Ultra-low flow electric tankless water heater

An electric tankless water heater for heating a continuous supply of water. The electric tankless water heater includes a heater assembly having a water inlet, a water outlet and a heating chamber defining a water flow path there between. A flow sensing device is coupled to the water flow path and configured to detect an ultra-low flow condition of water within a heating chamber of the heater assembly. In response to the detection of an ultra-low flow condition, or higher flow conditions, a controller regulates the amount of electrical current flowing through to achieve the desired temperature of water at the water outlet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure generally relates to an electric tankless water heater. More specifically, the present disclosure relates to an ultra-low flow electric tankless water heater system.

2. Description of Related Art

Tankless water heaters are used to increase the temperature of water supplied from a water source. Such water heaters often include an inlet, an outlet, a conduit for transporting water from the inlet to the outlet, and at least one heater element for increasing the temperature of the water prior to the water exiting the outlet.

In order to achieve a desired temperature of water exiting the outlet, it is often necessary to control the electrical energy supplied to one or more heater elements. The heating element(s) must be of sufficient wattage to maintain the desired outlet water temperature at the maximum flow rate of the tankless water heater. Obviously, if the wattage is insufficient, the temperature of water provided at the maximum flow rate will not be the desired temperature. However, with high wattage heating element(s), supplying hot water at very low flow rates is not possible without the risk of overheating the tankless water heater. For this reason, the heating element(s) is not activated until a minimum flow rate is detected. This minimum flow rate is, accordingly, a flow rate at which overheating will not occur based on the wattage of the heating elements and/or the control thereof.

Detecting low flow rates also has its own difficulties. Typically, expensive and complicated flow sensors are required.

While existing electric tankless water heaters have proven acceptable for their intended purpose, a continuous need for improvement remains in the relevant art.

BRIEF SUMMARY

In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present disclosure provides an electric tankless water heater with ultra-low flow activation, and more specifically, one with a reliable and cost effective flow sensing device that can detect ultra-low flow. In accordance with the present invention, ultra-low flow activation (such as 0.1 to 0.3 gallons per minute (GPM)) can be achieved without requiring an expensive and/or complicated flow sensor.

In one aspect, the invention provides a tankless water heater for heating a continuous supply of water. The tankless water heater includes a heater assembly having a water inlet, a water outlet and a heating chamber including a housing defining a water flow path between the water inlet and the water outlet. A temperature sensor is configured to measure the temperature of water flowing through the heating chamber of the heater assembly. A flow sensing device is configured to measure a flow condition of water through a flow path within the heater assembly. The flow sensing device includes a sensing chamber coupled to the flow path and configured to induce a relative negative pressure in the sensing chamber at an ultra-low flow rate. Coupled to the flow sensing device is a switch. Control circuitry coupled to the switch, the temperature sensor and one or more heating elements located within the flow path, regulates the amount of electrical current flowing through the heating elements in response to the flow condition measured by the flow sensing device.

In another aspect, the flow sensing device includes a pressure chamber isolated from the sensing chamber.

In a further aspect, a diaphragm separates the pressure chamber from the sensing chamber.

An additional aspect, portions of the housing define the pressure chamber and portions of a cover coupled to the housing defining a sensing chamber.

In yet another aspect, the pressure chamber and the sensing chamber are separated by the diaphragm, which is retained between the cover and the housing.

In still a further aspect, a switch activator is provided in the sensing chamber.

In an additional aspect, the switch activator has an end biased by a biasing member in a first direction, the switch activator being configured to move in a second direction opposite of the first direction upon sensing of the ultra-low flow condition.

In still another aspect, a diaphragm defines a portion of the sensing chamber and the switch activator is biased toward the diaphragm.

In yet a further aspect, the switch activator includes a proximal end within the sensing chamber and a distal end located adjacent to the switch and configured to engage the switch.

In an aspect of the invention, an electric tankless water heater for heating a continuous supply of water is provided. The electric tankless water heater includes a heater assembly having a water inlet, a water outlet and a heating chamber defining a water flow path between the water inlet and the water outlet; a temperature sensor configured to measure the temperature of water flowing through the heating chamber of the heater assembly; a flow sensing device configured to detect an ultra-low flow condition of water within the heating chamber of the heater assembly; a heating element located in heating chamber; and a control circuitry coupled to the heating element, the temperature sensor and the flow rate sensor, the control circuitry is configured to control the amount of electrical current flowing through the heating elements in response to the flow condition measured by the flow sensor.

In another aspect, the flow sensing device includes a pressure chamber isolated from a sensing chamber.

In a further aspect, a diaphragm separates the pressure chamber from the sensing chamber.

In an additional aspect, the sensing chamber is in fluid communication with the water flow path between the water inlet and the water outlet.

In yet another aspect, portions of the housing define the pressure chamber and portions of a cover coupled to the housing defining the sensing chamber.

In still a further aspect, the flow sensing device includes a pressure chamber isolated from a sensing chamber and further comprises a switch activator at least partially provided in the sensing chamber.

In an additional aspect, the switch activator includes an end biased by a biasing member in a first direction toward the pressure chamber, the switch activator being configured to move in a second direction opposite of the first direction upon sensing of the ultra-low flow condition.

In still another aspect, the switch activator includes a proximal end within the sensing chamber and a distal end located outside of the sensing chamber and adjacent to the switch, the distal end being configured to engage the switch.

Further objects, features and advantages will become readily apparent to persons skilled in the art after review of the following description with reference to the drawings and the claims that are appended to inform a part of this specification.

DETAILED DESCRIPTION

Referring now to the drawings, a tankless water heater embodying the principles of the present disclosure is generally illustrated inFIG. 1and designated at10. In this regard, while the tankless water heater10is generally shown and described herein as being a heater for a continuous water supply, it will be appreciated that the tankless water heater10may be used for heating a continuous or intermittent supply of other fluid(s) within the scope of the present disclosure.

As illustrated inFIGS. 1, 2, and/or3, the tankless water heater10includes as its principal components a heater assembly12including a housing13, a temperature sensor14, a flow sensing device16, control circuitry18, and a power source20. The heater assembly12further include a fluid inlet22, a fluid outlet24, a heating chamber26, a first heating element28, and a second heating element30. The heating chamber26defines at least part of a water flow path32between the fluid inlet22and the fluid outlet24. As illustrated inFIG. 2, the flow path32defines a reverse bend or serpentine shape, and the heating chamber26defines a single heating chamber having a reverse bend or serpentine shape extending along its length from the fluid inlet22to the fluid outlet24. While illustrated as having a reverse bend or serpentine shape, the heating chamber26may have alternate shapes and configurations depending on the particular application, as well as the overall size and shape of the heater assembly12. The heating chamber26may further define a circular cross-sectional shape along its length from the fluid inlet22to the fluid outlet24. In this regard, the heating chamber26may define a constant diameter along the flow path32.

The first heating element28is disposed in the heating chamber26and is provided with a first wattage. The wattage of the first heating element28will depend on the particular design of the tankless water heater10. Generally, the wattage may be between 720 Watts and 8550 Watts. The second heating element30is also disposed in the heating chamber26and may operate up to and including a second wattage. Like the first heating element28, the wattage of the second heating element30will also depend on the particular design of the tankless water heater10. The second wattage may be the same as or different from the first wattage. Generally, its wattage will also be between 720 Watts and 8550 Watts.

The first and second heating elements28,30are preferrably formed of a resistive heating material. In this regard, the first and/or second heating elements28,30may be formed from an electrically conductive material, such as a metallic material (e.g., molybdenum, tungsten, tantalum, niobium, and alloys thereof), for example, through which electricity may flow and provide resistive heat to the heater assembly12.

In some implementations, one or both of the first and second heating elements28,30may be sheathless. In this regard, the first and/or second heating elements28,30may omit sheathing and coatings, such as a ceramic coating covered by a stainless steel sheath or other coating or cover material. As such, the first and/or second heating elements28,30, including the resistive heating material forming at least a part thereof, may be directly disposed within the heating chamber26and directly in contact with the fluid flowing through the heating chamber26.

With reference toFIG. 2, the temperature sensor14measures the temperature of the fluid flowing through the heating chamber26of the heater assembly12, and is in communication with the control circuitry18. In this regard, the temperature sensor14is preferably provided in the heater assembly12downstream of the heating elements28,30, or proximate the fluid outlet24, to measure the temperature of the fluid as it is about to exit the water heater10.

The flow sensing device16measures a flow condition of fluid along the flow path32and within the heating chamber26of the heater assembly12, and is also in communication with the control circuitry18. The flow sensing device16may be coupled to the heater assembly12along the flow path32or more particularly, as shown, proximate the fluid outlet24to measure the flow condition of the fluid flowing along the flow path32proximate the fluid outlet24. As will be explained in more detail below, the flow sensing device16communicates the flow condition to the control circuitry18. As used herein, the flow condition is the flow rate (e.g., gallons per minute) of the fluid flowing along the flow path32, but may optionally include other parameters of the fluid flow.

The control circuitry18is coupled to, or otherwise in communication with, the first heating element28, the second heating element30, the temperature sensor14, and the flow sensing device16. In this regard, the control circuitry18uses signals received from the temperature sensor14and/or the flow sensing device16to control the operation of the tankless water heater10. For example, during operation of the tankless water heater10, and in response to signals received from the temperature sensor14and/or the flow sensing device16, the control circuitry18may regulate the amount of electrical current flowing through the first and second heating elements28,30.

With reference toFIGS. 1 and 2, the power source20may be provided as an alternating current source, such as an 110 v outlet (or higher voltage), a generator or a direct current source, such as a battery, for example. As seen inFIG. 2, the first heater element28is coupled to a first pole42and is also coupled to the control circuitry18at the first pole42, such that electrical power can be selectively transmitted by the control circuitry18, through operation of relays, for example, to the first pole42and from the first pole42to the first heater element28. The second heater element30is illustrated as being connected in series with the opposing end of the first heater element28by a coupling43and, at the opposing end of the second heating element30to a second pole44. The second heater element30is also coupled to the control circuitry18via the second pole44. The control circuitry18is a simple control circuit designed to, upon detection of a flow condition, energize the first and second heating elements28,30to provide heated water to the outlet at a predetermined temperature. Such types of control circuitry18are well known and within the skill of those in the field of the present invention and, therefore, is not further described herein.

Referring now toFIG. 3, a cross-section view through the flow sensing device16utilized in accordance with the principles of the present invention is illustrated therein. As seen therein, a portion of the housing13of the heater assembly12forms part of the flow sensing device16and cooperates with a diaphragm60to define a sealed pressure chamber62. The diaphragm60is retained over the pressure chamber62by a cover64secured by fasteners (not shown) to the housing13. Retained in this manner, the diaphragm60extends completely about the perimeter of the pressure chamber62so as to seal off and isolate a volume of air within the pressure chamber62. Preferably, the diaphragm60is flexible and formed of rubber.

The cover64, which is also illustrated inFIGS. 4 and 5, includes a recess66that cooperates with the diaphragm60to define a sensing chamber68on the side of the diaphragm62opposite from the pressure chamber62. The sensing chamber68is in fluid communication with the water traversing the flow path32through the heating chamber26. In one embodiment, the sensing chamber68is in communication with the flow path32via a port70, defined in part71by the cover63and in part72by the housing13. Alternatively, the sensing chamber68may be in communication with the flow path32with the port70being defined in part72by the housing and in part by a recessed relief area73defined about the perimeter of the recess66in the cover64, in which case the part71of the cover64is omitted. The relief area73is readily seen inFIG. 4and is show inFIGS. 3 and 5by dashed lines.

Also provided in the sensing chamber68is one end of a switch actuator74. The switch actuator74includes an actuator rod74with a proximal end in the sensing chamber68and a distal end outside of the chamber68and the cover64. The proximal end of the actuation rod74is provided with an actuation knob78that is preferably centrally located within the sensing chamber. Where the actuation rod76extends through the cover64, the actuation rod76passes through a pivot80that forms a fluid tight seal with the cover64and the actuation rod76. The actuation rod76is biased such that the proximal end, or more specifically the actuation knob78, is biased toward the diaphragm60. In illustrative example, biasing may be achieved by a biasing member77, such as a coil spring. The pivot80allows the actuation rod76to pivot in such a manner that when the proximal end of the actuation rod76moves toward the cover64, the distal end of the actuation rod76moves in an opposite direction, which causes engagement with and activation of a switch82. Preferably, the switch82is proportional in its operation and provides varying signals to the control circuitry18depending on the degree of activation by the activation rod76.

The flow sensing device16may additionally include a rigid activation plate84provided in the sensing chamber68over the diaphragm60to engage and interact with the activation knob78on the proximal end of the activation rod76. The activation plate84provides a rigid, smooth and durable surface toward which the activation knob78may be biases and over which the activation knob78may engage and slide.

During operation of the flow sensing device16, as the flowing fluid, such as water, moves along the flow path32past the port70and out of the fluid outlet27, the flow of liquid draws on the sensing chamber68and induces a negative pressure in the sensing chamber68relative to the pressure chamber62. As a result, the diaphragm60is biased/caused to deform toward the cover64. This in turn causes a similar movement of the activation plate84and the proximal end of the activation rod76. As proximal end of the activation rod76moves toward the cover64, the distal end of the activation rod76moves to engage the switch82, designated at86. The flow sensing device16is highly sensitive and capable of initially sensing ultra-low flows, flows above 0.0 GPM and up to 0.4 GPM, and more preferably in the range of about 0.1 to 0.3 gallons per minute.

The switch82is optionally proportional so that, depending on the degree of pivot of the activation rod76, the rate of the liquid flow along the flow path32and out of the housing13can be similarly determined by the control circuitry18.

In operation, upon an ultra-low flow of water, the flow of water in the flow path32will pass the port enroute to the water outlet24. This ultra-low flow induces a negative pressure in the port70and in the sensing chamber68. Since the pressure chamber62is then at a higher pressure relative to the sensing chamber68, the diaphragm60flexes toward the sensing chamber68displacing the activation plate84and the proximal end of the switch activator74. As generally discussed above, the activation rod76then pivots about pivot80, against the force of the biasing member (spring)77. Moving in the direction of arrow86, the distal end of the activation rod76engages and activates switch82, causing operation of the control circuitry18.

As a person skilled in the art will really appreciate, the above description is meant as an illustration of at least one implementation of the principles of the present invention. This description is not intended to limit the scope or application of this invention since the invention is susceptible to modification, variation and change without departing from the spirit of this invention, as defined in the following claims.