Patent Application
20060222349
This invention relates to water heater controls.
More particularly, the present invention relates to controls for water heaters employing resistive heating elements.
More particularly, the present invention relates to methods of operating a controller for water heaters.
The need for heated fluids, and in particular heated water, has long been recognized. Conventionally, water has been heated by heating elements, either electrically or with gas burners, while stored in a tank or reservoir. While effective, energy efficiency and water conservation can be poor. As an example, water stored in a hot water tank is maintained at a desired temperature at all times. Thus, unless the tank is well insulated, heat loss through radiation can occur, requiring additional input of energy to maintain the desired temperature. In effect, continual heating of the stored water is required. Additionally, the tank is often positioned at a distance from the point of use, such as the hot water outlet. In order to obtain the desired temperature water, cooled water in the conduits connecting the point of use (outlet) and the hot water tank must be purged before the hot water from the tank reaches the outlet. This can often amount to a substantial volume of water.
Many of these problems have been overcome by the use of tankless water heaters. However, heating water accurately and efficiently in a consistent and safe manner can be problematic with current tankless systems. It is, for example, difficult and highly inefficient to heat water to a desired useable state each time hot water is used. Applying full power to heating elements for short periods and randomly is very fatiguing on components and causes substantial wear and degradation. Further, in many prior art types of water heaters the water is over heated, too much water is heated, or the water is heated above a maximum desired temperature all of which wastes power and adds to the eventual deterioration of the system.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object the present invention to provide a new and improved control circuitry for tankless water heaters.
It is another object of the present invention to provide control circuitry for tankless water heaters that more closely controlls the temperature of the water during usage.
It is another object of the present invention to provide control circuitry for tankless water heaters that more closely provides a desired amount of water at a desired temperature.
Briefly, to achieve the desired objects of the present invention in accordance with a preferred embodiment thereof provided is a control circuitry for use with a tankless water heater system including a water heater module with a plurality of water conduits connected in series. The control circuitry includes a plurality of water heater elements, one each associated with each of the plurality of water conduits. A controller includes a central processing unit (CPU) with an operating program and each of the plurality of water heater elements are coupled to the CPU. The CPU is programmed to individually activate one of the water heater elements to a predetermined power level in response to a demand for heated water. The number of water heater elements activated and the power level of the activation is determined by the demand for heated water.
In a specific embodiment, control circuitry for a tankless water heater system is disclosed. The tankless water heater system includes a water heater module with four water conduits connected in series, the series connection being further connectable to a cold water supply and to provide a heated water flow to a heated water demand site. The control circuitry includes four water heater elements, one each associated with each of the plurality of water conduits. A controller in the control circuitry includes a CPU programmed with an operating program. A plurality of sensors are positioned in the water flow and electrically coupled to the controller with at least one of the plurality of sensors providing an indication of the water temperature in an outlet of the series connection. Connecting and operating circuitry couples each of the plurality of water heater elements to the CPU. The CPU is programmed to control the connecting and operating circuitry in accordance with indications from the plurality of sensors to individually activate a first water heater element to a first power level for a first heat required in response to a demand for heated water. For heat required greater than the first heat required and less than a second heat required in response to a demand for heated water the CPU increases the power level of the first water heater element in predetermined increments.
The CPU is programmed to control the connecting and operating circuitry in accordance with indications from the plurality of sensors to individually activate a second water heater element of the four water heating elements to the first power level for the second heat required. For heat required greater than the second heat required and less than a third heat required in response to a demand for heated water the CPU increases the power level of the second water heater element in predetermined increments. The CPU is also programmed to individually activate a third water heater element of the four water heater elements to the first power level for the third heat required. For heat required greater than the third heat required and less than a fourth heat required in response to a demand for heated water the CPU increases the power level of the third water heater element in predetermined increments. The CPU is also programmed to individually activate a fourth water heater element of the four water heater elements to the first power level for the fourth heat required. For heat required greater than the fourth heat required and less than a fifth heat required in response to a demand for heated water the CPU increases the power level of the fourth water heater element in predetermined increments.
The foregoing and further and more specific objects and advantages of the invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof, taken in conjunction with the drawings in which:
Turning now to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is directed to
Referring to
Power module 22 includes a terminal and breaker switch combination 25 to provide safety and reduce associated elements needed for installation. No separate or outside breaker box is necessary for the installation of system 10. Controller 50 receives water flow and water temperature data, controlling water heater module 30 by actuating solid-state relay switches 23. System 10, in the preferred embodiment, also includes mechanical relays 27, which act as safety shut-offs when a predetermined temperature is equaled or exceeded. These relays are coupled to controller 50 only for sensing information but are mechanically independent therefrom. Electrical power runs from breakers 25 through mechanical relays 27 to solid state relays 23. When signaled from controller 50, solid-state relay switches 23 provide power to module 30.
Turning now to
Turning now to
Referring now to
Heating elements 40 are secured in position within the ports of top head manifold 37 generally by some form of removable engagement mechanism. The purpose for providing an easily disengagable engagement between heating elements 40 and the ports is to permit quick and easy exchange of heating elements 40. Heating elements 40 can have greater or lesser heating capability. Thus, if higher temperatures, greater flow rates or just larger volumes of water are desired, higher output heating elements 40 can replace lower output elements in water heater modules 30. Also, in case of failure or reduced capabilities of one or more heating elements 40, easy and quick replacement is desirable.
As an example, a water heater system 10 having a single module 30 is installed at a location. Over time, larger volumes of water are used, increasing the flow rate of water through water heater module 30 and maxing out its performance. Instead of having to replace the entire module to upgrade the performance, the lower capacity heating elements are replaced with greater capacity elements. At some point, if performance needs to increase past the level of replacing heating elements, additional water heater modules can be installed to expand the system, as will be described presently.
With reference to
Referring back to
As can be understood from the description, top head manifold 37 and bottom head manifold 38 permit conduits 35 to share much of the thermal energy generated by heating elements 40 instead of radiating the energy to the surrounding environment. Additionally, while a distinct flow path sequentially through conduits 35 having heating elements 40 is provided, top head manifold 37 and bottom head manifold 38 cooperate to form a single container with respect to pressure water heater module 30. Due to this unique characteristic, a pressure relief valve 95 can be employed for increased safety. Pressure relief valve 95 is coupled to side port 47 of top head manifold 37.
As briefly mentioned previously, a flush mechanism 100 can be added to the system if desired as shown in
With reference to
A temperature control sensor 115 is inserted into port 55d through an aperture provided for that purpose. Temperature control sensor 115 senses outlet water temperatures exceeding a specific temperature. When temperatures equal to or exceeding a predetermined temperature are detected, over temperature sensor 115 cuts power to mechanical relays 27, preventing power from reaching relays 23. This circuit is a safety which bypasses controller 50 and shuts down heating elements 40 even if controller 50 signals relays 23 to apply power. A grounding lug 118 is inserted into port 55a through aperture 56b. Grounding lug 118 permits grounding of the electronic components with module 30.
Still referring to
As briefly touched upon previously, tankless water heater system 10 can be expanded to increase its capacity by including multiple water heater modules 30. Referring to
While controller 50 is employed with a water heater module 30 in the present embodiment, one skilled in the art will understand that controller 50 can also be employed with other water heater systems and tankless systems, such as those employing water heater chambers which for purposes of this disclosure can also be referred to as conduits, coupled in series, each having a heating element associated therewith. These chambers/conduits are individual elements coupled in series by piping as opposed to a unitary modular element.
Turning now to
Some of the sensing and driver circuits that are in or associated with controller 50 include a power regulator and voltage sensor 60 that is connected through a 28 volt transformer 61 to power module 22, a pulse input 66 that receives signals from flow sensor 110, an analog input 67 that receives analog signals from flow sensor 120 (if present), and a temperature control input 68 that receives inlet temperature from inlet temperature sensor 112. Flow sensor 110, flow sensor 120, and inlet temperature sensor 112 are all serially connected into cold water inlet line 90 in series with heaters 40a through 40d. Also, optionally, serially connected in cold water inlet line 90 is a cutout valve 69 that is controlled and driven by a coil driver 70 illustrated as a portion of controller 50. A thermal cutout switch 80 is serially connected in the hot water outlet line 92 (also in series with heaters 40a through 40d) and is controlled and driven by a coil driver 81 illustrated as a portion of controller 50.
In this embodiment, a coil driver 82, illustrated as a portion of controller 50, is connected to drive cleanout valve 104. The clean out process can be initiated automatically at predetermined times (generally determined by noting accumulated materials over a period of usage) through steps programmed into CPU 52. When the cleaning process is occuring, power will be interupted to heating elements 40 by CPU 52. As described briefly above, the cleaning process can be performed manually either by including a manually and automatically operable cleanout valve 104 or by only including a manually operable cleanout valve 104. In any case, water heater module 30 is cleaned by operating cleanout valve 104 and draining (flushing) water from the bottom to an external drain.
A drip/leak sensor 82, located at the bottom of water heater module 30, is connected to a leak sensor input 83, illustrated as a portion of controller 50. If water is present, as sensed by drip/leak sensor 82, power to heaters 40 will be automatically removed by CPU 52. If an automatic cutout valve (e.g. cutout valve 69) is included in controller 50, the valve will be operated by CPU 52 to disrupt the incoming flow of cold water.
Also included in controller 50 is an expansion interface 85 included for future expansion of the system. As described, controller 50 includes software stored in non-volatile memory (not illustrated) that programs CPU 52 to run a specific heating operation or program. If the program needs to be updated by changing circumstances or by an increase in heaters, etc., a programming device can be attached to controller 50, through a future expansion I/O 86 connected to expansion interface 85, and a new program can be uploaded. Generally, no integrated circuits need to be replaced for this process, which lowers the cost of upgrading control cicuit 24. However, if determined to be preferrable, replacement of the integrated circuitry is a viable option.
Controller 50 further includes four drivers, designated 87, electrically connected to solid-state relay switches 23a, 23b, 23c, and 23d. In this embodiment each of the four drivers 87 is a 24 volt DC 20 mA driver controlled by CPU 52. To ensure the correct heat for the most efficient power usage, when a heating cycle begins, a single one of heating elements 40a, 40b, 40c, or 40d is brought on initially, followed by another and another until all of the heaters are on. In this process the initial heater experiences more use than the other heaters and, therefore, to ensure all heaters are used evenly, the heater selected to begin a cycle rotates through the four heating elements 40a, 40b, 40c, and 40d. In this embodiment, controller 50 is programmed to change or alternate the staring heating element each time a heating cycle begins. It will be understood, however, that a power use (e.g. the amount of power applied, length of time applied, etc.) counting or monitoring process could be incorporated into the software of CPU 52 so that heating elements 40a, 40b, 40c, and 40d are cycled in an order that distributes usage evenly.
Referring additionally to
At this time all four heating elements 40a, 40b, 40c, and 40d are operating at 75% full power (see step 24 in
In addition to the incrementing of power described above, controller 50 uses a unique form of synchronous AC power control. The synchronous power control involves switching power to heating elements 40 through 40d, off or on, at the exact time that the AC voltage passes through zero volts (zero crossing). Also, CPU 52 determines the shortest number of power cycles that can implement the desired power level. Whereas, existing water heaters utilize power control that turns on power to the heaters for some portion of a fixed number of power cycles. The present novel system more evenly averages power usage and minimizes disturbances to other equipment attached to the power source.
Tankless water heater 10 can also be programmed to operate in an economy mode. In this mode the maximum power delivered to heating elements 40a through 40d is limited (e.g. 87.50% or even 75%). Full temperature can be attained in this mode by reducing the water flow, which can be achieved, for example, by including a controllable valve in the water inlet line. In many markets, energy costs change for some time periods of the day or week. Thus, for such situations, tankless water heater 10 can be automatically switched into the economy mode of operation. For example, week days can be broken into four time periods with each period having a predetermined power mode. Weekends can have a different power mode, depending upon the specific requirements determined by the owner/operator.
In the present embodiment, CPU 52 includes in its program steps for monitoring the heating efficiency. Heating elements can fail to produce heat, at which point the failed heating elememnt needs to be replaced. If, for example, a dramatic reduction in efficiency is detected, controller 50 will enter a special test mode to discover the failed heating element. In the special test mode, CPU 52 activates each heating element 40 through 40d individually and looks for a temperature rise. If a temperature rise is not sensed, the heating element being activated will be determined to be failed and will no longer be used. A light or other indicator can be used to warn an operator of the failure.
Similarly, controller 50 can include a program for detecting a faulty thermal sensor 114. If heating circuits are energized. A temperature rise is expected. Thus, a thermal sensor testing mode can be incorporated into the program of CPU 52. If, for example, a heating element is activated and no rise in temperature is detected, the thermal sensor test mode will be activated. In this mode, CPU 52 activates the heating elements 40a through 40d and looks for a temperature rise. If no rise is detected, the unresponsive temperature sensor will be noted as failed.
In still a further safety mode of operation, controller 50 can monitor the amount of water flowing through tankless water heater 10 in each single use. Controller 50 can be set to allow a limited or predetermined maximum volume to flow or limit the time of operation to a prescribed period of time. After the maximum volume of water has flowed through tankless water heater 10, heating will be disabled. Also, an automatic shutoff valve (e.g. cutout valve 69) can be installed and will be controlled to disrupt incoming water when the maximum volume has been reached. Thus, when faucets are inadvertently left on or breaks or other failures occur, water flow can be stopped, rather than continue to flow.
Outlet temperature sensor 114, or an additional sensor, can also sense the heating chamber temperature and when the outlet temperature exceeds a safe level (generally a temperature near the thermal cutout temperature) CPU 52 interrupts power to heating circuits 40a through 40d. If the thermal cutout temperature is actually reached, thermal cutout valve 80 is operated by CPU 52 to prevent the overheated water from flowing. Also, if cutout valve 69 is an automatic valve it may be operated by CPU 52 at this time to disrupt incoming water. Further, controller 50 continuously monitors the heating chamber temperature since for example, if the heater freezes the water it contains will expand and may burst the heating chamber. If the temperature comes close to freezing, a brief heating cycle will be activated by CPU 52 to prevent the heating chamber from freezing. One further feature that can be incorporated is an ultraviolet purification system. While water is flowing through the heating chamber the ultraviolet purification system can be activated by CPU 52 to purify the water as it flows through the system.
Thus, a new and improved tankless water heater controller is disclosed that heats water very accurately and efficiently as it is needed. Since only the amount of water needed is heated and since the temperature is closely controlled the system is very efficient. Further, a plurality of safety features are incorporated to ensure safe operation as well as safe use of the water. The new and improved control circuitry for tankless water heaters more closely controls the temperature of the water during usage. Also, the new and improved control circuitry for tankless water heaters more closely provides a desired amount of water at a desired temperature.
Various changes and modifications to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof, which is assessed only by a fair interpretation of the following claims.
Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is:
