Determining heating element and water heater status based on galvanic current

Systems and methods for determining heating element and water heater status based on galvanic current are provided. An exemplary water heater includes a tank for holding a volume of water and an anode rod extending into the water. The anode rod has a core made of a conductive material. The water heater also includes at least one heating element configured to heat the water when energized. The water heater includes a current measurement circuit configured to generate a feedback signal describing a galvanic current flowing from the core of the anode rod to an electrical ground. The water heater also includes a controller configured to receive the feedback signal from the current measurement circuit and to control one or more operations of the water heater based on the feedback signal.

FIELD OF THE INVENTION

The present disclosure relates to a water heater. More particularly, the present disclosure relates to determining heating element and water heater status based on galvanic current.

BACKGROUND OF THE INVENTION

Most modern water heaters are constructed of a steel tank with a glass lining. Passive anode rods are a vital component to water heaters utilizing a steel tank or other forms of tanks susceptible to corrosion. An anode rod can act as a sacrificial anode that provides protection against tank corrosion. In particular, the anode rod acts as a sacrificial anode by way of galvanic corrosion.

As a result of the galvanic corrosion, a galvanic current can flow from the anode rod to a cathode to which the anode rod is electrically connected. The cathode is commonly the exterior of the tank connected to an earth ground. The anode rod is depleted by the galvanic corrosion and therefore acts as a sacrificial anode.

Water heaters also frequently include one or more heating elements positioned inside the tank and configured to heat water stored in the tank. For example, a heating element can provide heat by way of electrical resistance. The heating element can resist an electrical current and therefore generate heat, raising the temperature of the water.

It is important to the proper operation of a water heater that an energization status of each heating element included in the water heater be known or able to be determined. In particular, to properly heat the water to a desired temperature and avoid dangerous conditions such as scalding water, a water heater must be able to determine whether or not a heating element is currently energized.

One particularly dangerous condition which must be avoided is operation of a heating element in a “dry tank.” More particularly, as discussed above, a heating element can be used to dissipate or provide a significant amount of heat. When the heating element is submerged in water, the water surrounding the heating element safely accepts or absorbs such heat.

However, when the water in the tank is depleted through use or otherwise reduced to a level where the heating element is no longer submerged, operation of the heating element can be dangerous. In particular, the heating element can overheat and catch fire, among other dangers.

Therefore, improved systems and methods for determining heating element and water heater status are desirable. In particular, improved systems and methods for determining heating element and water heater status which leverage the presence of a galvanic current are desirable.

BRIEF DESCRIPTION OF THE INVENTION

One aspect of the present disclosure is directed to a water heater. The water heater includes a tank for holding a volume of water and an anode rod extending into the water. The water heater also includes at least one heating element configured to heat the water when energized. The water heater includes a current measurement circuit configured to generate a feedback signal describing a galvanic current flowing from the anode rod to an electrical ground. The water heater also includes a controller configured to receive the feedback signal from the current measurement circuit and to control one or more operations of the water heater based on the feedback signal.

Another aspect of the present disclosure is directed to a method of operating a water heater. The method includes receiving a feedback signal describing a galvanic current flowing from an anode rod included in the water heater to an electrical ground. The method includes energizing a first heating element. The first heating element is configured to heat a volume of water stored in the water heater when energized. The method includes monitoring, based on the feedback signal, for an increase in galvanic current when the first heating element is energized.

Another aspect of the present disclosure is directed to a method of operating a water heater having a first heating element and a second heating element. The method includes monitoring a galvanic current flowing from an anode rod positioned inside the water heater to an electrical ground. The method includes determining an energization status of each of the first heating element and the second heating element by comparing the galvanic current to a plurality of galvanic current profiles. The plurality of galvanic current profiles include a first galvanic current profile describing the behavior of the galvanic current when the neither the first heating element nor the second heating element are energized. The plurality of galvanic current profiles include a second galvanic current profile describing the behavior of the galvanic current when the first heating element is energized and the second heating element is not energized. The plurality of galvanic current profiles include a third galvanic current profile describing the behavior of the galvanic current when the second heating element is energized and the first heating element is not energized. The plurality of galvanic current profiles include a fourth galvanic current profile describing the behavior of the galvanic current when both the first heating element and the second heating element are energized.

DETAILED DESCRIPTION OF THE INVENTION

Generally the present disclosure is directed to systems and methods for determining heating element and water heater status based on galvanic current. In particular, according to the present disclosure, detectable changes in galvanic current characteristics can be used to determine whether one or more heating elements are submerged and operating. As such, a water heater can include a current measurement circuit that generates a feedback signal describing the galvanic current. Further, a controller can control one or more operations of the water heater based on the feedback signal.

An anode rod is a commonly included component in modern water heaters. The anode rod can act as a sacrificial anode which protects the interior of a tank from corrosion by suffering galvanic corrosion in place of the tank. In particular, the anode rod can have a more negative electrochemical potential than the tank to be protected and therefore act as the anode in a galvanic reaction.

A galvanic current can be generated due to the corrosion of the anode rod. The galvanic current can flow from the anode rod to an electrical ground which is electrically connected to the anode rod. Often such electrical ground is the exterior of the tank connected to an earth ground. As used herein, the term “galvanic current” refers generally to the current flowing from the anode to the electrical ground, whether such current is entirely the result of galvanic corrosion or includes current generated by other environmental factors.

According to an aspect of the present disclosure, the galvanic current flowing from the anode rod to the electrical ground can be monitored for detectable changes. In particular, when a water heater heating element is energized or otherwise enabled, a significant increase in galvanic current occurs. Such increase in galvanic current can be due to the heat produced by the element and/or leakage current from the heating element.

A current measurement circuit can be placed between the anode rod and the electrical ground. The current measurement circuit can generate a feedback signal that describes one or more characteristics of the galvanic current. As an example, the current measurement circuit can amplify a voltage across a shunt resistor in the path of galvanic current flow.

A controller of the water heater can control one or more operations of the water heater based on the feedback signal. As an example, the controller can control energization of one or more of the heating elements included in the water heater based on the feedback signal. For example, the controller can alter the heating element between energization states such as off and on.

As another example, the controller can receive additional signals or information from other components of the water heater, such as, for example, a temperature sensor, a current transformer, or a water level sensor. The controller can operate the water heater based on the feedback signal and one or more of the additional signals.

FIG. 1depicts an exemplary water heating system100according to an exemplary embodiment of the present disclosure. Water heating system100can include tank102that holds a volume of water103. An anode rod104can pass through an opening at the top of tank102and extend downwards into water103. For example, anode rod104can be mounted to tank102at the opening where anode rod104enters tank102. Anode rod104can be isolated from direct electrical connection to tank102by means of a insulated cap or liner placed between anode rod104and tank102at the place of mounting.

With reference toFIG. 2, a cross-sectional view of an exemplary anode rod104according to an exemplary embodiment of the present disclosure is depicted. Anode rod104can have a core106and an outer region208. Core106can extend coaxially with outer region208throughout anode rod104such that core region106is coaxially surrounded by outer region208. Other suitable configurations can be used to satisfy the present disclosure in addition to the configuration shown inFIG. 2.

Outer region208can be made of any suitable material. For example, outer region208can be made of magnesium, aluminum, or an aluminum-zinc alloy. Core106can be made of any conductive material. As an example, core106can be a conductive wire, such as, for example, a steel wire.

Returning toFIG. 1, water heating system100can further include a first heating element108and a second heating element110. First and second heating elements108and110can be attached to an interior of tank102. For example, heating elements108and110can be disposed at different heights within tank102.

Heating elements108and110can be configured to heat water103when energized. As an example, heating elements108can110can be resistance heating elements which generate heat by resisting an electric current. However, heating elements108and110can each be any suitable device, structure, or circuit for generating heat to raise the temperature of water103.

Water heating system100can further include temperature sensors112and114. Temperature sensors112and114can be positioned inside the tank proximate to heating elements108and110. In particular, temperature sensor112can be positioned proximate to heating element108while temperature sensor114can be positioned proximate to110.

Temperature sensors112and114can respectively provide a temperature signal describing a temperature in their respective local regions. For example, temperature sensor112can provide a temperature signal describing an ambient temperature about sensor112. As an example, temperature sensors112and114can be thermistors.

Water heater system100can further include a water level sensor115. Water level sensor115can detect when the water103in tank102has reached a particular level. Water level sensor115can be any suitable device for detecting the presence of water103.

According to an aspect of the present disclosure, anode rod104can act as a sacrificial anode to protect the interior of tank102from corrosion. In particular, anode rod104can suffer galvanic corrosion in place of tank102. Such galvanic corrosion can generate a galvanic current flowing from anode rod104to an electrical ground118. Electrical ground118can be the exterior of the tank102which is connected to an earth ground.

The galvanic current can flow from anode rod104to electrical ground118by way of electrical conductor120. For example, electrical conductor120can be connected to core106of anode rod104. Electrical conductor120can be made of any suitable conductive material and can include one or more wires, filters, or other suitable components.

Electrical conductor120can allow flow of the galvanic current from anode rod104to a current measurement circuit116. Current measurement circuit116can measure or otherwise monitor the galvanic current flowing from anode rod104to electrical ground118. Current measurement circuit116can generate a feedback signal describing the galvanic current. For example, the feedback signal can describe a general amplitude of the galvanic current. As another example, the feedback signal can be processed or otherwise used to calculate a general amplitude of the galvanic current.

One of skill in the art will appreciate that many components of water heating system100have been omitted fromFIG. 1in order to simplify the system for illustration and presentation. For example, water heating system100can include a water inlet pipe, a water exit pipe, a dip tube, one or more valves, a flow meter, a mixer, power source components, or any other suitable components necessary or desirable for water heater operation.

FIG. 3depicts an exemplary current measurement circuit116according to an exemplary embodiment of the present disclosure. Current measurement circuit can include a shunt resistor302and an operational amplifier304.

Shunt resistor302can be positioned in the path of galvanic current flow from anode rod104to electrical ground118. Shunt resistor302can provide any suitable magnitude of resistance. Generally, however, the resistance provided by shunt resistor302should be very small in order to minimize the resistive effect of shunt resistor302on galvanic current flow.

Operational amplifier304can be a differential operational amplifier that amplifies the voltage across shunt resistor302. Operational amplifier304can be a discrete circuit or a high accuracy integrated circuit that includes precise resistors to minimize variation. The output of operational amplifier304can be a feedback signal306. Feedback signal306can optionally be filtered or processed prior to being delivered to the water heater controller. In such fashion, one or more characteristics or attributes of the galvanic current flowing from anode rod104to electrical ground118can be measured or monitored.

FIG. 4depicts an exemplary water heater control system400according to an exemplary embodiment of the present disclosure. In particular, control system400can include a controller402.

Controller402can be any suitable computing device and can include one or more processors, a memory, or other suitable components. In particular, the memory can store computer-readable instructions that are executed by the processor in order to perform one or more algorithms. In some implementations, controller402is an application specific integrated circuit.

Controller402can control energization of a first heating element108and a second heating element110by providing control signals to an energization control circuit406. In particular, based on the control signals from controller402, energization control circuit can either respectively allow or disallow a power signal from power source404to first heating element108and/or second heating element110. As an example, energization control circuit can modify an AC power signal provided by power source404in order to energize heating elements108and110using a DC power signal.

According to aspects of the present disclosure, controller402can also receive signals or other information from a current measurement circuit116, one or more current transformers408, one or more thermistors410, and water level sensor115. Controller402can control operations of the water heater based on such signals.

For example, current measurement circuit116can provide a feedback signal306to controller402that describes a galvanic current flowing from an anode rod to an electrical ground. As another example, thermistor410can provide a temperature signal describing a local temperature about thermistor410.

As yet another example, current transformers408can provide a power draw signal describing an energization current drawn by either first heating element108or second heating element110. For example, controller402can provide a control signal to energization control circuit406instructing energization control circuit406to energize first heating element108. In response, energization control circuit can energize first heating element108using power from power source404.

Thus, first heating element108can draw an energization current in order to generate heat to raise the temperature of the water. Current transformer408can monitor or measure such energization current and generate a power draw signal describing the energization current. Current transformer408can provide the power draw signal to controller402.

Controller402can control energization of heating elements108and110based the signals received from current measurement circuit116, thermistor410, current transformers408, and/or water level sensor115. As an example, controller402can discontinue energization of first heating element108when first heating element108is energized and feedback signal306indicates that the galvanic current did not increase when first heating element108was initially energized.

As another example, controller402can discontinue energization of first heating element108when the temperature signal provided by thermistor410indicates that the local temperature is increasing and feedback signal306indicates that the galvanic current is not increasing. Such combination of signals can indicate the first heating element108is generating heat but is not safely submerged in water.

As yet another example, controller402can discontinue energization of first heating element108when the power draw signal provided by current transformer408indicates that first heating element108is drawing an energization current and feedback signal306indicates that the galvanic current is not increasing. Such combination of signals can indicate that the first heating element108is operating but is not safely submerged in water.

As another example, controller402can provide a heating element error indication when water level sensor115indicates that the tank is full of water and feedback signal306indicates that galvanic current did not increase when first heating element108was energized.

Controller402can also provide a plurality of indications or messages to a user interface412. For example, user interface412can include a display. Controller402can send a message to user interface412for presentation on the display. User interface412can provide controller402with one or more user-entered commands.

FIG. 5depicts an exemplary graph500of galvanic current versus time according to an exemplary embodiment of the present disclosure. In particular, graph500depicts a plot502of galvanic current versus time. As will be discussed, plot502shows detectable changes in galvanic current when a heating element is energized.

At time504first heating element108ofFIG. 1is energized or otherwise enabled. At time506, energization of first heating element108is discontinued. As can be seen from plot502, energization of first heating element108caused a detectable change in galvanic current. In particular, energization of first heating element108resulted in a detectable increase in galvanic current.

At time508second heating element110ofFIG. 1is energized or otherwise enabled. At time510, energization of second heating element110is discontinued. As can be seen from plot502, energization of second heating element110caused a detectable change in galvanic current. In particular, energization of second heating element110resulted in a detectable increase in galvanic current.

FIGS. 6A and 6Bdepict a flowchart of an exemplary method (600) of operating a water heater according to an exemplary embodiment of the present disclosure. While exemplary method (600) will be discussed with reference to exemplary water heating system100ofFIG. 1and exemplary control system400ofFIG. 4, method (600) can be implemented using any suitable water heater control system. In addition, althoughFIGS. 6A and 6Bdepict steps performed in a particular order for purposes of illustration and discussion, methods of the present disclosure are not limited to such particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the method (600) can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

Referring now toFIG. 6A, at (602) a feedback signal describing a galvanic current can be received. For example, controller402can receive feedback signal306from current measurement circuit116. Feedback signal306can describe a galvanic current flowing from anode rod104to electrical ground118ofFIG. 1.

At (604) a first heating element can be energized. For example, controller402can send a control signal to energization control circuit406. In response, energization control circuit406can energize first heating element108.

Based on the feedback signal received at (602), an increase in galvanic current can be monitored for at (606) when the first heating element is initially energized at (604). For example, controller402can analyze feedback signal306to monitor for an increase in galvanic current when first heating element108is initially energized.

Controller402can monitor for an increase in galvanic current by periodically sampling feedback signal306. For example, controller402can calculate, for each sample with respect to the previous sample, a change in value of feedback signal306. Controller402can monitor for a change in value that indicates an increase in value greater than a threshold increase. An increase in feedback signal value greater than the threshold increase can indicate that first heating element108is submerged in water and properly operating.

As another example, controller402can calculate, for each sample with respect to the previous sample, a percent increase in feedback signal306. Controller402can monitor for a percent increase greater than a threshold percentage. A percent increase in feedback signal306greater than the threshold percentage can indicate that first heating element108is submerged in water and properly operating.

At (608) it is determined whether an increase in galvanic current was detected at (606). If it is determined that an increase in galvanic current was detected at (606), then it can be assumed that the first heating element is submerged in water and operating properly. Therefore, energization of the first heating element can be safely continued at (610).

However, if it is determined at (608) that an increase in galvanic current was not detected at (606), then it can be assumed that either the first heating element is not operating properly or is not submerged in water and is therefore susceptible to the dangers of a dry tank. Therefore, energization of the first heating element can be discontinued at (612) in order to avoid potential dry tank dangers. For example, controller402can send a control signal to energization control circuit406to discontinue energization of first heating element108.

At (614) a second heating element can be energized. For example, controller402can send a control signal to energization control circuit406. In response, energization control circuit406can energize second heating element110. More particularly, as shown inFIG. 1, second heating element110can be positioned within thank102at a lower height than first heating element108. Thus, although first heating element108may not be submerged and therefore susceptible to dry tank dangers, second heating element110may still be safely submerged in water.

Based on the feedback signal received at (602), an increase in galvanic current can be monitored for at (616) when the second heating element is initially energized at (614). For example, controller402can analyze feedback signal306to monitor for an increase in galvanic current when second heating element110is initially energized.

Referring now toFIG. 6B, at (618) it is determined whether an increase in galvanic current was detected at (616). If it is determined that an increase in galvanic current was detected at (616), then it can be assumed that the second heating element is submerged in water and operating properly. Therefore, energization of the second heating element can be safely continued at (620).

However, if it is determined at (618) that an increase in galvanic current was not detected at (616), then it can be assumed that either the second heating element is not operating properly or is not submerged in water and is therefore susceptible to the dangers of a dry tank. Therefore, energization of the second heating element can be discontinued at (622) in order to avoid potential dry tank dangers. For example, controller402can send a control signal to energization control circuit406to discontinue energization of second heating element110.

At (624) it is determined whether a full tank signal has recently been received. For example, water level sensor115can provide controller402with an indication that tank102is full of water.

If it is determined at (624) that a full tank signal has recently been received then one or more error indications can be provided at (626). In particular, if a full tank indication has been received but an increase in galvanic current is not detected when either the first or second heating elements are energized, then one or more components of the water heating system are not working properly.

For example, the water level sensor may be providing an incorrect signal that the tank is full of water. As another example, one or both of the first and second heating elements may not properly be receiving or dissipating an energization current. As yet another example, the galvanic current feedback system could be malfunctioning.

Controller402can provide one or more error indications to user interface412which notify the user that an error has occurred. Alternatively or in addition, controller402can provide the one or more error indications to other internal components of the water heater or via a network interface to a utility provider or other entity.

If it is determined at (624) that a full tank signal has not recently been received, then the most appropriate conclusion is that neither the first nor the second heating elements are safely submerged in water. Therefore, at (628) a dry tank indication can be provided. For example, controller402can provide a dry tank indication to user interface412, other internal water heater components, or to a remote entity by way of a network connection.

One of skill in the art will appreciate that additional steps analogous to steps (624)-(628) can be performed in between steps (612) and (614) of method (600) or directly after step (620). More particularly, a determination can be made as to whether first heating element108is malfunctioning or experiencing a dry tank even if energization of second heating element110properly registers an increase in galvanic current.

FIG. 7depicts a flowchart of an exemplary method (700) of operating a water heater according to an exemplary embodiment of the present disclosure. While exemplary method (700) will be discussed with reference to exemplary water heating system100ofFIG. 1and exemplary control system400ofFIG. 4, method (700) can be implemented using any suitable water heater control system. In addition, althoughFIG. 7depicts steps performed in a particular order for purposes of illustration and discussion, methods of the present disclosure are not limited to such particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the method (700) can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure.

At (702) a galvanic current flowing from an anode rod positioned inside a water heater to an electrical ground can be monitored. For example, current measurement circuit116can monitor the galvanic current flowing from anode rod104to electrical ground118. Current measurement circuit116can generate a feedback signal306that describes the galvanic current. Current measurement circuit116can provide feedback signal306to controller402. As an example, controller402can monitor the galvanic current by periodically analyzing a plurality of samples of feedback signal306.

At (704) an energization status of each of a first heating element and a second heating element can be determined by comparing the galvanic current to a plurality of galvanic current profiles. For example, as can be seen fromFIG. 5, energization of either first heating element108or second heating element110can result in a distinct change in behavior or characteristics of galvanic current. Simultaneous energization of both first heating element108and second heating element110can result in another distinct change in behavior or characteristics of the galvanic current.

Therefore, a galvanic current profile can be determined which describes the particular change in behavior or characteristics of the galvanic current upon the energization of first heating element108, second heating element110, both first heating element108and second heating element110, or neither first heating element108nor second heating element110. Thus, the prevailing behavior or characteristics of the galvanic current can be compared with the plurality of galvanic current profiles to determine an energization status of each of first heating element108and first heating element110.

As the electrical properties of the water stored in the tank and/or the electrical properties of the anode rod can change over time, the plurality of galvanic current profiles can be stored in memory and then updated or revised according to a calibration algorithm.

At (706) the water heater is operated based at least in part on the energization statuses determined at (704). For example, energization of either or both of the first or second heating elements can be initiated or discontinued based upon the energization statuses determined at (704). As another example, an error indication or a dry tank indication can be provided.