APPARATUS AND CONTROL METHOD FOR A HYBRID TANKLESS WATER HEATER

• US 20100195991A1
• Filed: 01/24/2010
• Published: 08/05/2010
• Est. Priority Date: 02/03/2009
• Status: Active Grant

• Current Assignee: Intellihot Inc.
• Original Assignee: Intellihot Green Technologies, Inc.
• Inventors: Adasam, Sivaprasad, Deivasigamani, Sridhar
• Granted Patent: US 8,498,523 B2
• Time in Patent Office: Days
• US Class Current: 392/308
• CPC Class Codes: F24D 17/0026 with conventional heating means F24D17/0036 takes precedence
• CPC Class Codes: F24D 17/0031 with accumulation of the heated water
• CPC Class Codes: F24D 17/0073 Arrangements for preventing the occurrence or proliferation of microorganisms in the water
• CPC Class Codes: F24D 17/0078 Recirculation systems
• CPC Class Codes: F24D 17/0089 Additional heating means, e.g. electric heated buffer tanks or electric continuous flow heaters, located close to the consumer, e.g. directly before the water taps in bathrooms, in domestic hot water lines
• CPC Class Codes: F24D 19/1036 Having differential pressure measurement facilities
• CPC Class Codes: F24D 19/1051 for domestic hot water
• CPC Class Codes: F24H 1/124 using fluid fuel
• CPC Class Codes: F24H 1/202 with resistances
• CPC Class Codes: F24H 1/52 incorporating heat exchangers for domestic water F24H1/50 takes precedence
• CPC Class Codes: F24H 15/144 Measuring or calculating energy consumption
• CPC Class Codes: F24H 15/156 Reducing the quantity of energy consumed; Increasing efficiency
• CPC Class Codes: F24H 15/238 Flow rate
• CPC Class Codes: F24H 15/31 of valves having only one inlet port and one outlet port, e.g. flow rate regulating valves
• CPC Class Codes: F24H 15/36 of burners
• CPC Class Codes: F24H 9/2021 Storage heaters
• CPC Class Codes: F24H 9/2035 using fluid fuel
• CPC Class Codes: G05D 23/1927 using a plurality of sensors G05D23/1902, G05D23/1917, and G05D23/1919 take precedence
• CPC Class Codes: G05D 23/1931 to control the temperature of one space
• CPC Class Codes: Y10T 137/1244 With freeze waste
• CPC Class Codes: Y10T 137/6579 : Circulating fluid in heat exchange relationship
• CPC Class Codes: Y10T 137/85978 : With pump
• CPC Class Codes: Y10T 137/86389 : Programmer or timer

Abstract

An on demand tankless water heater system that is capable of quickly delivering water within a desired temperature range. The tankless water heater provides a hybrid heating method that contains a primary heating system and a secondary heating system disposed in a buffer tank that cooperate to facilitate control of output water temperature during water usage. A pressure differential switch detects low flow demand and allows the secondary heating system to provide immediate heating to the water. This secondary heating system provides a faster temperature response and fine tuning of output water temperature.

Claims

1. A hybrid tankless water heating system having a system input and a system output and configured to provide a water supply, wherein said hybrid tankless water heating system is housed in an enclosure having a top, comprising a heat exchanger having an input and an output, and a buffer tank having an input and an output, wherein said input of said buffer tank is fluidly connected to said output of said heat exchanger thereby positioning said buffer tank at a downstream location from said heat exchanger.

2. The hybrid tankless water heating system of claim 1, wherein said system further comprises an internal recirculation flow watercourse which fluidly connects said output of said buffer tank to said input of said heat exchanger thereby creating a means for simultaneously circulating water through both said buffer tank and said heat exchanger.

3. The hybrid tankless water heating system of claim 2, wherein said system further comprises an internal recirculation system having a timer integrated therewith such that said internal recirculation system is activated for a predetermined length of time, thereby minimizing a temperature variation and a wait time of said system output water.

4. The hybrid tankless water heating system of claim 1, wherein said system further comprises a differential pressure switch system having a first sensing end and a second sensing end, where said first sensing end is disposed onto said input of said heat exchanger and said second sensing end is disposed onto said output of said buffer tank, whereby said differential pressure switch system is configured to detect low water flow situations.

5. The hybrid tankless water heating system of claim 4, wherein said system further comprises a burner and a differential pressure switch system that is functionally connected to said burner wherein detection of a slight pressure change pre-activates said burner, thereby decreasing a delay associated with water flow type detection.

6. The hybrid tankless water heating system of claim 4, wherein said system further comprises a differential pressure switch control monitor that is functionally connected to a pressure switch system wherein detection of an extended uniform low pressure differential generates an alarm signal.

7. The hybrid tankless water heating system of claim 1, wherein said buffer tank further comprises a thermally insulative material disposed about an outer most portion of said buffer tank, whereby a thermal loss associated with said buffer tank is minimized.

8. The hybrid tankless water heating system of claim 2, wherein said buffer tank further comprises an auxiliary means for heating, whereby said auxiliary means for heating provides an additional thermal energy to increase a heating rate of a water flow of said system output, thereby minimizing a water temperature variation and a wait time of said system output.

9. The hybrid tankless water heating system of claim 8, wherein said auxiliary means for heating is an energy selected from the group consisting of solar energy, geothermal energy, microwave energy and electric energy.

10. The hybrid tankless water heating system of claim 2, wherein said buffer tank further comprises a means for mixing, whereby a substantially uniform temperature is created within said buffer tank, and includes exactly one temperature sensor located within said buffer tank, wherein said substantially uniform temperature of said buffer tank is measured.

11. The hybrid tankless water heating system of claim 1, wherein both said system input and system output are disposed about said top of said enclosure of said hybrid tankless water heating system, thereby streamlining installation and minimizing a pressure loss in an installation having a low-level placement.

12. The hybrid tankless water heating system of claim 1, further comprising an external circulation system, wherein both said system input and system output are fluidly connected to each other via said external circulation system such that said water supply is set in motion for a predetermined length of time, thereby minimizing a water temperature variation and a wait time of said system output.

13. The hybrid tankless water heating system of claim 3, further comprising an antibacterial hot water flush mode feature for said internal recirculation system, wherein said antibacterial hot water flush mode feature sanitizes said water supply.

14. The hybrid tankless water heating system of claim 12, further comprising an antibacterial hot water flush mode feature for said external circulation system, wherein said antibacterial hot water flush mode feature sanitizes said water supply.

15. The hybrid tankless water heating system of claim 1, wherein said hybrid tankless water heating system further includes a means for generating an alarm signal activated by a cooperating sensor, wherein said cooperating sensor is a sensor selected from the group consisting of a moisture sensor, condensate level sensor, and flue gas temperature sensor, thereby providing a means for detecting a plurality of common system problems.

16. The hybrid tankless water heating system of claim 1, wherein said hybrid tankless water heating system further includes a backup power mode, thereby providing limited hot water use and protection against freezing during main power failure.

17. A method for controlling thermal spikes caused by overheating in a water supply of a water supply system, the method comprising the steps of:

providing a tankless water heater having a blower, a heat exchanger and a burner, wherein the burner has a thermal output providing a means for heating the water supply,

providing a means for detecting a decrease in a flow rate of the water supply,

measuring the flow rate of the water supply to detect a decrease in the flow rate, and

activating the blower when a decrease in the flow rate of the water supply has been detected, thereby dissipating excess heat from the heat exchanger to the environment.

18. The method for controlling thermal spikes of claim 17, wherein the method further comprises the step of reducing thermal output of the burner, thereby reducing the thermal energy delivered to the water supply.

19. A method for controlling thermal spikes caused by overheating in a water supply of a water supply system, the method comprising the steps of:

providing a tankless water heater having a blower, a burner, a heat exchanger and an internal circulation system,

providing a means for detecting a decrease in a flow rate of the water supply,

measuring the flow rate of the water supply to detect a decrease in the flow rate, and

activating the internal circulation system when a decrease in the flow rate has been detected, thereby distributing excess heat contained in the heat exchanger over a volume of water contained in the internal circulation system to cool the water supply.

20. The method for controlling thermal spikes of claim 19, wherein the method further comprises the step of activating the blower, thereby accelerating the dissipation of thermal energy of the water supply.

21. The method for controlling thermal spikes of claim 19, wherein the method further comprises the step of reducing thermal output of the burner, thereby reducing the thermal energy delivered to the water supply.

22. A method for controlling thermal spikes caused by overheating in a water supply of a water supply system, the method comprising the steps of:

providing a tankless water heater having a blower, a heat exchanger, a burner and an external circulation system wherein the burner has a thermal output providing a means for heating the water supply,

providing a means for detecting a decrease in a flow rate of the water supply,

measuring the flow rate of the water supply to detect a decrease in the flow rate, and

activating the external circulation system when a decrease in the flow rate of the water supply has been detected, thereby dissipating excess heat from the heat exchanger to the environment.

23. A method for increasing a water supply temperature delivered by a tankless water heater having an output temperature sensor, wherein the water supply temperature is detected by the output temperature sensor, the method comprising the steps of:

providing a user'"'"'s temperature acclimation profile having a plurality of predetermined water supply temperatures over a plurality of predetermined time increments, and

activating a means of adjusting the water supply temperature to the predetermined water supply temperatures at the plurality of predetermined time increments.

24. The method for increasing water supply temperature delivered by a tankless water heater of claim 23, wherein the activating step is manually initiated such that a user input is required.

25. The method for increasing water supply temperature delivered by a tankless water heater of claim 23, wherein the activating step is automatically initiated such that a user input is not required.

26. A hybrid tankless water heating system having a system input for an inlet flow and a system output for an outlet flow, the hybrid tankless water heating system comprising:

a heat exchanger having an input and an output, a buffer tank having an input and an output, and a three way valve having a valve input, a first valve output and a second valve output, wherein

the output of the buffer tank is fluidly connected to the system output,

the input of the buffer tank is fluidly connected to the first valve output of the three way valve,

the second valve output of the three way valve is fluidly connected to the system output,

the output of the heat exchanger is fluidly connected to the valve input of the three way valve, and

the input of the heat exchanger is fluidly connected to the system input; and

wherein the three way valve has a plurality of valve states corresponding to three basic predetermined flow conditions consisting of;

flow from the valve input of the three way valve being entirely directed to the first valve output,

flow from the valve input of the three way valve being entirely directed to the second valve output, and

flow from the valve input of the three way valve being divided between the first valve output and the second valve output in a predetermined ratio.

27. The hybrid tankless water heating system of claim 26, wherein the system further comprises a single pump fluidly connected to the system output disposed at a location that is downstream from both the output of the buffer tank and the second valve output of the three way valve.

28. The hybrid tankless water heating system of claim 26, wherein the system further comprises a flow limiting valve fluidly connected to the system input disposed at an upstream location from both the output of the buffer tank and the heat exchanger such that the inlet flow and the outlet flow is reduced such that a condition where target temperature cannot be achieved due to excessive flow is overcome.

29. The hybrid tankless water heating system of claim 26, wherein the system further comprises a dedicated system water output line having a dedicated water temperature output, and a dedicated three way valve having a dedicated valve output, a first dedicated valve input and a second dedicated valve input, and a controller functionally connected to the dedicated three way valve, wherein

the dedicated valve output of the dedicated three way valve is fluidly connected to the dedicated system water output line,

the first dedicated valve input is fluidly connected to the system input,

the second dedicated valve input is fluidly connected to the system output, and

the controller adjusts the dedicated three way valve such that the dedicated water temperature output is achieved on the dedicated system water output line.

30. The hybrid tankless water heating system of claim 26, wherein the system further comprises an external auxiliary device circuit having

an auxiliary heat sink having an auxiliary heat sink input and an auxiliary heat sink output,

an auxiliary valve having an auxiliary valve output and an auxiliary valve input, and

a controller functionally connected to the auxiliary valve, wherein

the auxiliary valve output is fluidly connected to the system input,

the auxiliary valve input is fluidly connected to the auxiliary heat sink output,

the auxiliary heat sink input is fluidly connected to the system output, and

the controller manages the auxiliary valve such that external recirculation causes a flow from the system output to the system input.

31. A method for controlling a water supply temperature in a hybrid tankless water heating system comprising the steps of:

providing a hybrid tankless water heating system comprising a blower, a burner, a buffer tank and an electric coil,

providing a means for detecting a water flow quantity,

detecting a water flow quantity with said means, and

activating a predetermined heating sequence when a water flow quantity is detected wherein the predetermined heating sequence is associated with a predetermined water flow demand such that the water supply is heated to a target temperature, thereby providing a method of achieving and controlling the target temperature associated with the predetermined water flow demand from the water supply.

32. The method for controlling water supply temperature in a hybrid tankless water heating system of claim 31, wherein the method further comprises the steps of detecting a low flow water flow quantity and activating the electric coil located within the buffer tank when a low flow water flow quantity is detected such that the water supply is heated to the target temperature.

33. The method for controlling water supply temperature in a hybrid tankless water heating system of claim 31, wherein the method further comprises the steps of detecting a high flow water flow quantity and concurrently activating the electric coil located within the buffer tank, the blower and the burner when a high flow water flow quantity is detected such that the water supply is heated to the target temperature.

34. The method for controlling water supply temperature in a hybrid tankless water heating system of claim 31, wherein the method further comprises the steps of:

detecting a medium flow water flow quantity, and when a medium flow water flow quantity is detected, concurrently

activating the electric coil located within the buffer tank,

activating the burner, and

modulating the blower

such that the water supply is heated to the target temperature.

35. The method for controlling water supply temperature in a hybrid tankless water heating system of claim 31, wherein the method further comprises the step of detecting a low flow water flow quantity, and when a low flow water flow quantity is detected, modulating the burner such that output of the burner is frequency modulated.

36. A method for reducing natural gas consumption in a hybrid tankless water heating system to avoid a gas over-demand situation, comprising the steps of:

providing a hybrid tankless water heating system comprising a burner having a gas consumption rate and at least one gas pressure sensor adapted to measure available gas pressure supplied to the burner,

measuring the available gas pressure using the gas pressure sensor to detect a potential a gas over-demand situation by comparing the available gas pressure to a predetermined gas over-demand threshold, and

reducing the gas consumption rate of the burner by predetermined levels when a potential gas over-demand situation is detected such that the gas consumption rate of the burner avoids the gas over-demand situation.

37. A method for producing a water output at a substantially constant predetermined temperature during an abrupt increase in water demand corresponding to a demand operating capacity, the method comprising the steps of:

providing a tankless water heating system that includes an output temperature sensor for measuring a water output temperature, an input temperature sensor for measuring a water input temperature, a flow sensor for measuring a flow rate, a water flow limiting valve, and a controller functionally connected to the water flow limiting valve, the output temperature sensor, the input temperature sensor, the flow sensor wherein the tankless water heating system is adapted to provide an operating capacity corresponding to the difference between the predetermined temperature and the water output temperature, the difference between the water output temperature and the water input temperature and the flow rate, wherein the controller compensates for a water output temperature that is lower than the predetermined temperature by producing a level of restriction at the water flow limiting valve,

measuring the water output temperature,

adjusting the water flow limiting valve when the operating capacity is lower than the demand operating capacity to reduce the water output such that the water output temperature is maintained substantially constant at the predetermined temperature, and

adjusting the water flow limiting valve when the operating capacity is equal or higher than the demand operating capacity to increase the water output at a rate such that the water output temperature is maintained substantially constant at the predetermined temperature,

thus resulting in the water output having a substantially constant temperature.

38. A method for updating a default schedule of operating points for use in a hybrid tankless water heating system, the method comprising the steps of:

providing a hybrid tankless water heating system comprising a blower monitor for determining a blower speed and a means for determining a burner heat output value, a controller functionally connected to said blower monitor and said means for determining said burner heat output value and said default schedule of operating points having a plurality of default burner heat output and blower speed value pairs stored in a memory of said controller;

creating a hot water demand in the system to generate a new operating point having a new burner heat output value and a new blower speed in order to form a new burner heat output and blower speed value pair;

identifying a position of said new operating point within said default schedule of operating points by comparing said new burner heat output to said plurality of default burner heat output values of said default schedule of operating points;

selecting at least two participating operating points from said default schedule of operating points by identifying at least two default operating points adjacent to said position of said new operating point;

obtaining a first ratio by dividing the difference between said new burner heat output value and said burner heat output value of a first participating operating point of said at least two participating operating points by the difference between said burner heat output value of a second participating operating point of said at least two participating operating points and said burner heat output value of said first participating operating point;

obtaining a second ratio by dividing the difference between said new blower speed and said blower speed of said first participating operating point by the difference between said blower speed of said second participating operating point and said blower speed of said first participating operating point;

obtaining an absolute difference between said first ratio and said second ratio; and

comparing said absolute difference to an acceptance threshold, whereby if said absolute difference is greater than said acceptance threshold, said new operating point will be discarded and if said absolute difference is less than said acceptance threshold, said new operating point will be inserted into said default schedule of operating points.