GB2271835A

GB2271835A - Unvented storage waterheaters

Info

Publication number: GB2271835A
Application number: GB9222470A
Authority: GB
Inventors: Richard Martyn Griffiths
Original assignee: IMI RANGE Ltd
Current assignee: IMI RANGE Ltd
Priority date: 1992-10-24
Filing date: 1992-10-24
Publication date: 1994-04-27
Anticipated expiration: 2012-10-24
Also published as: GB2271835B; GB9222470D0

Abstract

in a mains-fed, unvented storage waterheater having an internal bubble top 17 for accommodating thermal expansion of stored hot water 2, the bubble top 17 may be intermittently replenished with air or other gas by providing a duct 18 fitted with a non-return valve 19 through which, when necessary, air or other gas may be fed by a pump or from a bottled source of compressed air. Alternatively, the bubble top 17 may be automatically and continually replenished with air via a duct 18', fitted with a non-return valve 19', that forms part of a venturi arrangement within the mains cold water feed pipe 4. In another embodiment, the top of the storage cylinder defines the bubble top 17. <IMAGE>

Description

Improvements in or Relating to Waterheaters This invention relates to waterheaters, and more particularly to mains-fed unvented storage waterheaters.

Our prior UK patent application No 2 254 679, the disclosure of which is incorporated herein by way of reference thereto, describes and claims such a waterheater that includes an internal "bubble top", defined by a separate chamber within the storage vessel, for accommodating thermal expansion of the stored, secondary hot water. That application refers to a prior, alternative proposal for providing an internal bubble top wherein the bubble top is defined by the upper part of the storage vessel itself.

Generally, it has been recognised that a problem may arise whereby, under certain conditions, the air comprised in an internal bubble top is absorbed by the water contained in the storage vessel to such an extent that the bubble top ceases to perform its function properly, resulting in the continual dribbling of water through the relief valve comprised in such waterheaters.

Our patent application referred to above describes one means of attempting to deal with this problem in the context of the invention described therein, but the normal method of recharging the bubble top with air in the alternative proposal referred to above is to lower the water level in the storage vessel by draining off some of the water via the temperature relief valve or the vessel drain valve, after first turning off the mains cold water feed and opening one of the domestic hot water taps, whereupon air is sucked into the upper part of the vessel via the open tap and its feed pipe. Such a procedure is, of course, somewhat inconvenient and may have to be carried out quite regularly.

The present invention is concerned with the provision of means whereby an internal bubble top of an unvented storage waterheater may be readily and reliably re-generated.

According to the present invention, therefore, there is provided a mains-fed unvented storage waterheater including an internal bubble top for accommodating thermal expansion of stored secondary hot water, characterised in that the waterheater further includes a duct having at one end an inlet for air and at the other end an outlet positioned to discharge said air into the bubble top, there being a non-return valve located within said duct intermediate the inlet and outlet.

Air may be introduced into the bubble top, via the duct, periodically as and when appropriate, for example by a manual pumping operation or from a source of compressed air. Preferably, however, air is introduced automatically and continually in response to the flow of mains cold water into the storage vessel, eg the cylinder, that occurs on a demand for domestic hot water. More particularly, the outlet of the duct may be part of a venturi arrangement within the mains cold water inlet of the waterheater, air being drawn in through the duct from the atmosphere via the non-return valve and thence entering the bubble top after rising through the mass of stored hot water in the form of bubbles.

Embodiments of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: FIGURE 1 is a diagrammatic view of a waterheater constructed in accordance with the invention, having one form of internal bubble top; FIGURE 2 is a similar view to that of Figure 1 but showing an alternative, preferred form of internal bubble top; and FIGURE 3 is a detail of the circled portion III of each of Figures 1 and 2.

Referring firstly to Fig 1, the unvented waterheaèr depicted comprises a lagged cylinder 1, for example of copper or steel, for storing secondary hot water 2 typically at about 60-65 "C. In a domestic context the capacity of the cylinder 1 is usually between 80 and 210 litres, depending on the likely demand for hot water. The secondary hot water 2 is conveyed to points of use via an outlet pipe 3 connected to the top of the cylinder 1, by means of pressurised cold water connected to the mains supply by a pipe 4. The pipe 4 includes a strainer 5, a pressure reducing valve 6, usually set at around 2 bar gauge (ie 3 bar absolute), a non-return valve and an expansion relief valve 8. The system further comprises a temperature relief valve 9 whose outlet, together with the outlet of the expansion relief valve, leads to a tundish 10.The secondary water 2 may be heated directly, for example by an electric immersion heater 11, and/or indirectly by a remote boiler via a coiled heat exchanger 12 located in the cylinder 1. In addition, the system includes an energy cut out device 13 that, in the event of the secondary hot water 2 attaining too high a temperature, prevents further heating of the secondary water 2 by closing a motorised valve 14 located in the primary circuit 15 of a boiler-heated system. The valve 15 is also actuable by a cylinder thermostat 16, typically set at 60 to 65 "C. Where the water 2 is heated by an immersion heater, a cut out device 13' is incorporated in the heater 11 and the water temperature is controlled by a thermostat 16' also incorporated in the heater 11.During service, when there is a demand for secondary hot water 2, cold water in the pipe 4 drives hot water, at high pressure, from the cylinder 1 through supply pipe 3 to the point of demand.

A bubble top 17 containing air is defined at the top of the cylinder 1 by the cylinder wall and the surface of the secondary hot water 2. The bubble top 17 serves to accommodate thermal expansion of the secondary water 2. Under certain conditions, the air comprised in the bubble top 17 may be absorbed by the water 2 to such an extent that, unless replenished, it ceases to function correctly. In accordance with the present invention, means are provided to effect replenishment. One such means comprises an inlet tube 18 fitted with a non-return valve 19, for example a "Schrader" valve. The valve 19, of course, normally prevents the air in the bubble top 17 from escaping, but permits air to be fed into the bubble top, as and when necessary, for example by using a pump or from a bottle of compressed air.As previously noted, that replenishment of the bubble top is required will be indicated by continual dribbling of water from the expansion relief valve 8.

An additional or alternative means is also shown in Fig 1 and, in detail, in Fig 3. Here, air is automatically drawn into the cylinder 1 through an inlet tube 18'/non-return valve 19' when mains cold water flows, at an adequate velocity, into the cylinder 1 via the supply pipe 4, ie when there is a significant demand for secondary hot water 2. With reference to Fig 3 in particular, it will be seen that the outlet end of the tube 18' is located adjacent to a restriction 20 in the bore of the supply pipe 4 so as to provide a venturi type of arrangement. As will be appreciated, when water issues from the pipe 4 upon a significant demand for secondary hot water, a sub-atmospheric pressure will be generated within the bore of the inlet tube 18' and air will therefore be drawn in from the atmosphere, the air rising as bubbles into the bubble top 17.

Fig 2 shows an unvented waterheater having an alternative form of bubble top 17 as described and claimed in our UK patent application No 2 254 678, to which the reader is referred. Here, the bubble top 17 is defined by a separate, inverted cup-shaped chamber 17' which is rigidly connected to the top interior of the cylinder 1 by a radially apertured, hollow stem 21 that communicates the interior of the vessel 1 with the outlet pipe 3. The waterheater depicted in Fig 2 is otherwise essentially identical to that shown in Fig 1 and includes like bubble top replenishment means.

It will be appreciated from the above that the bubble top of a waterheater of the invention may readily be replenished with air without the need, in particular, to drain off any water from the storage cylinder.

An additional advantage that derives from the present proposals is that the non-return valve 19 or 19' may serve as an anti-vacuum device which otherwise needs to be provided, for example as part of the temperature relief valve 9.

Whilst we refer above to the bubble top containing air, it is to be understood that an alternative gas or mixture of gases could be used, although it is of course conventional and convenient to use air.

Claims

CLAIMS:

1. A mains-fed unvented storage waterheater including an internal bubble top for accommodating thermal expansion of stored secondary hot water1 characterised in that the waterheater further includes a duct having at one end an inlet for air and at the other end an outlet positioned to discharge said air into the bubble top, there being a non-return valve located within said duct intermediate the inlet and outlet.

2. A waterheater according to claim 1 wherein the duct is so located that its outlet opens directly into the bubble top.

3. A waterheater according to claim 1 or claim 2 wherein the inlet of the duct is adapted, when necessary, to be connected temporarily to a pump or other source of compressed air for replenishing the bubble top with air.

4. A waterheater according to claim 1 or claim 2 wherein the inlet of the duct is permanently connected to a valved bottle of compressed air, the valve being opened when necessary in order to replenish the bubble top with air.

5. A waterheater according to claim 1 wherein the outlet of the duct is located within the mains cold water feed to the waterheater and the inlet of the duct is open to atmosphere, the arrangement being such that air will, in response to the flow of mains cold water into the waterheater, be drawn in through the duct from the atmosphere via the non-return valve and thence enter the bubble top after rising in the form of bubbles through the mass of stored hot water.

6. A water heater according to claim 5 wherein the inlet of the duct is part of a venturi arrangement within the mains cold water feed to the waterheater.

7. A mains-fed unvented storage water heater substantially as hereinbefore described with reference to, and as illustrated in, Fig 1, Figs 1 and 3, Fig 2 or Figs 2 and 3 of the accompanying drawings.