Abstract:
The disclosure relates generally to steam humidifiers with an auto-cleaning feature, and more particularly, to steam humidifiers that include an auto-cleaning feature for automatically cleaning impurities and/or other byproducts from the steam humidifier while still operating the humidifier in a relatively efficient manner. In some illustrative embodiment, this may be accomplished by providing some level of flexibility of when an auto-cleaning routine is initiated and performed. For example, tank flushing may be initiated and performed preferentially during non-heating states of the steam humidifier, which may potentially decrease down time and increase attainable output capacity and efficiency of the steam humidifier.

Description:
TECHNICAL FIELD 
     The disclosure relates generally to humidifiers, and more particularly, to steam humidifiers with an auto-cleaning feature. 
     BACKGROUND 
     In dry or colder climates, it is often desirable to add moisture to the air that is inside of an enclosed space such as a building in order to maintain suitable humidity levels. There are a variety of products on the market today that employ various techniques to provide humidification including, for example, steam injection, water atomization, and evaporation. Such humidifiers are often used in conjunction with forced air residential and commercial heating, ventilation, and air conditioning (HVAC) systems. 
     A steam type humidifier typically heats water to make steam, and then provides the steam into a desired air stream, such as a duct of a forced air HVAC system. Such steam humidifiers are typically connected to a water source of the building, and draws the water from the water source into a water tank. The water in the water tank is then heated to produce steam. In many cases, the water contains certain impurities such as certain minerals, chemicals and/or other impurities. When this water is boiled, some or all of the impurities tend to be left behind, and if not properly removed, can build up and ultimately clog the humidifier. 
     What would be desirable, therefore, is a steam humidifier that includes an auto-cleaning feature for automatically cleaning the impurities and/or other byproducts from the steam humidifier, while still operating the humidifier in an efficient manner. 
     SUMMARY 
     The disclosure relates generally to steam humidifiers with an auto-cleaning feature, and more particularly, to steam humidifiers that include an auto-cleaning feature for automatically cleaning impurities and/or other byproducts from the steam humidifier while still operating the humidifier in a relatively efficient manner. In some illustrative embodiment, this may be accomplished by providing some level of flexibility of when an auto-cleaning routine is initiated and performed. For example, tank flushing may be initiated and performed preferentially during non-heating states of the steam humidifier, which may potentially decrease down time and increase attainable output capacity and efficiency of the steam humidifier. 
     In an illustrative but non-limiting example, the disclosure provides a method for flushing a steam humidifier having a water reservoir. The steam humidifier may have a heating state for generating steam and a non-heating state. The steam humidifier may be configured to alternate between the heating state and the non-heating state during normal operation to provide a desired level of humidity to an inside space. A humidistat or the like that is positioned in the inside space may control when the steam humidifier is the heating and non-heating states. 
     The method for flushing the steam humidifier may include executing a flush routine, during which the water reservoir is flushed, and after the flush routine is executed, alternating between the heating state and the non-heating state for a run time period. A defined window of time follows the end of the run time period, and if the steam humidifier enters the non-heating state during the defined window of time, the flush routine may be executed again. Following this, the steps of alternating between heating and non-heating states during the run time period, and executing the flush routine if the steam humidifier enters the non-heating state during a window of time following the run time period are repeated one or more times. In some cases, this method may be extended to include executing the flush routine at the end of the window of time if the steam humidifier has not entered the non-heating state during the defined window of time. 
     In another illustrative but non-limiting example, the disclosure may provide a steam humidifier having a heating state and a non-heating state. The steam humidifier may include a water-heating reservoir and a controller configured for commanding flushing of the water-heating reservoir. The controller may command flushing of the water-heating reservoir if a minimum time interval has elapsed since a last flushing and if the steam humidifier is in the non-heating state, or if a maximum time interval has elapsed since the last flushing. 
     The above summary is not intended to describe each and every disclosed illustrative example or every implementation of the disclosure. The Description that follows more particularly exemplifies the various illustrative embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The following description should be read with reference to the drawings. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the disclosure. The disclosure may be more completely understood in consideration of the following detailed description of various illustrative embodiments in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an illustrative steam humidifier; 
         FIG. 2  is a schematic time sequence illustrating aspects of an illustrative method of flushing a steam humidifier; 
         FIG. 3  schematically illustrates one way of defining a window of time; 
         FIG. 4  is a schematic time sequence illustrating aspects of another illustrative method of flushing a steam humidifier; 
         FIG. 5  is a schematic time sequence illustrating aspects of an optional extension to the method of  FIG. 4 ; and 
         FIG. 6  is a schematic time sequence illustrating aspects of yet another illustrative method of flushing a steam humidifier. 
     
    
    
     DESCRIPTION 
     The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized. 
       FIG. 1  is a perspective view of an illustrative steam humidifier  100 . Steam humidifier  100  includes a water-heating tank or reservoir  102 , and a heating element (not shown; disposed in tank  102 ) in thermal communication with water in the tank  102 . When the tank  102  is filled with water to a suitable level, the humidifier  100  may be disposed in a heating state where power, typically electrical power, is provided to the heating element to boil or otherwise heat the water to produce steam, which is typically introduced into an airstream within an HVAC duct to which the humidifier may be attached. The steam humidifier  100  may generally alternate or cycle between heating and non-heating states, depending on the demand for humidity by the system. Entry of water into the tank may be controlled by a water supply valve  106  coupled to a water supply. Drainage from the tank may be controlled by a water drain valve  108  coupled to a water drain. 
     Over time, heating of water and production of steam will result in a buildup of byproducts such as sediment, minerals, debris, and the like. These byproducts, if allowed to accumulate, may result in one or more undesirable effects, such as reduced heat transfer from the heating element, reduced capacity in the tank  102 , clogging of the water drain valve  108 , etc. Therefore, it is desirable to remove these byproducts of steam production from the tank  102 . Removal of the byproducts may be achieved by, for example, flushing the tank from time to time. Flushing generally may be accomplished, by, for example, draining water from the tank by opening water drain valve  108 , and filling the tank by opening water supply valve  106 . Any appropriate sequence of controlling valves  106  and  108  may be practiced. For example, draining may be followed by filling, with no overlapping time where both valves  106 ,  108  are open, or both valves may be open simultaneously such that water entering the tank from the water supply valve may flowingly transport debris out through the open drain valve. Other sequences of valve operations may also be useful. 
     A controller (not shown) may be included as part of humidifier  100 , or may be provided externally and interfaced with the humidifier. The controller may be configured to command flushing of the humidifier when appropriate conditions are met, and/or command steps to be performed in executing a humidifier flush routine, such as opening and closing valves  106 ,  108 , as well as possibly controlling other aspects of humidifier operation. 
       FIG. 2  is a schematic time sequence illustrating aspects of an illustrative method of flushing a steam humidifier, such as steam humidifier  100  of  FIG. 1 , or any other suitable steam humidifier. In the time sequence illustrations of  FIG. 2 , time progresses forward toward the right. The illustrative method starts with execution of a flush routine at  202 . At the end  204  of the initial flush routine  202 , a run time period  206  commences. During the run time period  206 , the humidifier may alternate between a heating state and a non-heating state, often under the control of a humidistat or the like, without interruption from a flush routine. Alternating between heating and non-heating states may depend on, for example, the current demand for humidity in the inside space of the building. In  FIG. 2 , a defined window of time  208  follows the end  210  of the run time period  206 . As shown, the start  212  of the window of time  208  coincides with the end  210  of the run time period  206 , but this is not required. After the start  212  of the window of time  208 , the steam humidifier may execute a flush routine when appropriate conditions are met, as described further herein. 
     During the window of time  208 , the steam humidifier may execute a flush routine when the steam humidifier enters a non-heating state. An example of this is represented in the time sequence as flush routine  214 . Executing a flush routine may include a number of steps, discussed here in connection with steam humidifier  100 , though the flush routine described may be executed with any suitable and compatible steam humidifier. Before flushing the water tank  102  of  FIG. 1 , it may be desirable or necessary to ensure that the water is at a safe or otherwise acceptable temperature. This may, for example, help avoid a scalding injury to anyone who might come into contact with the flushed water, to avoid damage to plumbing not intended for high temperatures, and/or for environmental considerations, etc. In cases where a flush routine has been entered after the humidifier  100  of  FIG. 1  enters a non-heating state, such as flush routine  214  of  FIG. 2 , executing the flush routine may include remaining in the non-heating state during the flush routine. In other cases, when a flush routine is commanded while the humidifier  100  is in a heating state, the flush routine may include reverting the humidifier to the non-heating state, and remaining in the non-heating state during the flush routine. Other steps taken to ensure that the water is at an acceptable temperature may include obtaining a measure of the water temperature, for example, with a temperature sensor (not shown). If the temperature is determined to be below a threshold value (“safe value”), flushing of the reservoir may proceed. If not, the water temperature measurement may be repeated until the water temperature is determined to be safe (e.g., below the threshold value). In some instances, a flush routine may include waiting for a cooling period of time before flushing the reservoir. 
     Executing a flush routine may take a non-negligible amount of time, particularly in view of temperature safety considerations and/or the water reheat times. During this non-negligible amount of time, the steam humidifier may be generally considered to be off-line and unable to provide humidity to a calling system. Ill-timed execution of such flush routines, for example, those that interrupt heating states during calls for humidity, may significantly degrade a steam humidifier&#39;s output capacity and/or performance. By waiting until a non-heating state begins, sometimes during the defined window of time  208 , the illustrative method of  FIG. 2  may avoid or at least reduce the negative impacts of some or all flush routines. 
     In certain scenarios, such as during a period of high demand for humidification, a steam humidifier may not enter a non-heating state for an extended period of time, and more particularly, may not enter a non-heating state during the defined window of time  208  following a run time period  206 . It is still desirable, nonetheless, to flush the humidifier from time to time to maintain performance of the steam humidifier. An illustration of such a scenario is presented in  FIG. 2 , as the time sequence progresses past flush routine  214 . At the end  216  of flush routine  214 , another run time period  218  commences. Following the end  220  of run time period  218 , another defined window of time  222  begins. During window of time  222 , the steam humidifier does not enter a non-heating state, and accordingly, a flush routine is not invoked during the window of time  222 . Upon reaching the end  224  of the window of time  222  without having executed a flush routine, the illustrative method of  FIG. 2  executes flush routine  226  regardless of the disposition of the humidifier in a heating or non-heating state. Upon completion of flush routine  226 , another runtime period  228  begins. The method generally may execute a flush routine once per window of time, either during a non-heating state during the window of time, or upon reaching the end of the window of time. In many instances, the method does not execute a flush routine more than once during a single window of time following a run time period. 
     The disposition of a window of time following a run time period may be defined in any appropriate way. For example, in some illustrative embodiments, a window of time commences immediately upon the end of a run time period, and extends for a defined window of time duration. In other illustrative embodiments, a window of time may be described in terms of other quantitative parameters.  FIG. 3 , for example, schematically illustrates one way of defining a window of time. A nominal flush time delay  302  is timed relative to the end  304  of a flush routine  306 . The nominal flush time delay  302  may represent a desired, but not required, time span between flush routines. A first predetermined time span  308  is the amount of time by which the start or beginning  310  of window of time  312  precedes the completion of the nominal flush time delay  302 . A second predetermined time span  314  is the amount of time by which the end  316  of the window of time  312  follows the completion of the nominal flush time delay  302 . The window of time  312  shown in  FIG. 3  may thus be defined in a method such as the method illustrated in  FIG. 2 , or any other suitable method. Further, the values of the parameters that describe such a window of time, as well as the magnitude of the run time period, may be configurable by an end user, by an installer, at the time of manufacture or design, or in any suitable way as desired. 
       FIG. 4  is a schematic time sequence illustrating aspects of another method of flushing a steam humidifier. The illustrated method starts with resetting a timer at  402 , where the timer reports an elapsed time since it was reset. Later, if the elapsed time since reset is greater than an interval T, and if a flush routine has not yet been executed during the elapsed time since reset, and if the steam humidifier is in the non-heating state, a flush routine is executed. In  FIG. 4 , the flush routine  404  meets these conditions and starts at  406 , immediately upon reaching elapsed time T. Executing a flush routine in the illustrative method of  FIG. 4  may be performed in any suitable way, including as disclosed in connection with the method illustrated in Figure. Upon reaching the end  408  of the flush routine  404 , the timer may be reset, as shown at  410 . Time progresses, and elapsed time T is again reached at  412 , but during this cycle, the humidifier is not found in the non-heating state, and so the method continues without executing a flushing routine. At  414  in  FIG. 4 , the elapsed time reaches T plus an overtime tolerance T O . Upon reaching this time (T+T O ), without having already executed a flush routine, the illustrative method proceeds to execute a flush routine  416 , regardless of the disposition of the humidifier in a heating or non-heating state. Upon completion of the flush routine  416  at  418  in  FIG. 4 , the timer may again be reset, as shown at  420 . In the illustrative method of  FIG. 4 , the period from T to T O  may correspond to the window of time shown and described with respect to  FIG. 2 . 
       FIG. 5  is a schematic time sequence illustrating aspects of an optional extension to the method of flushing a steam humidifier illustrated in  FIG. 4 . The optional extension provides for flushing the humidifier opportunistically before an elapsed time T after the previous reset has been reached, if the temperature of the water in the reservoir is low enough to allow immediate flushing without requiring waiting for the water to cool to a safe temperature. In this extension, an under time tolerance T U  may be defined, and if the elapsed time since reset is less than the interval T, but greater than T−T U , and if the flush routine has not yet been executed during the elapsed time since reset, and if the steam humidifier is in the non-heating state, and if the water temperature of the water in the reservoir is at or below a threshold value, the reservoir may be flushed. In essence, allowing the possibility of flushing opportunistically is another way to provide maintenance flushing while minimally impacting humidifier output capacity and efficiency. When water is sufficiently cool in the reservoir, the step of cooling prior to flushing, which costs time, may be avoided, with only the penalty of flushing the reservoir a little earlier than nominally planned (when within T U  of reaching time T). 
     Referring specifically to  FIG. 5 , a timer is reset at  502 . At  504 , the timer has not yet reached an elapsed time interval of T, but the time is within T U  of reaching time T. At  506 , the time has still not reached T, but temperature of the water in the reservoir has dropped to or below a threshold value and the humidifier is in the non-heating state, so a flushing routine  508  starts. Flushing routine  508  is initiated relatively quickly, as no cooling period is needed, and ends at  510 , upon which the timer is reset again, as shown at  512 . Moving forward from the reset at  512 , conditions for starting a flushing routine are not satisfied again until  514 , which occurs after the under time opportunity period between T−T U  and T. That is, at  514 , the humidifier is shown entering the non-heating state when the timer is at an elapsed time greater than interval T. It is contemplated that the values of parameters of the method illustrated in  FIG. 5 , such as T, T O , and T U , may be determined by an end user, by an installer, at the time of manufacture or design, or in any other suitable way as desired. 
       FIG. 6  is a schematic time sequence illustrating aspects of another illustrative method of flushing a steam humidifier. In this illustrative method, one or more flushing windows are determined, with each flushing window having a window start time and a window end time. In  FIG. 6 , three flushing windows have been determined. A first window  602  has a start  604  and an end  606 . A second window  608  has a start  610  and an end  612 . A third window  614  has a start  616  and an end  618 . First, second, and third are used here merely as labels and do not necessarily designate order relative to a method start time. Any suitable method may be used to determine the one or more flushing windows of the method illustrated in  FIG. 6 . For example, the windows may be determined by an end user, by an installer, at the time of manufacture or design, by a control algorithm, or in any suitable manner, as desired. In some illustrative embodiments, two or more flushing windows space in time by at least four hours are determined. In some illustrative embodiments, two or more flushing windows may be determined for every day, with the flushing windows at substantially similar times of each day. It may be desirable to place flushing windows at similar times every day, for example, when humidity demand is likely to be lower, or when flushing would be less disruptive to occupants or activities. 
     The conditions for executing flush routines relative to the windows  602 ,  608 ,  614  of  FIG. 6  may be similar to the conditions discussed in connection with the illustrative methods discussed herein. As shown in  FIG. 6 , during the first flushing window  602 , the humidifier remains in a heating state and no flush routine is entered until reaching the end  606  of the window  602 , upon which flush routine  620  executes regardless of the heating or non-heating state of the humidifier (the humidifier is placed in a non-heating state). After flush routine  620  ends, the humidifier may proceed without consideration of entering another flush routine until the second flushing window  608  commences at  610 . In the illustrative diagram of  FIG. 6 , the humidifier is still be in a heating state at  610 , and flush routine  622  does not execute until  624 , when the humidifier enters a non-heating state. During the third flushing window  614 , flush routine  626  only starts after a non-heating state is entered by the humidifier at  628 . 
     In the illustrative method of  FIG. 3 , the timing of flushing windows is determined by a determining step, and the timing of a particular flushing window does not necessarily depend directly upon the execution of the immediately preceding flushing routine. In contrast, in the method shown in  FIG. 2 , a run time period generally commences at the end of an immediately preceding flush routine. Commonly, in that method, a window of time would immediately follow a run time period, and hence a fixed period of time may separate windows of time from immediately preceding flush routines. In the method of  FIG. 6 , the time span separating a flushing window from an immediately preceding flush routine may be varied, as desired. 
     Methods of the present disclosure may be implemented in any suitable way, with any suitable equipment. For example, a steam humidifier like or similar to steam humidifier  100  of  FIG. 1  may be provided with a controller or controllers capable of commanding and/or controlling flush routines using any of the methods disclosed herein. In some illustrative embodiments, after-market controllers may be provided that may be retrofitted to work with existing steam humidifiers to practice methods disclosed herein. 
     In one embodiment, a steam humidifier having a heating state and a non-heating state is provided. The humidifier may include any or all features of steam humidifier of  FIG. 1 . The humidifier may have a water-heating reservoir and a controller configured for commanding flushing of the water-heating reservoir. The controller may command flushing of the water-heating reservoir if a minimum time interval has elapsed since a last flushing, and if the steam humidifier is in the non-heating state. The controller also may command flushing if a maximum time interval has elapsed since the last flushing. The controller may be configured to initiate a flushing routine for flushing the water heating reservoir. The flush routine may include determining that a water temperature in the water-heating reservoir is below a threshold value, draining the water-heating reservoir after the water temperature in the water-heating reservoir is determined to be below a threshold value, and refilling the water-heating reservoir after the water-heating reservoir is drained. The humidifier may include a temperature sensor for sensing the temperature of the water in the water-heating reservoir and communicating the temperature to the controller. The humidifier may include valves fluidly coupled to a water drain and a water supply, controllable by the controller, so as to drain water from and direct water into the water-heating reservoir. 
     The disclosure should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the invention can be applicable will be readily apparent to those of skill in the art upon review of the instant specification.