This invention relates to an enclosed fluid-containment vessel for use with a sealed central heating system and an unvented hot water system supplied with water from a regulated pressure source.

A known form of such a fluid-containment vessel is disclosed in EP-A-260989 and comprises an arrangement of chambers forming an indirect hot water cylinder and expansion tank and a further chamber forming a heating system expansion tank, the further chamber being formed by the provision of two spaced disc-like partition walls welded to the interior of the vessel in an upper region thereof. The further chamber is subjected to repeated thermal cycling resulting in repeated expansion and contraction of the partition walls which introduces the danger of weld break-down thereby leading to mixing of the water from the two systems which is highly undesireable because the water in the central heating system is comparatively impure and would lead to contamination of the comparatively pure water in the hot water system.

It is an object of the present invention to provide a new and improved enclosed fluid-containment vessel for use with a sealed central heating system and unvented hot water system supplied with water from a regulated pressure source.

According to the present invention there is provided an enclosed fluid-containment vessel for use with a sealed central heating (CH) system and an unvented hot water (HW) system supplied with water from a regulated pressure source, said vessel comprising a first chamber forming an indirect HW cylinder and integral expansion tank and having a header region for storing air surmounting a lower region for storing water, said lower region incorporating heater means for heating stored water and for thereby releasing dissolved air from said water whereby to fill

the header region with air, first upper port means adjacent the top of said lower region for delivering stored fluid to the exterior of the vessel and second lower port means remote from the top of said lower region for receiving water to be stored from the exterior of the vessel; a second chamber forming a CH system expansion tank and having a header region for storing air surmounting a lower region for storing water, said second chamber comprising an auto air vent means arranged to enable venting of the second chamber to the exterior of the vessel when the stored water level in the second chamber is less than a set level, said lower region comprising port means for transmitting CH system fluid to and from the exterior of the vessel; the arrangement of said first and second chambers being such that each header region has a predetermined volumetric capacity which is greater than that required to accommodate thermal expansion of water from the pertaining chamber lower region; and a fluid transmitting passageway extending between said first and second chambers, said passageway opening into the respective header regions at a level which is above that attained by thermal water expansion from the pertaining chamber lower region, wherein said first and second chambers are formed by the walls of said vessel on opposite sides of a single disc-like partition welded to the vessel walls, and said fluid transmitting passageway comprises a tube mounted on and projecting from said partition.

By virtue .of the fact that there is only one partition separating the first and second chambers one such chamber is formed at the top of the vessel and thermal cycling does not impose any serious problem since the single partition is comparatively free to expand and contract within the vessel. Advantageously, the single partition is ring corrugated. Consequently, the problem of weld break-down is substantially mitigated.

Embodiments of the present invention will now be described by way of example with reference to accompanying drawings, in which:

Fig. 1 schematically illustrates the known form of fluid containment vessel.

Fig 2 illustrates a first vessel in accordance with the present invention; and

Fig. 3 illustrates a second vessel in accordance with the present invention.

The fluid-containment vessel 1, which is illustrated in Fig. 1, is described in detail in EP-A-260989 which additionally describes the full operational detail of the vessel and which is to be referred to for additional information. For the purposes of clarity, however, a brief description of the vessel 1 is herein provided. Vessel 1 comprises a lowermost chamber A, which functions as a hot water storage tank and which is in fluid communication with an uppermost chamber C via a passageway 5 in the form of a pipe extending through partition walls 2-3 which are disc-like formations welded to the walls of the vessel 1 and which, together with the vessel wall, forms a third chamber B which functions as a central heating system expansion tank. A vent tube 6 extends from the top of chamber B to the top of chamber C. A further tube 7 extends from the bottom of chamber C, and therefore through chamber B, to the bottom of chamber A for the purpose of providing a water re-circulation path between chambers A and C. Cold water to be stored in vessel 1, particularly in chamber A thereof is delivered from the street mains via pipe 16 with stop cock 11 to a pressure regulating valve 13 and enters the lower end of chamber A via a one-way valve 14. Between regulator 13 and valve 14, port 15 is provided to enable pressure-regulated cold water to be delivered to a variety of other appliances (such as taps) not shown.

Chamber A contains a heater 17 whereby water in

chamber A can be heated, and this hot water gravitates through pipe 5 to chamber C where it is drawn off via port 8 in the side wall of vessel 1. The action of heating the water in chamber A causes release of dissolved air and this gathers in the domed portion 4 of vessel l so that the upper end of tube 6 opens into this air volume.

The sealed central heating system (not shown) is provided with an expansion pipe which is connected to port 10 of chamber B and it will be appreciated that heater 17 is conveniently formed as a water heated coil connected to the central heating system. Chamber B is provided with an • auto air vent 18 which is set to vent to atmosphere the interior of chamber B when the water level therein falls below a set level. A similar vent 19, is optionally provided in chamber C. Chamber C is also provided with a pressure relief and anti-vacuum valve 9. A similar valve 12 is provided at the top end of chamber A.

In normal operation of vessel 1, chamber A is completely water filled as is pipe 5, whereas chambers B and C are only partly water filled, the header regions, of chambers B and C being air filled and inter-communicating via tube 6. The magnitude of this air volume varies as the water content of vessel 1 varies in temperature due to thermal expansion when the water is heated. The repeated thermal cycling which occurs within the vessel results in ^• partitions 2 and 3 experiencing repeated expansion and contraction forces which tend to crack or loosen the annular weld which joins each of partitions 2 and 3 to the wall of vessel 1. In this connection it will be appreciated that the vessel 1 is normally made of copper or other metal (such as stainless steel) .

Fig. 2 illustrates a first vessel 20 in accordance with the present invention and which comprises all of the components of the vessel 1 of Fig. 1 except as herein-after explained. Thus vessel 20 comprises a single first chamber 21 formed by the walls of the vessel 20 and

having the same functional effect as the chambers A and C together of Fig. 1.

A second chamber 22 is located within vessel 20 and is separated from chamber 21 by a single disc-like partition wall 3. Partition wall 3 may be ring corrugated. Tube 6 is secured to partition wall 3 and extends upwardly therefrom to open into the header region of chamber 22 within dome 4. Chamber 22 has the same functional effect as chamber B in Fig. 1.

Fig 3 illustrates a second vessel 30 in accordance with the present invention and which comprises all of the components of the vessel 1 of Fig. 1 except as hereinafter explained. Thus, vessel 30 comprises a single first chamber 21 formed by the walls of the vessel 30 and having the same functional effect as the chambers A and C together of Fig. 1. A second chamber 22 having the same functional effect as chamber B of Fig. 1, is located within vessel 30 and is separated from chamber 21 by a single disc-like partition wall 3, from which tube 6 extends upwardly into the header region of chamber 21 within dome 4.

It will be appreciated that in Fig. 2 chamber 22 is at the top end of the vessel 20, whereas in Fig. 3, chamber 21 is at the top end of the vessel 30. Chamber 21 is of substantially larger capacity than chamber 22 in order to accommodate the conventionally large volume of stored hot water for the hot water system. In each case, however, the chambers, 21, 22 are separated only by a single partition wall 3, which is peripherally welded to the walls of the pertaining vessel 20, 30 and which carries the tube 6, the length of which depends upon the location of the partition wall 3 within the vessel.

The vessels 20, 30 form two chambers 21, 22 each of which, in use, is only partly water filled and tube 6 opens into the respective air-filled header regions of the chambers 21, 22. The location of port 8 and auto air

vent 19 determines the extent of the air filleα neaαer in chamber 21. The mechanical construction of the vessel 20, 30 is relatively simple because of the provision of only a single disc-like partition 3 which is connected to the walls of the vessel only around the outer perimeter so that it is comparatively free to expand and contract within the vessel so that the problem of weld break-down is substantially reduced.