HYBRID HEATER FOR POOLS AND SPAS

Abstract

A swimming pool or spa may include hybrid heater. The hybrid heater includes an enclosure, a first heat source within the enclosure, and a second heat source within the enclosure. The first heat source may include an electric heater. A method of heating a swimming pool or spa using the hybrid heater includes receiving information about a desired temperature of the pool, determining an operating mode of the hybrid heater based on the received information, and controlling the hybrid heater pursuant to the determined operating mode.

Description

FIELD OF THE INVENTION

This application relates to heaters for water-containing vessels such as swimming pools and spas.

BACKGROUND

Swimming pools and spas commonly include water heaters for controlling the temperature of the water in the pool or spa. Different types of heaters have traditionally been used, including heat pumps or gas heaters, and each type of heater has certain advantages and disadvantages. As an example, users often make an impulsive decision to use their spa or pool and do not turn on the heater ahead of time, and thus must wait on the heater to heat the pool or spa. While gas heaters may be quick to heat the pool or spa compared to a heat pump (e.g., 30 minutes using the gas heater vs. 3 hours using the heat pump), a supply of gas is not always available, and certain locations may only have a heat pump available. Some users may employ multiple pieces of equipment to heat the water faster (e.g., a heat pump and a gas heater), but having multiple pieces of equipment is costly, takes up more space, and may not provide optimized heating. Moreover, as mentioned, certain types of heaters (e.g., gas heaters) may be unavailable in certain locations. Certain types of heaters may also be susceptible to environmental conditions that further decrease their performance. As an example, ice may build up on coils of a heat pump when the heat pump is operated in colder temperatures. Some heat pumps may include a defrost cycle feature, which works by reversing the heat pump for a period of time until the ice melts, but such defrost cycle features further extend the time needed to heat up the pool or spa because the pool or spa is not heated during the defrost cycle.

SUMMARY

Described herein are hybrid heaters and associated systems and methods for heating pools and spas.

According to some embodiments, a hybrid heater includes an enclosure, a first heat source within the enclosure, and a second heat source within the enclosure. In various embodiments, the first heat source includes an electric heater.

According to certain embodiments, a method of heating a pool using a hybrid heater includes receiving information about a desired temperature of the pool and determining an operating mode of the hybrid heater based on the received information. The method may include generating an output pursuant to the determined operating mode. In some embodiments, generating the output may include controlling the hybrid heater pursuant to the determined operating mode.

According to certain embodiments, a hybrid heater includes an enclosure, an electric heat pump within the enclosure, and an electric resistance heater within the enclosure.

Various implementations described herein may include additional systems, methods, features, and advantages, which cannot necessarily be expressly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within the present disclosure and protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The specification makes reference to the following appended figures, in which use of like reference numerals in different figures is intended to illustrate like or analogous components.

FIG. 1 illustrates a heating system for a pool, spa, or other water-containing structure according to embodiments.

FIG. 2 is a flow chart of a method of controlling a hybrid heater according to embodiments.

FIG. 3 is a flow chart of a method of controlling a hybrid heater according to embodiments.

FIG. 4 is a flow chart of a method of controlling a hybrid heater according to embodiments.

DETAILED DESCRIPTION

Described herein are hybrid heaters and associated systems and methods for heating pools and spas. The hybrid heaters generally include a first heat source or heating device and a second heat source or heating device within a common enclosure, and the first heating device includes an electric resistance heater. The second heating device may be other types of heaters, and in certain embodiments, the second heating device is a heat pump. As such, while the following description will make specific reference to the “heat pump,” the description is applicable to any type of second heating device.

Advantageously, the hybrid heaters described herein provide a single piece of equipment that can operate in multiple modes depending on the heating or setting need. For example, depending on need, the hybrid heater may be operated such that water for the pool or spa is provided by operating only the electric resistance heater, only the heat pump, or both the first electric resistance heater and the heat pump.

In certain embodiments, a controller of the hybrid heater may generate an output response based on setting provided by the user. In some embodiments, generating the output response may include, but is not limited to, controlling the hybrid heater to operate in various modes based on settings provided by a user (e.g., a desired temperature) and/or feedback from a sensor associated with the hybrid heater. As one non-limiting example, based on a received setting from the user to reach a set temperature with the least energy consumed, the controller may control the hybrid heater to operate in a normal mode in which only the heat pump is operating. As another non-limiting example, based on a received setting from the user to reach a set temperature in the shortest possible time, the controller may control the hybrid heater to operate in a fast heat mode in which both the electric resistance heater and the heat pump are operating. As yet another non-limiting example, based on a received setting to maintain the hybrid heater above a predetermined temperature, the controller may operate the hybrid heater in a low ambient mode in which either the electric resistance heater is operating or a combination of the heat pump and the electric resistance heater are operated to maintain the temperature (e.g., to prevent icing). Various other modes of operating the hybrid heater may be employed, and the aforementioned examples should not be considered limiting. Moreover, various other benefits and advantages may be realized with the hybrid heaters described herein, and the aforementioned benefits and advantages should not be considered limiting.

FIG. 1 illustrates a heating system 100 for a pool, spa, or other water-containing structure (hereinafter “pool 102”) that includes a hybrid heater 104 for selectively heating water for the pool 102. The pool 102 is in fluid communication with the hybrid heater 104 such that water is supplied from the pool 102 to the hybrid heater 104 (water on this path represented by arrow 106) and returned from the hybrid heater 104 to the pool 102 (water on this path represented by arrow 108).

The hybrid heater 104 includes a housing 110, a first heating device 112 within the housing 110, and a second heating device 114 within the housing 110. The housing 110 may include one or more inlets for receiving the water 106 from the pool 102 and one or more outlets for returning the water 108 back to the pool 102 after passing through the hybrid heater 104.

In certain embodiments, the first heating device 112 is an electric resistance heater that utilizes electric currents to create heat. In some embodiments, the electric resistance heater includes a resistive element or resistor that is placed in contact with the water and an electric current is supplied to generate heat in the resistive element, which in turn heats the water. In other embodiments, the electric resistance heater may pass current directly through the water itself, thereby utilizing the water as the resistor.

The second heating device 114 may be various types of heaters, and in the embodiment illustrated, the second heating device 114 is a heat pump. In some embodiments, the second heating device 114 and the first heating device 112 utilize the same power source (e.g., electricity), although they need not in other embodiments.

In addition to the heaters 112, 114, the hybrid heater 104 includes a controller 116 (e.g., processor and/or memory), which may be provided at various locations as desired. The controller 116 is communicatively coupled to the heaters 112, 114 and selectively controls the heaters 112, 114 as discussed in detail below. In various embodiments, the controller 116 may generate other outputs in addition to or in place of controlling the heaters 112, 114 as desired.

Optionally, one or more sensors 118 may be provided. The sensors 118 may detect and/or monitor various parameters about the heating system 100, including but not limited to a temperature or other characteristic of water in the pool 102, a temperate or other characteristic of water 106 received by the hybrid heater 104, a temperature or other characteristic of the water 108 returned to the pool 102, a heating output or performance of the heater 112 and/or the heater 114, an operating status of the first heating device 112, an operating status of the second heating device 114, environmental conditions around the hybrid heater 104 and/or the pool 102, combinations thereof, and/or other parameters as desired. The sensor(s) 118 may be at various locations as desired, including on and/or included with the hybrid heater 104 or at locations remote from the hybrid heater 104. The sensor(s) 118 may be communicatively coupled to the controller 116 to selectively provide the detected information to the controller 116.

Optionally, the hybrid heater 104 includes one or more features for receiving settings or input from a user. Such features may include, but are not limited to, a user interface on the heater, a communications module enabling wireless or wired communication with some external device (e.g., a user’s cell phone, computer, etc.), combinations thereof, and/or other features as desired. The features for receiving the settings and input from the user may be communicatively coupled to the controller 116 to selectively provide the settings and input to the controller 116. Non-limiting examples of user input that may be used by the controller 116 include, but are not limited to, a desired temperature, a timeframe in which the desired temperature should be reached, a desired energy mode, etc.

The controller 116 may control the hybrid heater 104 to provide a heating output based on a particular need. Such control by the controller 116 may include controlling the hybrid heater 104 such that only the first heating device 112 is operating, only the second heating device 114 is operating, or both the first heating device 112 and the second heating device 114 are operating. In certain embodiments, the controller 116 controls the hybrid heater 104 based on the settings input from the user and/or based on the information detected by the sensor(s) 118. In various embodiments, the hybrid heater 104 is operable in a plurality of operating modes and based on the settings input from the user and/or the information from the sensor(s) 118, the controller 116 may determine the operating mode for the hybrid heater 104 and control the heaters 112, 114 pursuant to the determined operating mode. The operating modes of the hybrid heater 104 may be predetermined or preprogrammed, and/or the operating modes may be determined by the controller 116. Examples of operating modes are discussed below, but the below examples should not be considered limiting, and other operating modes may be employed as desired.

In one non-limiting example, the controller 116 may operate the hybrid heater 104 in a normal mode in which only the second heating device 114 (i.e., heat pump) is operating. In one embodiment, the controller 116 may control the hybrid heater 104 to be in the normal mode based on a user input from the user to reach a set temperature with the least energy consumed.

In another non-limiting example, the controller 116 may operate the hybrid heater 104 in a fast heat mode in which both the first heating device 112 and the second heating device 114 are activated. In one embodiment, the controller 116 may control the hybrid heater 104 to be in the fast heat mode based on a user input from the user to reach a set temperature in a shortest possible time.

In another non-limiting example, the controller 116 may operate the hybrid heater in a low ambient mode in which only the first heating device 112 is operating or both the first heating device 112 and the second heating device 114 are operated in combination. In certain embodiments, the hybrid heater 104 may be operated in the low ambient mode to prevent icing on the hybrid heater 104. In one embodiment, the controller 116 may control the hybrid heater 104 to be in the low ambient mode based on an ambient temperature (e.g., detected by a sensor 118) dropping below a threshold temperature or based on information received about a forecasted drop in temperature below the threshold temperature.

In certain embodiments, in addition to controlling an activation or deactivation of the heaters 112, 114, the controller 116 may control a performance or heating output of the heaters 112, 114. As one non-limiting example, the controller 116 may modulate or otherwise control the electric current provided to the heater 112 and/or the heater 114 to control a heating pattern provided by the hybrid heater 104. As another non-limiting example, the controller 116 may modulate or otherwise control the hybrid heater 104 using a time-based or mode-based control (e.g., the controller 116 may only modulate the power source to the heaters in certain modes and/or time periods during a day). In certain embodiments, modulating and/or otherwise controlling the electric current (or other power source) to control the heating output may optimize heating performance and improve energy efficiency, prevent or minimize coils from icing, and/or maximize current output from a breaker. As used herein, “modulating,” “modulation,” and the like refer to a variable control of a power source to the heaters 112, 114 of the hybrid heater 104 and is not limited to electric current as the power source. As a non-limiting example, one of the heaters of the hybrid heater 104 may use gas and/or other power sources as desired, and the controller 116 may modulate or control the power source (e.g., gas flow) such that the heater provides a varying heat output.

FIG. 2 illustrates a non-limiting example of a method controlling the hybrid heater 104 based on user input. In certain embodiments, at least some steps of the method of FIG. 2 are performed by the controller 116 to control the hybrid heater 104. In some non-limiting examples, the method illustrated in FIG. 2 may be used by the controller 116 to control the hybrid heater 104 pursuant to the normal mode or the fast heat mode, among other possible modes.

In a block 202, the method includes receiving an activation of the overall hybrid heater 104 from the user (e.g., the user turns on the hybrid heater 104). Block 202 may also include receiving a desired water temperature. In certain embodiments, block 202 is performed by receiving the activation and desired temperature on a user interface of the hybrid heater 104 and/or receiving the information wirelessly.

In a block 204, the method includes determining an operating mode of the hybrid heater 104 based on the data received in block 202. In some embodiments, block 204 includes determining the operating mode based on a mode selected by the user (e.g., a “quick heating” mode or an “energy efficient heating” mode) and/or based on a desired time to reach the desired temperature (e.g., reach a desired temperature at a particular time, such as 2 PM, or within a time period, such as in 2 hours).

In a block 206, the controller 116 determines whether a shortest heating time is desired based on the information received in blocks 202 and the operating mode determined in block 204.

In a block 208, based on the controller 116 determining that the shortest heating time is desired, the controller 116 may activate both heaters 112, 114 such that both heaters 112, 114 are operating.

In a block 210, based on the controller 116 determining that the shortest heating time is not desired, the controller 116 may activate the heater 114 (heat pump). In one non-limiting example, block 210 optionally may include modulating or otherwise controlling or varying the power source to the heaters 112, 114 to control the heat output based on the hybrid heater 104 being in a particular operating mode (e.g., the normal mode).

FIG. 3 illustrates a non-limiting example of a method of controlling the hybrid heater 104 based on sensor or data input. In certain embodiments, at least some steps of the method of FIG. 3 are performed by the controller 116 to control the hybrid heater 104. In some non-limiting examples, the method illustrated in FIG. 3 may be used by the controller 116 to control the hybrid heater 104 pursuant to the normal mode or the fast heat mode, among other possible modes.

In a block 302, the method includes receiving an activation of the overall hybrid heater 104 from the user (e.g., the user turns on the hybrid heater 104). Block 302 may also include receiving a desired water temperature. In certain embodiments, block 302 is performed by receiving the activation and desired temperature on a user interface of the hybrid heater 104 and/or receiving the information wirelessly.

In a block 304, the method includes receiving heating parameters from internal or external sources. In some embodiments, block 304 includes receiving information from the one or more sensors 118. As a non-limiting example, block 304 may include receiving a water temperature, air temperature, humidity, etc. from one or more sensors 118 associated with the hybrid heater 104 or from another external source such as a weather application. Additionally, or alternatively, block 304 may include receiving heater parameters from the user using a user interface, wireless communication, or as otherwise desired.

In a block 306, the method includes determining an optimal heating output of the first heating device 112 (electric resistance heater) and the second heating device 114 (heat pump) based on the information received in block 304. Optionally, block 306 includes determining an operating mode for the hybrid heater 104 based on the information received in block 304.

In a block 308, the method includes controlling the first heating device 112 and the second heating device 114 pursuant to the determined optimal heating output and/or determined operating mode that was determined in block 306. In some embodiments, block 301 optionally includes modulating and/or otherwise controlling or varying the power source to the heaters 112, 114 to control the heat output from the heaters 112, 114. In one non-limiting example, block 308 optionally may include modulating or otherwise controlling or varying the power source to the heaters 112, 114 to control the heat output based on the hybrid heater 104 being in or controlled pursuant to a particular operating mode (e.g., the normal mode).

In a block 310, the method includes continuing the receive input information (similar to block 304) and adjust output levels for each of the heaters 112, 114 (similar to block 308) while the hybrid heater 104 is activated. In some embodiments, block 310 optionally includes modulating and/or otherwise controlling or varying the power source to the heaters 112, 114 to control the heat output from the heaters 112, 114. In one non-limiting example, block 310 optionally may include modulating or otherwise controlling or varying the power source to the heaters 112, 114 to control the heat output based on the hybrid heater 104 being in or controlled pursuant to a particular operating mode.

FIG. 4 illustrates a non-limiting example of a method controlling the hybrid heater 104 based on an ambient temperature. In certain embodiments, at least some steps of the method of FIG. 4 are performed by the controller 116 to control the hybrid heater 104. In some non-limiting examples, the method illustrated in FIG. 4 may be used by the controller 116 to control the hybrid heater 104 pursuant to the low ambient mode.

In a block 402, the method includes receiving an activation of the overall hybrid heater 104 from the user (e.g., the user turns on the hybrid heater 104). Block 402 may also include receiving a desired water temperature. In certain embodiments, block 402 is performed by receiving the activation and desired temperature on a user interface of the hybrid heater 104 and/or receiving the information wirelessly.

In a block 404, the method includes determining whether an ambient temperature is below a predetermined threshold. In some embodiments, block 404 includes receiving the ambient temperature from one or more of the sensors 118 or from another source such as a weather app and comparing the received ambient temperature to the predetermined threshold. As one non-limiting example, the predetermined threshold may be set by the user and/or preprogrammed to 0° C.

In a block 406, based on the controller 116 determining that the ambient temperature is below the predetermined threshold in block 404, the controller 116 may cause operation of the first heating device 112, the second heating device 114, or both. As one non-limiting example, if the ambient temperature is less than 0° C., the controller 116 may cause operation of the first heating device 112 and/or the second heating device 114 to provide sufficient heating to minimize or prevent potential icing on of the hybrid heater 104 due to the ambient temperature being below freezing.

In a block 408, based on the controller 116 determining that the ambient temperature is at or above the predetermined threshold in block 404, the controller 116 may cause operation of the second heating device 114. As one non-limiting example, if the ambient temperature is greater than 0° C., the controller 116 may cause operation of the second heating device 114, which may be more energy efficient while providing sufficient heating because there is no current risk of icing.

While the methods illustrated in FIGS. 2-4 were described separately, in various embodiments the methods may be performed simultaneously, in various sub-combinations, and/or as otherwise desired. Moreover, as mentioned, in other embodiments, the controller 116 may control the hybrid heater 104 pursuant to other operating modes, and/or the controller 116 may generate other output responses as desired. Other output responses may include, but are not limited to, providing information to a remote device and/or to a user via a remote device, user interface, and/or as otherwise desired.

Exemplary concepts and combinations of features of the invention may include:

A. A heater comprising an enclosure, a first heat source within the enclosure, and a second heat source within the enclosure, wherein the first heat source comprises an electric heater.

B. The heater according to statement A., wherein the second heat source and the first heat source utilize a same type of power source.

C. The heater according to statement A. or B., wherein the second heat source comprises an electric heat pump.

D. The heater according to any one of statements A. - C., further comprising a controller configured to selectively control operation of the first heat source and the second heat source.

E. The heater according to statement D., wherein the controller is configured to control operation of the first heat source and the second heat source based on at least one of information provided by a sensor associated with the heater or information provided by a user or other source.

F. The heater according to statement D. or E., wherein the controller is configured to receive information about a desired temperature, determine an operating mode based on the received information, and control the first heat source and the second heat source pursuant to the determined operating mode.

G. The heater according to statement F., wherein the operating mode comprises at least one of an activation or deactivation of the first heat source, an activation or deactivation of the second heat source, a heating duration, a heating output level of the first heat source, a heating output level of the second heat source, and/or heating pattern from the first heat source and the second heat source for optimized energy efficiency.

H. The heater according to any one of statements D. - F., wherein the controller is configured to control operation of the first heat source and the second heat source such that only the first heat source is operating, only the second heat source is operating, or both the first heat source and the second heat source are operating.

I. The heater according to any one of statements A. - D., further comprising at least one sensor associated with the heater.

J. The heater according to any one of statements A. - D., further comprising a user interface on the enclosure.

K. The heater according to any one of statements A. - D., wherein the heater comprises a normal mode in which only the second heat source is operating, a fast heat mode in which both the first heat source and the second heat source are operating, and a low ambient mode in which either only the first heat source is operating or the first heat source and the second heat source are operating to minimize or prevent icing.

L. A heater comprising an enclosure, an electric heat pump within the enclosure, and an electric resistance heater within the enclosure.

M. The heater according to statement K., further comprising any one or more features according to statements B. and D. - K.

N. A method of heating a pool using a heater, the method comprising receiving information about a desired temperature of the pool, determining an operating mode of the heater based on the received information, and controlling the heater pursuant to the determined operating mode, wherein the heater comprises an enclosure, a first heat source within the enclosure, and a second heat source within the enclosure, and wherein the first heat source comprises an electric resistance heater.

O. The method according to statement N., wherein determining the operating mode comprises determining the operating mode from predefined operating modes, and wherein the predefined operating modes comprise a normal mode in which only the second heat source is operating, a fast heat mode in which both the first heat source and the second heat source are operating, and a low ambient mode in which either only the first heat source is operating or the first heat source and the second heat source are operating to minimize or prevent icing.

P. The method according to statement N., wherein receiving the information about the desired input comprises receiving the information on a user interface on the enclosure of heater or receiving the information via wireless transmission by a controller of the heater.

Q. The method according to statement N., wherein controlling the heater comprises controlling at least one of an activation or deactivation of the first heat source, an activation or deactivation of the second heat source, a heating duration, a heating output level of the first heat source, a heating output level of the second heat source, and/or heating pattern from the first heat source and the second heat source for optimized energy efficiency.

R. The method according to statement N., wherein controlling the heater comprises activating only the first heat source, activating only the second heat source, or activating both the first heat source and the second heat source.

S. The heater according to any one of statements A. - D., wherein the electric heater is an electric resistance heater.

These examples are not intended to be mutually exclusive, exhaustive, or restrictive in any way, and the invention is not limited to these example embodiments but rather encompasses all possible modifications and variations within the scope of any claims ultimately drafted and issued in connection with the invention (and their equivalents). For avoidance of doubt, any combination of features not physically impossible or expressly identified as non-combinable herein may be within the scope of the invention.

The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope of the invention. Additionally, the word “pool” and phrase “swimming pool” as used herein may also refer to spas or other water containing vessels or structures used for recreation or therapy, including both artificial and natural vessels, structures, and the like.

Claims

1. A heater for a swimming pool or spa, the heater comprising an enclosure, a first heat source within the enclosure, and a second heat source within the enclosure, wherein the first heat source comprises an electric heater.

2. The heater according to claim 1, wherein the second heat source and the first heat source utilize a same type of power source.

3. The heater according to claim 1, wherein the second heat source comprises an electric heat pump.

4. The heater according to claim 1, further comprising a controller configured to selectively control operation of the first heat source and the second heat source.

5. The heater according to claim 4, wherein the controller is configured to control operation of the first heat source and the second heat source based on at least one of information provided by a sensor associated with the heater or information provided by a user or other source.

6. The heater according to claim 4, wherein the controller is configured to receive information about a desired temperature, determine an operating mode based on the received information, and control the first heat source and the second heat source pursuant to the determined operating mode.

7. The heater according to claim 6, wherein the operating mode comprises at least one of an activation or deactivation of the first heat source, an activation or deactivation of the second heat source, a heating duration, a heating output level of the first heat source, a heating output level of the second heat source, and/or heating pattern from the first heat source and the second heat source for optimized energy efficiency.

8. The heater according to claim 4, wherein the controller is configured to control operation of the first heat source and the second heat source such that only the first heat source is operating, only the second heat source is operating, or both the first heat source and the second heat source are operating.

9. The heater according to claim 1, further comprising at least one of: a sensor associated with the heater; ora user interface on the enclosure.

10. The heater according to claim 1, wherein the electric heater is an electric resistance heater.

11. The heater according to claim 1, wherein the heater comprises a normal mode in which only the second heat source is operating, a fast heat mode in which both the first heat source and the second heat source are operating, and a low ambient mode in which either only the first heat source is operating or the first heat source and the second heat source are operating to minimize or prevent icing.

12. A heater for a swimming pool or spa, the heater comprising an enclosure, an electric heat pump within the enclosure, and an electric resistance heater within the enclosure.

13. The heater according to claim 12, further comprising at least one sensor associated with the heater.

14. The heater according to claim 12, further comprising a controller configured to receive information about a desired temperature, determine an operating mode based on the received information, and control the electric heat pump and the electric resistance heater pursuant to the determined operating mode.

15. The heater according to claim 12, further comprising a controller configured to control operation of the electric heat pump and the electric resistance heater such that only the electric heat pump is operating, only the electric resistance heater is operating, or both the electric heat pump and the electric resistance heater are operating.

16. A method of heating a pool using a heater, the method comprising receiving information about a desired temperature of the pool, determining an operating mode of the heater based on the received information, and controlling the heater pursuant to the determined operating mode, wherein the heater comprises an enclosure, a first heat source within the enclosure, and a second heat source within the enclosure, and wherein the first heat source comprises an electric resistance heater.

17. The method according to claim 16, wherein determining the operating mode comprises determining the operating mode from predefined operating modes, and wherein the predefined operating modes comprise a normal mode in which only the second heat source is operating, a fast heat mode in which both the first heat source and the second heat source are operating, and a low ambient mode in which either only the first heat source is operating or the first heat source and the second heat source are operating to minimize or prevent icing.

18. The method according to claim 16, wherein receiving the information about the desired input comprises receiving the information on a user interface on the enclosure of heater or receiving the information via wireless transmission by a controller of the heater.

19. The method according to claim 16, wherein controlling the heater comprises controlling at least one of an activation or deactivation of the first heat source, an activation or deactivation of the second heat source, a heating duration, a heating output level of the first heat source, a heating output level of the second heat source, and/or heating pattern from the first heat source and the second heat source for optimized energy efficiency.

20. The method according to claim 16, wherein controlling the heater comprises activating only the first heat source, activating only the second heat source, or activating both the first heat source and the second heat source.