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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic refrigeration and air
conditioner monitor and alarm system for use in monitoring and analyzing
the temperature of an air conditioning or refrigeration system's suction
line for variances that indicate malfunctions or abnormal operation of the
system, and wherein the system further provides an alarm in those
instances in which the system is operating outside the preferred
temperature range, thus indicating inefficient or abnormal operation of
the air-conditioning or refrigeration system.
2. Description of the Background Art
Agencies or associations like the Air-Conditioning & Refrigeration
Institute (ARI) and the American Society of Heating, Refrigeration, and
Air-Conditioning Engineers (ASHRAE) set the standards that drive the air
conditioning and refrigeration industry. All technical references and
studies used to illustrate and document the principles presented herein
are made with reference to established standards published by the ARI in
their book titled "Refrigeration and Air-Conditioning", 2nd edition,
copyrighted 1987, 1979 by Prentice-Hall, Inc., which is hereby
incorporated by reference.
In its most basic form, all Air-Conditioning and Refrigeration systems are
heat-energy-transfer devices. They are only capable of absorbing heat from
a heat source and rejecting that heat into a heat sink. Air-Conditioning
systems absorb heat from within a structure via the evaporator coil and
reject that heat outside into a condensing coil. The rate at which it does
this is dependent on the amount of heat available and the rate of
transfer. The rate of transfer will depend on maintaining the proper
temperature difference between the refrigerant and the material from which
the heat is to be extracted or to which the heat is to be rejected. As the
second law of Thermodynamics states "to cause heat energy to travel, a
temperature difference must be established and maintained."
With regards to the heat source (evaporator coil), is there a sufficient
heat source to satisfy the capacity of the system? If a system is capable
of extracting 24,000 BTU/hr (2 ton air-conditioning unit) with a 20
degrees F. temperature difference (TD), this amount of heat must be
available. If air is the means of carrying the heat from the product to be
cooled to the evaporator for extraction, the correct amount of air must
pass through the coil. If insufficient air is being supplied because of a
dirty filter (the most common air flow problem), slow pumping fan or
blower, dirty coil fins or any other reason for reduction in the air
quantity, the amount of heat absorbed is reduced. With the absorbed heat
reduced, the coil operates at a lower temperature, the refrigerant boiling
point is lower, and system capacity is lost. This also applies if the heat
is transferred by means of a liquid. A reduction in the quantity of the
liquid through the heat exchanger reduces heat absorbed, lowers the coil
boiling point, and lowers suction pressure and system capacity.
With regards to the heat sink, problems are usually easier to diagnose
because the change in the system becomes more radical with a change in
operating conditions of the heat sink. When the air through the air cooled
condenser is reduced, head pressures and compressor amperage draw go up
and system capacity drops. When the liquid through the liquid condenser is
reduced, head pressures rise together with amperage draw of the compressor
and reduction in capacity results. The effect on capacity is not as great,
however, as a change in load on the evaporator, so problems usually exist
and grow until a radical departure from normal occurs. Up to this point,
air-conditioning has been discussed as the process of removing heat picked
up from the evaporator and dissipating that heat into the outside air via
the condensing coil. The concepts described below are fundamental to all
air-conditioning equipment.
Whenever an air-conditioning system is called upon for cooling, three or
four things happen simultaneously:
First the compressor is energized and begins operation, pumping vaporized
refrigerant out of the evaporator, compressing it and sending it to the
condenser. This immediately creates a difference in pressure between the
high and low sides of the system.
The condenser fan is energized and begins blowing outside air across the
condenser coils so that the heat within the refrigerant vapor will be
dissipated to the outside air.
A metering device, whether it be an expansion valve (TEV) or a capillary
tube, will begin passing liquid refrigerant into the evaporator so that it
can begin to pick up heat from the airstream around the evaporator.
If the system is not on continuous blower operation, the evaporator blower
will come on. The blower will funnel the warm air from the space to be
cooled across the surface of the evaporator coil so that the heat
contained in the air can be picked up by the refrigerant passing through
the evaporator coil.
Some systems will have better or poorer operating efficiencies. It should
also be noted that the operating temperatures and pressures will change in
a system depending on the heat load presented to the evaporator.
Under theoretical conditions, the refrigerant entering at the metering
device is in a liquid form at a 114 degrees F. temperature (having been
subcooled 16 degrees F. after leaving the condenser), approximately 299
psig, and has a heat content or enthalpy of 45 BTU's. The liquid
refrigerant passes through the metering device, be it an expansion valve
(TEV) or capillary tube, into the low side of the system, and immediately
expands and cools part of the refrigerant. As the liquid passes through
the evaporator coil, it picks up heat from the airstream around it and
begins changing to a vapor. At the exit of the evaporator, the vapor has a
temperature of approximately 45.degree. F. and a pressure of about 77
psig. Before entering the compressor, it is superheated 10.degree. F. to
55.degree. F., but the pressure remains constant at 77 psig. Its enthalpy
or heat content, however, will have increased to 100 BTU's, having picked
up 64 BTU's of latent heat from the room air and one BTU of sensible heat
due to superheat.
The vapor is then pumped into the compressor shell where it passes over the
motor and picks up additional heat from the motor, amounting to
approximately 24 more BTU's, giving the vapor a total additional heat
content of 89 BTU's. As it passes into the compressor cylinder, the vapor
is compressed. At this time, its temperature will be raised to about
230.degree. F. and the pressure, during the short time that it is in the
compressor cylinder, will be raised considerably. Its heat content, or
enthalpy, after the heat of compression, will amount to about 134 BTU's.
The vapor passes from the compressor discharge port through the discharge
line and into the top row of the condenser. At this point, its temperature
is 130.degree. F., it is at about 299 psig and after the first one or two
rows in the condenser, will lose about 20 BTU's, so its heat content will
be 144 BTU's per pound.
As it passes through the remaining rows in the condenser, the vapor loses
more heat to the outside air and changes state from a gas back into a
liquid. As it gets to the bottom row of the condenser, all of the
refrigerant will have changed to a liquid. It will be at 130.degree. F.
and 299 psig, with a heat content or enthalpy of 51 BTU's. The loss of 83
BTU's to the outside air is all latent heat due to its change of state
from a gas to a liquid.
Upon leaving the condenser, the liquid is subcooled, thus eliminating
another 6 BTU's. So, as it approaches the metering device for another
circuit through the system, the liquid will be back to its original
conditions: 114.degree. F. temperature, 299 psig, with a heat content of
45 BTU's.
The following paragraphs will analyze the problems associated with Air
Conditioning and explore how those problems affect a system's performance
and operating cost.
The following paragraphs limit the discussion to those problems and
solutions that apply to Air-Conditioning systems. Problems in
Air-Conditioning systems are classified in only two categories: Air and
the Refrigerant circuit. The only problem with air is the reduction in
quantity which is common with matted inside air filters, blower or fan
motor problems, etc. Problems in the refrigerant circuit can be further
broken down into two categories: (1) refrigerant quantity, and (2)
refrigerant flow rate. Any problem in either category will affect the
temperatures and pressures that will occur in the unit when the correct
amount of air is supplied over the DX coil for the capacity of the unit.
The use of the word "normal" does not imply a fixed set of pressures and
temperatures. These will vary with each make and model of the system.
There are a few temperatures that are fairly consistent throughout the
industry that can be used for comparison and must be modified according to
the EER rating of the unit. These are (1) DX coil operating temperatures,
(2) condensing unit condensing temperatures, and (3) refrigerant
subcooling.
With reference to a capillary tube system, the system charge or refrigerant
level is extremely critical and must be maintained within a -5% tolerance
to be properly maintained. Capillary tube systems represent the majority
of residential Air-Conditioning systems (approximately 90%) as well as a
growing number of the commercial and industrial applications. This is
largely due to the cost reduction and lower compressor starting-torque
requirements associated with a capillary tube design. Refrigerant charge
has a large effect on the performance of Air-Conditioning units. For this
example, the effect on the performance of a 2 HP Air-Conditioning unit
operating at 90.degree. F. outside ambient and 75.degree. F. inside dry
bulb and 63.degree. F. wet bulb at 50% relative humidity (RH) will be
explored. This example assumes that the systems of the unit began in
proper operating conditions or had been otherwise working correctly.
With the refrigerant charge at 100% of the required amount, the net
capacity of the unit was 26,400 BTU/h. When the refrigerant charge was
increased 5% (3 oz.), the capacity dropped to 24,600 BTU/h; with an
increase of another 5% (3 oz.), the capacity dropped to 19,000 BTU/h. A
total overcharge of 9 oz. reduced the capacity to 13,000 BTU/h.
Working the other way from the correct charge, when the quantity was
reduced 5% (3 oz.), the net capacity dropped to 25,000 BTU/h, another 5%
(2.5 oz.) reduced the capacity to 22,000 BTU/h. A further reduction of 5%
(2.5 oz.) reduced the capacity to 18,000 BTU/h. From this it can he
concluded that the correct charge results in the best net capacity of the
system.
At 100% of charge the kilowatt requirement of the unit to handle the load
was 3.195 kW; at 5% overcharge, 3.45 kW; at a 110% overcharge, 3.97 kW;
and at 115% overcharge, 4.8 kW. With a reduced charge at 95% undercharge
it was 2.97 kW; at 90% undercharge, 2.77 kW; and at 85% undercharge, 2.57
kW.
The true comparison of the system is the operating efficiency, the energy
efficiency ratio (EER). This denotes the heat transfer ability of the
refrigeration system, expressed in BTU/h, compared to the watts of
electrical energy necessary to accomplish the heat transfer. This
comparison is expressed in BTU/h/Watt of electrical energy and is
determined by dividing the net capacity in BTU/h by watts of electricity
needed to produce the capacity.
Now to be given is the EER rating of the example unit at the various
refrigerant charge levels. At 100% of refrigerant charge, the EER rating
was 8.4 (the optimum rating for this example unit); at 105%, 7.45; at
110%, 5.1; and at 115%, 2.4. With the undercharge at 95% of charge, an 8.2
EER resulted; at 90%, 7.7; and at 85%, 6.75. This points out that with a
refrigeration system using capillary tubes, the refrigerant quantity in
the system must be accurate. The charge tolerance is plus zero minus 1
ounce. The optimum refrigerant charge levels mentioned above are for the
compressor only. The remainder of the refrigerant in a system of a given
capacity occupies the evaporator, suction and discharge lines. Also, for
the purpose of association, for each 12,000 BTU/hr capacity of a system,
the equivalent tonnage is 1 ton. For example, a 2 ton (2 HP) compressor
has a capacity of 24,000 BTU/hr.
In most systems some overcharging can be tolerated, but an undercharge is
rarely acceptable. Overcharging will create high head pressure and high
temperature, with all the resultant problems, such as motor overloading,
sludge formation, and compressor valve failure. High head pressures can
also result in poor load control, with liquid refrigerant flooding to the
compressor. Although the biggest problem with undercharging is that of
capacity, it may also create frost conditions on the evaporator in higher
temperature refrigeration equipment, and may also cause high evaporator
superheats. As some hermetic compressor motors depend on suction gas for
cooling, they can be damaged by overheating due to high suction gas
temperatures. Both overcharging and undercharging should be avoided, since
either condition can do serious harm to or destroy system components. A
system undercharge is the most common aspect to be concerned with since it
covers 90% or better of the existing systems in operation. This is due to
normal system leakage over time, also by problems associated with loose
fittings, punctured evaporator or condenser coils, or any other leaks in
the systems suction or discharges lines.
Restriction in the outdoor air flow through the condenser coil is typically
the result of either a matted or otherwise plugged condenser coil fins or
a defective fan motor. In the case of be evaporator coil, restricted air
flow is usually resultant from matted air filters, blower motor imbalance,
plugged coil fins on the evaporator, or blockage of the return air ducts.
At approximately a 30% reduction in air flow, a system's efficiency will
drop to about 94% of capacity. And at a 50% reduction in air flow, a
system's efficiency will drop to about 86% of capacity.
At approximately a 30% reduction in air flow, a system's capacity will drop
to about 96%. And at a 50% reduction in air flow, a system's capacity will
drop to about 92% of capacity.
The value and benefits that proper system maintenance has on the
performance, life expectancy, and operating cost of any Air Conditioning
and Refrigeration system should now be clear.
The following paragraphs will explore the problem of lost efficiency.
Annually, many millions of dollars are spent in the research and
development of new, more energy efficient Air Conditioning and
Refrigeration equipment as well as new ways to make better use of our
natural resources in the production of electrical energy. Home and
business owners alike are investing in this new technology with the end
result of lowering their annual cooling cost. These investments range from
purchases of new, High Efficiency Air Conditioning equipment to making
every available modification to structures in an effort to make them more
energy efficient (e.g. improving the insulation, weather stripping,
programmable thermostats, etc.). Also, many efforts have been made by
utility companies and our government to make the consumers of electrical
energy better informed on the means and methods available to make better
use of our precious resources. This is evident with the mass distribution
of brochures or other information detailing the different means and
methods currently available to help the consumer to save energy. This is
also evident with the introduction of consumer rebates from utility
companies on purchases of energy efficient appliances and with the
exhaustive testing by manufacturers to assign an efficiency rating to
their products (EER ratings).
With the massive utilization and cost of Air Conditioning and Refrigeration
technology in most every aspect of our society, it is only common sense
that improvements in this area can yield the best returns for the
consumers investments in energy efficiency. As the previous section
detailed, poor preventive maintenance on Air Conditioning appliances not
only has a dramatic effect on the system's performance and operating cost,
but on the appliance's life expectancy as well. Just as one can not expect
to maintain the optimum mileage on their automobile if the air filters,
oil and tires aren't checked or replaced regularly, neither can one expect
their new High Efficiency Air Conditioning unit to perform cost
effectively with the lack of the same maintenance.
Unfortunately, in the real world, savings from investments in energy
efficiency are quickly spent because simple preventive maintenance
measures are either being overlooked or forgotten about completely, and
equipment malfunctions are left unattended for long periods of time. Even
though most Air Conditioning appliances built today can withstand a
tremendous amount of punishment and have High Efficiency ratings (EER
ratings) of 10 or better, operating costs can, and do, go well above what
is expected of the system. At best, small businesses and particularly
residential consumers, rely solely on either some sort of loose preventive
maintenance schedule to check air filters or an annual system check to
assure their equipment is operating efficiently. These measures, though
beneficial, often fall far short of what is necessary to keep the
consumer's equipment operating efficiently. If most consumers realized
that their equipment was costing them too much to operate because of a
matted air filter or low refrigerant charge (the most common service
related problems), they would obviously take the necessary steps to
correct the problem. Usually, the equipment is left to operate and the
problem goes unnoticed until it has made the consumer aware of the problem
physically by an uncomfortable indoor air temperature on a hot summer day.
And this is possibly after weeks or months of inefficient operation along
with the associated increased operating cost. With an unconfirmed but
conservative estimate of 70% to 80% of the Air Conditioning systems being
operated inefficiently, the amount of wasted energy caused by poor
maintenance is staggering. When one considers the cost of that wasted
energy on a national level, the figures are nothing short of obscene.
Inventors have in the past sought solutions to the above problems. U.S.
Pat. No. 3,544,722 by C. Hartfield et al., issued Dec. 1, 1970 entitled
Security System describes a general alarm system for summoning assistance
in response to a plurality of mishaps, such as break-in, fire, cold
storage failure and so forth in response to sensors.
U.S. Pat. No. 3,441,929 by W. E. Coffer et al issued Apr. 29, 1969 entitled
Remote Reporting System describes a general alarm system for reporting
burglary, fire, refrigeration failure, etc. It depends on signalling a
dedicated receiving station and indicate the different conditions by means
of signals generated by motor driven cams.
U.S. Pat. No. 4,028,688 by J. B. Goleman issued Jun. 7, 1977, entitled
Refrigeration Unit Air Temperature Detection Alarm System describes a
refrigeration alarm system comprising temperature sensors, automatic
telephone dialer and recorded message announcer. It also describes the use
of a wireless radio connection between freezer compartments and the alarm
system.
U.S. Pat. No. 4,146,886 by S. W. Timblin issued Mar. 27, 1979 entitled
Freezer Alarm With Extended Life describes a freezer alarm device for
locally indicating a freezer malfunction. It has no remote reporting
capability.
U.S. Pat. No. 4,278,841 by Regennitter et al., issued Jul. 14, 1981,
entitled Multiple Station Temperature Alarm System describes a freezer
monitor system with wireless radio connection between the freezer
compartments and the alarm system. The invention also describes an
automatic telephone dialer combined with a recorded message circuit to
deliver a message when the call is answered.
Numerous innovations for an electronic refrigeration and air conditioner
monitor and alarm system have been provided in the prior art that are
described as follows. Even though these innovations may be suitable for
the specific individual purposes to which they address, they differ from
the present invention as hereinafter contrasted.
U.S. Pat. No. 5,262,758
System and Method for Monitoring Temperature
Young K. Nam
A temperature monitoring system comprises a sensor for measuring the
surrounding temperature, a timer for generating clock data, a controller
for reading temperatures at predetermined intervals and storing selected
temperature data and corresponding time data in memory, input switches for
entering commands and data, a data display, and first and second alarm
indicators. The controller operates in predetermined steps to activate the
first alarm to indicate a current alarm condition and to activate the
second alarm to indicate a past alarm condition. The controller
selectively switches the display between normal and alarm modes to show
differing time and temperature data depending on the temperature
conditions monitored.
U.S. Pat No. 5,136,281
Monitor for remote alarm transmission
James P. Bonaquist
A remote monitoring apparatus comprises a computer program controlled
monitor for detecting changes in condition responsive relay switches to
generate a data signal identifying the change of switch condition, a
report assembler which prepares a report in a preselected format
identifying the apparatus location and including the data signal
generated, and a modem for automatically transmitting the assembled report
to a selected number of remote locations connected with the monitoring
site by a telecommunication network. The monitoring apparatus repeatedly
accesses the telecommunication network until a successful communication
has been transmitted to each remote location. The apparatus also senses
the loss of a continuous, primary power source and includes a back-up
power supply. The program limits the number of unsuccessful attempts which
can be made with the back-up power supply and preserves the assembled
reports for later transmission when power has been fully restored. In
addition, the remote locations to be contacted can be changed as desired,
the format of the reports can be adjusted and the normal and alarm
conditions of the relay switches can be adjusted as desired to increase
the versatility of the monitoring device.
U.S. Pat. No. 5,008,655
Visual alarm device interconnectable to existing monitoring circuitry
Robert A. Schlesinger, Kimuel L. Hill, Hamid S. Ali, and Mark E. Watson
A visual alarm device monitors the condition of a control and indication
circuit and gives a distinct visual alarm upon detection of an abnormal
condition in the monitored circuit. The device uses the indicator lights
of the monitored circuit itself to give the visual alarm. The alarm device
interconnects with the monitored circuit locally requiring no new cabling
and remains in a passive state until an abnormal condition is detected.
When the monitored circuit is rendered inoperative by a thermal overload
trip, the alarm device becomes active to flash the indicator lights to
provide a distinct visual alarm. Included in the device is a test switch,
an appropriate voltage converter, an oscillator, and a power indication
light.
U.S. Pat. No. 4,882,564
Remote Temperature Monitoring System
Paul Monroe and James Kurth
A remote temperature sensing and warning system for a temperature
controlled vehicle comprising a remote temperature controlled vehicle
comprising a remote temperature sensing unit for measuring the temperature
in the transport container and transmitting the temperature signal within
a repeating time frame through the existing vehicle wiring to a remote
receiver; the receiver decoding and converting the signal into a
displayable form to continuously display the current temperature of the
transport container; the receiver further detecting out of range
temperatures and signal transmission errors and providing visual and aural
alarms therefrom.
U.S. Pat. No. 4,675,654
Alarm monitoring device
Bobby E. Copeland
An alarm monitoring system which simultaneously provides a bright alarm
light and audible alarm upon the occurrence of an abnormal condition in a
function being monitored. The alarm light is reduced to a dim illumination
upon acknowledging of the alarm condition by the operator and the audible
alarm is also deactivated. The dimmed alarm indication reduces detrimental
effect of night vision while maintaining notice of an abnormal condition.
Upon acknowledging the alarm condition, an electro-mechanical relay having
two normally closed contacts and one normally opened contact is energized
to redirect current flow to the alarm indicator lamp through a resistor
and cause the dimmed illumination of the indicator lamp. A plurality of
alarm indicator circuits are connected in parallel and have diodes
connected in the circuitry to prevent electrical feedback in the system
from causing false alarm indications in the corresponding alarm circuits.
A test switch is provided which allows trouble shooting of the apparatus
while the system is in normal use or out of use.
U.S. Pat. No. 4,644,478
Monitoring and alarm system for custom applications
Lawrence K. Stephens and Robert B. Hayes
A monitoring and alarm system of general purpose design can be customized
for use with many different applications to provide sophisticated alarming
and control functions based on logical relationships among several sensed
variables. A central processing unit is connected to receive a plurality
of inputs from various sensors, the variety and type of which are the
choice of the user depending on the specific application to which the
monitoring and alarm system is to be connected. The central processing
unit is programmed to provide the user with an interactive display to
first define the variables in the application and the states and/or limits
of the variables. This action defines a logical group. Next, the user
enters the alarm/action functions to be performed on the condition that
all the conditions in the logical group are true. Once this interactive
process has been completed, the central processing unit performs the alarm
and control functions specified by the user.
U.S. Pat. No. 4,612,775
Refrigeration monitor and alarm system
Michael A. Branz and Paul F. Renuad
A refrigerant monitor and alarm includes a sensor positioned to detect the
level of liquid state refrigerant in the system and provide an electrical
output signal therefrom, a digital display for displaying the refrigerant
level, a circuit coupling the digital display to the sensor for actuating
the digital display, and a heat reclaim system lockout circuit coupled to
the sensor. In a preferred embodiment, the level display is a bar-graph
LED-type display incorporated on a control panel also including a
refrigerant level alarm and other parameter alarms.
U.S. Pat. No. 4,612,537
Alarm system for monitoring the temperature of a liquid contained in a
reservoir
Andre Maltais and Andre Nadeau
An alarm system and method for monitoring the temperature of a liquid
contained in a reservoir. The system comprises a temperature sensing probe
for sensing the temperature of the liquid. A sensing circuit is associated
with the probe to generate a temperature indicating signal representative
of the liquid temperature. A calibration circuit is provided for
calibrating the temperature signal relative to a reference signal.
Converter means is provided to convert the calibrated temperature signal
to a binary signal indicative of sensed temperatures of the liquid whereby
to feed comparator circuits having preset limit detectors to initiate an
alarm signal when the temperature signal exceeds a predetermined value.
The comparator circuits also feed a display device to indicate the
temperature of the liquid.
U.S. Pat. No. 4,588,987
Display system for monitoring and alarm system
Lawrence K. Stephens
A display system is provided for a monitoring and alarm system. The
monitoring and alarm system includes a central processing unit and a
plurality of sensors polled by the central processing unit. A display
which is part of the central processing unit is used to prompt user inputs
to group a plurality of the sensed variables and the states and limits of
each of the variables in a group. The display system is employed by the
user to generate a schematic display of the system or environment being
monitored. In the process of generating the schematic display, the user
links alarm areas on the schematic display with a group or single variable
defined by the user. In addition, the user links message areas on the
schematic display with user defined messages to be displayed in the event
all the conditions defined by the states and limits of variables in a
group are true. After each schematic has been generated, it is stored
together with the data defining the linked areas of the display. A stored
schematic display may then be invoked, and once invoked, messages and
status conditions are displayed in response to the sensed conditions of
groups of variables sensed by said monitoring and alarm system.
U.S. Pat. No. 4,583,682
Air conditioning monitoring device
Orlando Hernandez
An electric device for monitoring the usage of equipment that is being
shared by one or more entities or individuals during a predetermined
schedule and that needs to be made available to any one of these entities
or individuals outside that schedule. The device includes timing means
programmable for any schedule and capable of activating complementary
relays, one of them a normally open and the other one a normally closed.
The contacts of one of these relays being connected to a suitable point in
the equipment being shared so that its operation may be interrupted or
turned on. A plurality of second relay means, one associated with each one
of the entities, are also connected to that point in the equipment so that
each entity may be able to connect the equipment. Also, there is an
elapsed time meter associated with each one of those second relay means so
that the time that the equipment is used, outside the predetermined
schedule can be tracked.
U.S. Pat. No. 4,553,400
Refrigeration monitor and alarm system
Michael A. Branz
A refrigerant monitor and alarm includes a sensor positioned to detect the
level of liquid state refrigerant in the system and provide an electrical
output signal therefrom, a digital display for displaying the refrigerant
level, and a circuit coupling the digital display to the sensor for
actuating the digital display. In a preferred embodiment, the level
display is a bar-graph LED-type display incorporated on a control panel
also including a refrigerant level alarm and other parameter alarms.
U.S. Pat. No. 4,482,785
Refrigeration monitor system with remote signalling of alarm indications
Christopher D. Finnegan and Arthur J. Geiss
A refrigeration monitor system for monitoring an unattended freezer
installation having a number of freezer compartments containing perishable
products. The system comprises a network of temperature sensors located in
the freezer compartments and connected to a common control which is
connected to one or more telephone lines. The common control is capable of
dialling in sequence any one of a group of selected alarm numbers. The
person answering the alarm call receives a recorded message and must
return a preselected answer code that is received by the system, and which
stops the system from sending more alarm calls. The system continues to
dial alarm numbers until it receives a satisfactory answer code. As a
further safety measure the system, upon initiating an alarm, sets an alarm
status indicator that must be manually reset within a preset time by the
person attending to the freezer installation in response to the alarm, or
else a new alarm sequence is automatically initiated.
U.S. Pat. No. 4,384,282
Device for Indicating a Freezing Temperature in a Selected Location
Everett G. Dennison, Jr.
The disclosed device comprises a pair of electrical conductors positioned
in an elongated flexible insulating member and enclosed in an elongated
tubular member which is filled with water or an aqueous solution having a
known freezing temperature. The tubular member is sealed at its ends with
the electrical conductors in their insulating member extending outwardly
of one of the sealed ends and is connected with an alarm actuating
circuit. A portion of the insulating member is removed from one of the
pair of electrical conductors adjacent one end of the same within the
tubular member and a portion of the insulating member is removed from the
other one of the pair of electrical conductors adjacent the opposite end
thereof so that an electrical circuit is completed through the water or
aqueous solution in the elongated tubular member and interrupted when the
water or aqueous solution freezes.
U.S. Pat. No. 4,256,258
Temperature monitor and alarm system
George W. Sekiya
The disclosed temperature monitoring and alarm circuit includes a
temperature responsive switch which opens when water temperature exceeds a
predetermined point. When the switch opens, a relay is de-energized,
thereby activating a latch which activates a visual alarm and closes off a
solenoid operated valve on the monitored water source until the over
temperature condition is corrected and the circuit is reset.
U.S. Pat. No. 4,024,495
Remote Temperature Change Warning System
Frank J. O'Brien
The disclosed remote temperature change warning system comprises a
temperature sensing circuit located in the refrigeration compartment of
the refrigeration vehicle and a detection circuit located on the vehicle
remote from the temperature sensing circuit and having means for
indicating to the vehicle operator the temperature condition in the
refrigeration compartment, the output of the temperature sensing circuit
and the input of the remote detection circuit being electrically connected
through the existing electrical wiring of the refrigeration vehicle.
U.S. Pat No. 3,753,259
Cooler and Freezer Failure Warning System
Raymond L. Donovan
The disclosed cooler and freezer failure warning System includes a source
of a rectified, pulsating, supply signal, a source of a lower regulated
signal supplied by the supply signal source, a temperature sensor
installed in a selected location a food case and responsively variable in
resistance according to its sensed temperature, means responsive to the
sensor resistance for producing a switch signal a predetermined
overtemperature condition, means responsive to the switch signal for
producing a delayed switch signal, a temperature alarm device, and an
alarm switch responsive to the delayed switch signal for applying the
supply signal to energize the temperature alarm device. The warning system
further includes fail-safe provisions for producing an alarm in the event
of sensor failure. A power failure alarm device responsive to a loss of
the regulated signal can also be included in the warning system.
U.S. Pat. No. 2,994,858
System for Signalling Failure of Refrigeration Devices
William E. Coffer
The disclosed signal system provides warning signals when dangerously high
temperature conditions exist in any of a group of cold storage cabinets.
This system is a high temperature detection and alarm system for a group
of refrigeration units. This system comprises a sensing circuit including
a plurality of normally open thermostatic switches each disposed within
one of a group of refrigeration units and is adapted to close when the
temperature in any of the units exceeds a predetermined maximum
temperature. Several signal devices are arranged in series with these
thermostatic switches and are adapted to emit a warning signal when the
switch in series with it is closed.
Johnson Controls recently manufactured a device which has an optical sensor
to view bubbles or refrigerant conditions in the lines by means of a sight
glass. A sight glass is a fitting equipped with a transparent window,
usually at both the top and bottom of the fitting, to allow the service
persons to actually view the condition of the refrigerant. The optical
sensing device would only be instrumental in detecting refrigerant related
problems on systems so equipped.
Paragon Electric Company, Inc. of Two Rivers, Wis. manufactures a device
which also addresses the same preventive maintenance concerns. This device
performs its function by analyzing the current draw on large, commercial
systems and correlates that information with a variety of possible system
problems. Its sole application is with very large, commercial
air-conditioning and refrigeration systems.
Numerous innovations for an electronic refrigeration and air conditioner
monitor and alarm system have been provided in the prior art that are
adapted to be used. Even though these innovations may be suitable for the
specific individual purposes which they address, they would not be
suitable for the purposes of the present invention as heretofore
described.
SUMMARY OF THE INVENTION
Most HVAC service personnel draw on experience and a variety of acceptable
methods when servicing equipment in the field. One of those methods is to
measure the temperature on the suction (return) line of a given system for
some indication of the possible problem. Most just resort to "feeling" the
suction line for a condition of too warm or too cold a temperature.
Ideally, the suction line of a properly operating system should "sweat".
The term "sweating" refers to the condition of condensation of moisture
from air on a cold surface, the suction line.
As was shown in the Description of the Background Art, the operating
efficiency of Air Conditioning and Refrigeration systems decreases
dramatically with even a minimal lack of system maintenance. As the
efficiency (or equivalent EER rating) of a system decreases, so does the
capacity of the system decrease. Regardless of the reasons associated with
this lack of efficient operation, the operating cost associated with its
operation can skyrocket.
It is not arguable that an inefficiently operating air-conditioning system
costs a great deal more to operate than one operating with proper
maintenance; neither is it arguable that correcting the problem reduces
energy consumption and operational cost. Residential and Commercial
consumers can benefit directly by lower monthly cooling bills and by
getting a longer, useful life from their air-conditioning and
refrigeration appliances. The utility companies load management programs
can also benefit by lowering their peak load demands. If the majority of
Air Conditioning systems being used at the peak load times were operating
even close to their efficient levels, the electrical demand can do nothing
but decrease. It should also be evident that any energy savings, however
minuscule, when multiplied by the large number of units operating
inefficiently today in the U.S. can be astounding.
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