or after a predetermined time, or may activate a valve to prevent flow from the water heater. Alternatively the temperature sensor may just change colour, or from transparent to opaque, to indicate to a service engineer that the temperature has been exceeded since the last visit.

Description

<Desc/Clms Page number 1> Improvements relating to water heaters Field of invention This invention concerns water heaters of the type in which cold water is stored in a reservoir above a second lower reservoir of heated water, for maintaining the level in the second reservoir. Background to the invention In water heaters of this type the heat from the lower reservoir has been found to raise the temperature of the volume of cold water to unacceptable levels and it is an object of the present invention to overcome this problem. Summary of the invention According to the present invention in a water heater of the type described comprising upper and lower reservoirs with an interconnecting passage for transferring cold water from the upper reservoir to the lower and an expansion pipe to permit heated water forced out of the lower reservoir by expansion to return to the upper reservoir, means is provided to thermally separate the body of water in the upper reservoir from the expansion pipe to reduce the transfer of heat from the expansion pipe to the water in the upper reservoir. The separation means may comprise a sleeve which surrounds the expansion pipe to at least the depth of the water in the upper reservoir.

The sleeve may be formed from thermally insulating material and may be in contact with the expansion pipe.

Alternatively the sleeve may be spaced from the expansion pipe by an air gap.

In one embodiment of the invention the expansion pipe is formed from metal such as copper and the sleeve is cylindrical and is also formed from metal such as copper and has

an internal diameter which is substantially greater than the outside diameter of the expansion pipe and extends from the base of the upper reservoir to a height therein which is greater than the depth of water in the upper reservoir, the sleeve and the pipe being coaxially arranged so that the sleeve is spaced from the pipe by the same distance around the whole of its circumference, and the spacing is selected so as to ensure that under normal conditions, with the annular space between the pipe and the sleeve filled with air, the transfer of heat from the wall of the pipe to the wall of the sleeve is insufficient to cause any significant rise in temperature of the water in the upper reservoir which surrounds the sleeve. Typically the upper end of the expansion pipe is bent to form an inverted U-bend or otherwise extended so that water forced up the expansion tube due to excess temperature will discharge into the reservoir, not the sleeve. Preferably the lateral separation of the discharge end of the expansion pipe from the upstanding part thereof is greater than the radial spacing of the sleeve wall from the upstanding expansion pipe, so that if any discharge does occur it is directed at the water in the reservoir and not into the annular space between the expansion tube and the sleeve. Preferably the level of cold water in the upper reservoir is maintained at a predetermined level by water level responsive valve means which permits the inflow of cold water into the upper reservoir only if the level of water therein is below the said predetermined level. Conveniently the valve means is a float operated valve such as is commonly employed in water cisterns and cold water storage tanks which have to be kept topped up by water from a water supply main. Since the reason for limiting the rise in temperature of the water in the upper reservoir is to reduce the risk of bacterial growth such as can cause legionnaires disease and organisms which can attack the gut, according to a preferred feature of the invention, temperature sensing means may be provided for sensing the temperature of the water in the upper

reservoir and means is provided responsive to a sensed rise in temperature of the water therein above a predetermined level to activate an alarm and/or activate valve means inhibiting the flow of water from the lower reservoir.

The alarm may be visual or audible or both.

If the removal of water from the lower reservoir is inhibited, preferably means is provided for indicating to the user why the system will not allow hot water to flow therefrom.

In a preferred arrangement means is provided for integrating the temperature excess with time and the generation of an alarm and/or the inhibition of hot water flow from the lower reservoir is deferred until the integration reaches a predetermined value. The temperature sensing means may comprise a metal alloy junction or semiconductor device whose electrical characteristics vary with temperature, and the means responsive to the temperature sensing means may comprise an electrical circuit adjusted to respond to the change in the said electrical characteristics indicative of an excess of temperature above the said predetermined level, and to generate an electrical control signal in response to a sensed change, to drive a sounder or illuminate a lamp or both. Where time integration is required the electrical circuit may include a timing device which is reset when the temperature condition is exceeded and if the temperature is still in excess of the predetermined value after the timing device has timed out to a predetermined interval of time, a control signal is generated to operate a sounder, or illuminate a lamp or both. The alarm may be generated proximate to the installation or at a remote location or both. If at a remote location, an identifying signal is preferably transmitted with the signal generating the alarm, to indicate where the installation is located in which the upper reservoir water temperature has triggered the alarm. If it is deemed sufficient to monitor whether the water temperature has exceeded the predetermined level during a period between service calls, a latching temperature sensing

means may be used instead, which merely activates if the design temperature for the upper reservoir has been exceeded since the last service call.

A latching device may comprise a chemical composition which changes colour or changes from transparent to translucent/or opaque if its temperature rises beyond a given temperature such as are employed in food storage containers which are to be stored in a frozen or chilled condition. The invention will now be described by way of example with reference to the accompanying drawings in which: Fig 1 is a side elevation partly in section of one embodiment of the invention Fig 2 is a similar view of another embodiment of the invention, and Fig 3 is a similar view of a further embodiment of the invention. In Fig 1 a lower hot water reservoir 10 is supplied with water from an upper cold water reservoir 12 via a pipe 14. The reservoir 12 is kept topped up in a conventional manner from a cold water supply eg the cold water supply mains. Heating means such as an electric powered immersion heater (not shown in Figs 1 & 2) heats the water in 10 and in the event of overheating and expansion occurring in 10, hot water is forced up vent pipe 16. In accordance with the invention a sleeve 18 surrounds the pipe 16 also spaced therefrom to create an annular air gap 20 to impede the transfer of heat from any hot water in 16 to the cold water in 12. Thermal insulation material 22 separates the two reservoirs. The pipes 14 and 16 may be formed from metal or a plastics material which is resistant to the flow of heat therealong so as to further limit the transfer of heat from 10 to 12.

In Fig 2 an air gap 24 exists between the two reservoirs to impede the transfer of heat therebetween and the pipes 14 and 16 are secured to the upper reservoir by means of thermally insulating plastics material collars 26, 28 respectively to impede transfer therebetween. In other respects Fig 2 is similar to Fig 1 and the same reference numerals have been employed. Fig 3 shows a different arrangement in which expansion pipe 16 is bent over at 30 to form an inverted U-bend to bring the discharge end beyond the wall of the sleeve 18. A float operated valve 32 and float 34 on an arm 36 is shown for controlling the flow of cold water from a supply main feed 38, and an immersion heater 40 is shown in the lower reservoir 10. The two reservoirs are separated by insulating material 42 although they may be separated alternatively by an air gap. Heat transfer is further reduced by forming the pipe 14 from a plastics material, and a lid 44 covers the open end of the reservoir 12. A temperature sensor is shown at 46 for connecting to an electrical circuit (not shown) for generating a control signal if the temperature of the water in 10 exceeds a given temperature and for controlling the current to the heater 40. A second temperature sensor is shown at 48 for connecting to another electrical circuit (not shown) for generating an alarm signal if the temperature of the water in 12 exceeds a different threshold such as 39 C, above which microbiological growth can occur of harmful organisms which can promote disease. Although the upper end of the expansion pipe 16 is shown as being bent to form an inverted U-bend so as to position the discharge end of the pipe beyond the wall of the sleeve, the extension of the pipe 16 laterally so as to discharge water into the reservoir beyond the sleeve wall, may be achieved for example by fitting an appropriately shaped extension tube, or tubes, to the upper end of the straight length of pipe 16.

Claims

Claims 1. In a water heater comprising upper and lower reservoirs in which cold water is stored in the upper reservoir for feeding the lower reservoir which contains water heating means, with an interconnecting passage for transferring cold water from the upper reservoir to the lower to maintain the level therein and an expansion pipe to permit heated water forced out of the lower reservoir by expansion to return to the upper reservoir, means is provided to thermally separate the body of water in the upper reservoir from the expansion pipe to reduce the transfer of heat from the expansion pipe to the water in the upper reservoir.
2. A water heater as claimed in claim 1 wherein the separation means comprises a sleeve which surrounds the expansion pipe to at least the depth of the water in the upper reservoir.
3. A water heater as claimed in claim 2 wherein the sleeve is formed from thermally insulating material.
4. A water heater as claimed in claim 3 wherein the sleeve is in contact with the expansion pipe.
5. A water heater as claimed in claim 2 or 3 wherein the sleeve is spaced from the expansion pipe by an air gap.
6. A water heater as claimed in claim 1 wherein the expansion pipe is formed from metal and the sleeve is cylindrical and is also formed from metal and has an internal diameter which is substantially greater than the outside diameter of the expansion pipe and extends from the base of the upper reservoir to a height therein which is greater than the depth of water in the upper reservoir, the sleeve and the pipe being coaxially arranged so that the sleeve is spaced from the pipe by the same distance around the

<Desc/Clms Page number 7>

whole of its circumference, and the spacing is selected so as to ensure that under normal conditions, with the annular space between the pipe and the sleeve filled with air, the transfer of heat from the wall of the pipe to the wall of the sleeve is insufficient to cause any significant rise in temperature of the water in the upper reservoir which surrounds the sleeve.
7. A water heater as claimed in claim 6 wherein the upper end of the expansion pipe is bent over to form an inverted U-bend or otherwise extended so that if water is forced up the expansion pipe due to excess temperature in the lower reservoir, it will be discharged in a generally downward direction, clear of the sleeve.
8. A water heater as claimed in claim 7 wherein the lateral separation of the discharge end of the inverted U-bend from the upstanding part of the expansion pipe is greater than the radial spacing of the sleeve wall from the upstanding expansion pipe, so that if any discharge does occur it is directed at the water in the reservoir and not into the annular space between the expansion pipe and the sleeve.
9. A water heater as claimed in any of claims 1 to 8 wherein the level of cold water in the upper reservoir is maintained at a predetermined level by water level responsive valve means which permits the inflow of cold water into the upper reservoir only if the level of water therein is below the said predetermined level.
10. A water heater as claimed in claim 9 wherein the valve means is a float operated valve.
11. A water heater as claimed in any of claims 1 to 10 further comprising temperature sensing means for sensing the temperature of the water in the upper reservoir and further means responsive to a sensed rise in temperature of the water therein above a predetermined level to activate an alarm and/or activate valve means inhibiting the flow of water from the lower reservoir.
12. A water heater as claimed in claim 11 wherein the alarm may be visual or audible or both.

<Desc/Clms Page number 8>
13. A water heater as claimed in claim 11 wherein means is provided for indicating to the user why the system will not allow hot water to flow therefrom.
14. A water heater as claimed in claims 11, 12 or 13 wherein means is provided for integrating the temperature excess with time and the generation of an alarm and/or the inhibition of hot water flow from the lower reservoir is deferred until the integration reaches a predetermined value.
15. A water heater as claimed in any of claims 11 to 14 wherein the temperature sensing means comprises a metal alloy junction or semiconductor device whose electrical characteristics vary with temperature.
16. A water heater as claimed in 15 wherein the means responsive to the temperature sensing means comprises an electrical circuit adjusted to respond to a change in the electrical characteristics indicative of an excess of temperature above the said predetermined level, and to generate an electrical control signal in response to a sensed change.
17. A water heater as claimed in claim 15 wherein time integration is required and the electrical circuit includes a timing device which is reset when the temperature condition is exceeded and if the temperature is still in excess of the predetermined value after the timing device has timed out to a predetermined interval of time, a control signal is generated.
18. A water heater as claimed in any of claims 11 to 17 wherein the alarm is generated proximate to the installation.
19.A water heater as claimed in any of claims 11 to 18 wherein the alarm is generated at a remote location.

<Desc/Clms Page number 9>
20. A water heater as claimed in claim 19 wherein an identifying signal is transmitted with the signal generating the alarm, to indicate where the installation is located in which the upper reservoir water temperature has triggered the alarm.
21. A water heater as claimed in any of claims 11 to 16 adapted to monitor whether the water temperature has exceeded the predetermined level during a period between service calls, wherein a latching temperature sensing means is used, which merely activates if the design temperature for the upper reservoir has been exceeded since the last service call.
22. A water heater as claimed in claim 21 wherein the latching device comprises a chemical composition which changes colour or changes from transparent to translucent/or opaque if its temperature rises beyond a given temperature.
23. A water heater as claimed in claim 1 constructed arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.