FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
A CONTROLLER AND A METHOD OF CONTROL FOR A WATER HEATER
EMERSON ELECTRIC CO.
a US Company of
8000 West Florissant Avenue, St. Louis, MO 63136 United States of America
Inventors:
1. KULKARNI AMOL
2. TAWARE SACHIN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF THE DISCLOSURE
The present disclosure generally relates to water heaters and their operation.
DEFINITIONS
The expression 'user set point temperature' used hereinafter in the specification refers to a user expected water temperature.
The expression 'offset' used hereinafter in the specification refers to a value which when subtracted from the set point temperature provides a temperature at which a water heater generates a heat call.
The expression 'water usage' used hereinafter in the specification refers to number of heat calls made in a pre-determined time duration and the heat call ON time.
These definitions are in addition to those expressed in the art.
BACKGROUND
Conventional water heater control is based on preset user set point temperature and a fixed offset (difference between set point and water temperature at which a heat call gets generated). When the water temperature drops to a value which is a difference between the set point temperature and a predetermined offset value, the controller of the conventional water heater generates a heat call. This call for heat remains active till the water temperature reaches the preset user set point. Once the desired temperature is attained, the water temperature gradually starts decreasing due to hot water usage or heat loss and the cycle repeats.

Conventional water heaters are thus limited by a fixed offset that results in generation of heat call even under no usage or low usage conditions which results in wastage of electric or gas energy. Most energy saving options available in the art for water heaters implement a change in the preset user set point based on water heater data that is sensed. A change in user set point results in discomfort to the user.
Water heater control typically includes different operating modes like vacation, warm, hot, very hot, and the like. Accordingly, the set point temperature is different for each of these modes to provide comfort. Hence applying the same offset adjustment to every mode of operation may also result in discomfort for the user.
For instance, if the vacation mode set point is 70 deg. F and the very hot mode set point is 150 deg. F, applying the same offset to both modes may not be appropriate.
There is thus felt a need for a controller and a method of control for water heaters that provides an energy efficient solution that does not compromise user's comfort and at the same time is flexible enough to be implemented in any type of water heater.
OBJECTS
Some of the objects of the present disclosure which at least one embodiment is adapted to provide, are described herein below:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide a controller and a method of control for a water heater for reduced energy consumption.
Another object of the present disclosure is to provide a water heater and a method of control for the water heater for reduced energy consumption without the need for any additional hardware.
Still another object of the present disclosure is to provide a water heater and a method of control for the water heater for reduced energy consumption without compromising the user's comfort.
Yet another object of the present disclosure is to provide a low cost water heater and a method of control for the same with reduced energy consumption.
One more object of the present disclosure is to provide a method of control for a water heater with reduced energy consumption that can be implemented in both gas and electric water heaters.
Still another object of the present disclosure is to provide an electric water heater and a method of control for the same with reduced energy consumption that improves life of relay and the heating element.
An additional object of the present disclosure is to provide a gas water heater and a method of control for the same with reduced energy consumption that improves relay life.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY
In accordance with an aspect of the present disclosure, there is provided a controller for a water heater, the controller comprising:
• a base repository comprising continually learned usage of the water heater including learned number of heat calls generated in a pre-determined time duration and learned heat call ON time;
• a tracking repository comprising current usage of the water heater including currently tracked number of heat calls made in the pre-determined time duration and currently tracked heat call ON time;
• a comparator adapted to compare the current usage of the water heater with the learned usage of the water heater to predict the current usage of water heater as any one of High, Medium, Low and No usage;
• first setting means to set a user set point temperature depending on user's comfort;
• second setting means to set a plurality of offsets comprising a first preset offset defining a temperature at which power is enabled when the High usage of water heater is detected and at least one alternate offset defining a temperature at which power is enabled when at least one of the Medium, the Low and the No usage of water heater is detected;
• a timer adapted to set a pre-determined time delay between the plurality of offsets; and
• a processor adapted to generate a heat call when the temperature of the water in the water heater drops from the preset user set point to at least one of the plurality of offsets, depending on at least one of the predicted current usage of the water heater and the preset user set point temperature.
Optionally, the controller for a water heater as described herein above further comprises:

• an override means adapted to override the at least one alternate offset; and
• a sensor adapted to sense rate of change of temperature of water.
Typically, in accordance with another aspect of the present disclosure, there is provided a method for controlling heat call generated in a water heater, the method comprising the steps of:
• continually tracking current usage of the water heater including currently tracked number of heat calls made in a pre-determined time duration and currently tracked heat call ON time;
• storing learned usage of the water heater including learned number of heat calls generated in the pre-determined time duration and learned heat call ON time;
• comparing the current usage of the water heater with the learned usage of the water heater to predict the current usage of water heater as any one of High, Medium, Low and No usage;
• presetting a user set point temperature depending on user's comfort;
• presetting a plurality of offsets comprising a first preset offset defining a temperature at which power is enabled when the High usage of water heater is detected and at least one alternate offset defining a temperature at which power is enabled when at least one of the Medium, the Low and the No usage of water heater is detected;
• setting a pre-determined time delay between the plurality of offsets; and
• generating a heat call when the temperature of the water in the water heater drops from the preset user set point to at least one of the plurality of offsets, depending on at least one of the predicted current usage of the water heater and the preset user set point temperature.
Optionally, the method as described herein above further comprises the steps of:
• detecting rate of change of temperature of the water; and

• overriding the at least one alternate offset.
Typically, the step of presetting a plurality of offsets includes the step of incrementing the first preset offset by a predetermined offset adjustment to define the at least one alternate offset.
Furthermore, the step of generating a heat call facilitates reducing the average temperature of water in the water heater.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
A controller and a method for control of a water heater in accordance with the present disclosure will now be explained in relation to the accompanying drawings, in which:
Figure 1 illustrates a block diagram for the controller in accordance with an aspect of the present disclosure, for a water heater;
Figure 2 illustrates a flow chart for the method of controlling heat call generated in a water heater, in accordance with another aspect of the present disclosure; and
Figure 3 illustrates a graphical representation of temperature versus time for a water heater in accordance with the present disclosure as compared to conventional water heaters.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The controllers in conventional water heaters (gas or electric based) operate with a pre-determined fixed offset. The water heater usage has no impact on the generated heat call. Hence in case of low usage or no usage, controllers of

conventional water heaters generate unnecessary heat calls due to heat loss which eventually results in wastage of electric or gas energy. Energy saving options known in the art involve adjustment of user set point temperature based on sensed data like rate of change of water temperature. Modification of user set point temperature is not an efficient solution since it may result in discomfort for the user.
To overcome these drawbacks in conventional water heaters, an energy saving controller is envisaged that works on multiple offsets and at the same time does not compromise user's comfort.
The controller and a method for control of a water heater in accordance with the present disclosure will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The controller and the method for controlling heat call generated in a water heater, in accordance with the present disclosure will be explained with reference to figures 1 through 3 wherein key elements are referenced generally by numerals as illustrated.

Figure 1 illustrates a block diagram for the controller 100 in accordance with an aspect of the present disclosure, for a water heater. The controller comprises a base repository (10), a tracking repository (12), a comparator (14), first setting means (16), second setting means (18), a timer (20) and a processor (22). The base repository (10) stores continually learned usage of the water heater. The usage of a water heater typically includes learned number of heat calls generated in a pre-determined time duration and learned heat call ON time. The tracking repository (12) stores current usage of the water heater including currently tracked number of heat calls made in the pre-determined time duration and currently tracked heat call ON time. The comparator (14) compares the current usage of the water heater with the learned usage of the water heater to predict whether the current usage of water heater is High, Medium, Low or No usage.
First setting means (16) enables the user to preset a user set point temperature depending on the user's comfort. Second setting means (18) enables the user to set a plurality of offsets comprising a first preset offset and at least one alternate offset. The first preset offset defines a temperature at which power is enabled when High usage of water heater is detected. One or more alternate offsets define temperatures at which power is enabled when Medium, low or No usage of water heater is detected. The user set point temperature is also a parameter on which the offsets are based.
The timer (20) sets a pre-determined time delay between the plurality of offsets such that the first preset offset is incremented by a predetermined offset adjustment to define at least one alternate offset.
The processor (22) generates a heat call when the temperature of the water in the water heater drops from the preset user set point to the predetermined offset,

depending on either the predicted current usage of the water heater and / or the preset user set point temperature.
Optionally, the controller (100) is provided with a sensor (24) to sense rate of change of temperature of water and override means (26) to override the predetermined alternate offset.
Figure 2 illustrates a flow chart for the method of controlling heat call generated in a water heater, in accordance with another aspect of the present disclosure. The method comprises the step of continually tracking current usage of the water heater including currently tracked number of heat calls made in a predetermined time duration and currently tracked heat call ON time. The learned usage of the water heater including learned number of heat calls generated in the pre-determined time duration and learned heat call ON time is stored for comparing with the current usage of the water heater to predict the current usage of water heater as any one of High, Medium, Low or No usage. A user set point temperature depending on user's comfort is preset. Again a plurality of offsets is preset. The plurality of offsets include a first preset offset that defines a temperature at which power is enabled when High usage of water heater is detected and at least one alternate offset that defines a temperature at which power is enabled when either Medium, Low or No usage of water heater is detected. A pre-determined time delay is set between the plurality of offsets such that the first preset offset is incremented by a predetermined offset adjustment to define at least one alternate offset. A heat call is generated when the temperature of the water in the water heater drops from the preset user set point to the predetermined offset depending on either the predicted current usage of the water heater and /or the preset user set point temperature.

Figure 3 illustrates a graphical representation of temperature versus time for a
water heater in accordance with the present disclosure as compared to
conventional water heaters.
TO represents the time at which water temperature attains user set set-point
value SP.
Tl represents the time to generate next heat call due to heat loss/water usage
during normal operation.
T2 represents the extra time required to generate a heat call due to the
incremented alternate offset value.
T3 represents the extra time required to heat the water due to the incremented
offset value.
Y represents the incremented offset value (Y is always > 0).
OFF 1 represents the first preset offset (fixed offset).
OFF2 represents the alternate offset.
AVG1 represents the average water temperature for a conventional water heater.
AVG2 represents the average water temperature for a water heater employing
the controller of the present disclosure operating with a plurality of offsets.
In an exemplary embodiment, if the user set point SP is 110 deg. F and the first preset offset OFF1 is 10 deg. F, when the water temperature is <= (set point SP - first preset offset OFF1), a heat call gets generated. In this case, a heat call will get generated at 100 deg. F (110 deg. F-10 deg. F).
The water temperature is at user set set-point value SP at time TO. During the time period Tl, the water temperature starts gradually decreasing because of hot water usage or heat loss. In conventional water heaters, a heat call gets generate at time HI.
In accordance with the present disclosure, the alternate offset OFF2 is preset based on water heater usage. In an exemplary embodiment, if OFF2 is set to 20

deg. F, a heat call will get generated at H2 (T1+T2), when water temperature is <= 90 deg. F.
In this case, AVG2 < AVG1. Since AVG2 is less, heat loss is less, heat loss being directly proportional to the difference between water temperature and ambient temperature. T2 will be considerably large and shall always be greater than Tl. Since the water temperature is maintained at a lower average temperature without changing the user set point SP, the consumed heat will be lower.
The relation between water heater usage and the different offsets for High, Medium, Low and No Usage of a water heater for a preset user set point temperature is explained using an exemplary table as indicated below:

No of Heat Calls Water Heater Usage Offset
>=11 High 10 (Default)
6 to 10 Medium 15
3 to 5 Low 18
<3 No 20
The above table merely showcases one of the 'n' number of probable methods of determining water heater usage. The method / algorithm for determining water heater usage may also be customer dependent. Again offsets for High, Medium, Low and No usage may also be customer dependent. The above values merely display the relation between water heater usage and the different offsets in accordance with an exemplary method. The number of heat calls in a predetermined time period (say 24Hrs) is not only dependent on actual number of heat calls generated by a water heater but is also dependent on heat call active time. Again, the adjusted offset is not based on water heater usage alone but is also based on the user set point.

Conventional water heaters providing energy saving solutions change the preset user set point based on water heater operational data. This may discomfort user in some cases as the preset user set point is changed to a new set point. But with the controller of the present disclosure, the offsets are adjusted based on water heater usage and not set point set by the user alone. There is therefore no compromise on user's comfort. Also the controller in accordance with the present disclosure can be implemented in both gas and electric based water heaters.
TECHNICAL ADVANCEMENTS AND ECONOMICAL
SIGNIFICANCE
The technical advancements offered by the present disclosure include the realization of:
• a controller and a method of control for a water heater for reduced energy consumption;
• a water heater and a method of control for the water heater for reduced energy consumption without the need for any additional hardware;
• a water heater and a method of control for the water heater for reduced energy consumption without compromising the user's comfort;
• a low cost water heater and a method of control for the same with reduced energy consumption;
• a method of control for a water heater with reduced energy consumption that can be implemented in both gas and electric water heaters;

• an electric water heater and a method of control for the same with reduced energy consumption that improves life of the relay and the heating element; and
• a gas water heater and a method of control for the same with reduced energy consumption that improves relay life.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose

of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

WE CLAIM:
1. A controller for a water heater, said controller comprising:
• a base repository comprising continually learned usage of the water heater including learned number of heat calls generated in a predetermined time duration and learned heat call ON time;
• a tracking repository comprising current usage of the water heater including currently tracked number of heat calls made in said predetermined time duration and currently tracked heat call ON time;
• a comparator adapted to compare said current usage of the water heater with said learned usage of the water heater to predict said current usage of water heater as any one of High, Medium, Low and No usage;
• first setting means to set a user set point temperature depending on user's comfort;
• second setting means to set a plurality of offsets comprising a first preset offset defining a temperature at which power is enabled when said High usage of water heater is detected and at least one alternate offset defining a temperature at which power is enabled when at least one of said Medium, said Low and said No usage of water heater is detected;
• a timer adapted to set a pre-determined time delay between said plurality of offsets; and
• a processor adapted to generate a heat call when the temperature of the water in the water heater drops from the preset user set point to
at least one of said plurality of offsets, depending on at least one of the predicted current usage of the water heater and the preset user set point temperature.

2. The controller for a water heater as claimed in claimed 1 further comprising:
• an override means adapted to override said at least one alternate offset; and
• a sensor adapted to sense rate of change of temperature of water.

3. A water heater comprising the controller as claimed in claim L
4. A method for controlling heat call generated in a water heater, said method comprising the steps of:

• continually tracking current usage of the water heater including currently tracked number of heat calls made in a pre-determined time duration and currently tracked heat call ON time;
• storing learned usage of the water heater including learned number of heat calls generated in said pre-determined time duration and learned heat call ON time;
• comparing said current usage of the water heater with said learned usage of the water heater to predict said current usage of water heater as any one of High, Medium, Low and No usage;
• presetting a user set point temperature depending on user's comfort;
• presetting a plurality of offsets comprising a first preset offset defining a temperature at which power is enabled when said High usage of water heater is detected and at least one alternate offset defining a temperature at which power is enabled when at least one of said Medium, said Low and said No usage of water heater is detected;
• setting a pre-determined time delay between said plurality of offsets; and
• generating a heat call when the temperature of the water in the water heater drops from the preset user set point to at least one of said

plurality of offsets, depending on at least one of the predicted current usage of the water heater and the preset user set point temperature.
5. The method as claimed in claim 4 further comprising the steps of:
• detecting rate of change of temperature of the water; and
• overriding said at least one alternate offset.

6. The method as claimed in claim 4, wherein the step of presetting a plurality of offsets includes the step of incrementing said first preset offsets by a predetermined offset adjustment to define said at least one alternate offset.
7. The method as claimed in claim 4, wherein the step of generating a heat call facilitates reducing the average temperature of water in the water heater.