U.S. patent application number 11/692117 was filed with the patent office on 2007-10-25 for water heating systems and methods.
Invention is credited to Wade C. Patterson, Terry G. Phillips.
Application Number | 20070246552 11/692117 |
Document ID | / |
Family ID | 38618565 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070246552 |
Kind Code |
A1 |
Patterson; Wade C. ; et
al. |
October 25, 2007 |
WATER HEATING SYSTEMS AND METHODS
Abstract
A water heating system has a controller that is electronically
actuated. In this regard, the controller controls an activation
state of at least one heating element by providing an electrical
control signal to a relay. In one embodiment, the controller has an
emergency shut-off apparatus that is mechanically actuated. Further
various features can be optionally implemented to help heat related
problems plaguing many conventional water heater controllers that
are electronically actuated.
Inventors: |
Patterson; Wade C.;
(Huntsville, AL) ; Phillips; Terry G.;
(Meridianville, AL) |
Correspondence
Address: |
THOMAS, KAYDEN, HORSTEMEYER & RISLEY, LLP
100 GALLERIA PARKWAY, NW
STE 1750
ATLANTA
GA
30339-5948
US
|
Family ID: |
38618565 |
Appl. No.: |
11/692117 |
Filed: |
March 27, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60786326 |
Mar 27, 2006 |
|
|
|
60908132 |
Mar 26, 2007 |
|
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|
Current U.S.
Class: |
236/21B |
Current CPC
Class: |
F24H 9/2014
20130101 |
Class at
Publication: |
236/021.00B |
International
Class: |
F24H 9/20 20060101
F24H009/20 |
Claims
1. A water heater controller, comprising: a relay for controlling
an activation state of a heating element; an emergency shut-off
apparatus for disabling the heating element if a temperature
exceeds a threshold, the emergency shut-off apparatus having a
temperature sensitive element that mechanically actuates based on
the temperature, the emergency shut-off apparatus having a
mechanical switch that is coupled to the relay, wherein actuation
of the temperature sensitive element changes a state of the switch;
and logic configured to receive temperature data indicative of a
temperature sensed by a temperature sensor, the logic further
configured to control a state of the relay based on the temperature
data.
2. The water heater controller of claim 1, wherein the logic is
configured to perform a comparison between the temperature data and
a threshold value, wherein the logic is configured to transmit an
electronic signal to the relay based on the comparison, and wherein
the relay transitions from an open state to a closed state in
response to the electronic signal thereby activating the heating
element.
3. The water heater controller of claim 1, wherein the logic is
configured to perform a comparison between the temperature data and
a threshold value, wherein the logic is configured to transmit an
electrical signal to the relay based on the comparison, and wherein
the relay transitions from a closed state to an open state in
response to the electronic signal thereby deactivating the heating
element.
4. The water heater controller of claim 1, wherein the emergency
shut-off apparatus, upon disabling the heating element, is
configured to ensure that the heating element remains disabled
until at least the emergency shut-off apparatus receives a user
input.
5. The water heater controller of claim 1, wherein the temperature
sensitive element comprises a bimetallic disc.
6. The water heater controller of claim 1, further comprising an
electrically conductive connection coupled to the emergency
shut-off apparatus, the connection composed of a metallic alloy
having an International Annealed Copper Standard (IACS) of greater
than 80%, a stress relaxation temperature greater than 105 degrees
Celsius, and a yield stress greater than 50 kilo-pounds per square
inch (ksi).
7. The water heater controller of claim 1, further comprising: a
thermally conductive base; a housing coupled to the base, the
housing composed of electrically insulating material; the
temperature sensor, wherein the temperature sensor contacts the
base.
8. The water heater controller of claim 7, wherein the relay is
mounted on a first side of a printed circuit board (PCB), and
wherein the temperature sensor is positioned on a second side of
the PCB that is opposite to the first side.
9. The water heater controller of claim 7, wherein the temperature
sensor is mounted on an element composed of thermally insulating
material and is electrically coupled to the PCB.
10. The water heater controller of claim 1, further comprising an
interface for electrically connecting an electrically conductive
wire to an electrically conductive connection, the interface having
a hole for receiving the wire.
11. The water heater controller of claim 10, wherein the connection
is coupled to the emergency shut-off apparatus.
12. The water heater controller of claim 10, wherein the connection
is coupled to the relay.
13. The water heater controller of claim 10, wherein the connection
has at least one rib for guiding the wire as the wire is being
inserted into the first hole.
14. The water heater controller of claim 10, further comprising a
housing covering the logic, the housing having a hole, wherein the
wire has a coating composed of insulating material, and wherein a
portion of the coating passes through the hole of the housing.
15. The water heater controller of claim 14, wherein at least a
portion of a wall of the housing contacts the coating, the portion
defining the hole of the housing.
16. The water heater controller of claim 14, wherein the interface
is composed of a metallic alloy having an International Annealed
Copper Standard (IACS) of greater than 80%, a stress relaxation
temperature greater than 105 degrees Celsius, and a yield stress
greater than 50 kilo-pounds per square inch (ksi).
17. The water heater controller of claim 10, further comprising: a
thermally conductive base; a housing coupled to the base, the
housing composed of an electrically insulating material; the
temperature sensor, wherein the temperature sensor contacts the
base.
18. The water heater controller of claim 17, wherein the relay is
mounted on a first side of a printed circuit board (PCB), and
wherein the temperature sensor is positioned on a second side of
the PCB that is opposite to the first side.
19. The water heater controller of claim 18, wherein the
temperature sensor is mounted on an element composed of thermally
insulating material and electrically coupled to the PCB.
20. A water heating system, comprising: a tank; a heating element
mounted on the tank; and a controller mounted on the tank, the
controller comprising: an emergency shut-off apparatus that is
mechanically actuated, the emergency shut-off apparatus coupled to
the heating element and having a temperature sensitive element that
mechanically actuates due to thermal stresses such that the heating
element is disabled if the temperature exceeds a threshold; a relay
coupled to the heating element; and logic configured to receive
temperature data indicative of a temperature sensed by a
temperature sensor, the logic further configured to control a state
of the relay based on the temperature data.
21. The system of claim 20, wherein the controller further
comprises: a thermally conductive base; a housing coupled to the
base, the housing composed of electrically insulating material; the
temperature sensor, wherein the temperature sensor contacts the
base.
22. The system of claim 21, wherein the relay is mounted on a first
side of a printed circuit board (PCB), and wherein the temperature
sensor is positioned on a second side of the PCB that is opposite
to the first side.
23. The system of claim 20, further comprising an electrically
conductive wire, wherein the controller further comprises: an
electrically conductive connection; and an interface having a hole,
the connection extending through the hole.
24. The system of claim 23, further comprising a housing covering
the logic, the housing having a hole, wherein the wire has a
coating composed of insulating material, and wherein a portion of
the coating passes through the hole of the housing.
25. The system of claim 23, wherein the connection is composed of a
metallic alloy having an International Annealed Copper Standard
(IACS) of greater than 80%, a stress relaxation temperature greater
than 105 degrees Celsius, and a yield stress greater than 50
kilo-pounds per square inch (ksi).
26. The system of claim 23, wherein the connection has at least one
rib for guiding the wire as the wire is being inserted into the
first hole.
27. A water heater controller, comprising: an electromechanical
switching means for controlling an activation state of the heating
element; means for disabling a heating element if a temperature
exceeds a threshold, the disabling means having a mechanical
switching means coupled to the relay and having a temperature
sensing means that mechanically actuates based on the temperature,
wherein actuation of the temperature sensing means changes a state
of the mechanical switching means; and means for receiving
temperature data indicative of a temperature sensed by a
temperature sensor, and for controlling a state of the relay based
on the temperature data.
28. A method for controlling a water heating system having a tank
and a heating element mounted on the tank, comprising the steps of:
disabling the heating element if a temperature exceeds a threshold,
the disabling step comprising the step of mechanically actuating a
temperature sensitive element based on the temperature; sensing a
temperature; transmitting temperature data indicative of the sensed
temperature; and controlling an operational state of the heating
element based on the temperature data, the controlling step
comprising the step of electrically actuating a relay based on the
temperature data.
29. The method of claim 28, wherein the disabling step comprises
the step of ensuring that the heating element remains disabled
until a user input is received.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 60/786,326, entitled "Water Heating System and
Method," and filed on Mar. 27, 2006, which is incorporated herein
by reference. This application also claims priority to U.S.
Provisional Application No. 60/908,132, entitled "Water Heating
Systems and Methods," and filed on Mar. 26, 2007, which is
incorporated herein by reference.
RELATED ART
[0002] For many decades, water heater controllers have been
mechanically actuated. In this regard, at least one temperature
sensitive switch is typically mounted on a side of a water tank.
Thermal stresses within the switch fluctuate as the temperature of
the water within the tank changes. If the temperature of water
within a region in close proximity to the switch falls below a
threshold, referred to as a "lower set point," mechanical forces
caused by thermal stresses in the switch actuate a mechanical
component of the switch thereby allowing electrical current to flow
to a heating element within the tank. Thus, the heating element
begins to heat the water in the tank. Once the temperature of the
water rises above a threshold, referred to as an "upper set point,"
mechanical forces caused by the thermal stresses actuate the
mechanical component of the switch yet again thereby stopping
current from flowing to the heating element. Thus, the heating
element stops heating the water in the tank. Accordingly, the
temperature of the water is kept within a desired range.
[0003] Recently, attempts have been made to migrate from
mechanically actuated controllers to electronically actuated
controllers. In this regard, rather than relying on a temperature
sensitive switch that is actuated by mechanical force resulting
from thermal stress, a temperature sensor, such as a thermistor, is
used to measure water temperature and provide data indicative of
the measured temperature. Electronic circuitry, which may include
software as well as hardware, then analyzes the temperature data to
determine when a heating element is to be activated. Although a
relay, which is typically an electro-mechanical component, can be
used to control whether current flows to the heating element and,
therefore, whether the heating element is activated, the state of
the relay and, therefore, the activation state of the heating
element are controlled via an electrical signal rather than
mechanical force induced by thermal stresses. In this sense, the
controller and, in particular, the switch (e.g., relay) used to
activate and deactivate the heating element are "electronically
actuated."
[0004] Electronically actuated controllers enable water heating
systems to be controlled via more complex algorithms. For example,
it is possible for the controller to analyze a usage history of the
water heating system and to automatically establish the set points
based on time of day and the usage history. Thus, the set points
can be set higher during expected periods of relative high use, and
the set points can be set lower during expected periods of relative
low use, thereby increasing the efficiency of the water heating
system.
[0005] However, several problems have been encountered in the
design and development of electronically actuated controllers, and
many of the problems are heat related. In this regard, the
temperature of the water in a water heating system is usually set
significantly higher than 100 degrees Fahrenheit (F) and, in some
cases, higher than 150 degrees F. Further, the electronics within
an electronically actuated controller produce additional heat
within the controller. Indeed, the relays used to control the
activation states of the heating elements typically carry 20 to 30
Amperes (A) of a 120 or 240 Volt (V) alternating current (AC)
signal and can, therefore, generate significant heat. Moreover, the
temperatures within the controller can reach levels that affect the
reliability of the controller's electronics.
[0006] In addition, as described above, an electronically actuated
controller typically uses temperature data from a temperature
sensor, such as a thermistor. For ease of installation and to help
reduce manufacturing costs, it would be desirable for such a
temperature sensor to be integral or embedded with the other
electronics of the controller. However, the heat from the other
electronics can affect the temperature readings of the temperature
sensor, thereby affecting the reliability of the temperature
measurements, if the temperature sensor is in close proximity to
the other electronics.
[0007] To alleviate some of the heat related problems, the size of
the controller can be increased. However, increasing the size of
the controller is generally undesirable for several reasons,
including increasing costs. In this regard, it is generally
desirable for an electronically actuated controller to be similar
in size to conventional, mechanically actuated controllers so that
conventional water tanks do not need to be redesigned. Indeed, if
an electronically actuated controller is about the same size as a
conventional, mechanically actuated controller, then a conventional
water tank that currently has a mechanically actuated controller
can be retrofitted with an electronically actuated controller at a
relatively low cost. Further, water tank manufacturers already have
assembly lines in place that may need to be changed, at a
relatively high cost, if the design of the water tank is changed to
accommodate a larger controller that is electronically
actuated.
[0008] Moreover, it is generally desirable for the size of an
electronically actuated controller to be minimized and, in
particular, to be at a size similar to or less than the size of
conventional controllers that are mechanically actuated, but such a
goal can be difficult to realize without a significant impact to
reliability in view of the heat related problems described
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The disclosure can be better understood with reference to
the following drawings. The elements of the drawings are not
necessarily to scale relative to each other, emphasis instead being
placed upon clearly illustrating the principles of the disclosure.
Furthermore, like reference numerals designate corresponding parts
throughout the several views
[0010] FIG. 1 is a block diagram illustrating an exemplary water
heating system.
[0011] FIG. 2 depicts an exemplary controller that is
electronically actuated and may be used to control a water heating
system, such as is depicted in FIG. 1.
[0012] FIG. 3 is a block diagram illustrating an exemplary water
heater controller, such as is depicted in FIG. 2.
[0013] FIG. 4 depicts an exemplary electrical interface, such as is
depicted in FIG. 3.
[0014] FIG. 5 depicts a top view of the electrical interface
depicted in FIG. 4.
[0015] FIG. 6 depicts a bottom view of a screw that may be used to
secure a wire inserted into an electrical interface, such as is
depicted in FIG. 4.
[0016] FIG. 7 depicts a side view of the screw depicted in FIG.
6.
[0017] FIG. 8 depicts a front view of an exemplary water heater
controller, such as is depicted in FIG. 3.
[0018] FIG. 9 depicts a side view of the water heater controller
depicted in FIG. 8.
[0019] FIG. 10 depicts a back view of the water heater controller
depicted in FIG. 8.
[0020] FIG. 11 depicts the water heater controller of FIG. 8
coupled to a conventional bracket that may be used to mount the
controller on a water tank.
[0021] FIG. 12 depicts an exemplary sensor holding apparatus
coupled to a conventional bracket that may be used to mount the
apparatus on a water tank.
[0022] FIG. 13 depicts the sensor holding apparatus of FIG. 12.
[0023] FIG. 14 depicts an opposite side of the base depicted in
FIG. 10.
[0024] FIG. 15 depicts a three-dimensional back view of the water
heater controller of FIG. 10 with its base removed, for
illustrative purposes, to expose internal components of the
controller.
[0025] FIG. 16 depicts the water heater controller of FIG. 15 with
a bi-metallic disc removed, for illustrative purposes, to expose a
plunger.
[0026] FIG. 17 depicts an exemplary water heater controller with
its housing removed for illustrative purposes to expose internal
components of the controller.
[0027] FIG. 18 is a block diagram illustrating an exemplary water
heater controller, such as is depicted in FIG. 17.
[0028] FIG. 19 depicts a three-dimensional perspective of the water
heater controller depicted in FIG. 17.
[0029] FIG. 20 depicts a cross-sectional view of an exemplary
electrical interface for a water heater controller, such as is
depicted in FIG. 19.
[0030] FIG. 21 depicts a three-dimensional perspective of an
electrical interface depicted in FIG. 20.
[0031] FIG. 22 depicts a bottom view of an exemplary connection end
that is inserted into the electrical interface of FIG. 21.
[0032] FIG. 23 depicts a three-dimensional perspective of the
electrical interface of FIG. 21 with a section of the controller's
housing shown for illustrative purposes.
[0033] FIG. 24 depicts a cross-sectional view of an exemplary
electrical interface for a water heater controller, such as is
depicted in FIG. 19.
[0034] FIG. 25 depicts a three-dimensional perspective of the
electrical interface depicted in FIG. 24.
[0035] FIG. 26 depicts a side view of an exemplary electrical
interface for a water heater controller, such as is depicted in
FIG. 19.
[0036] FIG. 27 depicts an exemplary housing section and various
other components for a water heater controller, such as is depicted
in FIG. 19.
[0037] FIG. 28 depicts the housing section of FIG. 27 with
electrical interfaces removed for illustrative purposes.
[0038] FIG. 29 depicts an exemplary housing section and various
other components for a water heater controller, such as is depicted
in FIG. 19.
[0039] FIG. 30 depicts the housing section of FIG. 29 with
electrical interfaces removed for illustrative purposes.
[0040] FIG. 31 is a block diagram illustrating an exemplary water
heater controller, such as is depicted in FIG. 17.
[0041] FIG. 32 is a three-dimensional perspective of an exemplary
water heater controller having thermally conductive elements for
heat sinking. The controller's housing and various other components
have been removed for illustrative purposes.
[0042] FIG. 33 depicts a three-dimensional back view of the water
heater controller of FIG. 32 with its base removed, for
illustrative purposes, to expose internal components of the
controller.
[0043] FIG. 34 depicts a temperature holding apparatus, such as is
depicted by FIG. 13, mounted on a tank via the bracket depicted by
FIG. 12.
DETAILED DESCRIPTION
[0044] FIG. 1 depicts a water heating system 50 in accordance with
an exemplary embodiment of the present disclosure. In this regard,
FIG. 1 depicts an exemplary water heater controller 52 that is
electronically actuated and is mounted on a side of a tank 53,
although the water heater controller 52 may be positioned at other
locations in other embodiments. The system 50 shown by FIG. 1 has
two heating elements, referred to as "upper heating element 55" and
"lower heating element 56." Each heating element 55 and 56
comprises an electrically resistive coil 57 that, when activated,
emits heat to water or other fluid within the tank 53 and a base 58
that is mounted to a side of the tank 53. The coil 57 is located
within the tank 53 and is submerged in the water held by the tank
53. Any known or future-developed heating element may be used to
implement either of the heating elements 55 or 56. For many
conventional heating elements, the base 58 is screwed into the tank
53 through a hole in the side of the tank 53.
[0045] The upper heating element 55 is mounted to an upper portion
of the tank 53 above the lower heating element 56, which is mounted
to a lower portion of the tank 53. However, other numbers and
arrangements of heating elements are possible in other embodiments.
Also mounted to a side of the tank 53 in FIG. 1 is a sensor holding
apparatus 59, which will be described in more detail hereinbelow.
As shown by FIG. 1, the tank 53 may be positioned on a stand 60,
although such a stand 60 is unnecessary and may be removed from the
system 50, if desired.
[0046] Cold water is drawn into the tank 53 via a pipe 63 coupled
to a water source 65. Operating under the direction and control of
the controller 52, the heating elements 55 and 56 heat the water
within the tank 53, and heated water is drawn out of the tank via
pipe 67. Various techniques may be used to control the heating
provided by the elements 55 and 56. In one exemplary embodiment,
the controller 52 has an embedded temperature sensor (e.g., a
thermistor), although such a sensor 66 (FIG. 3) may be located
elsewhere, such as mounted to a side of the tank 53, in other
embodiments. In general, the controller 52 activates the upper
heating element 55 to cause this element 55 to emit heat when the
temperature sensed by the sensor 66 falls below a specified
threshold, referred to as a "lower set point." After activating the
upper heating element 55, the controller 52 keeps the element 55 in
an activated state until the temperature sensed by the sensor 66
exceeds a threshold, referred to as an "upper set point." Once this
occurs, the controller 52 deactivates the heating element 55 such
that it stops heating the water within the tank 53. As such, the
water in the upper portion of the tank 53 can be maintained in a
desired temperature range.
[0047] In addition, the sensor holding apparatus 59 has an embedded
temperature sensor (e.g., a thermistor), although such a sensor 68
(FIG. 3) may be located elsewhere in other embodiments. In general,
the controller 52 activates the lower heating element 56 to cause
this element 56 to emit heat when the temperature sensed by the
sensor 68 falls below a specified threshold, referred to as a
"lower set point." After activating the lower heating element 56,
the controller 52 keeps the element 56 in an activated state until
the temperature sensed by the sensor 68 exceeds a threshold,
referred to as an "upper set point." Once this occurs, the
controller 52 deactivates the heating element 56 such that it stops
heating the water within the tank 53. As such, the water in the
lower portion of the tank 53 can be maintained in a desired
temperature range. Exemplary techniques for controlling the
operation of heating elements 55 and/or 56 are described in the
following commonly assigned patent applications: U.S. patent
application Ser. No. 10/772,032, entitled "System and Method for
Controlling Temperature of a Liquid Residing within a Tank," and
filed on Feb. 4, 2004; U.S. patent application Ser. No. 11/117,069,
entitled "Water Heating System and Method for Detecting a Dry Fire
Condition for a Heating Element," and filed on Apr. 28, 2005; and
U.S. patent application Ser. No. 11/677,312, entitled "Water
Heating Systems and Methods for Detecting Dry Fire Conditions" and
filed on Feb. 21, 2007. Each of the foregoing patent applications
is incorporated herein by reference.
[0048] FIG. 2 depicts an exemplary embodiment of the controller 52.
As will be described in more detail hereafter, the controller 52 is
coupled to a plurality of conductive wires 75-79 to enable the
controller 52 to selectively activate the heating elements 55 and
56 (FIG. 1). Each wire 75-59 preferably has a coating 81 composed
of electrically insulating material that covers the wire except for
the ends of the wire. Moreover, once the wires 75-59 are installed,
as will be described in more detail hereafter, they are
substantially unexposed.
[0049] The electrical components of the controller 52 are
preferably housed within and covered by a housing 84. The housing
84 has holes respectively corresponding with the wires 75-79 to
enable the wires to be electrically connected to electrical
components within the housing 84. For example, as shown by FIG. 2,
the housing 84 has a hole 86 corresponding with the wire 76. During
installation, the wire 76 is inserted through the hole 86 and
coupled to electronic components within the housing 84. Further,
the housing 84 has a hole 87 corresponding with the wire 77. During
installation, the wire 77 is inserted through the hole 87 and
coupled to electronic components within the housing 84. Holes
corresponding to the wires 75, 78, and 79 exist on the opposite
side of the controller 52 to enable these wires 75, 78, and 79 to
be similarly coupled to electronic components within the housing
84.
[0050] In one exemplary embodiment, the housing 84 comprises two
sections 85 and 83 that can be removed separately. In this regard,
section 83 can be removed from section 85. Therefore, the section
83 can be removed from the controller 52 without removing section
85. Alternatively, both sections 83 and 85 can be removed from the
controller 52 with or without removing section 83 from section 85.
In other embodiments, other numbers of housing sections are
possible.
[0051] As shown by FIG. 3, the controller 52 comprises a plurality
of electrical interfaces 95-99 that are electrically coupled to the
wires 75-59, respectively. FIGS. 4 and 5 depict an exemplary
embodiment for the electrical interface 96. The other interfaces 95
and 97-99 may be identically configured relative to interface
96.
[0052] As shown by FIG. 4, the electrical interface 96 comprises a
block 101 of conductive material having a hole 104 for receiving a
coupler 121, such as a screw, (FIG. 6) and a hole 105 for receiving
the wire 76. Note that, in one embodiment, each coupler 121 is
implemented as a screw and will be referred to hereafter as such.
However, each coupler 121 may be implemented as other types of
devices, such as a bolt, in other embodiments. Moreover, the
coupler 121 may be any device that applies pressure to the wire
inserted in hole 105 so that frictional forces secure such wire to
the interface 96.
[0053] The walls of the hole 104 are preferably threaded. Further,
the hole 105 is aligned with the hole 86 (FIG. 2) of the housing 84
so that the wire 76 can be inserted through holes 105 and 86 and
exposed by hole 104. Thus, by inserting a screw 121 through the
hole 104 and screwing it down, the screw 121 eventually contacts
and presses against the wire 76. The force applied to the wire 76
by the screw rigidly holds the wire 76 within the block 101 so that
the wire 76 is not easily removed from the block 101. In other
words, the screw 121 is preferably screwed down until the wire 76
is secured to the block 101. Note that the wires 75 and 77-79 may
be similarly secured to the interfaces 95 and 97-99,
respectively.
[0054] The housing 84 has a hollow peg 116 (FIG. 2) extending from
a surface of the housing 84. The hole passing through the peg 116
is aligned with the hole 104 (FIG. 4) such that a screw 121 can be
inserted through the peg 116 and into the hole 104. Further, the
hole in the peg 116 provides access to the screw as it is being
screwed into the block 101. In this regard, a screwdriver can be
inserted through the peg 116 and used to rotate the screw until it
is sufficiently pressed against the wire 76. Other pegs 115 and
117-119 may be similarly aligned with holes in the interfaces 95
and 97-99 and used to secure the wires 75 and 77-79 to these
interfaces 95 and 97-99, respectively.
[0055] FIGS. 6 and 7 show an exemplary screw 121 that may be used
to secure any of the wires 75-59 to the interfaces 95-99 as
described herein. The screw 121 has a hollow point on the end that
contacts the wire being secured by the screw 121. In particular,
the end of the screw 121 that contacts the wire has a cavity 122,
as shown by FIGS. 6 and 7. Therefore, the end of the screw 121 has
a rim 123 that contacts the wire being secured by the screw 121.
FIG. 6 depicts a bottom view of the screw 121 showing the rim 123
and walls defining the cavity 122. The existence of the cavity 122
decreases the surface area contacting the wire thereby increasing
the pressure applied by the screw 121 to the wire. As shown by FIG.
7, the screw 121 has threads 124, and the screw 121 has a head 126,
which may have small channels (not shown) on its surface for
receiving a screwdriver.
[0056] Note that, when the wires 75-79 are secured to the
interfaces 95-99 as described herein, the ends of wires 75-79 shown
in FIG. 2 are substantially unexposed. In this regard, the coating
81 of each wire 75-79 covers the wire except for the tip that is to
be inserted into the housing 84. Further, the housing 84 is
preferably composed of an electrically insulating material, such as
plastic. Moreover, the housing 84 covers and protects the
interfaces 95-99 and the wire tips inserted into them, and the
coatings 81 cover the remaining portions of the wire ends shown in
FIG. 2. Having the wire ends completely covered by the housing 84
and the coatings 81 helps to reduce the chance of an inadvertent
electrical contact with the wires 75-79. Also, if any water is
splashed on the controller 52, the housing 84 and coatings 81
should prevent such water from reaching the wires 75-79. Moreover,
to provide better electrical insulation for the wires, the ends of
the pegs 115-119 may be capped to prevent exposure of the screws
121 used to secure the wires 75-59 to the controller 52.
[0057] To ensure that no portions of the wire ends inserted into
the housing 84 are exposed, the housing holes through which the
wire ends are inserted are preferably dimensioned large enough such
that the respective wire and its coating fit through the hole. For
example, hole 86 (FIG. 2) is preferably dimensioned large enough so
that the wire 77 and its coating 81 fit through the hole 86, and
hole 87 is dimensioned large enough so that the wire 76 and its
coating fit through the hole 87. In one embodiment, each such hole
is just large enough to allow the respective wire and coating to
pass. Indeed, the housing wall defining the hole preferably
contacts the wire coating so that water cannot penetrate the
housing 84 through the hole.
[0058] As shown by FIG. 3, control logic 125 within the controller
52 generally controls the operation of the heating elements 55 and
56 (FIG. 1). The control logic 125 can be implemented in software,
hardware, or a combination thereof. In one exemplary embodiment,
the control logic 125 is implemented in software and executed by an
instruction executing apparatus, such as a microprocessor (not
specifically shown), for example. The instruction executing
apparatus preferably has input and output ports for enabling the
control logic 125 to transmit and receive information to and from
other components of the controller 52 and/or system 50.
[0059] Note that the control logic 125, when implemented in
software, can be stored and transported on any computer-readable
medium. A "computer-readable medium" can be any means that can
contain, store, communicate, propagate, or transport a program for
use by or in connection with an instruction execution apparatus.
The computer readable-medium can be, for example but not limited
to, an electronic, magnetic, optical, electromagnetic, infrared, or
semiconductor apparatus or propagation medium.
[0060] Referring to FIG. 3, the controller 52 preferably comprises
a data interface 128 for enabling the control logic 125 to
communicate data signals with components external to the controller
52. In this regard, the data interface 128 is preferably
electrically coupled to and secured to one or more wires 131 (FIG.
2) that are coupled to one or more external devices. For example,
one of the wires 131 may be coupled to the temperature sensor 68
used to control the lower heating element 56. Moreover, data
indicative of the temperatures sensed by this sensor 68 may be
transmitted to the control logic 125 via the interface 128. In the
exemplary embodiment shown by FIG. 2, the interface 128 is covered
by an insulator 133 that is composed of insulating material, such
as rubber. A hole in the insulator 133 allows one or more wires to
be coupled to the interface 128.
[0061] In one embodiment, the wires 131 may be coupled to an
additional controller (not shown), a display device, or other
device for performing various functions regarding the control of
the system 50. Exemplary devices that may be coupled to the wires
131 or otherwise coupled to the controller 52 are described in U.S.
patent application (attorney docket number 321904-1150), entitled
"Modular Control System and Method for Water Heaters," and filed on
Mar. 27, 2007, which is incorporated herein by reference.
[0062] In one exemplary embodiment, the wires 75 and 76 are coupled
to a power source (not shown) and provide electrical power to the
controller 52. This power is not only used to power various
components, such as the instruction executing apparatus used to
execute the instructions of the control logic 125, but is also used
to selectively power and, therefore, activate the heating elements
55 and 56. Note that the controller 52 may have a transformer (not
shown in FIG. 3) for changing the voltage of the electrical power
delivered to one or more components. For example, the power source
may provide a 120 or 240 Volt (V) alternating current (AC) power
signal, and a transformer may transform such power signal to a
direct current (DC) signal having a desired voltage, such as 5 V,
for example, for powering at least some components of the
controller 52. In one exemplary embodiment, a 120 V AC power signal
is used to power the heating elements 55 and 56, but a 5 V DC
signal is used to power at least a portion of the control logic 125
and/or an instruction executing apparatus that is used to execute
instructions of the control logic 125, if the control logic 125 is
implemented in software.
[0063] The interface 95 secured to the wire 75 is electrically
coupled to the interface 98 through a relay 144 and a mechanical
switch 143 of an emergency shut-off apparatus 152, which will be
described in more detail hereafter. The interface 95 is also
electrically coupled to the interface 99 through a relay 145 and
switch 143. If the switch 143 is in a closed state, then the
voltage of the wire 75 is applied to the relays 144 and 145. If the
switch 143 is in an open state, then the interfaces 98 and 99 are
electrically isolated from the wire 75 by the switch 143.
[0064] In addition, the interface 96 secured to the wire 76 is
electrically coupled to the interface 97 through a mechanical
switch 146 of the emergency shut-off apparatus 152. If the switch
146 is in a closed state, then the voltage of the wire 76 is
applied to the interface 97. If the switch 146 is in an open state,
then the interface 97 is electrically isolated from the wire 76 by
the switch 146.
[0065] The apparatus 152 is configured to detect when a temperature
of the water within the tank 53 has exceeded a predefined threshold
indicating that the water temperature is reaching an unsafe range
and/or indicating that the water heating system 50 may have a
malfunction. In response to such a detection, the apparatus 152
disables at least the heating elements 55 and 56 until the
apparatus 152 later receives a manual input indicating that
operation of the heating elements 55 and 56 is to be restarted. In
one embodiment, the apparatus 152 disables the heating elements 55
and 56 by placing the switches 143 and 146 in open states such that
the interfaces 97-99 are electrically isolated from interfaces 95
and 96 and, therefore, from wires 75 and 76 coupled to the power
source (not shown). When the apparatus 152 receives a manual input
from a user indicating that operation of the heating elements 55
and 56 is to be restarted, the apparatus 152 transitions each of
the switches 143 and 146 from an open state to a closed state,
provided that the temperature detected by the apparatus 152 has
fallen to a normal range below the predefined threshold.
[0066] Various safety standards require that the operation of the
components for shutting off power to the heating elements 55 and 56
in an emergency to be separate from the operation of the components
used to control the heating elements 55 and 56 in normal operation.
To comply with such requirements, the operation of the components
of the emergency shut-off apparatus 152 is preferably separate from
and independent of the operation of the control logic 125.
[0067] Further, the emergency shut-off apparatus 152 may be
implemented in hardware, software, or a combination thereof. In the
embodiment depicted by FIG. 3, the apparatus 152 is implemented
exclusively in hardware and is mechanically actuated. In this
regard, the disabling of the heating elements 55 and 56 is achieved
by mechanical forces resulting from thermal stresses. In
particular, the emergency shut-off apparatus 152 comprises a
temperature sensitive element (not shown in FIG. 3), such as a
bimetallic disc, that moves due to thermal stresses when the
temperature of the disc exceeds a threshold. Further, such movement
of the temperature sensitive element changes the state of the
switches 143 and 146 (i.e., places them in open states) so that no
current flows through the apparatus 152 from the interfaces 75 and
76. When the heating elements 55 and 56 are to be enabled, a user
input mechanically forces the temperature sensitive back to its
original position prior to disabling the heating elements 55 and
56. Moreover, the states of the switches 143 and 146 are controlled
via mechanical forces rather than electrical control signals. An
exemplary configuration of an emergency shut-off apparatus 152 that
is mechanically actuated is described in U.S. patent application
Ser. No. 11/105,889, entitled "Trip-Free Limit Switch and Reset
Mechanism," and filed on Apr. 15, 2005, which is incorporated
herein by reference.
[0068] In other embodiments, the emergency shut-off apparatus 152
may be electronically actuated, and portions of the apparatus 152
may be implemented in software, if desired. In this regard, rather
having a temperature sensitive element that moves due to thermal
stresses, the apparatus 152 may be configured to sense a
temperature and provide electrical signals for controlling relays
(not shown in FIG. 3), in lieu of mechanical switches 143 and 146,
in order to enable or disable the heating elements 55 and 56 as
appropriate. However, as will be described in more detail
hereafter, using an emergency shut-off apparatus 152 that is
electronically actuated may, at least to some extent, increase
temperatures within the controller 52 and/or increase the size
requirements of the controller 52. In particular, to meet the
safety standards discussed above regarding separate control of the
emergency shut-off apparatus 152 and control logic 125, the same
circuitry used to control the relays 144 and 145 should not be used
to control the apparatus 152. Thus, if the emergency shut-off
apparatus 152 is electronically actuated, then additional circuitry
may be required relative to the circuitry that is required to
implement the control logic 125.
[0069] In addition, in one embodiment, the switches 143 and 146 are
also coupled to a transformer that transforms the power from the
interfaces 95 and 96 into a form suitable for powering various
components of the controller 52, such as the control logic 125.
Thus, in an emergency shut-off condition, power is cut-off to the
control logic 125 as well as the heating elements 55 and 56.
Indeed, if desired, the apparatus 152 may cut power to all
electrically-powered components of the controller 52.
[0070] The wire 77 is electrically coupled to the upper and lower
heating elements 55 and 56 (FIG. 1). Thus, if the switch 146 has
not been placed in an open state by the apparatus 152, then the
voltage of the wire 76 is applied to both heating elements 55 and
56. In another possible embodiment, an additional electrical
interface (not shown) may be used to electrically couple the
interface 96 to one heating element 55 or 56 while the interface 97
is used to electrically couple the interface 96 to the other
heating element 55 or 56. Such a configuration may eliminate
splicing of the wire 77 secured to the interface 97. Any such
additional interface may be coupled to the interface 96 through a
switch controlled by the apparatus 152 so that the wire 76 can be
electrically isolated from the additional interface by the
apparatus 152 in the event of a detection of an emergency shut-off
condition.
[0071] The wire 78 is electrically coupled to the upper heating
element 55. If the control logic 125 determines that the upper
heating element 55 is to be activated, the control logic 125 places
the relay 144 into a closed state. In this regard, the control
logic 125 transmits, to the relay 144, an electrical control signal
for transitioning the relay 144 to a closed state. In such case,
the voltage of the wire 75 is applied, through the switch 143 and
relay 144, to the wire 78 and, therefore, the upper heating element
55 thereby activating the upper heating element 55, assuming that
the apparatus 152 has not placed the switch 143 in an open state.
If the control logic 125, however, determines that the upper
heating element 55 is to be deactivated, the control logic 125
places the relay 144 into an open state. Accordingly, the wire 75
is electrically isolated from the wire 78 and, therefore, the upper
heating element 55 thereby deactivating the upper heating element
55. In this regard, the heating element 55 is preferably activated
only when electrically coupled to both wires 75 and 76 via the
controller 52 and, therefore, receiving power from the power source
(not shown) connected to these wires 75 and 76.
[0072] The wire 79 is electrically coupled to the lower heating
element 56. If the control logic 125 determines that the lower
heating element 56 is to be activated, the control logic 125 places
the relay 145 into a closed state. In this regard, the control
logic 125 transmits, to the relay 145, an electrical control signal
for transitioning the relay 145 to a closed state. In such case,
the voltage of the wire 75 is applied, through the switch 143 and
relay 145, to the wire 79 and, therefore, the lower heating element
56 thereby activating the lower heating element 56, assuming that
the apparatus 152 has not placed the switch 143 into an open state.
If the control logic 125, however, determines that the lower
heating element 56 is to be deactivated, the control logic 125
places the relay 145 in an open state. Accordingly, the wire 75 is
electrically isolated from the wire 79 and, therefore, the lower
heating element 56 thereby deactivating the lower heating element
56. In this regard, the heating element 56 is preferably activated
only when electrically coupled to both wires 75 and 76 via the
controller 52 and, therefore, receiving power from the power source
(not shown) connected to these wires 75 and 76.
[0073] As shown by FIG. 2, the controller 52 comprises a rotatable
dial 160 that can be turned to manually set the upper set points
for the heating elements 55 and 56. In one mode of operation, the
controller 52 controls the activation states of both heating
elements 55 and 56 using the temperature value indicated by the
dial 160 as the upper set point for both elements 55 and 56. In
such mode, the lower set point for both elements can be a
predefined amount (e.g., twenty degrees Fahrenheit) below the upper
set point indicated by dial 160. Various other techniques for
establishing the upper and lower set points are possible.
[0074] Also shown by FIG. 2 is a thermally conductive base 166 that
is attached to the housing 84. This base 166 has two wings 167 and
168 with two holes 169 and 170, respectively, for enabling the
controller 52 to be mounted on the tank 53. In this regard, screws
may be inserted through the holes 169 and 170 and into the tank 53
thereby securing the controller 52 to the tank 53. FIG. 8 depicts a
front view of an exemplary controller 52 illustrating the wings 167
and 168 of the base 166. FIG. 9 depicts a side view of the
controller 52 that is depicted in FIG. 8, and FIG. 10 depicts a
back view of this controller 52.
[0075] Referring to FIGS. 2 and 8-10, the base 166 has two notched
edges 192 and 193 to facilitate mounting of the controller 52 on
the tank 53. In this regard, FIG. 11 shows the controller 52 joined
with a conventional bracket 211 typically used for mounting heating
elements to tanks of water heaters. In this regard, the bracket 211
has a hole 214 through which the base 58 of a heating element 55 or
56 may be inserted. Note that FIG. 12, shows a bracket 221
identical to the bracket 211 shown by FIG. 12. Moreover, the
bracket 211 of FIG. 11 has two arms 224 and 225 that form a notch
226 between the two arms 224 and 225. When the bracket 211 is used
to mount the controller 52 to the tank 53, the bottom of the
controller 52 is positioned within the notch 226 as shown by FIG.
11. Each arm 224 and 225 has a respective hole, such that the
corresponding edge 192 or 193 can extend through the hole. For
example, as shown by FIG. 11, the arm 225 has a hole 231 through
which a portion of the edge 192 extends when the end of the arm 225
is inserted into the notch 195 as shown by FIG. 11. A portion of
the edge 193 similarly extends through a hole in the arm 224. Via
such a mounting, the bracket 211 presses the base 166 against the
tank 53.
[0076] As shown by FIG. 11, a bottom portion of the controller 52
is dimensioned to fit within the notch 226 of the bracket 211
defined by the two arms 225 and 226. A top portion of the
controller 52 outside of the notch 226 is larger than the bottom
potion. In at least one exemplary embodiment, such as the
embodiment described hereafter with reference to FIG. 17, the
emergency shut-off apparatus 152, a transformer 667, and at least
one relay 144 or 145 are located in the top portion, and the
control logic 125 and temperature sensor 66 are located in the
bottom portion between the arms 225 and 226. Such positioning, at
least to some extent, helps to keep the control logic 125 and
temperature sensor 66 away from the relatively high heat generated
by the aforedescribed components in the top portion.
[0077] Moreover, a bracket 221 identical to the bracket 211
described above may be used to mount the sensor holding apparatus
59 to the tank 53. FIG. 13 depicts an exemplary sensor holding
apparatus 59. The temperature sensor 68 (FIG. 3) is embedded in or
otherwise coupled to the apparatus 59. The temperature sensor 68
may contact the side of the apparatus 59 that is mounted against
the tank 53 in order to enhance the sensor's sensitivity to the
tank's temperature. Further, the side of the apparatus 59
contacting the sensor 68 may be thermally conductive.
[0078] As shown by FIG. 13, the apparatus 59 has two notched edges
252 and 253. Between the two edges 252 and 253 are a plurality of
substantially parallel fins 255 forming a plurality of channels
256. Further, the edges 252 and 253 have notches 258 and 259,
respectively, to facilitate mounting of the apparatus 59 to the
tank 53 via the bracket 221 of FIG. 12. In this regard, the bracket
221 has a hole 264 through which the base 58 of a heating element
55 or 56 may be inserted. Further, the bracket 221 has two arms 274
and 275 that form a notch 276 between the two arms 274 and 275.
When the bracket 221 is used to mount the sensor holding apparatus
59 to the tank 53, the apparatus 59 is positioned within the notch
276 as shown by FIG. 12. Each arm 274 and 275 has a respective hole
284 and 285, such that the corresponding edge 253 or 252 can extend
through the hole. For example, as shown by FIG. 12, the arm 274 has
a hole 284 through which a portion of the edge 253 extends when the
end of the arm 274 is inserted into the notch 259 (FIG. 13) as
shown by FIG. 12. Further, the arm 275 has a hole 285 through which
a portion of the edge 252 extends when the end of the arm 275 is
inserted into the notch 258 (FIG. 13) as shown by FIG. 12. FIG. 34
depicts the sensor holding apparatus 59 mounted to the tank 53 via
the bracket 221. As shown by FIG. 34, the base 58 of the heating
element 56 passes through the hole 264 of bracket 221. Further, the
bracket 221 presses the apparatus 59 against the tank 53.
[0079] FIG. 10 shows the base 166. The side of the base 166 shown
in FIG. 10 is exposed when the housing 84 is attached to the base
166. FIG. 14 shows the opposite side of the base 166 depicted in
FIG. 10. In this regard, FIG. 10 shows the side that faces the tank
53 when the controller 52 is mounted on the tank 53, and FIG. 14
shows the side internal to the controller 52 when the housing 84
and other components of the controller 52 are assembled. The side
of the base 166 shown in FIG. 10 has a circular ring 292, which
will be described in more detail hereafter. The ring 292 may have
other, non-circular shapes in other embodiments.
[0080] FIG. 15 depicts the controller 52 of FIG. 10 with the base
166 removed to expose a printed circuit board (PCB) 305 within the
controller 52. Various electronics for controlling the operation of
the system 50 may be mounted on the PCB 305. FIG. 15 shows a
bimetallic disc 308 that may be used to implement a portion of the
emergency shut-off apparatus 152 (FIG. 3). In this regard, when the
base 166 is attached to the housing 84, the bi-metallic disc 308
contacts the ring 292 depicted in FIG. 14. If the temperature of
the water within the tank 53 reaches a certain threshold, heat from
the water causes the bimetallic disc 308 to actuate or move due to
thermal stresses within the disc 308. In this regard, the disc 308
changes from a concave to a convex position thereby moving the
center of the disc 308 out of the interior of the ring 292.
Actuation of the disc 308 in this way moves a plunger 312 (FIG. 16)
resulting in the switches 143 and 146 (FIG. 3) being transitioned
to an open state thereby disabling the heating elements 55 and 56.
Once the system 50 has been inspected and the temperature of the
water within the tank 53 returned to a normal range, the disc 308
can be manually moved back to its pre-actuation state.
[0081] FIG. 16 shows the controller 52 of FIG. 15 with the disc 308
removed to show an end of the plunger 312. Moreover, the plunger
312 is coupled to a button 315 (FIG. 2) that can be depressed to
return the disc 308 to its pre-actuation state. In this regard,
manually pressing the button 315 moves the plunger in a direction
toward the disc 308 mechanically forcing the disc 308 back to its
concave position. Exemplary configurations and operations of the
apparatus 152 are described in more detail in U.S. patent
application Ser. No. 11/105,889.
[0082] Between the PCB 305 and the base 166, which has been removed
from FIGS. 15 and 16 for illustrative purposes, is a strip 317 of
thermally insulating material, such as plastic. Attached to the
strip 317, on a side opposite of the PCB 305, is the temperature
sensor 66. Having the strip 317 positioned between the sensor 66
and the PCB 305 helps to shield the sensor 66 from heat generated
by electronics mounted on the PCB 305. Further, by positioning
electronics that generate a relatively high amount of heat on the
opposite side of the PCB 305 (i.e., between the PCB 305 and housing
84), the PCB 305 also helps to shield heat from the sensor 66.
[0083] The sensor 66 can be electrically coupled to the PCB 305 via
one or more wires extending through and/or over the strip 317 so
that the sensor 66 can be electrically coupled to the control logic
125 via conductive connections on the PCB 305. When the base 166 is
attached to the housing 84, the sensor 66 is preferably in contact
with the base 166 to increase the sensor's sensitivity with respect
to temperature changes in the base 166. A segment 318 of adhesive
material may adhere the strip 317 to the base 166 to ensure that
the strip 317 does not move relative to the base 166 and,
therefore, that the sensor 66 remains in contact with the base 166.
Moreover, during operation, the base 166 contacts a side of the
tank 53, which is heated by the water within the tank 53, and the
temperatures sensed by the sensor 66 are indicative of the water
temperature within the tank 53.
[0084] FIG. 17 depicts an electronically actuated water heater
controller 52 in accordance with one exemplary embodiment with the
housing 84 removed for illustrative purposes. As shown by FIGS. 17
and 18, the electrical interface 97 is coupled to a conductive wire
521, in addition to wire 77. In this embodiment, the wire 77 is
electrically coupled to one of the heating elements 55 or 56, and
the wire 521 is electrically coupled to the other heating element.
For example, the wire 77 may be electrically coupled to the upper
heating element 55 and the relay 144 such that electricity passes
through the wires 77 and 78, as well as heating element 55, when
the control logic 125 places the relay 144 in a closed state. In
such an example, the wire 521 may be coupled to the lower heating
element 56 and the relay 145 such that electricity passes through
the wires 79 and 521, as well as the lower heating element 56, when
the control logic 125 places the relay 145 in a closed state.
[0085] In the embodiment shown by FIG. 17, each electrical
interface 95-99 comprises a block of conductive material and shall
be referred to hereafter as a "terminal block." However, other
configurations of the interfaces 95-99 are possible in other
embodiments. FIG. 17 depicts a transformer 667 that is used to
transform the AC signal received from wires 75 and 76 to a lower
voltage DC signal for use by various components of the controller
52, such as the control logic 125.
[0086] The terminal block 95 is electrically coupled to the
emergency shut-off apparatus 152 via conductive connections 565 and
566, which are joined and pressed together by a conductive rivet
569 passing through both connections 565 and 566. Similarly, the
terminal block 96 is electrically coupled to the emergency shut-off
apparatus 152 via conductive connections 555 and 556, which are
joined and pressed together by a conductive rivet 559 passing
through both connections 555 and 556.
[0087] As shown by FIG. 19, an end 571 of the connection 565 (FIG.
17) passes through a hole 574 in the terminal block 95. A top side
of the connection end 571 that contacts a screw 121, as described
in more detail below, is flat. Thus, the entire periphery of the
screw rim 123 (FIG. 6) contacts the connection end 571 thereby
helping to ensure that force is applied from the screw 121 to the
connection end 571 in an even and predictable manner. However, in
other embodiments, the top side of the connection end 571 can have
other shapes, and it is unnecessary for the entire periphery of the
screw rim 123 to contact the connection end 571 in all
embodiments.
[0088] To connect the wire 75 to the terminal block 95, the wire 75
is inserted through the hole 574 such that the wire 75 is
positioned between the connection end 571 and a floor 577 formed by
the conductive terminal block 95, as shown by FIGS. 19 and 20. In
the embodiment shown by FIG. 19, the floor 577 is flat, but other
shapes for the floor 577 are possible in other embodiments. A
coating 81 of electrically insulating material covers portions of
the wire 75 outside of block 95.
[0089] Once the wire 75 is inserted into the hole 574 of the
terminal block 95, the screw 121 is then rotated such that it is in
contact with the end 571 and presses the end 571 against the wire
75 thereby decreasing contact resistance for the electrical current
that is to flow between the wire 75 and the connection end 571.
Generally, the tighter that the screw 121 is screwed against the
connection end 571, the greater is the force that presses the
connection end 571 against the wire 75 thereby decreasing contact
resistance.
[0090] As shown by FIG. 20, the wire 75 and its coating 81 pass
through a hole 572 in the housing 84. The hole 572 is preferably
dimensioned such that it is just large enough for the wire 75 and
its coating 81 to fit. Indeed, the housing wall defining the hole
572 preferably contacts the entire outer periphery of the coating
81 so that water cannot penetrate the housing 84 through the hole
572. Further, there is a gap 574 between the housing 84 and the
terminal block 95. Such a gap 574 allows some of the coating 81 to
pass into the housing 84 helping to ensure that any portion of the
wire 75 exposed by the coating 81 is within the housing 84 and,
therefore, unexposed to a user of the controller 52. Accordingly,
water should be prevented from reaching the terminal block 95 or
the tip of the wire 75 that is exposed by the coating 81, and a
user should be prevented from inadvertently touching the wire 75.
Similar techniques may be used to ensure that the tips of the other
wires 76-79 and 521 not covered by a coating 81 are entirely within
the housing 84 and, therefore, not exposed to a user of the
controller 52. In such manner, water that may be splashed on the
controller 52 can be prevented from reaching any of the
current-carrying components of the controller 52 thereby obviating
the need of a separate cover to shield the controller 52 in order
to comply with safety requirements or satisfy safety concerns.
[0091] As shown by FIGS. 21 and 22, a bottom side of the connection
end 571 has a plurality of ribs 591 for guiding the wire 75 as it
is being inserted into the hole 574 of the terminal block 95. In
the instant embodiment, the connection end 571 has two ribs 591,
but other numbers of ribs are possible in other embodiments. The
ribs 591 are elongated and extend generally in a direction parallel
to the direction of insertion for the wire 75. Further, various
shapes for the ribs 591 are possible. For example, if desired,
sides of the ribs 591 may be tapered, and corners or other edges
may be rounded. The wire 75 just fits within a channel 593 formed
by the two ribs 591 shown in FIGS. 21 and 22. Moreover, the ribs
591 guide the wire 75 through the channel 593 thereby ensuring that
the centerline 75 of the wire 75 is substantially aligned with the
centerline of the screw 121. Having the wire 75 and screw 121
substantially aligned, as described above, generally helps to
decrease contact resistance. In this regard, aligning the wire 75
and screw 121 generally helps to increase the pressure applied to
the wire 75 by the connection end 571, thereby decreasing contact
resistance. Ideally, the centerlines of the screw 121 and wire 75
intersect, but at least some degree of tolerance is acceptable
without having a significant impact to contact resistance.
[0092] FIG. 23 shows the controller 52 with the housing section 83
(FIG. 2) removed for illustrative purposes. As shown by FIG. 23,
the terminal block 95 fits within a channel 602 formed by the
housing section 85. However, other positions of the terminal block
95 are possible in other embodiments. In addition, the
configuration of the terminal block 96 is identical to that of the
terminal block 95, and the wire 76 may be connected to the terminal
block 96 in the same manner that the wire 75 is connected to the
terminal block 95. In this regard, an end of the connection 555
(FIG. 17) passes through a hole in the terminal block 96, and a
screw 121 can be rotated to press such connection end against the
wire 76, which is also inserted through the hole in the terminal
block 96. Further, a bottom side of the end of the connection 555
is ribbed like the connection end 571 described above in order to
guide the wire 76 as it is being inserted into the terminal block
96. However, other configurations of the terminal blocks 95 and 96,
as well as other techniques for connecting the terminal blocks 95
and 96 to wires 75 and 76, respectively, are possible in other
embodiments.
[0093] Referring to FIG. 19, the terminal block 98, like the
terminal block 95 described above, has a hole 614 through which a
wire 78 is inserted. Further, a conductive connection 622
electrically couples the terminal block 98 to the PCB 305. However,
the connection 622 contacts the floor of the terminal block 98
within the hole 614 such that the wire 78 is positioned between the
screw 121 and the connection 622 when the wire 78 is inserted into
the terminal block 98, as shown by FIG. 24. The connection 622 has
a plurality of ribs 626 for guiding the wire 78 as it is being
inserted into the terminal block 98, similar to the ribs 591 (FIG.
24) that guide the wire 75. In this regard, the ribs 626 help to
align the centerline of the wire 78 with the centerline of screw
121 such that a firm, reliable contact between the screw 121 and
the wire 78 is ensured. Moreover, once the wire 78 is inserted
through the hole 614, the screw 121 is preferably tightened such
that it presses the wire 78 against the connection 622.
[0094] As shown by FIG. 25, an inner wall 628 of each rib 626 is
curved having a radius of curvature similar to that of the wire 78.
Moreover, the wire 78 fits flush against the inner wall 628 of each
rib 626 thereby enabling the wire 78 to be precisely aligned with
the screw 121.
[0095] As shown by FIGS. 19 and 25, the terminal block 99 is
electrically coupled to the PCB 305 via a conductive connection
632. The configuration of the terminal block 99 and connection 632
may be identical or similar to that of the terminal block 98 and
connection 622, respectively. Thus, the wire 79 may be connected to
the terminal block 99 in the same or similar manner that wire 78 is
connected to the terminal block 98.
[0096] As shown by FIG. 17, the terminal block 97 is electrically
coupled to the emergency shut-off apparatus 152 via conductive
connections 661 and 662, which are joined and pressed together by a
conductive rivet 665 passing through both connections 661 and 662.
As shown by FIG. 26, an end 672 of the connection 661 passes
through a hole 675 in the terminal block 97. Further, the end 672
has a rib 677 on its lower surface. Like the ribs 591 of FIG. 22,
the rib 677 is elongated and extends generally in a direction
parallel to the direction of insertion of the wires 521 and 77.
Further, various shapes of the rib 677 are possible. The rib 672
guides the wires 521 and 77 as these wires are being inserted
through the hole 675. In this regard, each wire 521 and 77 is
inserted into the hole 675 on an opposite side of the rib 677
relative to the other wire. Each wire 521 and 77 just fits between
the rib 677 on one side and an inner wall of the terminal block 97
on the other side. The rib 677 helps to prevent the wires 521 and
77 from interfering with one another as they are inserted through
the hole 675. Once the wires 521 and 77 are inserted into the hole
675, the screw 121 can be rotated such that it presses the
connection end 672 against each of the wires 521 and 77 thereby
forming a reliable electrical connection between the connection 661
(FIG. 17) and the wires 521 and 77.
[0097] In one exemplary embodiment, the housing 84 forms guides
that can help with assembly of the controller 52 during
manufacture. For example, FIG. 27 depicts an interior of the
housing section 83. The housing section 83 has a raised ridge 723
formed on its interior surface to help with positioning of the
terminal blocks 96 and 97. In this regard, referring to FIGS. 27
and 28, the raised ridge 723 has a cavity 724 for each block 96 and
97, and each such block just fits in its respective cavity 724. In
this regard, a periphery of each respective cavity 724 is similar
to an outer periphery of the block 96 or 97 situated in it. Thus,
by placing each block 96 and 97 within its respective cavity 724,
it can be ensured that each block 96 and 97 is correctly positioned
with a relatively high degree of precision. Further, the raised
ridge 723 helps to keep the terminal blocks 96 and 97 in place once
they have been positioned. In addition, other raised ridges formed
by either of the housing sections 83 or 85 may similarly form
cavities to help position other components correctly.
[0098] FIG. 29 depicts an interior portion of the housing 85 with
the PCB 305 removed for illustrative purposes. As shown by FIGS. 29
and 30, a raised ridge 745 may be used to help position the
terminal block 99 in a similar manner that the raised ridge 723 of
FIG. 27 can be used to help position terminal blocks 96 and 97. In
this regard, the ridge 745 forms a cavity 747 having a periphery
similar in shape to an outer periphery of block 99. Further, a
raised ridge 746 may be used to help position the terminal block 98
in a similar manner that the raised ridge 723 of FIG. 27 can be
used to help position terminal blocks 96 and 97. In this regard,
the ridge 746 forms a cavity 748 having a periphery similar in
shape to an outer periphery of block 98.
[0099] The current-carrying components, such as terminal blocks
95-99 and connections 565, 566, 555, 556, as well as conductive
connections on the PCB 305, can be composed of any conductive
material, such as copper, bronze, brass, gold, etc. In one
exemplary embodiment, each such current-carrying component is
composed of a metallic alloy, such as K88(C18080), which is a
copper alloy having better stress relaxation properties relative to
many other materials typically used for conductive connections.
Moreover, heat can be an important issue, particularly when the
controller 52 is sized to a small enough scale such that it can
fit, as a drop-in replacement, for conventional mechanical
controllers that are mounted via the brackets shown in FIGS. 11 and
12. Further, stress relaxation can be more pronounced in higher
temperature environments, such as may be the case within the
controller 52, and can increase the contact resistance of the
current carrying components. Thus, in order to keep contact
resistance at relatively low levels, thereby helping to reduce
temperatures within the controller 52, material having the
following properties is preferably used for the current carrying
components: an International Annealed Copper Standard (IACS) of
greater than approximately 80%, a yield stress greater than
approximately 50 ksi (kilo-pounds per square inch), and a stress
relaxation temperature greater than approximately 105 degrees
Celsius. The copper alloy, K88(C18080), satisfies such parameters,
but other types of material may also satisfy the foregoing
parameters and/or be used for the current-carrying components in
other embodiments.
[0100] In one exemplary embodiment, as depicted by FIG. 31, the
controller 52 comprises at least one temperature sensor 701, such
as a thermistor, in addition to the sensor 66. Such a sensor 701 is
preferably positioned in close proximity to one or more of the high
temperature components, such as the emergency shut-off apparatus
152, transformer 667, or relays 144 or 145. For example, the sensor
701 may be positioned on or close to one of the relays 144 or 145
and be used to detect failure or imminent failure of such relay, as
described in U.S. patent application Ser. No. 11/117,068, entitled
"System and Method for Detecting Failure of a Relay Based Circuit,"
and filed on Apr. 28, 2005, which is incorporated herein by
reference. In one exemplary embodiment, the temperature sensor 701
is mounted on the PCB 305 and electrically coupled to the control
logic 125.
[0101] If desired, the control logic 125, based on temperature data
indicative of the temperatures sensed by the sensor 701,
compensates the temperature data received from the sensor 66 in an
effort to determine a more accurate temperature reading for
comparison to the upper and/or lower set point of the upper heating
element 55. For example, depending on the readings by the sensor
701, the control logic 125 may try to determine the extent to which
heat from the apparatus 152, transformer 667, and/or relays 144
and/or 145 has affected a temperature reading from the sensor 66.
The control logic 125 may then adjust the reading from the sensor
66 to account for the heating effects of the apparatus 152,
transformer 667, and/or relays 144 and/or 145.
[0102] There are various methodologies that may be employed to
compensate the temperature data from sensor 66 based on readings
from the sensor 701. For example, in one embodiment, the controller
52 is tested for many different conditions to empirically determine
the effect of the heat from at least one high temperature component
to the reading from sensor 66. For example, during operation of the
controller 52 or similar controller, readings from the temperature
sensor 66 may be recorded by the control logic 125 or a test
instrument that may be connected to the temperature sensor 66 for
the purpose of conducting a test. Further, an additional
temperature sensor (not shown), referred to a "test sensor" is
coupled to the tank 53, and the temperature readings from the test
sensor are simultaneously recorded with those from the sensor 66.
Since the test sensor is not embedded in the controller 52, heat
from the high temperature components of the controller 52 should
not have a pronounced effect on the readings by the test
sensor.
[0103] Moreover, the recorded readings of the test sensor and the
temperature sensor 66 may then be analyzed to determine how heat
from the high temperature components affected the readings of the
temperature sensor 66. In this regard, it may be assumed that any
difference between two simultaneous readings by the test sensor and
the temperature sensor 66 is attributable to heat from the high
temperature components. Thus, a determination can be made as to how
the temperature readings of the temperature sensor 66, under
various conditions, should be adjusted to account for heat from the
high temperature components. The control logic 125 may then be
configured to adjust the temperature readings from the sensor 66
accordingly.
[0104] Note that the adjustment applied to the readings from the
sensor 66 may take into account other factors in addition to the
readings from the temperature sensor 701. For example, the length
of time that one or more heating elements 55 or 56 have been
activated may be a factor. As a mere example, based on the test
results, it may be determined that a reading from the temperature
sensor 66 is usually about a particular number (e.g., two) degrees
F. higher than a simultaneous reading from the test sensor when
either element 55 or 56 has been activated for longer than a
particular number (e.g., ninety) seconds if the reading from sensor
701 is above a particular temperature threshold (e.g., 150 F). In
such an example, the control logic 125, during normal operation,
may be configured to subtract two degrees F. from the temperature
reading from the sensor 66 if the reading from the sensor 701 is
above the temperature threshold and if either heating element 55 or
56 has been activated for longer than ninety seconds. It should be
noted that the values and factors described in the foregoing
example have been presented for illustrative purposes, and it
should be apparent to one of ordinary skill in the art that other
values and factors may be employed in other examples. Further,
other techniques for testing the controller 52 and/or using the
test results to compensate the temperature readings from the sensor
52 are possible. In addition, the temperature readings from the
sensor 66 can be adjusted in different ways to compensate for the
heat from one or more of the high temperature components based on
at least one reading from the sensor 701.
[0105] In one exemplary embodiment, as depicted by FIG. 32, the
controller 52 comprises at least one element 722 of thermally
conductive material for helping to sink heat generated by various
high temperature components, such as the apparatus 152, transformer
667, and/or relays 144 and 145, for example. In the embodiment
depicted by FIG. 32, each such element 722 is mounted on the PCB
305 and passes through the PCB 302 to contact the base 166, as
depicted by FIG. 33. FIG. 33 depicts two thermally conductive
elements 722, but other numbers of such elements 722 may be used in
other embodiments. Heat from at least one high temperature
component passes through at least one thermally conductive element
722 to the base 166 (FIG. 10), which is in contact with the tank
53. Although the tank 53 may be at a high temperature, such as 150
degrees F. or more, it is likely that the tank's temperature is
lower than the temperature within the controller 52. Thus, the tank
53 serves as a heat sink. To enhance the heat sinking, at least one
of the thermally conductive elements 722 may directly contact one
or more high temperature components, such as the apparatus 152,
transformer 667, or a relay 144 or 145.
[0106] By configuring a water heater controller, as described
herein, many of the heat related problems that plague
electronically actuated controllers can be alleviated. In this
regard, the exemplary designs of the electrical interfaces
described above help to ensure reliable electrical connections with
relatively low contact resistance, thereby helping to reduce
temperatures within the controller. Temperatures can also be
reduced by using a metallic alloy for the current-carrying
components. Such metallic alloy preferably has good electrical
conductivity and sufficient mechanical strength at high temperature
to resist stress relaxation, which could otherwise lead to higher
contact resistance over time as the controller operates in a high
temperature environment. Further, an emergency shut-off apparatus
that is mechanically actuated, such as the one described in U.S.
patent application Ser. No. 11/105,889, is likely to produce less
heat as compared to one that is electronically actuated. Such a
lower heat producing emergency shut-off apparatus can be used while
at the same time allowing the heating elements to be electronically
actuated during normal operation.
[0107] In addition, using a mechanically actuated emergency
shut-off apparatus has an additional safety benefit in that the
control of the emergency shut-off apparatus is separate from the
control of the relays that are controlled based on comparisons of
temperature readings to set points during normal operation. Indeed,
applicable Underwriters Laboratories, Inc. (UL) standards in the
United States require the control of the emergency shut-off
apparatus be independent of the control of the switches that are
used to activate and deactivate the heating elements during normal
operation. To meet such UL requirement using an electronically
actuated emergency shut-off apparatus would likely require
additional circuitry that would produce at least some additional
heat, as well as possibly increase the cost and overall size
requirements of the controller to at least some extent.
[0108] Further, the temperature sensor is located at an end of the
controller away from several components that produce a relatively
high amount of heat, such as the emergency shut-off apparatus and
the switches (e.g., relays) that control the activation states of
the heating elements. In addition, the temperature sensor is
located on a side of the PCB opposite to the foregoing components,
helping to shield the temperature sensor from the heat produced by
such components. Further, the temperature sensor is mounted on a
separate strip of thermally insulating material to further shield
the temperature sensor.
[0109] Moreover, by configuring a water heater controller in
accordance with the exemplary embodiments of the present
disclosure, the size of the water heater controller can be kept
relatively small, such as similar to or smaller than the sizes of
conventional water heater controllers that are mechanically
actuated, yet exhibit a relatively high degree of reliability and
ease of use. Further, such a water heater controller can be
manufactured and installed at a relatively low cost.
* * * * *