System and method for indirectly metering hot water consumption

Abstract

A system and method for metering hot water consumption individually in an apartment building using a centralized hot water supply. The system comprises a separate hot 10 and cold water 12 supply line,

Description

Field of the Invention This invention relates to water metering systems, particularly to an improved system and method for indirectly metering hot water consumption in centralized hot water supply systems using a water meter in the cold water line Background of the Invention Conventional methods of metering hot water consumption often require separate meters and complex plumbing arrangements, especially in systems with centralized hot water supply. This invention simplifies the metering of hot water by using the already present cold water supply meter as a proxy, leveraging a controlled return line mechanism. The system is particularly useful in jurisdictions where sub-metering by private entities is restricted due to regulatory, consumer protection, or billing transparency concerns. Summary of the Invention The invention provides a system and method for metering the hot water consumption of individual apartments in buildings with a centralized hot water supply. The key innovation lies in injecting cold water into the hot water return line in proportion to the hot water consumed, thereby enabling the calculation of hot water usage based on readings from the cold water meter. The hot water return line is regulated using a Pressure Independent Control Valve. Advantages • Eliminates the need for separate hot water meters for every apartment • Useful in jurisdictions where sub-metering by private entities is restricted due to regulatory, consumer protection, or billing transparency concerns. • Uses existing domestic water utility-meter and reduces cost and complexity of hot water metering • Maintains proper circulation in the hot water system • Ensures constant return flow volume to the central hot water system • Prevents backflow with strategically placed check valves The invention will now be described by referring to the accompanying drawing: Fig. 1 - Schematic of a hot water metering system using cold water injection Detailed Description Referring to the Fig. 1, the system comprises the following components: • A hot water supply line (10) from a central hot water supply system. • A cold water supply line (12). • A branch line (8) connecting from the hot water supply line (10) at junction point (6) to the flow switch (24). • A hot water outlet (14) for end-user consumption. • A hot water return line (16) directing water back to the central hot water supply system. • A check valve (20) positioned on the hot water supply line (10). • A first connecting pipe (28) between the check valve (20) and the junction point (34). • A water meter (26) installed on the cold water supply line (12). • A solenoid valve (22) installed immediately after the cold water meter (26). • A second check valve (32) positioned downstream of the solenoid valve (22). • A second connecting pipe (30) between the check valve (32) and the junction point (34). • A pressure independent control valve (18) positioned to regulate the hot water return flow. • A flow switch (24) installed on the branch line (8) near the hot water outlet (14). • A junction point (34) where the first and second connecting pipes meet upstream of the pressure independent control valve (18). The operation is as follows: 1. Hot water from the central supply flows through supply line (10), reaches the first junction point (6), and branches through line (8) to the flow switch (24). 2. Cold water enters the system from the utility provider's supply (12) and passes through the cold water meter (26). 3. When there is hot water demand at the outlet (14), the flow switch (24) detects this demand via the branch line (8) and triggers the control logic; and 4. The solenoid valve (22) opens allowing cold water to flow through the meter and into the return line. 5. Cold water flows through water meter (26), through the solenoid valve (22), and through the check valve (32) and connecting pipe (30) toward the second junction point (34) and into the return line. 6. The check valve (20) prevents hot water from flowing backward through the connecting pipe (28) during this process. 7. The cold water flow is directed through the pressure independent control valve (18) and into the hot water return line (16). 8. The pressure independent control valve (18) ensures that the volume of water returning to the central hot water supply system remains constant at all times. This constant return flow is critical for maintaining system balance and enables the cold water meter (26) to accurately reflect hot water consumption at outlet (14). 9. The hot water return line (16) directs water back to the central hot water system at this constant volume. 10. When there is no hot water demand, the solenoid valve (22) closes. Hot water circulates through the check valve (20), first connecting pipe (28), second junction point (34), and back through the return line (16), maintaining the same constant return volume regulated by the pressure independent control valve (18). 11. A slightly lower pressure is maintained in pipe (30) relative to pipe (28) to facilitate directional flow control and ensure that hot water return flow via the main circulation loop is prioritized. 12. The check valves (20, 32) prevent backflow and ensure proper direction of water flow throughout the system. 13. The water meter records cold water usage during hot water consumption.

Claims

1. A system for metering hot water consumption, comprising:• a hot water supply line (10) connected to a central hot water supply system;• a cold water supply line (12) connected to a utility provider;• a first junction point (6) where said hot water supply line branches;• a branch line (8) connected to said first junction point;• a hot water outlet (14);• a flow switch (24) positioned on said branch line near said hot water outlet;• a water meter (26) installed on said cold water supply line;• a check valve (20) positioned on said hot water supply line after said first junction point;• a solenoid valve (22) positioned on said cold water supply line after said water meter;• a check valve (32) positioned after said solenoid valve;• a first connecting pipe (28) connected to said check valve (20);• a second connecting pipe (30) connected to said check valve (32);• a second junction point (34) where said first connecting pipe and said second connecting pipe meet;• a pressure independent control valve (18) connected to said second junction point; and• a hot water return line (16) connected to said pressure independent control valve and returning to said central hot water supply system.

2. A method of metering hot water usage comprising:• detecting hot water demand using a flow switch (24) positioned on a branch line (8) near a hot water outlet (14);• opening a solenoid valve (22) on a cold water supply line (12) in response to said detected demand;• measuring cold water flow through a water meter (26) on said cold water supply line;• directing said measured cold water through a check valve (32) and a second connecting pipe (30) to a junction point (34);• directing water from said junction point through a pressure independent control valve (18); and• returning a volume of water equivalent to the consumed hot water to a central hot water system via a return line (16).

3. The system of claim 1, wherein said pressure independent control valve (18) maintains a constant volume of water returning to the central hot water supply system at all times.

4. The system of claim 1, further comprising a control unit configured to operate said solenoid valve based on signals received from said flow switch.

5. The method of claim 2, wherein the pressure independent control valve (18) ensures that the volume of cold water measured by the water meter (26) equals the volume of hot water consumed at the outlet (14).

6. The system of claim 1, wherein the check valves (20, 32) prevent backflow and ensure proper direction of water flow throughout the system.

7. The system of claim 1, wherein the branch line (8) directs hot water from the hot water supply line (10) to the flow switch (24) and subsequently to the hot water outlet (14).

8. The system of claim 1, wherein during periods of no hot water demand at the outlet (14), the solenoid valve (22) is closed and hot water circulates through the check valve (20), the first connecting pipe (28), the pressure independent control valve (18), and back through the hot water return line (16).

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