Embodiments relate to water heaters.
Gas-fired water heaters include heat exchangers that transfer the heat from the products of combustion to the water surrounding the heat exchanger. The temperature near the surface of the heat exchanger may sometimes be significantly higher than the temperature of other portions of the water tank. Such a temperature may make the surface of the heat exchanger more vulnerable to corrosion.
Additionally, commercial gas-fired water heaters typically operate at higher duty cycles compared to residential water heaters. Such high duty cycles also increase the average temperature near the surface of the heat exchanger because the heat exchanger is activated for longer periods of time. The increased average temperature makes the surface of the heat exchanger in commercial gas-fired water heaters more vulnerable to corrosion. For example, the duty cycle of commercial water heaters may be between 15%-40% higher than the duty cycle of a similar residential water heater. Such increased duty cycles may significantly increase the average temperatures on the heat exchanger in comparison to other surfaces of the water tank. For example, in one study, it was found that the temperature of the surface of the heat exchanger was approximately 40° F. higher than the other surfaces of the water tank when the burner is activated. In the same study, it was found that the surface of the heat exchanger has a corrosion rate that is approximately 20% higher when heat is applied (e.g., the burner is powered) compared to when no heat is applied (e.g., the burner is off).
In one embodiment, the application may provide an exemplary water heater including a water tank for water to be stored, a powered anode extending into the tank and configured to generate an electrical anode current, a combustion chamber, and an exhaust structure. The water heater also includes a flue in fluid communication between the combustion chamber and the exhaust structure, and a controller. The combustion chamber includes a burner operable to burn a mixture of air and fuel generating products of combustion, the products of combustion flowing through the flue to the exhaust structure to heat the water in the tank. The controller coupled to the powered anode and operable to determine a duty cycle of the burner, determine whether the duty cycle of the burner exceeds a threshold, increase a protection parameter of the powered anode based on a duty cycle of the burner, and operate the powered anode at the increased protection parameter.
In another embodiment, the application provides an exemplary method of operating a gas water heater. The method includes determining, by the electronic processor, a duty cycle of a burner of the water heater, and determining, by the electronic processor, whether the duty cycle of the burner exceeds a high threshold. Increasing, by the electronic processor, a protection parameter associated with a powered anode extending into a tank of the water heater in response to the duty cycle of the burner being above the high threshold. The method further comprising operating the powered anode according to the increased protection parameter.
Other aspects of the application will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawing. The application is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
A water inlet line 120 and a water outlet line 125 are in fluid communication with the water tank 105. In the illustrated embodiment, the water inlet line 120 and the water outlet line 125 are in fluid communication with the water tank 105 at a top portion of the water heater 100. In other embodiments, the water inlet line 120 may be at a bottom portion of the water heater 100, while the water outlet line 125 may be at the top portion of the water heater 100. In yet another embodiment, the water inlet line 120 may be the top portion of the water heater 100, while the water outlet line 125 may be at the bottom portion of the water heater 100. The inlet line 120 includes an inlet opening 130 for adding cold water to the water tank 105, and the outlet line 125 includes an outlet opening 135 for withdrawing hot water from the water tank 105 for delivery to a user.
The water heater 100 also includes a combustion chamber assembly 140, an air intake assembly 145, and an exhaust structure 150. In the illustrated embodiment, the combustion chamber assembly 140 is positioned under the water tank 105 and supports the water tank 105. In other embodiments, the combustion chamber assembly 140 is positioned above the water tank 105. The water heater 100 also includes a flue 155 in fluid communication with the combustion chamber assembly 140 and the exhaust structure 150. The air intake assembly 145 includes a blower 157, which draws ambient air and provides the air to the combustion chamber assembly 140.
The combustion chamber assembly 140 includes a burner 160, a gas valve 165, a flame sensor 170, and an igniter 175. The combustion chamber assembly 140 receives air from the air intake assembly 145. The igniter 175 is then powered to a predetermined temperature (or for a predetermined period of time). Once the igniter 175 reaches a temperature capable of initiating a flame, the gas valve 165 is opened. Gaseous fuel flowing through the gas valve is mixed with primary air from the air intake assembly 145. The blower 157 mixes the ambient air with the gaseous fuel to form a partially premixed combustible mixture, which is pushed toward the burner 160. This combustible mixture is ignited by the igniter 175, which causes the burner 160 to generate hot products of combustion. The flame sensor 170 is positioned proximate (for example, next to) to the igniter 175 and generates a signal indicative of whether a flame is present. The combustion chamber assembly 140 is surrounded by a high temperature insulation 177 to retain the heat from the hot products of combustion.
The hot products of combustion flow upward through the flue 155 toward the exhaust structure 150. As the products of combustion flow through the flue 155, heat is transferred from the products of combustion to the flue wall and to the water surrounding the flue 155. For this reason, the flue 155 is sometimes referred to as the heat exchanger of the water heater 100. In the illustrated embodiment, the hot products of combustion flow upward through the flue 155. In other embodiments, however, when the combustion chamber assembly 140 is positioned above the water tank 105, for example, the hot products of combustion flow downward through the flue 155. In such embodiments, the exhaust structure 150 may be positioned at a lower portion of the water heater 100. In yet other embodiments, the hot products of combustion may flow downward during a first portion of the flue 155 and may flow upward during a second portion of the flue 155. Although illustrated as being substantially straight, in other embodiments, the flue 155 may take other forms or shapes, for example but not limited to, a substantially helical shape.
The water heater 100 also includes a powered anode 180. In the illustrated embodiment, the powered anode 180 is threaded or otherwise secured into an anode spud 185 located at the top portion of the water heater 100. However, in other embodiments, the anode spud 185 may be located at the side of the shell 110, or at the bottom portion of the water heater 100. In operation, the powered anode 180 generates a current which reduces and/or eliminates the rate of corrosion of the tank 105. In some embodiments, the water heater 100 may include more than one anode or electrode. In some embodiments, for example, a reference electrode is positioned to measure a reference current, which is then used to control the powered anode 180. In other embodiments, multiple powered anodes 180 may be provided to increase protection delivered to the water tank 105. In the illustrated embodiment, the water heater 100 includes a single powered anode 180. If additional electrodes are included in the water heater 100, the control will mirror that of a single powered anode 180, and/or some of the electrodes are instead used for measuring reference parameters.
The operation of the powered anode 180 and the burner 160 are controlled by a control circuit 200 (
The input/output devices 215 output information to the user regarding operation of the water heater 100 and may also receive one or more inputs from the user. In some embodiments, the input/output devices 215 may include a user interface for the water heater 100. The input/output devices 215 may include a combination of digital and analog input or output devices required to achieve control and monitoring for the water heater 100. For example, the input/output devices 215 may include a touch screen, a speaker, buttons, and the like, to output information and/or receive user inputs regarding the operation of the water heater 100 (for example, a temperature set point at which water is to be delivered from the water tank 105). The electronic processor 205 controls the input/output devices 215 to output information to the user in the form of, for example, graphics, alarm sounds, and/or other known outputs. The input/output devices 215 are operably coupled to the electronic processor 205 to control temperature settings of the water heater 100. For example, using the input/output devices 215, a user may set one or more temperature set points for the water heater 100.
The input/output devices 215 may also be configured to display conditions or data associated with the water heater 100 in real-time or substantially real-time. For example, but not limited to, the input/output devices 215 may be configured to display characteristics of the burner 160 (for example, whether the burner is activated or malfunctioning), temperature of the water, and/or other conditions of the water heater 100. In some embodiments, the input/output devices 215 may also generate alarms regarding the operation of the water heater 100.
The input/output devices 215 may be mounted on the shell of the water heater 100, remotely from the water heater 100, in the same room (for example, on a wall), in another room in the building, or even outside of the building. The input/output devices 215 may provide an interface between the electronic processor 205 and a user interface that includes a 2-wire bus system, a 4-wire bus system, and/or a wireless signal.
The memory 220 stores one or more algorithms and/or programs used to control the blower 157, the burner 160, the powered anode 180, and/or other components of the water heater 100. The memory 220 may also store operational data of the water heater (for example, when the burner 160 has been activated, historical data, usage patterns, and the like) to help control the water heater 100.
The burner controller 225 is in electrical communication with the electronic processor 205 and the memory 220 to control the combustion components of the water heater 100. In particular, the burner controller 225 controls the blower 157, the burner 160, igniter 175, and the gas valve 165. For example, the burner controller 225 determines when the gas valve 165 is to be opened, the igniter 175 is to be powered, and the like. The burner controller 225 also receives output signals from the flame sensor 170. In some embodiments, the burner controller 225 also receives sensor signals from the temperature sensor 230 to determine when the burner 160 is to be activated. In some embodiments, the burner controller 225 includes a second electronic processor separate from the electronic processor 205 to independently control the blower 157, the burner 160, and the gas valve 165. In other embodiments, however, the electronic processor 205 executes control of the blower 157, the burner 160, and the gas valve 165 directly (for example, without the burner controller 225).
The electronic processor 205 is coupled to the power regulator 210, the input/output devices 215, the memory 220, the burner controller 225, the temperature sensor 230, and the powered anode 180. The electronic processor 205 receives an output signal from the temperature sensor 230 indicating the temperature of the water in the water tank 105. In some embodiments, the water heater 100 includes more than one temperature sensor 230 positioned in various portions of the water heater 100 to measure the temperature of the water at various locations. The electronic processor 205 accesses the memory 220 to retrieve information relevant to the operation of the water heater 100. For example, the electronic processor 205 may retrieve information regarding the usage patterns for the water heater 100, the previous activations of the burner 160, and the like. The electronic processor 205 uses the information retrieved from the memory 220 to control the powered anode 180. In some embodiments, the electronic processor 205 also outputs control signals to the burner controller 225 regarding the operation of the blower 157, the burner 160, and/or the gas valve 165. The burner controller 225 then executes the commands based on the received control signals.
The electronic processor 205 controls the powered anode 180 by controlling the anode current. The anode current may be controlled by changing the protection parameters of the powered anode 180, which include an applied voltage to the powered anode 180, a setpoint voltage (or target voltage), an applied current, a minimum current threshold, a maximum current threshold, among others. The effectiveness of the powered anode 180 is at least partially based on the values of each of the protection parameters. For example, if a higher degree of protection for the water tank 105 is desired at least one of the protection parameters is increased. On the other hand, if a lower degree of protection is desired at least one of the protection parameters is decreased. A lower degree of protection may be desired to reduce hydrogen sulfide levels in the water tank 105 such that an unpleasant odor is reduced.
The electronic processor 205 implements a control algorithm such that the powered anode 180 provides sufficient protection to the water heater 100. Typically, the protection parameters of the powered anode 180 are determined based on, for example, a water conductivity and/or a “natural potential” of the water heater 100. For example, in one embodiment, the electronic processor 205 may determine a level of water conductivity (e.g., low water conductivity, medium water conductivity, or high water conductivity) and apply different anode currents based on the determined level of water conductivity. In such embodiments, the electronic processor 205 applies higher anode currents with increasing levels of water conductivity.
In other embodiments, the electronic processor 205 applies a voltage to the powered anode 180 such that the powered anode voltage remains near a setpoint voltage (or target voltage). The setpoint voltage is based on a “natural potential” of the water tank 105 to properly account for the changing amount of exposed steel in the water tank 105. In some embodiments, the setpoint voltage is adjustable also based on the water conductivity such that the setpoint voltage considers not only the current amount of exposed steel in the water tank 105, but also the conductivity of the water. As discussed above, when the water conductivity is lower, the anode current decreases (for example, the voltage applied to the powered anode 180 also decreases). When the water conductivity is higher, the anode current increases (for example, the voltage applied to the powered anode 180 also increases). Notably, in some embodiments, the applied voltage and the setpoint voltage are negative quantities. This application may refer to the applied voltage and/or the setpoint voltage as increasing or decreasing. Please note that these increases and decreases refer specifically to the magnitude of the applied voltage and/or the setpoint voltage. In other words, increasing a setpoint voltage may include changing the setpoint voltage from −2.6V to −2.9V. Therefore, as discussed above, when the water conductivity is lower, the magnitude of the applied voltage decreases, and when the water conductivity is higher, the magnitude of the applied voltage increases.
The typical increase in anode current provided with the control algorithms described above may still not be sufficient to properly protect the surface of the heat exchanger (i.e., the flue 155), especially when the water heater 100 operates at high duty cycles. Commercial water heaters typically operate at higher duty cycles (e.g., when compared to their residential counterparts) and experience a majority of corrosion on the surface of the heat exchanger (i.e., the flue 155) due to the high temperatures of the water near the flue 155. Therefore, the electronic processor 205 controls the powered anode 180 implementing a control method that can properly protect the surface of the flue 155 of commercial water heaters (or other water heaters operating at high duty cycles).
The electronic processor 205 may access both the overall duty cycle and the recent duty cycle from the memory 220. The electronic processor 205 may update the calculation of the overall duty cycle on every activation of the burner 160, or may update the overall duty cycle by batches per a predetermined scheduled (for example, every week the new activation data is considered when calculating the overall duty cycle). As discussed above, the recent duty cycle is recalculated according to an update cycle.
The electronic processor 205 next determines whether the duty cycle of the water heater 100 exceeds a first threshold (step 310). The first threshold represents a duty cycle that affects the average temperature of the flue 155 due to the amount of time that the burner 160 is activated. In the illustrated embodiment, the first threshold may correspond to a duty cycle of 25%. When the duty cycle of the water heater 100 does not exceed the first threshold, the electronic processor 205 operates the powered anode at the first value of the protection parameter (step 315). On the other hand, when the duty cycle of the water heater 100 does exceeds the first threshold, the electronic processor 205 increases the first value to a second value of the protection parameter (for example, the applied voltage, the setpoint voltage, and/or the applied current) of the powered anode 180 (step 320). The electronic processor 205 then operates the powered anode 180 according to the second value of the protection parameter (step 325).
In the illustrated embodiment, the value for the protection parameter is increased by approximately 30% after the electronic processor 205 determines that the duty cycle of the water heater 100 exceeds the first threshold. However, no further increments of the value(s) for the protection parameters are performed based on the duty cycle of the water heater 100. In other embodiments, however, the protection parameter is increased based on a difference between the first threshold and the duty cycle of the water heater 100 (for example, the duty cycle of the burner 160). For example, the increase in the protection parameter of the powered anode 180 is approximately proportional to the duty cycle of the water heater 100. In other words, as the duty cycle of the water heater 100 increases, the protection parameter of the powered anode 180 increases proportionately. In other embodiments, the protection parameter is increased according to a difference between the duty cycle of the water heater 100 and a normalized duty cycle value. In some embodiments, the electronic processor 205 may determine a different set of values for the protection parameters based on the duty cycle of the water heater 100. For example, the electronic processor 205 may access a look-up table that indicates a range of duty cycles for the water heater 100, and corresponding values for the protection parameters of the powered anode.
Additionally,
After the electronic processor 205 determines the values for the protection parameters (for example, steps 315, 325), the electronic processor 205 may continue to evaluate the performance of the powered anode 180 to ensure that the water heater 100 is sufficiently protected. In some embodiments, the electronic processor 205 may periodically make a measurement indicative of the conductivity of the water and/or the conductivity of the powered anode 180 (for example, a measurement of the anode current or voltage) and compare the measurement to a target value. The electronic processor 205 may then adjust the applied voltage and/or current of the powered anode 180 to ensure the measurement reaches and remains at the target value. In other embodiments, the electronic processor 205, after operating the powered anode at the current values for the protection parameters or at the increased values, does not update the values used for the protection parameters until a new call for heat is received by the electronic processor 205. As discussed above, after the electronic processor 205 determines that the duty cycle of the water heater 100 exceeds the first threshold, every time a new value for a protection parameter is calculated and/or accessed from memory, the electronic processor 205 may automatically increase the original value for the protection parameter (for example, by approximately 30%).
The conductivity of the water in the water tank 105 also affects the corrosion rate of the water tank 105 and the flue 155. In low water conductivity conditions, the water tank 105 may be adequately protected with a lower anode current density, and the increased water resistance inherently reduces the anode currents. Therefore, a lower voltage is typically applied to the powered anode 180 (for example, based on typical control by the electronic processor 205). These lower anode currents, however, do not consider the increased risk of corrosion at the surface of the flue 155 in a water heater 100 operating at high duty cycles. Additionally, when the water heater 100 operates at a high duty cycle in high water conductivity conditions, the anode current quickly reaches a maximum current threshold. Therefore, the electronic processor 205 implements an enhanced version of the control algorithm of
When the electronic processor 205 determines that the water conductivity is low, the electronic processor increases the setpoint voltage for the powered anode 180 (step 360). As discussed above, in low water conductivities and high duty cycles, the anode currents tend to be lower, thereby decreasing the protection to the water tank 105. By increasing the setpoint voltage, the powered anode 180 can more effectively protect portions of the water tank 105 that have higher average temperatures due to the high duty cycle of the water heater 100 (for example, the surface of the heat exchanger). When the electronic processor 205 determines that the water conductivity is high and the water heater 100 is operating at a high duty cycle, the electronic processor 205 increases the maximum current threshold such that a higher current can be applied to the powered anode 180 (step 365). Additionally, in some embodiments, the electronic processor 205 may determine that the water heater 100 operates in ultra-low water conductivity conditions. In such conditions, the electronic processor 205 operates the powered anode according to a minimum current threshold. When the water heater 100 operates at high duty cycles in such ultra-low water conductivity conditions, the electronic processor 205 increases the minimum current threshold to account for the increased risk of corrosion of the water tank 105.
As mentioned above, after the electronic processor 205 determines the values of the protection parameters (for example, step 420), the electronic processor 205 may periodically determine whether the powered anode 180 operates at a target level, or may, in other embodiments, determine new values (and new increased values) of the protection parameters when a new call for heat is received.
In some conditions, however, increasing the protection parameters when the burner is in operation, does not provide sufficient increased protection of the water tank 105. One such condition includes a water heater 100 that is in operation and sustains a large draw of water. During a large draw of water from the water tank 105, a temperature (and in particular, a lower temperature) of the water in the water tank 105 significantly decreases. A decrease in water temperature typically results in a lower powered anode current.
A drop in temperature while the water heater 100 is in a standby mode may not affect the protection of the water heater 100 significantly. When the burner 160 is in operation, however, the water heater 100 remains at an increased risk of corrosion. Therefore, the electronic processor 205 implements a method 450 (
While the lower temperature remains above the temperature threshold, the electronic processor 205 continues to operate the powered anode at the second value of the protection parameter (step 465). On the other hand, when the electronic processor 205 determines that the lower temperature is below the temperature threshold, the electronic processor 205 increases the second value to a third value for the protection parameter (step 470), and operates the powered anode 180 at the third value of the protection parameter (step 475). In the illustrated embodiment, the temperature threshold corresponds to 110° F. In other embodiments, however, the temperature threshold may be lower or higher than 110° F. Additionally, in some embodiments, the increase from the second value to the third value of the protection parameter may be, for example, a 30% increase.
As show in
Referring back to step 615, the electronic processor 205 updates the baseline current by the following equations:
baseline current=baseline current−baseline current/7
baseline current=baseline current+(Daybaseline/7)
These equations, however, assume that the baseline current values are known for the last seven days (thus the use of 7 in the denominator). Therefore, when the known baseline values span less than seven days, the equations used by the electronic processor 205 change slightly, and the electronic processor 205 calculates the baseline current using the following equation instead:
baseline current=baseline current+((Daybaseline−baseline)/(number of days))
where the number of days corresponds to the number of days for which baseline current information is known plus one. As seen in the equations above, the variable Daybaseline is used to calculate the baseline current.
The electronic processor 205 then determines whether the water heater 100 is in a post-purge state (step 625). When the electronic processor 205 determines that the water heater 100 is not in the post-purge state, the electronic processor 205 proceeds to step 605 until the water heater 100 enters the post-purge state or a new day begins. When the electronic processor 205 determines that the water heater 100 is in the post-purge state, the electronic processor 205 measures the anode current (step 630) with, for example, a current sensor. A post-purge state occurs after the burner 160 stops firing and the blower 157 continues to operate to clean the combustion products out through the exhaust structure 150. The electronic processor 205 measures the anode current during the post-purge state because the water in the water tank 105 is at a maximum, steady-state temperature (because it has just been heated by the burner 160), but the burner 160 is not in operation.
After measuring the current, the electronic processor 205 determines whether the list of currents include 5 measurements (step 635). When the list of currents does not yet have 5 measurements, the electronic processor 205 adds the measured current (from step 630 to the list of currents (step 640), and then returns to step 605 to wait for another post-purge period. Otherwise, when the list of currents already includes 5 measurements, the electronic processor 205 determines whether the measured current is greater than the minimum current in the list of currents (step 645). When the measured current is greater than the minimum current in the list of currents, the electronic processor 205 replaces the minimum current of the list of currents with the measured current (step 650). By replacing the minimum current with the measured current when the measured current is greater than the minimum current, the list continues to store the maximum 5 anode currents. When the measured current is not greater than the minimum current in the list of currents, the electronic processor 205 proceeds back to step 605 and waits for another post-surge state to measure another anode current. Therefore, at the end or the beginning of each day a new baseline current is calculated based on the 5 highest anode currents previously measured.
average=average+(anode current measurement−average/n)
where n is the current number of samples.
When the electronic processor 205 determines that the number of samples for the selected time period have been taken, the electronic processor 205 uses the rolling average to calculate the baseline current (step 725). The electronic processor 205 performs the following two-step average calculation to determine the baseline current for the water heater 100:
average=average−(average/N)
average=average+((anode current measurement)/N)
where N is the desired number of samples to average over. In some embodiments, these equations are then used by the electronic processor 205 for the remaining installation time of the water heater 100. As shown in the two equations immediately above, the currently calculated average is used to calculate the baseline, such that the baseline is recalculated every minute (at each measurement increment). In some embodiments, the rolling average continues to be updated while the burner 160 is in operation using values before the adjustments described by
The electronic processor 205 updates the mean and variance according to the following equations:
Mean=mean−(mean/60)
Mean=mean+(current measurement/60)
Variance=variance−(variance/60)
Variance=((current measurement−mean)/60)̂2
where current measurement refers to the current measured at step 815 of
Mean=mean+((current measurement−mean)/number of samples taken)
Variance=variance+(((current measurement−mean)̂2)/(60×(number of samples taken+1))
After the electronic processor 205 updates the mean and variance, the electronic processor 205 determines whether the updated variance is less than the variable PreviousVariance or whether PreviousVariance is set to zero (step 830). The electronic processor 205 determines that the previous variance is set to zero on the first implementation of the method 800 of
When the electronic processor 205 determines that the mean is not greater than the variable Daybaseline, the electronic processor 205 proceeds to step 805 to continue measuring anode currents. On the other hand, when the electronic processor 205 determines that the mean is greater than the variable Daybaseline, the electronic processor 205 sets the variable Daybaseline to the mean (step 840). As discussed above, Daybaseline is then used to calculate the baseline current.
As discussed above, the conductivity of the water in the water tank 105 may also affect the corrosion rate of the water tank 105 and of the flue 155. As mentioned with respect to
When the electronic processor 205 determines that the water conductivity is low (e.g., as compared to a normal or medium water conductivity), the electronic processor 205 increases the current applied to the powered anode 180 inversely proportionally to the low water conductivity (step 915). For example, as the water conductivity decreases, the electronic processor 205 increases the current applied to the powered anode 180 (to counteract a typical decrease in anode currents in low conductivity conditions). The increase in the applied current increases the protection provided by the powered anode 180 in low conductivity states such that the surface of the flue 155 can be better protected.
On the other hand, when water conductivity is high, the anode current is more likely to reach the maximum current threshold quickly. The maximum current threshold limits the protection the powered anode 180 is able to provide to the water tank 105. Therefore, when the electronic processor 205 determines that the water conductivity is very high (e.g., greater than 400 μS/cm), the electronic processor 205 increases the maximum current threshold (step 920). By increasing the maximum current threshold, the electronic processor 205 improves available protection during operation of the burner 160. Additionally, in some embodiments, the electronic processor 205 may determine that the water heater 100 operates in ultra-low water conductivity conditions. In such conditions, the electronic processor 205 operates the powered anode according to a minimum current threshold. When the burner 160 operates in such ultra-low water conductivity conditions, the electronic processor 205 increases the minimum current threshold to account for the increased risk of corrosion of the water tank 105. The method 900 of
The methods 300 and 350 of
When the electronic processor 205, however, determines that the updated duty cycle remains below the high duty cycle threshold (for example, is less than approximately 25%), the electronic processor 205 then determines whether the updated duty cycle is below a low duty cycle threshold (step 1020). In the illustrated embodiment, the low duty cycle threshold corresponds to approximately 10%, though in other embodiments, the low duty cycle threshold may be different. When the electronic processor 205 determines that the updated duty cycle is below the low duty cycle threshold, the electronic processor 205 sets the protection parameter at a low protection level (step 1025). For example, the electronic processor 205 sets the maximum current for the powered anode 180 at a low current level such as, for example 200 mA. In other embodiments, the low protection level may correspond to a different maximum current. When the electronic processor 205 determines that the updated duty cycle is not below the low duty cycle threshold, the electronic processor 205 sets the protection parameter at a medium protection level (step 1030). The medium protection level is lower than the high protection level and higher than the low protection level. In the illustrated embodiment, the medium protection level corresponds to 300 ma.
After the electronic processor 205 sets the protection level based on the updated duty cycle at steps 1015, 1025, 1030, the electronic processor 205 determines whether the number of increasing duty cycles is greater than a first predetermined threshold (step 1035). That is, the electronic processor 205 determines how many times the updated duty cycle is greater than the old duty cycle (i.e., the duty cycle before the last operation of the burner 160). The electronic processor 205 then compares the number of times that the updated duty cycle has increased to the first predetermined threshold. In one example, the electronic processor 205 determines whether there have been at least two increasing duty cycles (e.g., the first predetermined threshold corresponds to two). In some embodiments, the electronic processor 205 analyzes only the last set of updates to the duty cycle corresponding to the first predetermined threshold and determines whether both updates increased the duty cycle. For example, when the first predetermined threshold corresponds to two, the electronic processor 205 may determine whether the last two updates to the duty cycle increased the duty cycle.
When the electronic processor 205 determines that the number of increasing duty cycles is greater (or equal to) the first predetermined threshold, the electronic processor 205 sets the protection parameter to the next higher protection level (step 1040). For example, if the protection parameter had originally been set to the low protection level (e.g., at step 1025), the electronic processor 205 increases the protection parameter to the medium protection level (e.g., the electronic processor 205 increases the maximum current from 200 mA to 300 mA). Similarly, if the protection parameter had originally been set to the medium protection level (e.g., at step 1030), the electronic processor 205 increases the protection parameter to the high protection level (e.g., the electronic processor 205 increases the maximum current from 300 ma to 400 ma). On the other hand, when the electronic processor 205 determines that the number of increasing duty cycles remains below the first predetermined threshold, the electronic processor 205 proceeds to determine whether the number of decreasing duty cycles is greater (or equal to) a second predetermined threshold (step 1045).
In the illustrated embodiment, the second predetermined threshold is higher than the first predetermined threshold. For example, the second predetermined threshold corresponds to four, while the first predetermined threshold corresponds to two. In other embodiments, the second predetermined threshold may correspond to, for example, eight. The electronic processor 205 then determines how many times the updated duty cycle is lower than the old duty cycle (i.e., the duty cycle before the last operation of the burner 160). The electronic processor 205 then compares the number of times that the updated duty cycle decreased to the second predetermined threshold. In one embodiment, the electronic processor 205 determines whether there have been at least four decreasing duty cycles. In some embodiments, the electronic processor 205 analyzes, for example, the last four updates to the duty cycle and determines whether all four have decreased the duty cycle. In other words, in some embodiments, the electronic processor 205 determines whether the duty cycle has decreased four consecutive times. For example, when the second predetermined threshold corresponds to four, the electronic processor 205 may determine whether the last four updates increased the duty cycle.
When the electronic processor 205 determines that the number of decreasing duty cycles is greater (or equal to) the second predetermined threshold, the electronic processor 205 sets the protection parameter to the next lower protection level. For example, when the electronic processor 205 originally sets the protection parameter at the high protection level (to 400 mA at, for example, step 1015), the electronic processor 205 lowers the protection parameter to the medium protection level (e.g., 300 mA) after four decreasing duty cycles. In another embodiment, when the electronic processor 205 originally sets the protection parameter at the medium protection level (at 300 mA at, for example, step 1030), the electronic processor 205 lowers the protection parameter to the low protection level (e.g., 200 mA) after four decreasing duty cycles. The electronic processor 205 continues to update the duty cycle on each operation of the burner 160 (step 1005) and adjusts the protection parameters of the powered anode 180 accordingly.
In some embodiments, the electronic processor 205 may also determine the setpoint temperature (e.g., the desired water temperature) and the differential water temperature (e.g., the difference between the setpoint temperature and the stored water temperature) to help determine the protection level for the protection parameter. For example, the electronic processor 205 may set the first predetermined threshold, the second predetermined threshold, or both based on the temperature differential. In one example, the electronic processor 205 may set the second predetermined threshold to two when the temperature differential is greater than a high differential threshold (e.g., ten degrees). In the same example, the electronic processor 205 may set the second predetermined threshold to six when the temperature differential is lower than a low differential threshold (e.g., six degrees).
Although the steps for the flowcharts above have been described as being performed serially, in some embodiments, the steps may be performed in a different order and two or more steps may be carried out in parallel to, for example, expedite the control process. Additionally, the electronic processor 205 may combine steps from each of the methods described above. For example, methods 500 and 600 of
Thus, the application provides, among other things, a system and method for controlling a powered anode. Various features and advantages of the application are set forth in the following claims.
This application claims priority to U.S. Provisional Application No. 62/419,207 filed on Nov. 8, 2016, the entire contents of which are included by reference herein.
Number | Date | Country | |
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62419207 | Nov 2016 | US |