U.S. patent application number 12/882237 was filed with the patent office on 2012-03-15 for external gas controller for tankless water heater.
Invention is credited to John Roy.
Application Number | 20120060772 12/882237 |
Document ID | / |
Family ID | 45805416 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120060772 |
Kind Code |
A1 |
Roy; John |
March 15, 2012 |
External Gas Controller For Tankless Water Heater
Abstract
This invention is directed to maintaining the output water
temperature of a tankless water heater to a constant temperature
regardless of changes in water flow rate and/or changes in the
temperature of the cold water feed. The water heater has a cold
water feed pipe, a fuel line and a hot water output pipe. A
temperature monitor attached to the water output pipe generates a
signal which varies in direct proportion to the changes in water
temperature of the heated water. This signal commands the control
motor which operates a fuel valve. The valve then in turn controls
the amount of fuel to the water heater. In operation, as the
temperature of the hot water changes, the control motor operates
the fuel valve to feed more or less fuel to the water heater,
maintaining a more constant water temperature regardless of the
water flow rate or the incoming water temperature.
Inventors: |
Roy; John; (Albuquerque,
NM) |
Family ID: |
45805416 |
Appl. No.: |
12/882237 |
Filed: |
September 15, 2010 |
Current U.S.
Class: |
122/14.2 |
Current CPC
Class: |
F23N 2241/04 20200101;
G05D 23/20 20130101; F24H 1/107 20130101; F23N 2235/16 20200101;
F23N 1/002 20130101; F23N 5/022 20130101; F24H 9/2035 20130101;
F23N 1/082 20130101 |
Class at
Publication: |
122/14.2 |
International
Class: |
F24H 9/20 20060101
F24H009/20 |
Claims
1. Apparatus for maintaining a constant output water temperature of
a tankless water heater where output water temperature changes can
occur due to changes in incoming water temperature or changes in
water flow rate comprising: a control valve coupled to a fuel line
source to control the fuel flow to the water heater; an
electromechanical device used to control the position of the fuel
control valve; and a temperature sensor that produces an electrical
signal which relates to the temperature of water to command the
electromechanical device; wherein the control valve, the
electromechanical device and the temperature sensor are coupled th
external components of the tankless water heater.
2. The apparatus of claim 1 wherein the control valve is a
modulated fuel valve.
3. The apparatus of claim 2 wherein the fuel valve is located to
control the flow of fuel before the fuel reaches the water
heater.
4. The apparatus of claim 1 wherein the temperature sensor is
coupled to monitor the temperature of the water as it leaves the
tankless water heater.
5. The apparatus of claim 4 wherein the temperature sensor is a
thermistor, a thermo coupler, an infrared detector, a solid state
temperature sensitive transistor, or a solid state IC.
6. The apparatus of claim 1 wherein the electromechanical device is
coupled to control the control valve.
7. The apparatus of claim 6 wherein the electromechanical device is
a stepper motor, a servo motor, a geared motor, a solenoid, or a
muscle wire that is coupled to control the fuel valve.
8. The apparatus of claim 1 wherein the fuel in the fuel line is
natural gas, or propane, or any other liquid or gas fuel
source.
9. The apparatus of claim 1 wherein the temperature monitor, the
control motor and the fuel control valve are adapted to be coupled
external to the tankless water heater of the type without a built
in feedback control loop.
10. The Apparatus of claim 1 wherein a logic device is coupled to
the water temperature sensor and the gas valve to prevent
oscillations in water temperature.
11. The apparatus of claim 10 wherein the logic device is a
microcontroller, a microprocessor, a CPLD, a FPGA, or other device
with capabilities to translate sensory inputs into signals and send
the signals to electromechanical devices for controlling the fuel
entering the tankless water heater.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to a tankless water
heater and more specifically to apparatus for heating water in a
tankless water heater where a temperature monitor which is coupled
to a control motor monitors the temperature of the hot water as it
leaves the tankless water heater through an external output pipe of
the water heater. Depending on the monitored temperature of the
water, a control motor opens and closes a gas valve to increase and
decrease the flow of gas to the tankless water heater to provide a
stream of constant temperature hot water regardless of flow rate or
the temperature of the cold feed water. In the present invention
the gas valve which is an off the shelf item and the monitor and
stepper motor are each located external to the tankless water
heater and can be installed on any inexpensive tankless water
heater.
[0003] 2. Description of Related Art
[0004] Water heaters that monitor the temperature of the water and
control the flow of gas to the water heater are known in the prior
art. More specifically, by way of example, U.S. PreGrant
Publication No. 2010/0133258 to Fima discloses a system that
monitors a relief valve coupled to a water heater to limit the
energy and water wasted resulting from the relief valve's
failure.
[0005] U.S. PreGrant Publication No. 2009/0129763 to Cabrera
discloses a sensor which measures the temperature of water flowing
through a pipe prior to heating and a sensor for measuring the flow
rate of water flowing through the pipe. A microprocessor receives
as input the temperature of water flowing through the pipe prior to
heating, the flow rate of water flowing through the pipe, and a set
point for a temperature of heated water.
[0006] U.S. Pat. No. 7,164,851 to Sturm, et al. discloses a central
processing unit (CPU) with an operating program and a plurality of
water heater elements coupled to the CPU which is programmed to
individually activate one of the water heater elements to a
predetermined power level in response to a demand for heated
water.
[0007] U.S. Pat. No. 6,552,283 to Cabrera, et al. discloses a flow
switch for tankless water heaters having a relay switch which, when
activated, signals to the water heater that hot water is required
which in turn activates heating elements of the water heater. When
the flow in the pipe subsides the water heater is deactivated.
[0008] U.S. Pat. No. 6,257,871 to Weiss, et al. discloses a
thermopile for controlling a damper and a main burner valve within
a gas-fired appliance. A control circuit includes a temperature
which determines that the temperature of water or air is below a
predetermined temperature a motor opens the damper and a valve.
[0009] U.S. Pat. No. 5,504,306 to Russell, et al. discloses a
tankless water heater which senses a water outlet temperature and
controls AC power through an on/off mechanism to regulate power to
heating elements embedded in the water stream. A microprocessor
performs a proportional, integrating and derivative calculation
which are used to determine the operating characteristics of the
heating system and to control the heating system.
[0010] U.S. Pat. No. 5,322,216 to Wolter, et al. discloses an
electronic sensing device which senses an outlet water temperature
of a heater, and a another electronic sensing device which senses a
midway water temperature of the heater. The burner output is
controlled to maintain a desired outlet temperature which is based
on changes in water flow and incoming water temperature.
[0011] U.S. Pat. No. 4,970,373 to Lutz, et al. discloses an
electronic temperature control system for a tankless water heater.
The control system has comparison circuitry for comparing the
difference between a water temperature selected from a temperature
selection device and an actual water temperature sensed by a
temperature sensing device.
[0012] U.S. Pat. No. 4,700,886 to McGhee, et al. discloses a
control which utilizes sensed gas pressure downstream of a
thermostat controlled valve as an indication of heat demand. A low
limit transducer maintains adequate heated water for casual uses
without excessive burner cycling. A flow transducer switches a
thermostat from a low limit set point to a high limit.
SUMMARY OF THE INVENTION
[0013] In an exemplary embodiment of the present invention, there
is disclosed apparatus for maintaining the output water temperature
of a tankless water heater at a constant temperature with changes
in water flow having a water pipe for feeding cold water to the
water heater, a gas line for feeding gas to the water heater and a
water pipe for carrying hot water from the water heater. A control
valve is coupled to the gas line to control the flow of gas to the
water heater, a control motor is coupled to the control valve to
control the flow of gas to the water heater and a temperature
monitor is coupled to the water pipe for carrying hot water from
the water heater. The temperature monitor generates a signal that
is fed to the control motor which varies as the water temperature
from the water heater varies. In operation, as the temperature of
the hot water changes, the control motor operates the gas control
valve to feed more or less gas to the water heater to maintain a
constant water temperature regardless of the rate of water flow or
the temperature of the cold water.
[0014] The more important features of the invention have thus been
outlined in order that the more detailed description that follows
may be better understood and in order that the present contribution
to the art may better be appreciated. Additional features of the
invention will be described hereinafter and will form the subject
matter of the claims that follow.
[0015] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not limited
in its application to the details of construction and the
arrangements of the components set forth in the following
description or illustrated in the drawings. The invention is
capable of other embodiments and of being practiced and carried out
in various ways. Also it is to be understood that the phraseology
and terminology employed herein are for the purpose of description
and should not be regarded as limiting.
[0016] As such, those skilled in the art will appreciate that the
conception, upon which this disclosure is based, may readily be
utilized as a basis for the designing of other structures, methods
and systems for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
[0017] The foregoing has outlined, rather broadly, the preferred
feature of the present invention so that those skilled in the art
may better understand the detailed description of the invention
that follows. Additional features of the invention will be
described hereinafter that form the subject of the claims of the
invention. Those skilled in the art should appreciate that they can
readily use the disclosed conception and specific embodiment as a
basis for designing or modifying other structures for carrying out
the same purposes of the present invention and that such other
structures do not depart from the spirit and scope of the invention
in its broadest form.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Other aspects, features, and advantages of the present
invention will become more fully apparent from the following
detailed description, the appended claim, and the accompanying
drawings in which similar elements are given similar reference
numerals.
[0019] FIG. 1 is a diagram of a tankless water heater that provides
a flow of constant temperature water regardless of the volume of
the water flow or the temperature of the cold feed water.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] There are several different types of tankless water heaters
that significantly vary in price ranges. There are water heaters
that have a feedback loop built-in to monitor output water
temperature and other tankless water heaters that do not have a
feedback loop to monitor output temperature for heating fuel source
control purposes. Tankless water heaters without a feedback loop do
not have an automated way to compensate for the seasonal variations
in ground temperature that affect the water going to the tankless
water heater. Therefore, in order to maintain a desired output
temperature of the water throughout the year, a user has to
manually adjust the flow of gas for heating the water.
[0021] The present invention is an external water sensor, external
electromechanical controller and external gas flow valve which can
be added to any tankless water heater to provide a water heater
which automatically controls the gas flow to maintain the water
temperature at a constant temperature regardless of the flow rate
or the temperature of the cold feed water.
[0022] Referring to FIG. 1, there is shown a schematic diagram of a
system 10 for providing a flow of constant temperature water
regardless of the rate of water flow or the temperature of the cold
feed water. In a preferred embodiment, an instantaneous tankless
water heater 12 which uses gas to heat the water is connected to an
inlet pipe 14 which supplies cold feed water to the tankless water
heater. The water heater is also connected to a gas line 16 which
supplies natural gas, propane or any other liquid or gas fuel to
the water heatrer.
[0023] Two valves are located on the water heater 12. One valve is
a manually adjustable valve 18 which is connected to the cold water
inlet pipe to control the flow of cold water to the water heater.
The other valve is a manually adjustable valve 20 which is
connected to the fuel line to control the flow of gas to the water
heater. The manually adjustable gas valve 20 is set to heat the
cold feed water which is fed to the tankless water heater to a
desired temperature of, for example 120 degrees F., when hot water
is being drawn from the heater at a specific flow rate through
outlet pipe 22 when, for example, a dishwasher or a cloths washer
is operating. Thus, when a person in the household draws hot water
while showering at the same time that the dishwasher or the cloth
washer is also operating, the person showering will not receive a
continuous flow of constant temperature hot water. Another problem
is that the temperature of the cold feed water to the water heater
will be different in the summertime than it is during the winter
time. For example, the reasons for changes in the water temperature
from a particular desired set point can include but is not limited
to changes in water flow or changes to the water temperature going
into the water heater which is caused by changes in the seasons
pre-heating of the ground that the water flows through to different
temperatures. In the summertime the cold feed water may be as warm
as eighty degrees F. and in the winter time the cold feed water may
be as cold as forty degrees F. Having a feedback system can defend
against any reason that could cause the water heater to heat the
water to the wrong temperature
[0024] The invention here disclosed is an add on external gas
controller for tankless water heaters which will automatically
compensate for various flow rates of cold feed water and will also
automatically compensate for temperature changes in the cold feed
water by increasing or decreasing the flow rate of the gas to the
water heater to provide a flow of hot water which has a constant
temperature regardless of the rate of flow of the water and the
temperature of the cold feed water.
[0025] A temperature sensor 24 is coupled to the hot water outlet
pipe 22 to monitor the temperature of the water as it leaves the
tankless water heater. The temperature sensor does not monitor the
water temperature within the water heater. The temperature sensor
used to measure the temperature of the water from the water heater
can be a thermo coupler, a thermistor, a digitized integrated
circuit sensor, a non-contact sensor that uses infrared or laser
measuring means, a solid state temperature sensitive transistor, a
solid state IC. etc. The output signal from the temperature sensor
is a voltage which varies as the temperature of the hot water
varies. The output signal from the sensor is fed to a motor which
could be a stepper motor, a servo motor, a geared motor, a
solenoid, a muscle wire that is coupled to control the fuel valve
or any device that can control a fuel valve which is located in
control box 26. A standard electrical plug adapted to be plugged
into a standard 115 volt AC wall outlet is connected to a step down
transformer and a rectifier to provide a potential of 5 Volts DC
which is the source of power to the control box 26. It is
understood that the required source of power to the control box can
be obtained from a 220 voltage source, a solar cell, a battery, or
be powered off of a 3V power source, a 12V system or a 24V system.
The electromechanical device such as a stepper motor located in the
control box is connected through a connecting rod 28 to the control
lever 30 of a fuel valve such as a gas ball valve 32 which is
located in the gas line 16. The fuel valve 32 is not limited to a
gas ball valve but can be any gas valve that can be adjusted to
different positions which can limit the fuel flow to the water
heater in small increments. Thus, depending on the value of the
voltage that is fed to the stepper motor from the temperature
monitor, the connecting rod will operate the control lever on the
ball valve to control the flow of gas to the tankless water heater
to provide a stream of hot water of a substantially constant
temperature regardless of the flow rate of the water or the
temperature of the feed water to the water heater.
[0026] In an embodiment a logic device can be coupled to the water
temperature sensor and the fuel valve to prevent oscillations in
water temperature. The logic device can be a microcontroller, a
microprocessor, a CPLD, a FPGA, or other device with capabilities
to translate sensory inputs into signals and send the signals to
the electromechanical device for controlling the fuel entering the
tankless water heater.
[0027] In an embodiment, the combination of the stepper motor and
the gas valve can be replaced with commercially available gas
valves that allow variable adjustment of the energy source for
tankless water heaters.
[0028] In another embodiment a sensor can be located to monitor the
water temperature prior to entry into the water heater and/or one
of more sensors can be located to measure the flow of water through
the pipes.
[0029] It is understood that this invention, although disclosed as
using inexpensive easily obtainable components, can use any type of
device that can monitor the temperature of the water coming out of
the water heater and can make the necessary adjustments to the
energy source going to the water heater without making any
modifications to the water heater itself.
[0030] While there have been shown and described and pointed out
the fundamental novel features of the invention as applied to the
preferred embodiments, it will be understood that the foregoing is
considered as illustrative only of the principles of the invention
and not intended to be exhaustive or to limit the invention to the
precise forms disclosed. Obvious modifications or variations are
possible in light of the above teachings. The embodiments discussed
were chosen and described to provide the best illustration of the
principles of the invention and its practical application to enable
one of ordinary skill in the art to utilize the invention in
various embodiments and with various modifications as are suited to
the particular use contemplated All such modifications and
variations are within the scope of the invention as determined by
the appended claims when interpreted in accordance with the breadth
to which they are entitled.
* * * * *