Apparatus and control method for a hybrid tankless water heater

• US 8,498,523 B2
• Filed: 01/24/2010
• Issued: 07/30/2013
• Est. Priority Date: 02/03/2009
• Status: Active Grant

• Current Assignee: Intellihot Inc.
• Original Assignee: Intellihot Inc.
• Inventors: Deivasigamani, Sridhar, Akasam, Sivaprasad
• Primary Examiner(s): CAMPBELL, THOR S
• Application Number:
  US12/692,628
• Publication Number:
  US 20100195991A1
• Time in Patent Office: 1,283 Days
• Field of Search: None
• 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: 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 and comprises:

a heat exchanger having an input and an output,

a buffer tank having an input and an output,

an internal recirculation flow watercourse,

a pump,

a modulating valve,

a main flow path having an inlet and an outlet, wherein said main flow path outlet is connected to said system 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, and said internal recirculation flow watercourse fluidly connects said main flow path inlet and said main flow path outlet, creating a means for simultaneously circulating water through both said buffer tank and said heat exchanger as modulated by said modulating valve and all of said heat exchanger, said buffer tank and said pump are fluidly disposed on said main flow path.

2. The hybrid tankless water heating system of claim 1, 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.

3. 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.

4. The hybrid tankless water heating system of claim 1, 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.

5. 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.

6. 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.

7. 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.

8. The hybrid tankless water heating system of claim 1, 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. 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 differential pressure switch system having a first sensing end and a second sensing end;

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, and 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.

11. The hybrid tankless water heating system of claim 10, 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.

12. The hybrid tankless water heating system of claim 10, 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.

13. 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;

a buffer tank having an input and an output;

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;

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; and

an antibacterial hot water flush mode feature for said internal recirculation system,

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, and said antibacterial hot water flush mode feature sanitizes said water supply.

14. 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:

an external circulation system;

an antibacterial hot water flush mode feature for said external circulation system;

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, 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, and said antibacterial hot water flush mode feature sanitizes said water supply.

15. 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 means for generating an alarm signal activated by a cooperating sensor;

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, and 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. 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.

17. The hybrid tankless water heating system of claim 16, 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.

18. The hybrid tankless water heating system of claim 16, 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.

19. The hybrid tankless water heating system of claim 16, 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.

20. The hybrid tankless water heating system of claim 16, 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.