WO2009081102A2

WO2009081102A2 - An improved water heater

Info

Publication number: WO2009081102A2
Application number: PCT/GB2008/004163
Authority: WO
Inventors: Willi Hecking
Original assignee: Baxi Heating (Uk) Limited
Priority date: 2007-12-21
Filing date: 2008-12-17
Publication date: 2009-07-02
Also published as: GB0724975D0; GB2468253B; GB2468253A; GB201010603D0; WO2009081102A3

Abstract

An unvented water heater (10), the heater (10) including a water tank (12) to store water, the water tank (12) incorporating a heating element (16) to heat the water, a water inlet pipe (25) to admit mains water into the tank (12) and a discharge pipe (22) enabling excess water to be discharged; the heater including an air-gap regeneration device (20) to introduce air into the tank, the device being operably connected to the inlet pipe (25) and the discharge pipe (22) to open and close said pipes (22, 25), pressure determining means to measure the pressure within the tank (12) and transmission means (23a) to pass the pressure data obtained from the pressure determining means to the device (20), the device (20) operating once the tank pressure has exceeded a pre-set pressure, an air inlet valve (24) admitting air into the tank (12).

Description

AN IMPROVED WATER HEATER

Field of the Invention

The field of the invention is that of unvented water heaters for domestic and semi- industrial usage. In particular the invention relates to a heater which includes a volume of air above the water level to improve safety.

Background to the Invention

Water heaters to supply hot water to domestic heating and hot water systems are well known and a variety of types of system is available. An important feature with any such system is safety of the boiler. Amongst the many aspects of safety which require consideration, those associated with the expansion of water at increased temperature are important.

As water is heated, often to close to its boiling point, the water expands and the volume occupied by the same mass of water becomes greater. Where the water is stored in a closed tank within the heater this can obviously lead to increases in pressure. Although safeguards are in place to prevent boiling, which would result in a dramatic volume increase, the heater still needs to be able to cope with the higher volume required by the water below the boiling point.

One solution to this problem is to strengthen the walls of the water tank to enable it to cope with the increase in pressure resulting from the expansion. This results however in a heater which is heavier than a relatively unstrengthened heater and requires in addition greater manufacturing and materials costs.

An alternative solution is to include an air gap above the surface of the water, which air gap, due to the compressibility of air can absorb the increase in pressure, and so reduce the amount of physical strengthening required. With time the air gap needs to be replenished primarily because of absorption of the air into the water. This is the case even when a baffle on the surface of the water is used to reduce the air loss. Such baffles have been effectively employed in the Megaflo® range of boilers manufactured by Heatrae Sadia. Replenishment is easily carried out, but an engineer is normally required to do this.

It is an object of the invention to provide a means of automatically replenishing the air gap and so address the above problem.

Summary of the Invention

According to a first aspect of the invention there is provided an unvented water heater, the heater including a water tank to store water, the water tank incorporating a heating element to heat the water, a water inlet pipe to admit mains water into the tank and a discharge pipe enabling excess water to be discharged;

the heater including an air-gap regeneration device to introduce air into the tank, the device being operably connected to the inlet pipe and the discharge pipe to open and close said pipes,

pressure determining means to measure the pressure within the tank and transmission means to pass the pressure data obtained from the pressure determining means to the device, the device operating once the tank pressure has exceeded a pre-set pressure,

an air inlet valve admitting air into the tank.

The invention enables a suitable air-gap to be easily maintained above the water in an unvented tank.

The device preferably includes a valve operable to simultaneously close the inlet pipe, the closure thereby opening the discharge pipe. This reduces the number of component parts.

The air-inlet valve is advantageously a one-way valve, allowing air into the tank and operating on a pressure differential between the inside of the tank and atmosphere being present. Further advantageously, the valve is under the control of the device.

Preferably, the air inlet valve is incorporated in the device allowing a device to be retro fitted to existing water heaters.

Preferably, the device includes a clock, wherein operation of the device only occurs at certain pre-set times.

The heater optionally includes a pressure determination means to determine the pressure difference between that in the tank and the atmosphere. Further optionally, the pressure determination means is a transducer.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings which show by way of example only, one example of a water heater including replenishment device. In the drawings:

Figure 1 illustrates a water heater with a tank pressure of 3 bar;

Figures 2 and 3 illustrate the heater of Figure 1 as the tank pressure increases;

Figure 4 illustrates operation of the device to enable air to be admitted to the tank. Detailed Description of the Invention

Figures 1-4 illustrate a water heater incorporating an air-gap regeneration system. In these Figures, elements common to each are given the same number.

In general terms, and referring particularly to Figure 1, a water heater 10 has an outer casing 11, housing a water tank 12 and allowing the passage of water pipes and instrumentation required.

Cold water to replenish water retained in the tank 12 is supplied from the mains supply via pipe 13 which enters the tank 12 at inlet port 14. A valve 15 enables the heater to be isolated from the mains supply 13 when necessary. The inlet port 14 is usually configured to ensure that cold water entering the tank 12 does not mix quickly with any hot water contained therein. The provision of a large volume of hot water is thereby ensured, without the hot water being unduly cooled by replenishment water entering the tank 12.

The tank 12 shown has a single heating element 16, although further elements are usually present to ensure rapid heating.

In the sealed system heater shown, a volume of air 17 is provided above the surface of the water 18. The air improves the safety of the system by providing a region into which the water 18 can expand as it expands on heating. A baffle 19 floats on the surface of the water 18 and minimises dissolution of the air into the water. The use of a baffle is well known in the art. Usually the baffle is generally disc shaped, although other configurations are known.

Over prolonged periods however, the air gap 17 does reduce in size, with a concomitant increase in pressure within the tank 12. In prior art heaters the air gap usually needed to be regenerated by an engineer specifically trained to carry out the task. This requirement obviously entailed higher cost and inconvenience to the user. The present invention provides an air-gap regeneration means which operates effectively and automatically to maintain the air- volume 17 without recourse to an engineer. The device 20 is mounted between the mains water supply and the inlet port 14. The device 20 comprises a valve 21 which enables the volume of water 18 in the tank to be linked on requirement either to the mains supply or to a discharge pipe 22. A transducer 23 measures the pressure within the tank 12 and the information thus generated passes to the device 20. A control board (not illustrated) determines whether water needs to be released from the tank 12 to discharge 22. The tank 12 includes a one-way air-inlet valve 24 connecting the air-gap 17 to atmosphere. The air-inlet valve can either be incorporated into the tank 12 itself or via the air-generation device 20.

Referring now also to the further Figures 2-4, the sequence of events operating is illustrated. In Figure 1, the pressure within the tank 12 is at 3 bar and the water level can be seen from the position of the baffle 19 to be quite low down. If the pressure is too low, then water from the mains supply is admitted to replenish the water in the tank 12.

As the air-gap 17 diminishes and the pressure within the tank 12 rises, the water level (Figures 2 and 3) can be seen to rise as illustrated by motion of the baffle 19, in the direction A. The increase in pressure is registered by the transducer 23 which communicates the information along wire 23 a to the device 20. Once the pressure reaches a pre-set value, typically around 5 bar, the device 20 acts to reduce the pressure and increase the size of the air-gap 17, as shown in Figure 4.

Firstly, the valve 21 closes the mains supply water and opens the path for the water 18 to be discharged out of the discharge pipe 22. The pressure within the tank 12, being greater than atmospheric forces water through the inlet port 14 and back up the inlet pipe 25 in the direction indicated by arrow C. Thence, the water flows through the device 20 and out of the pipe 22.

As the water level in the tank 12 drops, as indicated by the arrow B in Figure 4, a partial vacuum is created above its surface. The partial vacuum draws air through the inlet valve 24, increasing the volume of the air-gap 17.

Once the amount of air required has entered the tank 12, the device 20 causes the valve 21 to close the path to the discharge pipe 22. The valve 21 opens the path between the mains supply and the tank 12 allowing water to enter the tank 12 to the level allowed by the air-gap 17. The amount of air allowed to enter can be pre-set into the device 20 in terms of time allocated to the process, the time being based on the known rate of air ingress.

In any event, the device 20 checks that the pressure is within acceptable parameters. Should this not be the case then further air is allowed into the tank 12 in the same manner as described above.

The device 20 can be programmed such that once it is informed by the transducer

23 that the air-generation process needs to be carried out, the device 20 waits until a quiet time in terms of hot water usage. For example, the device can be set such that the process only takes place between midnight and 4am when disturbance is likely to be at a minimum. Alternatively, the device 20 can be provided with a memory area, in which are stored the times when the building being supplied with hot water uses said hot water. Replenishment is then carried out when the usage is statistically at its lowest.

In the embodiment shown, the air-inlet valve 24 is mounted directly to the tank 12. However, the valve can be directly mounted to the device 20 which facilitates conversion of existing water heaters to usage of the system. In a further embodiment, the device 20 actively opens the valve 24 which can increase control of the rate of air allowed into the tank 12.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention.

Claims

1. An unvented water heater (10), the heater (10) including a water tank (12) to store water, the water tank (12) incorporating a heating element (16) to heat the water, a water inlet pipe (25) to admit mains water into the tank (12) and a discharge pipe (22) enabling excess water to be discharged;

the heater including an air-gap regeneration device (20) to introduce air into the tank, the device being operably connected to the inlet pipe (25) and the discharge pipe (22) to open and close said pipes (22, 25),

pressure determining means to measure the pressure within the tank (12) and transmission means (23a) to pass the pressure data obtained from the pressure determining means to the device (20), the device (20) operating once the tank pressure has exceeded a pre-set pressure,

an air inlet valve (24) admitting air into the tank (12).

2. A heater according to Claim 1, wherein the device includes a valve (21) operable to simultaneously close the inlet pipe, the closure thereby opening the discharge pipe.

3. A heater according to Claim 1 or Claim 2 wherein the air-inlet valve (24) is a one-way valve, allowing air into the tank (12) and operating on a pressure differential between the inside of the tank (12) and atmosphere being present.

4. A heater according to any preceding claim, wherein the air inlet valve is under the control of the device.

5. A heater according to any preceding claim, wherein the air inlet valve (24) is incorporated in the device allowing a device to be retro fitted to existing water heaters.

6. A heater according to any preceding claim, wherein the device includes a clock.

7. A heater according to claim 6, wherein operation of the device only occurs at pre-set times.

8. A heater according to any preceding claim including a pressure determination means (23) to determine the pressure difference between that in the tank and the atmosphere.

9. A heater according to claim 8 wherein the pressure determination means is a transducer.

10. A heater substantially as herein described with reference to and as illustrated in the accompanying drawings.