Note: Descriptions are shown in the official language in which they were submitted.
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HEATING SYSTEM
Cross-Reference to Related Applications
This application is a continuation-in-part of U.S. Patent Application Serial
No. 10/421,365, filed April 22, 2003 entitled "Heating System", and
incorporated herein by
reference. This application also claims priority to U.S. Provisional Patent
Application Serial
No. 60/380,586, filed May 14, 2002 and entitled "Heating System".
Field of the Invention
The present invention relates generally to heating systems, and more
specifically, to a
hydronic heating system and method for recreational-vehicle (RV), marine and
home
heating applications that includes a system for altitude compensation for
diesel-fire heaters,
and an automatic air bleeder for removing unwanted air bubbles from heater
fuel.
Background of the Invention
Heating systems for campers and recreational vehicles are widely known.
Conventional water heating systems for recreational vehicles generally fall
into two classes.
The first class includes systems that have a heating elements) that extends
into a cavity that
holds several gallons of water. The heating element ultimately heats the
entire volume of
water in the cavity. Drawbacks to this first class include a lack of
continuous hot water. In
addition, the first class of systems takes a relatively long period of time to
heat water. The
second class involves systems that heat a relatively small volume of water
with a gas or
electric heating device. Conventional systems of the second class include
propane, or other
open flame "flash furnace" heating systems that directly heat domestic water
supplied to the
system. Open-flame systems like these are relatively expensive and relatively
unsafe when
used in a recreation vehicle. In addition, a propane system is ineffective to
provide a
constant supply of hot water.
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For heating devices used in the above heating systems, there are certain
problems
caused when changes in atmospheric pressure (due to changes in altitude or
weather)
undesirably affects heating-fuel combustion. Conventional heating devices
(heaters) are
not constructed to change the combustion parameters, and as a result they do
not perform
optimally when such changes occur. The result is that heater exhaust emissions
increase
causing smoke, and giving off undesirable smells/odors. Carbon also
accumulates on the
heater-burner tube and other system components. Overall, conventional heater
performance/efficiency becomes low, maintenance becomes expensive, and
ultimately the
heater becomes damaged.
Accordingly, for applications where the heater is used in different
atmospheric
pressure conditions, there is a need for the heater to be constructed to
adjust combustion
parameters based upon changes in atmospheric pressure to maintain low exhaust
emissions (e.g. Recreational Vehicle (RV) and household applications),
maintain optimal
performance, and reduce the risk of heater damage or need for maintenance.
Generally, conventional diesel-fired heaters can characterized as high-
pressure and
low-pressure, where the pressure (high or low) refers to the pressure between
the fuel
pump and the fuel-atomizing device associated with the heater. In connection
with low-
pressure diesel-fired heaters for RV, there have been conventional proposals
to deal with
the situation where the RV (and heater) increase altitude by using a so-called
zero-
pressure regulator and a Venturi fuel-atomizing system to reduce the amount of
fuel
which is burned in the combustion process at higher altitude. One drawback to
this
method is that heat outputlefficiency drops with each incremental increase in
altitude at
an approximate rate of 5% for every 3000 ft.
Another problem associated with conventional diesel-fired heaters is that the
associated fuel pump supplies fuel that is mixed with undesirable air bubbles.
Passing
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through the fuel-atomizing component of conventional systems, these air
bubbles cause
gaps in the fuel supply which can cause heater de-activation (so-called "flame
out"
conditions). When the heater flames out, a while cloud of smoke is generated
because
conventional control circuitry cannot immediately stop the fuel-delivery
subsystem. As a
result, fuel is sprayed into a hot combustion chamber for a period of time.
This situation
causes the smoke, or in the worst case where the fuel re-ignites, explosions.
Objects of the invention include solving the problems associated with changes
in
atmospheric conditions, and those associated with air bubbles in the heater
fuel.
Summary of the Invention
The present invention overcomes the drawbacks of conventional systems by
providing a water heating system that uses a heated fluid storage tank to
deliver a continuous
supply of water heated to a desired temperature, such as between 100°-
130°F. The system
also may combine a heated fluid storage tank with an altitude sensitive burner
type furnace
to provide multiple sources of heat for the heating system.
To achieve the desired altitude compensation capability, the system includes a
controller (preferably a micro-controller) that adjusts certain system
components in response
to changes in atmospheric pressure conditions that are measured by an
atmospheric-pressure
sensor component of the invention. For example, for low-pressure-type diesel-
fired heaters,
the invention is constructed to increase the amount of combustion air in
response to a sensed
increase in altitude. By increasing the pressure of the compressed air so that
changes in
altitude will not affect the quantity of fuel absorbed through the heater
nozzle (under
Venturi effect), the altitude-compensation controller (or circuit) of the
invention will
adjust the amount of the combustion air by controlling the sped of the
combustion fan or
the surface (size) of the combustion-air-intake opening. This controller and
method
maintains a constant heat output regardless of changes in atmospheric pressure
such as
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changes in altitude or weather.
The automatic air bleeder of the invention includes a suitable sensor (such as
an
optical or ultrasonic one) mounted adj acent a suitable air accumulator (for
optical sensors,
substantially transparent or clear glass, or a~ plastic tube are suitable; for
ultrasonic
sensors, plastic or rubber tubes are suitable). Also included is an air-
release solenoid and
a fuel return line.
Brief Description of the Drawings
Figs. 1 is a schematic diagram of a heating system according to one embodiment
of the present invention.
Fig. 2 is a schematic diagram of an altimeter connected to the motor of a fan
usable in the heating system of the invention.
Fig. 3 is a schematic diagram of an altimeter with a flash micro-controller of
the
invention.
Fig. 4 is a schematic diagram of an automatic air-bleeder feature of the
invention.
Fig. 5 is a schematic diagram showing a heater feature of the invention for
use in
applications for low-pressure-type heaters and that shows altitude
compensation via fan-
speed control.
Fig. 6 is a schematic diagram showing a heater feature of the invention for
use in
applications for low-pressure-type heaters and that shows altitude
compensation via
control of the combustion-air-intake surface.
Fig. 7 is a schematic diagram showing a heater feature of the invention for
use in
applications for high-pressure-type heaters and that shows altitude
compensation via
controlling the flow of fuel from the fuel pump.
Fig. ~ is a schematic diagram showing a heater feature of the invention for
use in
applications for high-pressure-type heaters and that shows altitude
compensation via
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control of the combustion-air-intake surface.
Fig. 9 is a schematic diagram showing a heater feature of the invention for
use in
applications for high-pressure-type heaters and that shows altitude
compensation via fan-
speed control.
Detailed Description and Best Mode of the Invention
A heating system according to one embodiment of the present invention is shown
at 10 in Fig. 1. The heating system may be used to provide a continuous supply
potable
hot water, and to provide heat to a coach or recreational vehicle.
Additionally, the heating
system may be used to warm the engine block of a coach in cold weather
climates to
make the engine easier to start.
Heating system 10 uses a main heating fluid circuit 12 to provide heat for the
potable hot water system, the coach heater system, and to warm the coach
engine block in
cold climates. A main circuit pump 13 circulates heating fluid through circuit
12. The
main heating fluid circuit 12 includes a heater/boiler 14 configured to heat a
volume of
heating fluid. Typically, the heater/boiler is configured to heat a heating
fluid such as
glycol; however, a mixture of glycol and water or other suitable high-heat-
capacity liquid
may be used as a heating fluid.
Still referring to Fig. 1, a diesel-fired burner 15 may heat heater boiler 14.
A
variable speed fan may provide burner 15 with air for combustion of diesel
fuel. The
variable speed fan may be connected to an atmospheric pressure sensor, as
shown at 16 in
Fig. 2. Atmospheric sensor 16 produces an electronic signal based on the
external
atmospheric pressure. The electronic signal is amplified at amplifier 1 ~ and
the signal is
then processed in a signal-conditioning circuit 20. Additional signal
conditioning may be
applied at 22 in the form of a PWM, DC-DC converter, voltage regulator, or
frequency
inverter. Finally the signal is sent to a variable-speed motor 24. Variable-
speed motor 24
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drives a fan, as shown in Figs. 5-9, that supplies air for combustion to
diesel-fired burner
15. As the atmospheric pressure sensor senses lower ambient air pressure it
may increase
the speed of variable-speed motor 24. Increasing the speed of the motor
increases the
amount of air blown in to the combustion chamber of the burner. The
atmospheric
pressure sensor may continuously vary the speed of the fan in response to
changes in the
atmospheric pressure.
Alternatively, the atmospheric pressure sensor may speed up the fan to
increase
the flow of air to the burner at discrete altitudes where ambient air pressure
drops below
specific thresholds. For example, from sea level to 2000 ft. the fan speed may
be low.
Above 2000 ft. up to around 6000 ft. the fan speed may be medium or higher
than the low
setting. Above 6000 ft. the fan speed may be high to compensate for the lower
density of
air at that altitude.
Referring again to Fig. l, main heating fluid circuit 12 further includes a
heated
expansion tank 26. Tank 26 may be heated by electric heating elements 28. A
suitable
heated expansion tank 26 is available commercially under the trade name
COMFORTHOTtm Typically, heating elements 16 are 2-kilowatt electric heating
elements; however, any suitable heating element may be used. Heating elements
28 are
inserted into tank 26 in a manner similar to a conventional residential
electric hot water
heater. Heat energy is stored in the tank 26, so in a sense tank 26 acts as a
heat battery for
the heating system capable of providing instant heat energy to any system that
requires it.
The electric elements maintain the heating fluid at an elevated temperature
without a
large energy demand, while there is little or no demand for heat from the
system. As
demand for heat increases burner 15 of tank 26 is activated and thus provides
additional
heat energy for heating water ultimately for use as shower water or as heating
fluid that is
used to heat the vehicle cabin or engine block.
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Main heating fluid circuit 12 also includes a domestic water heat exchanger
32.
Heating fluid in the main heating circuit flows through domestic water heat
exchanger 32
to heat water. Water in the domestic water system is heated by transferring
heat from the
heating fluid to domestic water in heat exchanger 32.
Domestic water system 34 supplies cold water to heat exchanger 32 for heating.
The heated water exits heat exchanger 32 and flows to a mixing valve 36 that
prevents hot
water from exceeding a certain temperature by mixing hot water from heat
exchanger 32
with cold water from the domestic water system.
Still referring to Fig. l, heating system 10 includes an engine-hookup loop
38, an
engine-hookup-loop pump 40 and an engine-heat exchanger 42. Main heating fluid
circuit
12 flows through one side of engine-heat exchanger 42. The engine-hookup loop
and
engine-heat exchanger may be used to extract excess heat from the engine of
the coach
while it is operating. Opening engine-hookup loop 38 supplies engine coolant
to one side
of heat exchanger 42. Heat exchanger 42 transfers engine heat to the heating
fluid in
main heating fluid circuit 12. Extracting heat energy from the coach's engine
reduces the
energy demands of the heating system.
Another benefit of engine-hookup loop 38 is that the heating system may be
used
to warm the engine block of the coach prior to starting the engine in cold
climates. By
pumping engine coolant through engine-heat exchanger 42 at the same time the
heating
fluid is circulating in circuit 12, heat is provided to the engine of the
recreational vehicle.
Preheating an engine block in cold climates makes it easier to start and
reduces wear and
tear on the engine.
A cabin-heating loop 44 may by attached to main-heating-fluid circuit 12 that
supplies heating fluid to heating fans (not shown) in the cabin of the vehicle
to provide
the cabin of the vehicle with heat. A cabin-loop solenoid 46 opens and closes
the cabin
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loop to selectively provide the cabin with heat. Fluid pump 13 provides the
pressure to
circulate heating fluid through the cabin-heating loop when the cabin loop
solenoid is
open. Each heating fan acts as a heat exchanger to warm air in the cabin.
Referring to Fig. 4, an air bleeder subsystem is shown that is connectable
within
the fuel line that draws fuel for the diesel-fired heater (burner)(see Figs. 5-
9 below the
fuel regulator and between the fuel pump and the fuel atomizing system). The
air bleeder
subsystem includes any suitable sensor, such as an optical air/air-bubble
detector or
ultrasonic sensor configured to detect a bubble in the fuel line. When a
bubble is detected
an air release solenoid opens the return line to bleed air back to the tank or
out a vent. The
bubble detector then detects that the bubble is no longer present and the
solenoid closes
the return line. The air bleeder enables the burner to run safely. Large air
bubbles can
extinguish the burner flame causing clouds of white smoke, exhaust emissions,
carbon
built-up and increase the cost of maintenance. In addition, re-igniting the
burner flame
repeatedly can damage the burner and cause premature wear.
Referring to Figs. 5-6, the heating system of the invention is shown including
the
micro-controller (Fig. 3). The heating system may be thought of as a heat-
management
system designed to optimize three sources of heat. Heat may be generated from
a vehicle
engine, a diesel furnace associated with a vehicle, or an electric-heating
element. Heat is
stored in heating fluid and used either to heat water (to be used by vehicle
users for
showering/washing) or to heat desired areas of the vehicle by directing the
heating fluid
through associated pipes. A control board is used to control delivery of heat
and other
decisions about the heat-management system. For example, the system may
activate
various heat sources to respond to desired heat demands, such as a requirement
for hot
shower water. Additionally, the control board may be configured to select one
of several
heat sources (for example, electricity via a suitable AC outlet, a burner, or
from the
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vehicle engine itself). While the vehicle is operating, the vehicle's engine
may be the best
most efficient source of heat for the demands of the system. The burner (which
may be
diesel powered) provides a heat source where electricity is unavailable. The
system may
monitor a variety of sensors for determining the level and temperature of
heating fluid
(e.g. glycol) in the heating system.
Altitude compensation feature of system and method invention.
Still refernng to Figs. 5-9, the heating system of the invention is shown for
use
with either low-pressure or high-pressure diesel-fired heaters (Figs. 5-6 for
low-pressure
ones and Figs. 7-9 for high-pressure ones). Referring to Fig. 5, an electronic
atmospheric
pressure sensor is connected to a micro-controller via an amplifier and
suitable auxiliary
conditioning circuitry. The controller is programmed to control the speed of a
combustion fan (which' provides a quantity of combustion air) or to control
the
surface/size of an air-intake opening while maintaining the speed of the
combustion fan
constant. The micro-controller is suitably programmed automatically to: (i)
increase the
speed of the combustion fan or the surface of the air-intake opening (also
referred to as an
orifice) upon receiving signal information from the altimeter/atmospheric-
change sensor
that the atmospheric pressure is lower (higher altitude or cold weather); or
(ii) decrease
the speed of the combustion fan or the surface of the air-intake opening if
the altimeter
sends signal information that atmospheric pressure is higher (lower
altitude/warmer
weather). In other words, based upon signal information from the altimeter
that an
incremental change in atmospheric pressure has occurred, the micro-controller
is
constructed automatically to change the speed of the combustion fan or the
surface of the
air intake orifice (increase for higher altitude/colder weather or decrease
for lower
altitude/warmer weather).
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The adjustment to the combustion air (speed of the combustion fan or surface
of
the air intake) is experimentally determined for each application and then
suitably stored
in the memory of the micro-controller via suitable data-entry components such
as a
keypad. Using a micro-controller (and preferably a flash micro-controller) and
customizable software for programming the micro-controller, the same hardware
can be
used for all the possible applications of low- or high- pressure heaters.
According to the system and method of the invention, for high-pressure heaters
the
fuel delivered to the fuel-atomizing subsystem is maintained substantially
constant
relative to atmospheric-pressure changes (altitude or weather changes). To
maintain the
same heat output, the same system and method as described for low-pressure
heaters is
utilized. If the desired application calls for lower heat output in lower
atmospheric
pressure conditions, the system and method of the invention is constructed to
control the
amount of fuel delivered using the same hardware as described above and shown
in Figs.
5-9 (atmospheric pressure sensor, amplifier, conditioning circuitry and micro-
controller)
in conjunction with a fuel metering device such as a fuel-metering pump or a
fuel-
metering valve.
Automatic air bleeder
Referring back to Fig. 4, the automatic air bleeder of the invention includes
a
suitable sensor (such as an optical or ultrasonic one) mounted adjacent a
suitable air
accumulator (for optical sensors, substantially transparent or clear glass, or
a plastic tube
are suitable; for ultrasonic sensors, plastic or rubber tubes are suitable).
Also included is
an air-release solenoid and a fuel return line.
To operate the automatic air bleeder, once the air in the air accumulator tube
reaches the level of the sensor, a pulse is generated by the conditioning
circuitry and the
air release solenoid will be open for short time to release the air
accumulated into the air
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accumulator. The duration of the pulse generated by the conditioning circuitry
is
proportional to the size of the air bubble detected. A return-fuel line is
mandatory for
safety reasons because when the air-release solenoid opens, a small amount of
fuel is
released back into the fuel tank. If there is no air in the fuel line, then
the solenoid is
closed (as it is when the fuel pump is deactivated/OFF).
The disclosure set forth above encompasses multiple distinct inventions with
independent utility. While each of these inventions has been disclosed in its
preferred
form, the specific embodiments thereof, as disclosed and illustrated herein,
are not to be
considered in a limiting sense as numerous variations are possible. The
subject matter of
the inventions includes all novel and non-obvious combinations and sub-
combinations of
the various elements, features, functions and/or properties disclosed herein.
