GB2487783A

GB2487783A - Pressure warning device for a hot water system

Info

Publication number: GB2487783A
Application number: GB1101974.2A
Authority: GB
Inventors: Christopher Adey; Martin Cooke; Simon Downie
Original assignee: Adey Holdings 2008 Ltd
Current assignee: Adey Holdings 2008 Ltd
Priority date: 2011-02-04
Filing date: 2011-02-04
Publication date: 2012-08-08
Anticipated expiration: 2031-02-04
Also published as: GB2487783B; GB201101974D0

Abstract

A pressure warning device 10 for a hot water system comprises a body 12 having an internal chamber 14, an inlet 16 to the chamber for connection to a filling loop and an outlet 18 to the chamber for connection to the hot water system, a pressure sensing means 30 for determining fluid pressure within the chamber, and at least one non-return valve 70 for preventing backflow through the inlet. An alarm means is adapted to indicate when the pressure detected in the chamber is above or below respective pre-determined thresholds. Preferably, the alarm means is audible and also includes a visual alert in the form of an array of LEDs 42. The device may be powered by a battery. In use, the pressure warning device is designed to be connected to a hot water heating system, such as a central heating system, at the position where the system is filled.

Description

PRESSURE WARNING DEVICE

The present invention relates to a pressure warning device for a hot water system.

BACKGROUND TO THE INVENTION

The hot water for a central heating system is generally provided by an oil or gas powered boiler. Often, the hot water circuit connected to the heat exchanger of the boiler is at pressure, for example, at around 1.5 Bar in a typical domestic installation.

As the water in the system heats up, then the pressure in the system also increases due to expansion of the system water. An accumulator is generally provided to absorb the expansion in the system water, but if for some reason the pressure exceeds the specification pressure for the boiler, then usually a pressure relief valve will vent the system to atmosphere. Typically the system is vented to a drain pipe with a visible drain. Once the pressure relief valve has actuated, then the boiler and the pressure relief valve need to be reset before the system can be used further.

In the event that there is a leak in the system, then the system water pressure may drop. If the system water pressure drops below the minimum pressure required for operation of the boiler, then the boiler will shut down and generally a plumber is required to address the problem of the leak, re-pressurise the system water, and restart the boiler.

In both of the above mentioned break down scenarios, typically there will be no warning prior to shut down of the boiler. Therefore, heating and hot water in a building are lost without warning and it may be some considerable time before a plumber is available to address the break down problem.

It is the object of the invention to provide a pressure warning device for a hot water system which substantially mitigates or reduces these problems.

STATEMENT OF INVENTION

According to the present invention there is provided a pressure warning device for a hot water system comprising a body having an internal chamber, an inlet to the chamber for connection to a filling loop and an outlet to the chamber for connection to the hot water system, pressure sensing means for determining fluid pressure within the chamber, at least one non-return valve for preventing backflow through the inlet, and an alarm means which is adapted to indicate when the pressure detected in the chamber is above or below respective pre-determined thresholds.

The alarm means provides an early warning system for detecting and indicating an undesirable increase or decrease in system water pressure before the pressure increase or decrease causes shut down of, for example, a boiler. It provides a window of opportunity for action to be taken to prevent the boiler from shutting down with the consequent loss of heating and hot water within a building. If a professional tradesman is required to address the problem, the early warning system enables a user to contact, for example, a plumber in advance of the shut down thus potentially saving time and money from waiting for the plumber and paying urgency charges. Water damage may also be avoided. The non-return valve ensures there is no backfiow of water through the inlet, thus preventing contamination of the water supply.

A housing may be mounted to the body, the pressure sensing means being mounted between the housing and the chamber of the body.

Preferably the pressure sensing means is a diaphragm sensor. Advantageously, the diaphragm sensor detects the water pressure within the chamber and provides a reading to the device. Water then exits the device through the outlet and towards the hot water system.

Although it is essential that a pressure sensing means is provided, it is envisaged that other suitable types of pressure sensing means could be used. However, the advantage of a diaphragm sensor is that it is widely available and cost-effective.

Preferably, the diaphragm sensor is at least partially covered in a ceramic material.

This makes the diaphragm sensor suitable for long term exposure to water, typically in a central heating system The ceramic layer renders the diaphragm sensor resistant to any chemical additives within the system water which could otherwise harm the diaphragm sensor.

An audible alarm may be incorporated into the device and may be an intermittent sound, the frequency of the emitted sounds increasing the further the pressure moves beyond one of said pre-determined thresholds, i.e. the sounds are closer together. The audible alarm allows the user to be alerted without the need for a visual check of the device.

Typically the pre-determined thresholds are 1.2 Bar and 3 Bar, but other suitable thresholds may be set. The change in the frequency of distinct sound emissions provides a guide to the status of the problem. An increase in frequency may indicate a deterioration of the situation and a decrease in frequency may indicate an improvement. If the frequency remains unchanged, then the pressure in the chamber is unchanged. For example, when the pressure within the chamber is 1.2 Bar, an intermittent sound may be activated. If the pressure remains at 1.2 Bar, then the frequency of the sound will remain unchanged. If the pressure drops, for example, to 1 Bar, the frequency of the intermittent sound may increase. If the pressure is then increased back, for example, to 1.2 Bar, the frequency of the sound may decrease.

Similarly, if the pressure exceeds 3 Bar, then the alarm will sound and increase in frequency as the pressure increases.

The alarm means may also be an array of LEDs, giving a visual representation of the pressure level within the chamber. As the pressure moves further beyond one of said pre-determined thresholds, the number of LEDs being illuminated increases. A pressure scale may be placed under the LEDs and in combination they provide the user with a clear indication of whether the pressure is within acceptable limits, too high, or too low.

The alarm means may alternatively or additionally include a bar symbol positional at any one of a plurality of pre-deterrnined positions on a display screen, and a coloured scale adjacent said plurality of pre-determined positions disposed on the housing, the position of the bar symbol relative to the coloured scale indicating the fluid pressure determined by the pressure sensing means. Such alarm means constitute a simple and intuitive means of communicating the pressure level. The alarm means is easy to understand, especially for the general public and people with little technical understanding of hot water heating systems.

The display screen, for example a text messaging display screen, may also be provided for displaying text instructions or fault code symbols in the event of the pressure moving beyond one of said pre-determined thresholds. It provides the user more information than just the pressure level by displaying instructions on how to resolve an issue. For example, if the pressure within the chamber is too low and the boiler needs to be re-filled, then text instructions can guide the user through the actions required and potentially avoid the cost of calling out a plumber.

Preferably, the device is powered by a battery. This allows for an easier installation of the device as a separate power source is not required and no connection need be made to the electricity supply of the hot water system, causing the system's energy efficiency to be reduced. It also allows the device to work independently from the hot water system.

A power indicator light may be disposed on the housing to indicate the state of the power supply to the device. This may be colour coded, for example, a green light for a full battery, a yellow light for a half full battery, and a red light when the battery is running out and a replacement is due imminently. The user is therefore given the opportunity to replace the battery before the power cuts off and disrupts the service of the device. Alternatively, a battery symbol may be provided on the display screen, indicating the charge remaining in the battery.

An instruction button may be disposed on the housing which upon activation causes the text instructions on be displayed on the display screen. The user may activate this at any time. A power button may also be disposed on the housing. This allows the user to activate the device only when required.

The body of the device may be threaded at the inlet and outlet to the chamber for connection to a filling loop and the hot water system, by way of a standard compression fitting. This allows the device to be easily fitted to an existing system.

A second non-return valve may be positioned in series with the first valve, acting as a back up to the first in preventing the backflow of water.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic perspective view of a pressure warning device in a first embodiment of the invention; Figure 2 shows a schematic front view of the pressure warning device of Figure 1; Figure 3 shows a schematic inlet end side view of the pressure warning device of Figure 1; Figure 4 shows a schematic cross-sectional view of the pressure warning device of Figure 1; Figure 5 shows a schematic perspective exploded view of the pressure warning device of Figure 1; Figure 6 shows a schematic perspective view of a pressure warning device in a second embodiment of the invention; Figure 7 shows an exploded view of the pressure warning device of Figure 6, and Figure 8 shows a schematic cross-sectional view of the pressure warning device of Figure 6.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring firstly to Figures 1, 2 and 4, a first embodiment of a pressure warning device is indicated generally at 10. The pressure warning device 10 includes a body 12 having a substantially circular internal chamber 14. An inlet 16 is positioned at the end of chamber 14 and an outlet 18 is positioned at the other end of the chamber 14. A substantially square shaped housing 20, for accommodating electronics of the device, is connected to the body 12. A face plate 22 providing a user interface is displayed on the top of the housing 20.

Figure 5 illustrates the detailed construction of the pressure warning device 10. A male thread 24 is positioned on the inlet 16 and outlet 18 to the chamber 14 to provide means for connection to a filling loop and a hot water system. A substantially circular boss 26 is disposed mid-way along the body 12, and a bore extends through the boss into the chamber 14. An adaptor 28 with a through bore has a circular projection on either side, one of the circular projections being adapted to be received in the bore of the boss 26. The projection on the other side of the adaptor 28 receives a substantially circular diaphragm pressure sensor 30 for detecting fluid pressure within the chamber 14.

The housing 20 is connected to the adaptor 28 through an aperture in the back of the housing 20. A printed circuit board 32, shaped to be complimentarily received by the housing 20, is situated at the bottom of the housing 20. A speaker 34 is disposed on the upper surface of the circuit board 32, providing one of the alarm means. A battery socket 36 is positioned under the speaker 34 on the circuit board 32 to receive a power supply. A battery 38 powers the device through connection to the battery socket 36.

A rectangular shaped text messaging display screen 40, mounted on a base plate 46, is situated at the top half and on top of the circuit board 32 where pre-programmed messages can be displayed. A plurality of LEDs 42 is situated above the battery 38, providing visual representation of the pressure level in the internal chamber 14.

The face plate 22 provides a cover to the housing 20 and contains a plurality of apertures for presenting the visual displays 40,42 to a user. A text display aperture 48 is shaped and positioned to display the text messaging display screen 40. A rectangular shaped transparent cover 44 has a border 58 and a recess 60 which is shaped to complimentarily fit into the text display aperture 48 of the face plate 22. It protects and displays the text messaging display 40 situated underneath. A LEDs aperture 50, situated below the text display aperture 48, is shaped and positioned to display the LEDs 42. A scale label 62 is printed, on the face plate 22, under the LEDs aperture 50 to indicate the detected pressure.

There are three substantially circular apertures 52,54,56 between apertures 48 and 50 to accommodate two buttons and a display light. Referring to Figures 3 and 5, an instruction button 64 is accommodated in the instruction button aperture 52 which, upon activation, enables text instructions on how to re-fill the boiler to be displayed on the display screen 40. A display light 66 is accommodated in the display light aperture 54 which indicates the battery level of the battery 38. The display light 66 is colour coded. A green light represents a full battery, a yellow light as half full, and a red light represents when the battery is running out and a replacement is due imminently.

Similarly, a system test button 68 is accommodated in the system test button aperture 56 which allows the user to test the display of characters on the text messaging display screen 40.

Referring to Figures 4 and 5, two non-return valves 70 are situated inside the inlet 16 of the internal chamber 14 in series to prevent backflow of water and contamination of the water supply to the hot water system. Each non-return valve is optional. When the non-return valves are omitted, the pressure warning system is particularly suitable for use with a hot water heating system having non-return valves afready in place. It is important that such existing non-return valves are positioned on the "filing loop" side of the hot water heating system.

In use, the pressure warning device 10 is connected to a hot water heating system at the position where the system is filled. One side of the device 10 is connected to the filling loop of the system. In usual operation, the system pressure will be around 1.5 Bar. If the pressure in the chamber 14 changes, it is detected by the diaphragm pressure sensor 30. When the pressure moves above or below certain pre-determined thresholds, for example, below 1.2 Bar or above 3 Bar, then the audible alarm is activated and an intermittent sound is transmitted through the speaker 34. As the pressure crosses the threshold further, the time between each intermittent sound decreases. This provides an indication that remedial action may be required to stabilise the operational pressure. A visual alert, in the form of the LEDs 42, indicates whether the pressure is too high or too low. If the cause for activation of the alarms is a result of too low a pressure within the chamber 14, then the user can activate the instruction button 64 and follow the instructions displayed on the display screen 40 to re-fill the system.

A second embodiment of the pressure warning device is indicated generally at 72 in Figures 6, 7 and 8. Parts in common with the first embodiment are referenced using the same reference numerals. The pressure warning device 72 includes a body substantially as described before with reference to body 12, with an inlet 16, outlet 18 and internal chamber 14. The ends of the body 12 are threaded in a conventional manner to form a compression fitting. In brief, each male thread 24 is matable with a nut 74 having a threaded internal bore 76. An olive 78 is passed over a free end of the piping (not shown). The piping and olive 78 are inserted into the inlet 16 and outlet 18 of the chamber 14. Each nut 74 engages with a male thread 24 and compresses the olive 78 against the piping to provide a secure connection between the pressure warning device 72 and the piping. Other connections means are possible, but a compression fitting is preferred.

A boss 80 extends from one side of the device 72. In this embodiment, the boss 80 includes a floor 82 to substantially partition the bore of the boss 80 from the internal chamber 14. A fluid access aperture 84 extends through the floor and permits fluid flow between the bore of the boss 80 and the internal chamber 14.

Two pairs of pin apertures 86 (see Figure 7) extend through the annular wall 88 of the boss 80. Each pair of pin apertures 86 is disposed on a cord of the circular cross-section. The two pairs of pin apertures 86 are disposed substantially symmetrically about the central axis of boss 80. The pin apertures 86 are used in combination with a generally U-shaped pin 90 for securing an adapter 92 in place within the boss 80. The diameter of the boss 80 is greater than the diameter of the bore through the inlet and outlet 16, 18 of the device 72 in order to accommodate the adapter 92.

The adapter 92 comprises first 94 and second 96 sensor support members. Both first and second sensor support members 94, 96 are annular, with a coaxial central bore 98 extending substantially through both first and second sensor support members 94, 96.

The first and second sensor support members 94, 96 are connectable together using a plurality of fastening means 100, such as screws, which pass through and/or engage with a plurality of first 102 and second 104 sensor support apertures, which are equi-angularly spaced around each first and second sensor support member respectively 94, 96.

The second sensor support member 96 sits in the boss 80 and includes an annular seat portion 106 for receiving the pressure sensor 30. The assembled adapter 92 serves to house the pressure sensor 30, which is positional on the seat portion 106. The seat portion 106 is a radially inwardly extending flange having a central aperture. The seat portion 106 is disposed at or adjacent to one end of the longitudinal extent of the second sensor support member 96, to the lower side of the support member, as viewed, proximate the floor 82. The first and second sensor support members 94, 96 connect together, effectively clamping the pressure sensor 30 in position inside.

An annular face seal 108 is disposed intermediate the pressure sensor 30 and the seat portion 98 to prevent fluid from travelling towards the control electronics.

Similar to the pin apertures 86, two pairs of location apertures 110 extend through the annular wall of the second sensor support member 96. Each pair of location apertures is disposed on a cord of the circular cross-section. The two pairs of location apertures 110 are disposed substantially symmetrically about the central axis of the second sensor support member 96.

The adapter 92 is mountable to the body 12 of the pressure warning device 72 by virtue of the generally U-shaped pin 90. The pin 90 has two elongate resilient leg portions 112 and an arcuate connector portion 114 connecting the two leg portions 112. The two leg portions 112 are substantially parallel to each other. A detent 115 is disposed at the end of each leg portion 112. The leg portions 112 of the pin 90 are engageable with the pin apertures 86 and the location apertures 110 of the boss 80 and second sensor support member 96 respectively. Each detent 115 passes through a location aperture 110 of the boss 80 and snap fits against the annular wall 88 of the boss 80 around the location aperture 110, thereby retaining the pin 90 in position.

Since the leg portions 112 are resilient, each detent 115 is disengageable from the location apertures 110, and therefore the pin 90 is removable from the boss 80.

An annular gasket or seal 116 is disposed around preferably the second sensor support member 96. The seal 116 may be made from EPDM rubber, although other materials suitable for use with high temperature applications may also be used.

A plurality of third 118 sensor support apertures extends axially through the first sensor support member 94 for receiving fastening means, such as screws. Such fastening means connect the adapter to housing 120.

As best seen in Figure 7, the housing 120 is substantially square shaped and accommodates the electronics of the device. The housing 120 is preferably made from a plastics material for ease of manufacturing. The housing 120 in this embodiment comprises a housing cover 122 detachably mountable to a housing base 124. The housing cover 122 is connectable to the housing base 124, for example with a push fit or using fastening means.

The housing base 124 is a shallow tray having a plurality of first tray apertures 126 arranged in a circle about a larger centrally located second tray aperture 128. The first tray apertures 126 are equi-angularly spaced around the second tray aperture 128. The first tray apertures 126 receive fastening means (not shown) used to mount the housing base 124 to the adapter 92. Such fastening means pass through the first tray apertures 126 into the plurality of third sensor support apertures 118 in the first sensor support member 94. The purpose of the second tray aperture 128 is to allow the pressure sensor 30 to communicate with the printed circuit board 32, typically by virtue of a plurality of electrical wires. Four mounting points 130 are disposed in each of the four corners of the housing base 124 for securing at least the printed circuit board 32 to the housing 120.

The printed circuit board 32, for controlling operation of the pressure warning device 72, is disposed intermediate the housing base 124 and a display screen 132.

In this embodiment, the display screen 132 is a conventional liquid crystal display (LCD) screen, although other types of appropriate display screen technology could feasibly be used. The display screen 132 is used in substitution for the text messaging screen 40 of the first embodiment. It is used for numerically displaying the pressure value 134 measured of the pressure sensor 30, for example, 1.5 bar, and also for displaying one or more pre-programmed messages 136 or fault codes, for example in the form of symbols. Each fault code may be explained, for example, in a handbook for the pressure warning device 72.

The display screen 132 also visually conveys the pressure value measured by the pressure sensor using a bar symbol 138 (indicated in phantom on Fig 6). The bar symbol 138 is visible at any one of a plurality of pre-deterrnined positions in a display stack 140 provided on the display screen 132.

A display screen aperture 142 extends through the housing cover 122. The housing cover 122 also includes a preferably rectangular recess 144 in an upper face 146 for receiving a protective screen 148.

The protective screen 148 is correspondingly shaped so as to be positional within the housing cover recess 144. The purpose of the protective screen 148 is to prevent or reduce damage to a display screen 132 below the protective screen 148. The protective screen 148 is typically made from a plastics material and is preferably scratch resistant. The display screen 148 is visible through the display screen aperture 142. A first portion 150 of the protective screen is transparent, whilst the remaining second portion 152 is opaque. The transparent first portion 150 generally corresponds with regions of the display screen 132 which display information.

A coloured scale 154 having a plurality of coloured segments 156 is provided on the opaque second portion 152 of the protective screen 148. The coloured scale 154 is used in assessing the significance of the pressure measured by the pressure sensor 30, as described in more detail below. Each coloured segment 156 is preferably rectangular to form a compact visual indicator. The coloured segments 156 are horizontally aligned along the lateral extent of the protective screen 148 in a further stack arrangement. The coloured scale 154 includes a red segment 158 disposed at either end of the stack. The four segments 160 in the middle of the coloured scale 154 are green. Two yellow segments 162 are disposed between the green segments 160 and each red segment 158. Feasibly, any number of coloured segments 156 may be used depending on the size of the assembled pressure warning device 72. Equally, any allocation of colours may be used.

Since the display stack 140 appears adjacent to the coloured scale in the assembled device 72, the position of the illuminated bar symbol 138 relative to the coloured scale 154 indicates whether the pressure being measured by the pressure sensor 30 is too high, too low, at an acceptable level, or at any point therebetween.

The seal 116 provides a barrier between the delicate electronics in the housing 120 and the pressurised fluid that passes through the in use body 12.

As with the first embodiment, the pressure warning device 72 may be battery powered.

In such an arrangement, the display screen 132 may be adapted to visually indicate the power being supplied to the device 72. The power indicator is a battery symbol 164, visible in use in the upper left side of the display screen 132 and having a similar form to some battery level indicators provided, for example, in mobile telephone phones. As the power remaining in the batteries decreases, segments of the battery symbol 164 are removed from the display, in a known manner.

The pressure warning device 72 may include an audible alarm as described previously.

In such an arrangement, a mute button 166, in communication with the printed circuit board 32 through an aperture in the housing cover 122, is provided to silence the alarm. Similarly, a reset button 168 may be provided for resetting operation of the pressure warning device 72.

The arrangement of the pin 90 and the pin and location apertures 86, 110 is advantageous as it allows a rotational orientation of the adapter 92 within the boss 80.

Such freedom of orientation is beneficial since the pressure warning device 72 may ultimately be mounted at any angle relative to the horizontal. Since the pin 80 is removable from the pin and location apertures 86, 110, the adapter 92 may be oriented it) as required before the pin is reinserted. This enables the user to orientate the housing 120, and therefore the display screen 132, relative to the body 12, according to preference.

In use, fluid pressure in the system is exposed to the pressure sensor through the fluid access aperture 84. When the pressure moves above or below certain pre-determined thresholds, for example, below 1.2 Bar or above 3 Bar, then the bar symbol 138 moves along the lateral extent of the display screen 132, through the display stack 140, adjacent to the coloured scale 154, to indicate whether or not action should be taken to address the change in pressure. When the bar symbol appears next to a red segment 158, the user determines that the pressure is unacceptably high or low and that action is clearly required in order to adjust the pressure in the hot water system. When the symbol appears next to a yellow segment 162, the user determines that the pressure has increased or decreased to a level that should probably be addressed. By contrast, when the symbol appears next to a green segment 160, the user determines that the pressure is within an acceptable range and that no action is required.

The invention, as described in the two embodiments, is beneficial because it provides early warnings, in both visual and audible forms, when pressure detected in the chamber is above or below respective pre-determined thresholds. This enables the user to either rectify the problem of system pressure himself, or to contact a professional tradesman, before the system shuts down causing interruption to heating and hot water supply within a building. Furthermore, the text messaging display and/or the fault codes provides the ability to convey more detailed instructions, such as on how to re-fill the hot water system, thus allowing the user to take correct steps to resolve the problem. The device contains its own power supply thus allowing for an easier installation of the device as a separate power source is not required and no connection need be made to the electricity supply of the hot water system, causing the system's energy efficiency to be reduced.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art and various features from the embodiments may be interchanged without departing from the scope of the present invention as defined by the appended claims.

Claims

CLAIMS1. A pressure warning device for a hot water system comprising a body having an internal chamber, an inlet to the chamber for connection to a filling loop and an outlet to the chamber for connection to the hot water system, pressure sensing means for determining fluid pressure within the chamber, at least one non-return valve for preventing backflow through the inlet, and an alarm means which is adapted to indicate when the pressure detected in the chamber is above or below respective pre-determined thresholds.
2. A pressure warning device as claimed in claim 1, in which a housing is mounted to the body, the pressure sensing means being mounted between the housing and the chamber of the body.
3. A pressure warning device as claimed in claims 1 to 2, in which the pressure sensing means is a diaphragm sensor.
4. A pressure warning device as claimed in any preceding claim, in which the alarm means is audible.
5. A pressure warning device as claimed in claim 4, in which the audible alarm is an intermittent sound, the frequency of the sounds increasing the further the pressure moves beyond one of said pre-determined thresholds.
6. A pressure warning device as claimed in claim 5, in which the pre-determined thresholds are 1.2 Bar and 3 Bar.
7. A pressure warning device as claimed in any preceding claim, in which the alarm means includes an array of LEDs.
8. A pressure warning device as claimed in claim 7, in which the number of LEDs being illuminated increases the further the pressure moves beyond one of said pre-determined thresholds.
9. A pressure warning device as claimed in claim 8, in which a pressure scale is placed adjacent the LEDs.
10. A pressure warning device as claimed in any preceding claim, in which a display screen is provided for displaying text and/or symbols for instructions in the event of the pressure moving beyond one of said pre-determined thresholds.
11. A pressure warning device as claimed in claim 10, in which the alarm means includes a bar symbol positional at any one of a plurality of pre-determined positions on the display screen, and a coloured scale adjacent said plurality of pre-determined positions disposed on the housing, the position of the bar symbol relative to the coloured scale indicating the fluid pressure determined by the pressure sensing means.iS
12. A pressure warning device as claimed in any preceding claim when dependent on claim 2, in which an adapter having a seat portion freely supports the pressure sensing means between the housing and the chamber of the body.
13. A pressure warning device as claimed in any preceding claim, in which the device is powered by a battery.
14. A pressure warning device as claimed in claim 13, in which a power indicator is provided to indicate the state of the power supply to the device.
15. A pressure warning device as claimed in claim 14, in which the power indicator is a colour coded power indicator light.
16. A pressure warning device as claimed in any preceding claim when dependent on claims 2 and 10, in which an instruction button is disposed on the housing which upon activation causes text instructions to be displayed on the display screen.
17. A pressure warning device as claimed in any preceding claim when dependent on claim 2, in which a power button is disposed on the housing.
18. A pressure warning device as claimed in any preceding claim, in which the body is threaded at the inlet and outlet to the chamber for connection to a filling loop and hot water system.
19. A pressure warning device as claimed in any preceding claim, in which a second no-return valve is positioned in series with the first.
20. A system pressure warning device substantially as described herein with reference to and as illustrated in Figures 1 to 5 of the accompanying drawings.
21. A system pressure warning device substantially as described herein with reference to and as illustrated in Figures 6 to 8 of the accompanying drawings.