Technical Field

1. The present technology relates generally to a metering device used to meter individual hot water usage in buildings with a centralised hotwater system.

Background

2. Hot water circulates in high rise buildings; vertically, by use of riser pipes.

3. From a main riser, branch pipes are taken off on each floor to reticulate hot water to the apartments located on that floor. Depending on the design of the building, the hot water may also be circulated horizontally on each floor. This is done to provide hot water as close as possible to each apartment, which reduces the time taken for hot water to be delivered to a tap fixture inside the apartment, as well as reducing water wastage when a user turns on the tap.

4. In most residential buildings, at a selected location in the hot water circulating system, a hot water meter is installed, as close as possible to an apartment, to measure the consumption of hot water by that device. This allows consumption of that hot water to be billed accordingly.

5. However, since the hot water meter is installed outside the apartment, and far from the outlet of any tap inside the apartment, a dead leg is created. A dead leg is the length of pipe measured from the hot water circulation loop to the end fixture. Usually the water in the dead leg is wasted because it is cold; also, it has been charged as hot water, but as mentioned, it was delivered cold. The location of the meter, being outside, generally inhibits the ability to continue circulating hot water into the apartment, because any water flowing through the meter is charged as consumption. Depending on the building design or utility guidelines, the location of the hot water meter may result in excessively long dead legs which may create unacceptably long delays of waiting for hot water delivery.

6. Faced with these issues, one of the options is to increase the number of risers (if centralising meters in cupboards). But this may significantly increase costs and reduce saleable real estate.

7. Another option is to move the hot water meter closer to the apartment if the utility allows it. However, in some circumstances there are fixtures on the far side of the apartment that still may have long delivery times for hot water. It also may be useful to install electric heat trace to maintain temperature in these dead legs. Heat trace is an electrical heating element run in physical contact along the length of a copper pipe to maintain the temperature of the hot water resting in a dead leg. There is a meter system which is known, that uses two meters, being a primary and a secondary meter. The primary meter is disposed on a flow or inlet water line. The secondary meter is disposed on a return water line. It works by reading pulses from the primary metering device, to record a measured flow to a memory, storage area, or register. Return pulses are also read from the secondary metering device, and any of these will ‘cancel’ the next pulse that is read from the primary device. Thereby the register will only ever read pulses from the primary metering device that have not been cancelled. In other words, it will only read the differential measurement between the two meters. When applied to a hot water circulating system, any water circulating through the primary metering device (supply side adding water meter) will also flow through the secondary metering device (returning side subtracting water meter). Assuming that no water is drawn off from the metered zone, then the pulses from each meter will be equal and the net consumption recorded, and actual, is zero. When hot water is drawn off from the metered zone, there will be a combination of circulating water and fixture draw off water that is being counted by the primary meter, however, water that is circulated and returned back through to the hot water plant via the secondary meter will be ‘subtracted’ from the primary meter and therefore will result in the meter showing the differential of the two meters which is the consumption drawn from the fixture. Due to the type of mechanical hot water meter usually being used, there is an inaccuracy of these meters of +/-3%. This inaccuracy sounds trivial, but such an inaccuracy during constant circulation could mean that over 100L a day is recorded as consumption, when in fact no water has been drawn off. 13. The present inventor seeks to provide a new apparatus which seeks to ameliorate one or more of the abovementioned disadvantages, and/or which at least provides a useful alternative to known measuring systems.

Summary

14. Broadly, the present technology provides a metering device or system configured to measure hot water in a recirculating hot water circuit and which, in operation, effectively takes into account re-circulating water in a calculation of consumption.

15. Also broadly, the present technology provides a method of metering hot water in a recirculating hot water circuit with at least two meters, which provides metered flow results optimised for an accuracy of one or more of the meters.

16. In accordance with one aspect of the present invention there is provided a method of metering hot water using at least two meters, each disposed in a recirculation loop, the method including the steps of: performing in a computing processor, an assessment process, which includes:

(a) Receiving a first pulse data element from a first meter;

(b) Receiving a second pulse data element from a second meter;

(c) Assessing the simultaneity of the first and second pulse data elements against a selected time period; and then either of the following two steps:

(d1 ) Cancelling the first and second pulse data elements if the first and second pulse data elements are separated in time by more than the selected time period; or

(d2) Recording a usage flow data element indicative of real usage if the first and second pulse data elements are separated in time by less than the selected time period.

17. The selected time period is based on the pulse rate of one or more metering devices, the circulation flow rate in the water provision system, and the accuracy of one or more metering devices.

18. In some embodiments, the processor calculates the selected time. In one embodiment, cancelling the first and second pulse data elements may be done by outputting a signal that does not include the first and second pulse data elements. In one embodiment, cancelling the first and second pulse data elements may be done by changing the state of a portion of a state machine. In one embodiment, recording the usage flow data element may be done in part by changing the state of a state machine. In one embodiment, the usage flow data element is indicative of real usage (as opposed to inaccurate measurements due to meter inaccuracies). In one embodiment, recording may be recording to memory, such as to a register, memory, storage, and/or outputting to an output device such as a display or transmitting to a portion of a processor such as a mobile device or other device. In one embodiment the method further includes the step of resetting the assessment process by discarding the first and second pulse data elements from the assessment process inputs in the processing module. In one embodiment, the processor is a state machine. In one embodiment, the resetting step includes changing the state of the state machine. In accordance with one aspect of the present invention there is provided a method of metering hot water using at least two meters, each disposed in a recirculation loop, the method including the steps of: in a computing processor, providing an assessment engine configured to perform an assessment process, which includes: receiving a first pulse signal having a first pulse data element and a second pulse signal having a second pulse data element;

(a) Assessing the simultaneity of first and second pulse data elements against a selected time period; and then either of the following two steps: (b1) Cancelling the first and second pulse data elements, by removing the first and second pulse data elements from the assessed pulse signals, if the first and second pulse data elements are separated in time by more than the selected time period; or

(b2) Recording a usage flow data element, indicative of water usage and based on the first and second pulse data elements, if the first and second pulse data elements are separated in time by less than the selected time period. In one embodiment the method includes the step of:

Receiving a differential pulse data element which represents a time period between a first and a second pulse data elements, being two adjacent pulses from the two meters. In one embodiment the method includes the step of conducting a setup process before step (a) of the assessment process which includes:

(x) receiving a count indicator data element from the first meter;

(y) providing the first pulse data element to the assessment process if the state of the count indicator data element is ON; or

(z) changing the state of the count indicator data element to ON if the state of the count state indicator data element is OFF. In one embodiment the method includes the step of causing one or more usage flow data elements to be displayed on a display. In one embodiment the method includes the step of receiving from a network card or wireless input, usage data elements from a water outlet leg and/or tap fitting for relay to the processor data input. In one embodiment the method includes the step of discarding the first and second pulses from a processor memory if the time elapsed between the first and the second pulses is greater than the threshold time. In one embodiment the method includes the step of calculating or setting the time elapsed or threshold time based on the combined accuracy of the first and second meters. In one embodiment the method further includes the step of calculating or setting the time elapsed or threshold time based on the flow rate in the circulating water circuit. In accordance with another aspect of the present technology there is provided a metering device for measuring flow in a circulation loop, the circulation loop including first and second flow meters, the device including: a processor including a processor data input port in electrical communication with first and second meter data output ports; and a processor data output; the processor configured to provide a setup module and an assessment module, wherein the setup module is configured to provide first and second offset meter pulse data to the assessment module for assessment against a threshold to assess whether a flow data element relates to an inaccuracy or real flow. In one embodiment the processor is a state machine which is adapted to change logic states depending on an input received. In one embodiment the metering device includes a display for displaying the output of the processor data output. In one embodiment the meters generally provide a pulse output. In one embodiment the metering device includes a network card or other wireless input for receiving consumption data from a water outlet leg or tap fitting for relay to the processor data input. In one embodiment the metering device includes a housing for housing the first and second meters and the processor. In one embodiment the display is mounted on the housing for local verification of flow measurement. In one embodiment there is provided onboard power for the processor and/or first and second meters. In one embodiment the method includes the step of discarding the first and second pulses from the processor memory if the time elapsed is greater than the threshold time. In one embodiment the method includes the step of calculating or setting the time elapsed or threshold time based on the combined accuracy of the first and second meters. In one embodiment the method further includes the step of calculating or setting the time elapsed or threshold time based on the flow rate in the circulating water circuit. In accordance with another aspect of the present technology there is provided a metering device for measuring flow in a circulation loop, the circulation loop including first and second flow meters, the device including: a processor including a processor data input port in electrical communication with first and second meter data output ports; and a processor data output; the processor configured to provide a setup module and an assessment module, wherein the setup module is configured to provide first and second offset meter pulse data to the assessment module; and wherein the assessment modules is configured to execute an assessment process, which includes:

(a) Assessing the simultaneity of first and second pulse data elements against a selected time period; and then either of the following two steps:

(b1 ) Cancelling the first and second pulse data elements, by discarding the first and second pulse data elements from a processor memory or by changing a processor state, if the first and second pulse data elements are separated in time by more than the selected time period; or

(b2) Recording a usage flow data element, indicative of water usage and based on the first and second pulse data elements, if the first and second pulse data elements are separated in time by less than the selected time period, thereby assessing whether a flow data element relates to an inaccuracy or real flow. Clarifications

47. In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date:

(a) part of common general knowledge; or

(b) known to be relevant to an attempt to solve any problem with which this specification is concerned.

48. It is to be noted that, throughout the description and claims of this specification, the word 'comprise' and variations of the word, such as 'comprising' and 'comprises', is not intended to exclude other variants or additional components, integers or steps.

Brief description of the drawings

49. To enable a clearer understanding the technology, a preferred embodiment of the technology will now be further explained and illustrated by reference to the accompanying drawings, in which:

50. Figure 1 is a schematic of a conventional centralised hot water system for a building, which also shows a metering device of an embodiment of the present invention;

51 . Figure 2 is a schematic of the internal modules in the metering device;

52. Figure 3 is a trace of meter pulse data elements from meters shown in Figure 1 , and a trace of an output from a pulse cancelling module in the device of the present technology;

53. Figure 4 is a flowchart of the steps taken in the processing modules of an embodiment of the device of the present technology;

54. Figure 5 is a state diagram illustrating the operation of the metering device; and Figure 6 is a flow diagram of method steps in accordance with an embodiment of the technology. s

Detailed description of an embodiment

HOT WATER FLOW to Device 1 Referring to the drawings, in Figure 1 there is shown a conventional centralised hot water supply to apartments in a building, shown as units 1 , 4 and 7. The proposed system of the present technology is shown metering water to Device 1. A building circulation loop 12 is shown supplying hot water to the building, which reticulates through hot water meter cupboard riser 9. A device circulation loop 8 extends from meter cupboard riser 9 to Device 1 shown for unit 1 10. There is a supply leg 11 , called the dead leg, which extends to various water fittings (not shown) in Device 1. The device circulation loop 8 is hot, but since there is not always flow in dead leg 11 that water in the dead leg is cold. Extending the circulation loop 8 as close as possible to the fittings (not shown) then, when a person wants hot water from the fittings in Device 1 , they waste as little cold water as possible. This is important because the water in the dead leg 11 is billed as hot water. Turning to Figure 2, there is a schematic view of the device 2 of the present technology. There is a processor which is configured to receive pulse data from the flow meters 1 and 4 through input ports 1a and 4a. The processor may comprise one or more processing modules, for example one or more microprocessors, microcontrollers, DSP’s, discrete components such as logic gates, and/or FPGA’s. In some embodiments the processing modules may be provided by a single physical processor. The first processing module to process the flow pulse data is a pulse cancellation processor model 19. This PCP module 19 inhibits any pulse data leaving the PCP module 19 if the flow pulse data from meters 1 and 2 are received within a predetermined or selected time period or threshold of one another. This is effectively a cancellation of the pulse data if there is no flow in the dead leg. To be clear, if there is simple recirculation in device loop 8, 14, then there should be cancellation of the two meter pulses 1 and 4 into ports 1 a and 4a. If there is usage or if there is an inaccuracy in the meters, then there will be an imbalance in the meter pulse data and the PCP will record a differential pulse (shown at 18 in Figure 3). The first processing module 19 outputs the first and second pulse data elements to a subsequent processing module and/or a memory element (e.g. a register, memory, storage, etc.) if the first and second pulse data elements are separated in time by less than the selected time period. The first processing module 19 outputs a signal to the subsequent processing module and/or the memory element that does not include the first and second pulse data elements if the first and second pulse data elements are separated in time by more than the selected time period. A second assessment module is provided at 20, called the Time Assessment Manager (TAM). This module 20 is in data communication with the PCP 19, such that data flows from the PCP 19 to the TAM 20 wirelessly or in a wired way, or by PCB tracks, or within the processor itself. Together, the TAM 20 and Logic Processor 21 are configured to check whether any differential pulses that are received from the PCP module 19 relate to real usage, or to other factors such as meter inaccuracy as follows: The TAM 20 is configured to commence a timer on receipt of a differential pulse and then wait for another differential pulse to arrive from the PCP 19. On receipt of another differential pulse from the PCP 19, the TAM 20 sends time differential data to the Logic Processor 21 . If the time differential is greater than a selected threshold, then the second pulse is discarded, but if the time differential is below a selected threshold, then a flow data element indicative of real usage is (or can be) recorded in a memory (not shown) as usage at 22. The flow data element can be transmitted to a billing module in real time or temporarily stored and transmitted later. The LP 21 is guided by an algorithm which is discussed below, which provides the size of the threshold against which it makes its assessment. Metering hot water in the dead leg 11.

65. In operation, hot water for apartment 1 (10) will flow from the building circulation loop 12 into hot water meter 1 , shown at 4. That meter 4 generates a pulse which is transmitted to the metering device 2 of the present technology.

66. Hot water will then flow through the device circulation loop 8, first through Hot Water leg 13. The hot water then circulates, counterclockwise, in the direction of the arrow, through the hot water return line 14 into Hot Water Meter 2 shown at 1. That meter 1 generates a pulse which is then transmitted to the metering device 2 of the present technology.

67. Hot water will then exit HWM 2 1 , into the building circulation loop 12 through balancing valve 15.

68. While the water is flowing in the hot water circuit 8, 14, the present technology accurately measures water flow through dead leg 11 and into apartment 1 shown at 10, without measuring recirculating water in the circuit 8,14. That process is set out below.

69. The general principle is that, since the flow meters 1 and 2 have inherent inaccuracies, those inaccuracies can be accounted for in a processor by being aware of, among other things, the baseline flow rate in the device recirculating circuit loop 8, 14.

70. In Figure 3, the pulses 16 and 17 that are sent from meter 4 and meter 1 will be continuously counted by the processor of device 2 in real time, and the pulses themselves will be continuously subtracted from one another using a method of pulse cancellation. In a perfect world (perfect accuracy of the meters), without any use of hot water from dead leg 11 , and using meters 1 and 4, the pulse cancellation signal 18 using those two meters will be zero.

71 . To be clear, the only time that pulse cancellation signal 18 will be non zero is:

1. if there is an inaccuracy in either one of the meters 1 and 4, OR,

2. if there is use of hot water from dead leg 11 .

72. In the case of use of hot water in dead leg 11 , the reason for the non zero pulse cancellation signal 18 is that there is more water flowing in leg 13 than in leg 14. Operation - advantages

73. One of the advantages of the system and device is that the pulse meters 1 ,4, are relatively inexpensive. Because they are fairly cheap, the readings are subject to a fairly wide window of inaccuracy. When they are coupled together in the way described herein, over time, there can be large drift errors introduced. This can lead to the user being charged for water which was not used. Rather than using a flow meter in the dead leg, this method of certain embodiments, using an algorithm based on flow rate and inaccuracy, to assess whether the flow pulse data should be discarded or retained, is very useful.

EXAMPLE - using a time window threshold for recording differential pulses.

74. A method of one embodiment provides a more accurate result, by using a threshold time that is set or calculated in the processor in accordance with the accuracy of the meters themselves. The meter arrangement is shown in Figures 7 and 8. The operation of the meter arrangement is shown in the state diagram in Figure 5, where the operation of meter 1 is shown at 90 (flow meter) and the operation of meter 2 is shown at 92 (return meter).

75. The method retains usage data elements, (being differential pulse data that occurs within a selected time threshold), and adds them together to form a total amount of fluid consumed, for transfer to a billing system via a network module. Any differential pulses that are assessed as being apart by more than a selected time period are not included in the calculation because that indicates to the processor that there was no takeoff from the delivery leg (ie the same amount delivered was returned), taking into account the inaccuracy of the meters.

76. The method includes, using at least two meters, each disposed in a recirculation loop, and using a computing processor to execute the steps of, as shown in Figure 6: providing an assessment engine that performs an assessment process, which includes:

(a) Step 500. Assessing the simultaneity of the first and second pulse data elements against a selected time period; and then either of the following two steps: (b1) Step 510. Cancelling the first and second pulse data elements if the first and second pulse data elements are separated in time by more than the selected time period; or

(b2) Step 520. Recording a usage flow data element if the first and second pulse data elements are separated in time by less than the selected time period. To calculate the selected time period, the computing processor is provided with an algorithm. First, the processor undergoes a setup process, below, set out under the heading On/Off state logic. PULSE COUNTING PROCESS

ON I OFF STATE LOGIC

If Meter 1 Pulse

Check count state

If count state = ON

Send differential pulse to time threshold logic

If count state = OFF

Change count state to ON

If Meter 2 Pulse

Change count state to OFF

TIME THRESHOLD LOGIC

Receive Differential Pulse

Check time between last differential pulse received

If time is < T

Output pulse signal

If time is => T

Discard value as inaccurate reading Time Formula T = K/ Q / (2 x A)

T = time in minutes

K = pulse rate of metering device, e.g. 10L per pulse Q = litres per minute (circulation flow rate) A = accuracy of measuring device (2x3% = 0.06) In accordance with the algorithm, the processor is provided with a circulation flow rate in the device circulation loop 8, 14 ( Figure 1). Let’s say it is 0.031/s. This may be done by a user input device such as a keyboard or touch screen after a display screen prompt, or other input device such as a microphone or other keys. The circulation flow rate in loop 8, 14 could also be pre-programmed onto the processor. A three-position switch could also be used to set the circulation flow rate to which the processor will accurately respond. The processor is then provided with data relating to the inaccuracy of the meters, which at a flow rate of 0.031/s as given in the example, is 3%. Again, as above, this could be input by a suitable user input device such as a keyboard, touch screen or microphone, or it could be pre-programmed onto the processor / chip I firmware. Then, the processor is provided with a meter litre count per pulse which in this case is 10L. Again, this can be via keyboard, touch screen or microphone, or it could be pre-programmed onto the processor/chip/firmware. Then, in accordance with the algorithm programmed into the processor, the interim solution is reached by finding a flow rate in different units:

0.031/s x 60 = 1.81/min

If each flow data pulse is provided by the first and second meters every 10L of fluid then it will take 10/1.8= 5.55 minutes for a pulse from the first and second meters.

Based on the combined inaccuracy (2 meters) of 6% (5.55 minutes/6%) it will take 92.6 minutes to reach 10L differential pulse at that specified accuracy

Therefore, on the one hand, if the reading of a differential pulse takes less than (<) 92.6 minutes, then the differential pulse data is recorded as water usage and the timer is reset.

On the other hand, if a differential pulse data packet takes more than (>) 92.6 minutes to be received, then the pulse is discarded and the timer is reset.

By doing this the inventor has fixed the inaccuracy to an average of 3%. This inaccuracy is within an acceptable range for a hot water metering system in Australia. The circulating flow rate in the reticulation system can be varied from 0.01 , to 0.02, to 0.03, to 0.04, to 0.05, to 0.06, to 0.07, to 0.08, to 0.09, to 0.1 L/s, all the way up to 0.2 or 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.1 L/s or 1 l/s for more industrial uses. The accuracy of the first and second meters can be between 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, or 20% and still provide useful results. The time window could be between 5mins, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 75, 80, 85, 90, 95, 100, 110, 115, 120, 125, 130, 145, 150, 200. The time window can be processed on a spreadsheet. In some embodiments, the processor could include one or more of a state machine, a mobile device, or it could be a PLC, or a raspberry pi, or arduino or other suitable processor. The processing could be done on board the processor, or the data could be sent by a network module to another processor linked by a network, wirelessly or by wires. At the end of a selected billing cycle, measured in days or weeks or months, the method includes the steps of adding together the recorded differential pulses to form a total fluid consumption and transmitting the to a billing module for billing to a client. The method described above is shown in a schematic state diagram in Figure 5. First, the state flow of the setup process is shown. The processor is reset. Then when a pulse from the flow meter 90 is detected, (Ch1 inc) the timer 1 and 2 is initiated. A schedule time is recorded and a differential time is recorded. This is point 1 on Figure 5. Then, the count state is checked. If Ch1 increases by 1 , then the meter sends the differential pulse data to the assessment engine. Alternatively, if not timer 1 timeout, then Ch1 diff++. Always init Timer 1 : Schedule time + differential time. This is just the same as, above, where the count state is checked:

If count state = ON

Send differential pulse to time threshold logic If count state = OFF

Change count state to ON

If Meter 2 Pulse

Change count state to OFF Then, the assessment engine assesses the simultaneity of the pulses from meter

1 and meter2 and the meters are reset and their count state is appropriately set. The assessment is performed in the engine as above described. Put another way, in broad terms, a state machine will always be in a state, as defined by the programmer. In the instance of the embodiment discussed herein, the differential pulse counter, this is defined in Figure 5 with the 0 initial state and will then transition into one of the 4 other states depending on the external input received from the pulse meters (ie channel 1 or channel 2 pulses). Depending on what state it is currently in and what input is received, the state machine will execute an action or transition to another state. The way the state logic cancels pulses is by moving from one state to another during normal circulating flow as the meters are pulsing at similar alternating intervals, thereby not counting a pulse during the process. For example, if the state machine was in State 1 (looking at the Figure 5 diagram) and receives a channel

2 pulse, it then goes to State 3. If the next input is a channel 1 pulse, it will go back to Sate 1 , and so on. In this way, no flow is recorded or a differential pulse being output from the machine and essentially has cancelled the pulse. If the state machine was in State 1 and because someone is using the shower there will be more pulses from the Channel 1 meter, therefore the next external input will be from the channel 1 meter again. The state machine moves to state 2, executes the algorithm, (assessing the simultaneity of the pulses according to the time comparison) which tells the machine to output a pulse. Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.