GB2580289A

GB2580289A - Pressure monitoring system for hot water tanks and method of operating same

Info

Publication number: GB2580289A
Application number: GB1817475.5A
Authority: GB
Inventors: Armstrong Peter
Original assignee: Mixergy Ltd
Current assignee: Mixergy Ltd
Priority date: 2018-10-26
Filing date: 2018-10-26
Publication date: 2020-07-22
Also published as: GB201817475D0

Abstract

A hot water tank system 10 for receiving water from a supply thereof having a water tank 12 for water to be heated and including an inlet 14, outlet 16 and a heater 18 for heating water within the water tank. A pressure reducing valve or one way valve 24 is positioned between the supply of water and the inlet to the water tank. An expansion chamber 26 having a first side for receiving water from the tank and a second side for receiving pressurised air is provided with an air re-fill valve 28 and a pressure sensor 30 for sensing the pressure within the hot water tank system and which is connected to a pressure monitor 32 to monitor the pressure within the tank and allow for the implementation of automated re-pressurisation as and when required.

Description

PRESSURE MONITORING SYSTEM FOR HOT WATER TANKS AND METHOD OF

OPERATING SAME

s The present invention relates to a pressure monitoring system for hot water tanks and a method of operating the same and relates in particular, but not exclusively, to a system and method of managing the pressure in pressurised hot water tanks such as may be used in domestic or industrial applications so supply hot water to end users.

Present hot water systems tend to comprise a tank for storing a quantity of hot water for use to by end users and include some form of pressurisation apparatus to place the contents of the tank under pressure to ensure an adequate flow of hot water is maintained at a desired level. The maintenance of a minimum pressure within the tank is critical to ensuring a consistent supply and under-pressurisation will result in poor water flow whilst over-pressurisation may result in hot water being vented from the tank and wasted. It is known to provide an external is or internal pressure reservoir connected to the tank which is pressurised by the user as and when required, but the management of re-pressurising is problematic as it is often difficult to understand how to pressurise the tank. The re-pressurisation of an internal pressure reservoir is difficult to achieve, and many householders are unable to do the task themselves which is problematic as under pressurisation will result in poor water delivery whilst over-pressurisation is likely to cause hot water to be vented from the tank until the pressure is reduced. External pressure reservoirs are more easily managed but, again, many householders are either unable or unwilling to perform the task. In either of these cases, the normal recourse is to a professionally qualified plumber or maintenance company who will need to dispatch an operative as such re-pressurisation requires on-site presence. In managed housing the re-pressurisation is often left to the management company who must operate a preventative maintenance schedule which is both expensive and difficult to manage as access to the household is difficult.

In view of the above, it will be appreciated that there exists a need for a pressure monitoring system and method of operating the same which is less problematic, easier to use and may, potentially, be automated and / or monitored / managed remotely and without access to the household in question. It is an object of the present invention to reduce and possibly eliminate one or more of the problems associated with the arrangements of the prior art. The present invention also aims at providing an arrangement which more readily lends itself to automation and / or remote monitoring or management.

According to a first aspect of the present invention there is provided a hot water tank system for receiving water from a supply thereof comprises or consists of a water tank for containing water to be heated and includes an inlet an outlet and a heater for heating water within the water tank. A pressure reducing valve and / or one-way valve may be provided between the supply of water and the inlet of the water tank. An expansion chamber may be provided and has a first side for receiving water from the tank and a second side for receiving pressurised air. The expansion tank may include an air re-fill valve. A pressure sensor may be provided for monitoring the pressure within the hot water tank system and the system may further includes a pressure monitor connected to the pressure sensor for monitoring the pressure detected thereby.

In one arrangement, said expansion chamber may comprise an external expansion vessel connected to the inlet between the one-way valve and the water tank and having a first side (A) for receiving water from the tank system and a second side (B) for receiving pressurised air from outside of the tank system and the air re-fill valve may be on the expansion vessel.

In an alternative arrangement, said expansion chamber may comprise an external expansion vessel connected to the outlet of the water tank nd having a first side for receiving water from the tank system and a second side for receiving pressurised air from outside of the tank system and wherein the air re-fill valve may be on the expansion vessel.

In a still further alternative arrangement, said expansion chamber may comprise an expansion chamber within the hot water tank and having a first side for receiving water from the tank system (10) and a second side for receiving pressurised air from outside of the tank system and an air re-fill valve may be connected to the expansion chamber.

In some arrangements said pressure sensor is connected to the air side of the external expansion vessel for monitoring the pressure of air therein. However, it may be connected on the water side in some other arrangements.

Advantageously, the arrangement may further include a comparator for comparing monitored pressure signals received by said pressure monitor and for comparing said signals thereby to determine a change in the pressure signals.

The arrangement may further include a calculator for receiving monitored pressure signals from said pressure monitor and for calculating a rate of change thereof.

The arrangement may further include an estimator for estimating the time remaining or volume of air remaining before depletion of the air supply within the expansion vessel.

In one arrangement a source of pressurised air is connected to the re-fill valve and said re-fill valve comprises a servo valve having an actuator operable to open and close said re-fill valve upon receipt of a control signal.

The arrangement may include a remote system monitor and further including a first transmitter s for transmitting monitored pressure information to said remote system monitor. When provided, said remote system monitor may include a second transmitter for transmitting a control signal to the actuator of the re-fill valve.

The external expansion vessel may comprise a closed vessel having a first inlet for receiving io water from the water tank and a second inlet for receiving air from a remote source thereof and a diaphragm or expandable balloon within said expansion vessel dividing said expansion vessel into an air side and a water side. Said diaphragm comprises a flexible diaphragm or may comprise a floating diaphragm.

In one arrangement there is provided a visual indicator for visually indicating information is relating to the pressure within the tank.

According to another aspect of the present invention there is provided a method of operating a hot water tank as claimed in any one of claims 1 to 14 including the steps of a) monitoring a pressure P within the tank; b) comparing said pressure with a pre-defined pressure (PDP); c) calculating the rate of change (ROC) of pressure P; d) estimating the time remaining (TR) before the monitored pressure P reaches said pre-defined pressure (PRP) e) transmitting a signal indicative of the time remaining (TR) to a further device.

The method may include the further steps of receiving a signal indicative of the time remaining on a further device in the form of a remote monitor and creating an action signal (AS) within said remote monitor dependent upon the value of the received signal and transmitting said action signal (AS) to a further device.

The method may also include the step of transmitting said action signal (AS) to a further device in the form of a visual display apparatus giving an indication of the time remaining before pressure P reaches the pre-defined pressure (PDP).

The method may also include the step of transmitting said action signal (AS) to a further device in the form of an actuator (42) connected to a control valve for introducing pressurised air into said air side of said tank (12).

Aspects of the present invention will now be more particularly described by way of example only with reference to the following drawings, in which: Figure 1 is a first schematic representation of components of the prior art arrangement for a hot water tank system; s Figures 2 and 3 are alternative schematic representations of components of the present arrangement in which the pressure monitor is applied to the tank itself or an external pressurising vessel on the inlet side of the tank; Figure 4 and 5 are still further schematic representations of the present arrangement in which the pressure sensor is provided on the side of the tank itself or an external pressure vessel on io the outlet side of the tank; and Figure 6 is a graph of system pressure over time.

Referring now to figures 1, a hot water tank system 10 known in the art includes a water tank 12 for containing water W and an inlet 14 which is, in turn, connected to receive water W from a supply thereof 90. An outlet 16 is used to supply heated water W to water consuming items such as washing machines, baths, showers etc whilst a heater or hearing element 18 is provided to heat the water W within the tank 12. Such a heater 18 could be an electrical heating element or a hot water coil which is provided with heating water from a remote boiler system (not shown). The water tank 12 is connected to an expansion chamber 26 which may be connected (not shown) on the outlet side by connecting to outlet 16 via connection 102 (shown in subsequent drawings or may be connected on the inlet side 14 via connection 104, as shown in figure 1. In effect, the first described connection is on the hot water side and the second described connection is on the cold supply side. The hot side connected expansion vessel will be referred to as item 26A whilst the cold water or inlet side connected expansion chamber will be referred to as item 26B. The cold water or inlet side expansion vessel 26B is connected to the inlet downstream of a pressure reducing valve 24 and, thus, experiences the pressure that exists within the tank itself. When the expansion vessel 26A is provided on the hot water side it may comprise a portion of the tank 12 itself or a separate discrete expansion chamber 26A, as best seen in figure 4. The hot side expansion vessel 26A will be exposed to the pressure P within the tank 12 either directly or via the connection 102. Each expansion chamber 26 has a first side A for receiving water from the tank 12 and a second side B for receiving pressurising gas G from a source thereof 300. Such gas may be air or any other inherently safe gas and may be provided from a pressurised source thereof or pressurised by a pump, both of which are described in detail later herein. Hot water tanks 12 also tend to include a pressure relief valves 104 and an overflow outlet 106 operably connected to said valve 104 such as to allow over-pressurised water to be vented from the tank 12 and the use of these is described later herein with reference to the problem that the present invention is aimed at addressing. In each of the embodiments, the expansion chamber 26A, 26B is s provided with a gas or air re-fill valve 28 which is connected for receiving pressurised gas to a source thereof shown schematically at 300.

Operation of the above-discussed prior art arrangement is problematic in so far as it requires the consumer or a qualified plumber to re-pressurise the tank if the pressure has fallen below that required for efficient water delivery. In addition, if the pressure rises above that desired io for efficient water delivery the pressure relief valve 104 will automatically operate and cause a portion of the contents of the water tank to be vented to atmosphere and expelled to an overflow pipe. Such venting will include a significant volume of water which may be at a temperature high enough to cause harm to a householder or plumber attempting to rectify the problem. The correction of under or over-pressurisation of a hot water tank is not easy to do by a householder as the householder would need to know what series of steps are required to safely re-pressurise the tank and as such processes can vary dramatically between hot water tank systems it is unlikely that a householder could safely perform this task and an expert plumber will be required to attend the household and execute the re-pressurisation process.

The present invention provides additional components over those described above such as to allow for the more effective monitoring and management of the re-pressurisation of the tank and is described below with reference more specifically to figures 2 to 5 which illustrate various different arrangements of the present invention and figures 6 and 7 which relate to the operation of the system now to be described. Referring to figures 2 to 5 in general, it will be appreciated that each has an expansion chamber 26 which may be provided on the inlet or cold-water side of the tank 14, as shown in figures 3 and 4 and referred to with reference 26A, or on the outlet or hot water side as shown in figures 4 and 5 and referred to with reference number 26B. In an alternative arrangement, the expansion chamber may be provided within the tank 12 itself and such an arrangement is referenced schematically by number 26T.

Regardless of the position of the expansion chamber 26 it comprises a first side A for receiving water from the tank and a second side B for receiving pressurised gas or air, the purpose of which will be described later herein.

A first of the additional components comprises a pressure sensor 30 which is provided to monitor the pressure within the tank 12 and which may be placed in one of several different locations depending on user or system preferences. In essence, the pressure sensor 30 need only be positioned somewhere where they can experience the pressure within the tank 12 so the options shown in the drawings are illustrative only and it will be appreciated that the pressure monitor could be placed in other locations. A second additional component comprises a pressure monitor 32 operably connected to said pressure sensor 30 by line 32a and which may be placed either close to the tank 12 or remote therefrom. Figure 2 provides the pressure sensor 28 on the inlet or cold-water side expansion chamber 26B whilst figure 3 illustrates the pressure sensor 28 on the tank 12 itself. Figure 4 illustrates the pressure sensor on the tank 12 whilst figure 5 illustrates the pressure sensor 28 on the expansion chamber 26A on the hot water or outlet side of the tank 12. Whilst it will be appreciated that the pressure sensor 28 may be connected at any point, it has been found desirable to connect it on the air or gas side of any system, as shown by way of example in figures 2 and 4 where the pressure sensor 28 is positioned on the air or gas side of the expansion chamber 26. Each sensor is connected by the prior mentioned line 32a to an associated pressure monitor 32. The expansion chamber 26 may be provided with a flexible diaphragm 26D dividing the first and is second sides A, B thereof or an expandable balloon 26E, shown in dotted lines for illustrative purposes only, may be used to define a barrier between the first and second sided A, B by having an inlet 261 connected to the water W within the tank 12 either via inlet 14 or outlet 16 or directly by virtue of being within the tank 12 itself.

A further but optional additional component may comprise a source of pressurised gas or air shown schematically at 300 but which may comprise a reservoir of compressed air or a compressor arranged to connect to the air re-fill valve 28 via supply pipe 28S. The re-fill valve 28 may comprise a servo valve having an actuator 42 for opening and closing said valve 28 such as to cause the re-pressurising of the system and may be connected to a remote or local controller 400 for causing operation of said valve 28 in a manner to be described later herein.

Connection may be by means of direct transmitter / receiver control line 110 if locally located or by means of a transmitter/receiver 500 which may be a wireless transmitter/receiver. The transmitter / receiver 500 may be split into a number of components such as a first transmitter 510 for transmitting monitored pressure information to said remote system monitor 100 and a second transmitter 520 for transmitting a control signal to the actuator 42 of the pressure re-so fill valve 28 such as to initiate control over the re-pressurising of the tank 12 as and when desired. The pressure monitor 32 may be connected to a system monitor 100 for allowing pressure data to be transmitted there to and such connection may be by means of a direct data line shown schematically at 32b, if a local connection is required, or may be by means of the transmitter / receiver 500, if a remote connection is required. An output such as a visual output may be provided as part of the system monitor 100 such as to present pressure information to an operator who may be remote from the tank 12 or proximal thereto.

The monitor 100 may further include a number of components such as a comparator 40 for comparing received pressure signals and for comparing them thereby to determine any change in pressure within the tank 12. It may also include a calculator 50 for receiving monitored pressure signals and for calculating a rate of change thereof and possibly also an estimator 60 for estimating the time remaining T to reaching a pre-defined pressure P DEF. Such a comparator 40, calculator 50 and estimator 60 may all be incorporated in a data processor device shown schematically in the figures as item 600.

Operation of the above-mentioned arrangements will now be explained with referend to the io drawings in general but also now to figure 6 which illustrates the change in pressure within the tank 12 over time. Most domestic and industrial hot water supply systems operate at a pressure of between 2 and 3 bar (29psi to 43psi) which is a pressure that is sufficient to ensure a steady flow if hot water to any device consuming it whilst being sufficiently low as to avoid unnecessarily pressurising the pipe system which could lead to failures and leakages therein.

However, the present invention is not considered to be limited to hot water tanks operating at this sort of pressure as the general inventive concepts may be applied to higher pressure systems and lower pressure systems as and where appropriate. Assuming the normal operational pressure is 2.5 bar then an over-pressurisation sufficient to cause the venting of the tank 12 via pressure relief valve 104 and outlet 106 might be at or above 3 bar whilst an under-pressurisation may be deemed to occur at 1.5 to 2 bar or below. The graph of figure 6 shows a normal system at 2.5 bar and a fully charged tank 12 ready to supply hot water W and from which it will be appreciated that over time-period P1 water is being withdrawn from the tank 12 and, hence, the pressure is dropping as the cold water re-supplying the tank will be filling it at a slightly slower rate than water is being withdrawn. Whilst the mains cold water supply is usually at a pressure above 2.5 bar, the pressure reducer 24 on the inlet 14 will act to reduce the pressure to the desired 2.5 bar and, hence, once the water drain has subsided, the pressure in the tank 12 will gradually rise during time-period P2 between time T1 and T2 until the tank 12 is re-filled. At such a point the temperature within the tank will be lower than desired and heater 18 is deployed to heat the water W to a desired temperature DT. The pressure will re-establish itself at the desired pressure DP of 2.5 bar and remain there for a further time-period P3 until a subsequent further draw of hot water is undertaken during time-period P4 when the entire process is repeated once again. Dotted lines U show how the pressure profile might alter if the system experiences a pressure leak and the pressure in the tank falls below the desired pressure DP of, for example, 2.5 bar. If the pressure drops too much the supply of hot water from the tank 12 may be prejudiced and the efficient operation of the system will be compromised. Dotted lines 0 illustrate how the pressure profile might alter if the pressure in the tank rises above the desired pressure DP and if the pressure rises above that required to cause venting by actuation of the pressure release valve 104, both pressure and hot water will be vented from the tank and compromise the efficiency of the system and possibly the safety of the householder or plumber attending the household.

s The present invention can address one or other or both the above-discussed under or over-pressurisation through the use of the pressure sensor 30 and suitable operational steps which can be undertaken before under or over-pressurisation occurs. For example, pressure sensor 30 will be detecting the pressure within the tank 12 and relaying it to pressure monitor 32 which is connected to the monitor 100 which monitors changes in pressure P. The comparator 30 may use the received pressure data (PD) to compare the present pressure P with prior stored pressure (PSP) data and the calculator 50 may calculate the rate of change of pressure from the received and stored pressure data. The estimator 60 may take the stored or present pressure and the calculated rate of change (ROC) of pressure and estimate the time remaining (TR) before the pressure in the tank 12 falls or rises to a pre-defined and possibly undesired pressure (PDP) which would require corrective action. This time remaining (TR) and / or the actual pressure P in the tank 12 may be transmitted to any further device such as a display output 200 for visual representation thereof to an operative or householder. It may also or alternatively be transmitted to a controller 400 which, upon receipt of said pressure data, may cause an action signal (AS) to be sent to the display apparatus 200 and / or to a further device.

The further device could, usefully, be the actuator 42 for the air or gas re-fill valve 28 which may be actuated by said actuation signal (AS) to cause the valve 28 to be opened and, thus, allow re-pressurising gas or air to be supplied through the re-pressurising valve 28 to re-pressurise the tank 12. Cessation of the re-pressurisation may be initiated by the controller 400 receiving a pressure signal matching the desired or pre-defined pressure (PDP) and the tank is now operational again without external involvement by the householder or a qualified plumber.

Claims

CLAIMS: 1. A hot water tank system (10) for receiving water from a supply thereof comprises: a) a water tank (12) for containing water to be heated and including an inlet (14) and outlet (16) and a heater (18) for heating water within the water tank (12); b) a pressure reducing valve (24) between the supply of water and the inlet (14) to the water tank (12); c) an expansion chamber (26) having a first side (A) for receiving water from the tank (12) and a second side (B) for receiving pressurised air; d) an air re-fill valve (28) connected to the expansion chamber (26); and e) a pressure sensor (30) for sensing the pressure within the hot water tank system (10); and f) a pressure monitor (32) connected to the pressure sensor (30).
2. A hot water tank system (10) as claimed in claim 1 and wherein said expansion chamber (26) comprises an external expansion vessel (26) connected to the inlet (14) between the one-way valve (24) and the water tank (12) and having a first side (A) for receiving water from the tank system (10) and a second side (B) for receiving pressurised air from outside of the tank system (10) and wherein the air re-fill valve (28) is on the expansion vessel (26).
3. A hot water tank system (10) as claimed in claim 1 and wherein said expansion chamber (26) comprises an external expansion vessel (26) connected to the outlet (16) of the water tank (12) and having a first side for receiving water from the tank system (10) and a second side for receiving pressurised air from outside of the tank system (10) and wherein the air re-fill valve (28) is on the expansion vessel (26).
4. A hot water tank system (10) as claimed in claim 1 and wherein said expansion chamber (26) comprises an expansion chamber (26) within the hot water tank (12) and so having a first side for receiving water from the tank system (10) and a second side for receiving pressurised air from outside of the tank system (10) and an air re-fill valve (28) connected to the expansion chamber (26).
5. A hot water tank system (10) as claimed in any one of claims 1 to 4 and wherein said pressure sensor (30) is connected to the air side of the external expansion vessel (26) for monitoring the pressure of air therein.
6. A hot water tank system (10) as claimed in any one of claims 1 to 5 and further including a comparator (40) for comparing monitored pressure signals received by said pressure monitor (32) and for comparing said signals thereby to determine a change in the pressure signals.
7. A hot water tank system (10) as claimed in claim any one of claims 1 to 6 and including a calculator (50) for receiving monitored pressure signals from said pressure monitor (32) and for calculating a rate of change thereof.
8. A hot water tank system (10) as claimed in claim 7 and further including an estimator (60) for estimating the time remaining before depletion (or volume) of the air supply within the expansion vessel (26).
9. A hot water tank system (10) as claimed in any one of claims 1 to 8 and further including a source of pressurised air (300) connected to the re-fill valve (28) and wherein said re-fill valve (28) comprises a servo valve having an actuator (42) operable to open and close said re-fill valve (28) upon receipt of a control signal.
10. A hot water tank system (10) as claimed in claim 6 and including a remote system monitor (100) and further including a first transmitter (510) for transmitting monitored pressure information to said remote system monitor (100).
11. A hot water tank system (10) as claimed in claim 10 and wherein said remote system monitor (100) includes a second transmitter (520) for transmitting a control signal to the actuator 42 of the re-fill valve (28).
12. A hot water tank system (10) as claimed in any one of claims 1 to 3 or 5 to 11 and wherein said external expansion vessel (26) comprises a closed vessel having a first inlet (261) for receiving water from the water tank (12) and a second inlet (26S) for receiving air from a remote source thereof (300) and a diaphragm (26D) or expandable balloon (26E) within said expansion vessel (26) dividing said expansion vessel (26) into an air side and a water side.
13. A hot water tank system (10) as claimed in claim 12 and wherein said diaphragm comprises a flexible diaphragm.
14. A hot water tank system (10) as claimed in any one of claims 1 to 13 and including a visual indicator (200) for visually indicating information relating to the pressure within the tank (12).
15. A method of operating a hot water tank (10) as claimed in any one of claims 1 to 14 including the steps of: f) monitoring a pressure P within the tank (10); g) comparing said pressure with a pre-defined pressure (PDP); h) calculating the rate of change (ROC) of pressure P; i) estimating the time remaining (TR) before the monitored pressure P reaches said pre-defined pressure (PRP) j) transmitting a signal indicative of the time remaining (TR) to a further device.
16. A method of operating a hot water tank (10) as claimed in claim 15 including the step of receiving a signal indicative of the time remaining on a further device in the form of a remote monitor (100) and creating an action signal (AS) within said remote monitor (100) dependent upon the value of the received signal and transmitting said action signal (AS) to a further device.
17. A method of operating a hot water tank (10) as claimed in claim 15 or claim 16 including the step of transmitting said action signal (AS) to a further device in the form of a visual display apparatus giving an indication of the time remaining before pressure P reaches the pre-defined pressure (PDP).
18. A method of operating a hot water tank (10) as claimed in any one of claims 15 to 17 including the step of transmitting said action signal (AS) to a further device in the form of an actuator (42) connected to a control valve for introducing pressurised air into said air side of said tank (12).