U.S. patent application number 11/147054 was filed with the patent office on 2006-12-07 for warm air furnace baselining and diagnostic enhancements using rewritable non-volatile memory.
This patent application is currently assigned to Honeywell International Inc.. Invention is credited to Victor J. Cueva, Bruce L. Hill, Michael W. Schultz, Rolf L. Strand.
Application Number | 20060275719 11/147054 |
Document ID | / |
Family ID | 37494531 |
Filed Date | 2006-12-07 |
United States Patent
Application |
20060275719 |
Kind Code |
A1 |
Hill; Bruce L. ; et
al. |
December 7, 2006 |
Warm air furnace baselining and diagnostic enhancements using
rewritable non-volatile memory
Abstract
A warm-air furnace is adapted to provide diagnostic enhancements
and more robust installation. In an embodiment, sensing equipment
aboard the furnace is used to determine a first performance metric
during installation of the furnace. That performance metric is then
compared with a baseline metric that may have been obtained at a
factory in order to obtain a performance variation value. At least
partially in response to the performance variation, a notification
is provided to a user. The notification may be an indication of
poor installation or shipping damage, present failure and/or
predicted future failure, for instance.
Inventors: |
Hill; Bruce L.; (Roseville,
MN) ; Strand; Rolf L.; (Crystal, MN) ;
Schultz; Michael W.; (Elk River, MN) ; Cueva; Victor
J.; (New Hope, MN) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
Honeywell International
Inc.
Morristown
NJ
|
Family ID: |
37494531 |
Appl. No.: |
11/147054 |
Filed: |
June 7, 2005 |
Current U.S.
Class: |
431/24 ;
126/99R |
Current CPC
Class: |
F23N 5/20 20130101 |
Class at
Publication: |
431/024 ;
126/099.00R |
International
Class: |
F23N 5/20 20060101
F23N005/20 |
Claims
1. A method for warm air furnace diagnostics comprising:
determining a first metric of performance of the furnace at a first
time; comparing the first metric of performance with a baseline
metric, whereby a performance variation value is obtained; and at
least partially in response to the performance variation, providing
a notification to a user.
2. The method of claim 1, wherein the first time is at installation
of the warm air furnace at a customer premises.
3. The method of claim 1, further comprising: obtaining the
baseline metric prior to shipping the warm air furnace from its
manufacturing facility.
4. The method of claim 1, wherein the baseline metric is a set of
at least one recommended operational value for a model furnace of
the same type as the furnace.
5. The method of claim 1, wherein determining a first metric of
performance comprises: initiating a predetermined furnace test
cycle; at a predetermined portion in the test cycle, obtaining a
measure; and storing the first metric in a data storage of the warm
air furnace;.
6. The method of claim 1, further comprising: storing the first
metric in a data storage of the warm air furnace.
7. The method of claim 6, wherein the data storage is a
non-volatile memory.
8. The method of claim 1, wherein the first metric is a set of at
least one measure selected from the group of flame current, inducer
current, fan current, pressure switch open time, pressure switch
close time, heat exchanger rate of temperature rise, air
temperature rise across the heat exchanger, furnace temperature,
heating run-time, cooling run-time, fan-only run-time, igniter
run-time, pressure switch cycle count, heating cycle count, cooling
cycle count, fan-only cycle count, and igniter cycle count.
9. The method of claim 1, further comprising: determining that the
variation is outside of a predetermined range; and determining that
the warm air furnace is not properly installed.
10. The method of claim 1, further comprising determining the
baseline metric at a second time, wherein the second time is after
beginning installation of the furnace at a customer premises, and
wherein the first time is subsequent to the second time.
11. The method of claim 1, further comprising: at the first time,
determining a value for an operational counter of the warm air
furnace, wherein the notification is at least partially based on
the value of the operational counter.
12. The method of claim 11, wherein the operational counter is one
of a run-time counter and a cycle counter.
13. The method of claim 1, further comprising, in response to the
comparison, diagnosing a fault condition.
14. A warm air furnace with diagnostics comprising: a data storage
for storing furnace performance data, wherein the furnace
performance data includes a baseline measure and a first metric; a
processor communicatively couple with the data storage; a set of
instructions stored in the data storage and executable by the
processor, wherein the set of instructions provide for (i)
comparing the first metric with the baseline metric, and (ii)
storing furnace performance data in the rewritable data storage;
and sensing circuitry for obtaining furnace performance data during
operation of the warm air furnace, wherein the sensing circuitry is
communicatively coupled with the processor.
15. The warm air furnace with diagnostics of claim 14, wherein the
first metric is a combination of at least one measure selected from
the group consisting of flame current, inducer current, fan
current, pressure switch open time, pressure switch close time,
heat exchanger rate of temperature rise, temperature change across
the heat exchanger, heating run-time, cooling run-time, fan-only
run-time, igniter run-time, pressure switch cycle count, heating
cycle count, cooling cycle count, fan-only cycle count, and igniter
cycle count.
16. The warm air furnace of claim 14, wherein the sensing circuitry
comprises: a current sensing device operable to measure current
consumption of the warm air furnace, wherein the measured current
consumption of the warm air furnace depends in part on whether an
ignition element, an inducer, and a fan are activated; and an
analog to digital converter connected to an output of the current
sensing circuit, wherein the analog to digital converter is
operable to convert the output of the current sensing circuit to a
digital representation of the measured current consumption, and
wherein the processor is operable to compare the digital
representation of the measured current consumption of the warm air
furnace with the baseline measure that is stored in data storage,
wherein the processor is operable to (i) detect a fault in the warm
air furnace if the comparison exceeds a threshold amount, (ii)
provide an indication of the fault, and (iii) identify at least one
component in the warm air furnace that may have caused the
fault.
17. The system of claim 16, wherein the current sensing device
includes a current transformer operable to provide an AC signal
output representative of current consumption.
18. The system of claim 14, wherein the data storage is at least
one storage medium selected from the group consisting of read-only
data storage, read-access data storage, electrically erasable
programmable read-only memory, and Flash memory.
19. A method for detecting a fault in a warm air furnace,
comprising in combination: measuring a level of current consumption
during at least one operational stage of the warm air furnace
wherein the level of current consumption of the warm air furnace
depends on whether an ignition element, an inducer, and a fan are
activated; determining a performance variation between the measured
level of current consumption and a previously measured value of
current consumption for the at least one operational stage; and
detecting a fault in the warm air furnace if the performance
variation exceeds a threshold amount.
20. The method of claim 19, further comprising identifying at least
one component in the warm air furnace most likely to have caused
the fault.
21. The method of claim 19, wherein the at least one operational
stage of the warm air furnace is selected from the group of modes
consisting of Idle, Inducer Start, Inducer Run, Ignition Element
On, Fan Start, and Fan Run.
22. The method of claim 19, further comprising identifying at least
one component within the warm air furnace most likely to have
caused the fault.
23. A method of maintaining a furnace comprising: determining a
first set of performance values for the furnace at a first time;
recording the first set of performance values in a data storage of
an electronic control device of the furnace; comparing the first
set of performance values to a historic set of performance values
for the furnace; and in response to a result of the comparing step,
predicting a future fault of an element of the furnace.
Description
BACKGROUND
FIELD OF THE INVENTION
[0001] The present invention relates generally to warm air
furnaces, and more particularly, to fault detection in a warm air
furnace.
BACKGROUND OF THE INVENTION
[0002] Many houses and other buildings use warm air furnaces to
provide heat. Generally, these furnaces operate by heating air
received through cold air or return ducts and distributing the
heated air throughout the building using warm air or supply ducts.
A circulation fan, operated by an alternating current (AC)
permanent-split-capacitor (PSC) motor, directs the cold air into a
heat exchanger, which may be composed of metal. The heat exchanger
metal is heated using a burner that burns fossil fuels. The burner
is ignited with an ignition device, such as an AC hot surface
ignition element. The air is heated as it passes by the hot metal
surfaces of the heat exchanger. After the air is heated in the heat
exchanger, the fan moves the heated air through the warm air ducts.
A combustion air blower, or inducer, is used to remove exhaust
gases from the building. The inducer is typically operated using an
AC shaded-pole motor.
[0003] Because furnaces play a critical role in the comfort and
safety of occupants of the building, it is important that the warm
air furnace remains functional and that any problems with furnace
operation be quickly diagnosed and corrected. Such diagnosis and
repair is often difficult due to the complexity of modern heating,
ventilation, and/or cooling systems. Therefore, it is desirable to
detect faults in the warm air furnace prior to failure.
[0004] Preventive detection and repair may prevent the occupants of
the building from either remaining in an uncomfortably cold
building or having to leave the building while waiting for a repair
technician to fix the warm air furnace. Therefore, a need exists to
detect faults in a warm air furnace while the furnace is operating.
Some faults occur even prior to installation, thus it is important
for the operation of a furnace that its initial installation in the
home or building be done correctly and with an eye toward
discovering faults due to installation or shipping. Therefore, a
need exists for a system of correctly installing furnaces to
correct installation and pre-installation faults.
[0005] The heating system in a building comprises the furnace, duct
work, and the building itself. Thus, a particular furnace model may
have different optimal operating conditions depending upon its
building of residence. In addition, the individual operating
conditions of the furnace-home combination may alter the expected
life of replaceable components of the furnace. Therefore, a need
exists for a system of discovering baseline optimal values for the
furnace-home combination and detecting changes in those values.
SUMMARY
[0006] The present invention provides an apparatus for warm air
furnace diagnostic enhancements and a method for using those
enhancements for baselining and more effective troubleshooting.
Generally, various embodiments may meet a number of objectives,
including: ensuring a more robust furnace installation at a
customer premises; dynamically identifying elements of the furnace
that may be subject to future fault; and identifying and/or
diagnosing current faults. Of course, some embodiments may meet
other objectives or have other uses.
[0007] In an exemplary embodiment, a warm air furnace ("furnace")
is equipped with a Flash based microcontroller or EEPROM memory
with a microcontroller to retain data in a non-volatile state.
Prior to shipment from a manufacturing facility, factory test
values for the furnace are measured to create a factory baseline.
The measurement may involve passing the furnace through a
predetermined furnace test cycle, and obtaining measures during the
test cycle, for instance. As examples of potential measurements
taken, key baseline furnace performance indicia to retain includes
but is not limited to flame current, hot surface ignition (HSI)
current, inducer current, fan current, pressure switch open and
close times, and heat exchanger rates of temperature rise. These
data are stored in the memory of the furnace and are accessible by
a technician at installation.
[0008] During installation, measurements may be taken of the
performance indicia and compared to the factory baseline.
Variations from the factory baseline may indicate improper
installation or damage during shipment. Alternatively, the
variations may indicate that a maintenance schedule of the
installed furnace should be revised or reconsidered. Thus,
according to an embodiment, the furnace may determine that a
variation is outside of a predetermined range of acceptable
variations and, as a result, modify the maintenance schedule to
recommend more immediate maintenance. An indication may be provided
to a technician or furnace user of the modified maintenance
schedule.
[0009] Even with proper installation, the installation baseline
measures may differ from the factory baseline measures--for
example, air flow rates may depend upon duct-work configuration and
building size, likewise, customized furnace options may also cause
installation baseline measures to differ from their factory based
counterparts. In a further embodiment, an installation baseline is
created during installation by measuring the baseline furnace
performance indicia and storing those indicia in the memory of the
furnace. The installation baseline is useful for predicting
wear-out of key system components and for helping in diagnosis of
fault conditions. According to the embodiment, the baseline
installation indicia are then compared with later obtained indicia
and with the run-time counter. The maintenance schedule of the
furnace may then be modified based on the comparison.
[0010] In yet another embodiment, the apparatus compares the stored
factory baseline and installation baseline and further compares
those figures to later obtained measures to determine the
performance of the furnace. In another embodiment, periodic
measurements are taken of the performance indicia and of run-time
counters to help predict system degradation. Such time-series
information is also useful for determining whether a particular
problem is due to acute failure or to a gradual decline in
performance.
[0011] According to the preferred embodiment, the warm are furnace
includes a data storage and a processor. The data storage may be
used to store furnace performance data as well as instructions that
are executable by a processor. Sensing circuitry is also provided
for obtaining furnace performance data during operation of the warm
air furnace. These various elements of the furnace may be
communicatively linked through a data bus. The instructions stored
in data storage may be machine language programs for obtaining
readings from the sensing circuitry, storing the readings in data
storage, comparing the various readings, and updating a maintenance
schedule based upon the comparisons, for instance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Presently preferred embodiments are described below in
conjunction with the appended drawing figures, wherein like
reference numerals refer to like elements in the various figures,
and wherein:
[0013] FIG. 1 is a block diagram of a warm air furnace with
diagnostics.
[0014] FIG. 2 is a block diagram of a control system for a warm air
furnace with diagnostics.
[0015] FIG. 3 is a flow chart of a method of operation of the warm
air furnace.
DETAILED DESCRIPTION
Exemplary Warm Air Furnace and Control
[0016] FIG. 1 shows a simplified block diagram of a warm air
furnace 100. The warm air furnace 100 includes a controller 102, a
gas valve 104, a burner 106, an ignition element 108, a circulator
fan 112, a heat exchanger 114, and a combustion air blower 116,
which is also referred to as an inducer. The warm air furnace 100
may include additional components not shown in FIG. 1, such as
sensors for detecting temperature and pressure, and filters for
trapping airborne dirt. Furthermore, warm air furnaces have various
efficiency ratings. Additional components may be necessary to
achieve different levels of efficiency.
[0017] The warm air furnace 100 depicted in FIG. 1 is fueled by
natural gas. However, the warm air furnace 100 may be fueled by
other fossil fuels, such as oil and propane. Different fuel sources
may require different components in the warm air furnace 100. For
example, a warm air furnace fueled by oil may include an oil
pump.
[0018] The warm air furnace 100 may be connected to a thermostat,
an exhaust vent, warm air or supply ducts, cold air or return
ducts, and a gas supply. The warm air furnace 100 may also be
connected to an alternating current (AC) power supply. The warm air
furnace may have at least one AC load. For example, the ignition
element 108 may be an AC hot surface ignition element, the fan 112
may include an AC motor, such as an AC permanent-split-capacitor
(PSC) motor, and the inducer 116 may include an AC motor, such as
an AC shaded-pole motor.
[0019] Generally, the warm air furnace 100 operates as follows. The
thermostat sends a "heat request" signal to the controller 102 when
the thermostat is adjusted upwards. The controller 102 may perform
a safety check, which may include checking a pressure switch
located within the warm air furnace 100. (The pressure switch is
not shown in FIG. 1.) Once the safety check is completed, the
controller 102 may activate the inducer 116 by turning on an
inducer motor, such as an AC shaded-pole motor. After turning on
the AC shaded-pole motor, the controller 102 may verify that the
pressure switch in the warm air furnace 100 closes. If the pressure
switch closes properly, the controller 102 may then activate the
ignition element 108.
[0020] The controller 102 may then open the gas valve 104, which
may activate the burner 106. The burner 106 may mix the natural gas
with air and burn the gas mixture. The ignition element 108 may
ignite the gas mixture causing a flame 110 to develop. Once the
flame 110 has been produced by the ignition element 108 and sensed
by a flame sense rod (not shown in FIG. 1), the ignition element
108 may be deactivated. The flame 110 may warm metal in the heat
exchanger 114.
[0021] After the heat exchanger 114 warms for a predetermined time,
typically 15 to 30 seconds, the fan 112 may be activated. The fan
112 may direct cold air received from the cold air ducts into the
heat exchanger 114. The heat exchanger 114 may separate the warm
air from exhaust gases. The fan 112 may cause the warm air to exit
the heat exchanger 114 through the warm air ducts, while the
inducer 116 may cause the exhaust gases to exit through an exhaust
vent connected to the outdoors.
[0022] The controller 102 may close the gas valve 104 when the
thermostat setting has been reached. The inducer 116 may be
deactivated after a predetermined time period, such as 30 seconds,
to ensure that the exhaust gasses have been removed from the heat
exchanger 114. The fan 112 may be deactivated after a predetermined
time period, such as 120 seconds, to ensure the heat from the heat
exchanger 114 is delivered to the warm air ducts. When the ignition
element 108, the fan 112, and the inducer 116 are turned off, the
warm air furnace 100 may be in an Idle mode.
[0023] During both the Idle mode and heating mode, it would be
beneficial to monitor the warm air furnace 100 and potentially
detect a fault condition prior to damaging the warm air furnace
100. In a preferred embodiment, a current sensing circuit may be
used to measure current levels at various points during a warm air
furnace 100 operating sequence. In an embodiment, the warm air
furnace may be adjoined with a cooling system such as an air
conditioner or a humidifier for example.
[0024] FIG. 2 is a block diagram of a monitoring and control device
200 according to an exemplary embodiment. Other monitoring and
control devices may be used. The monitoring and control device 200
may be located within the controller 102, although elements of the
monitoring and control device 200 may be distributed throughout the
furnace 100. Alternatively, the monitoring and control device 200
may be located separately or within another component of the warm
air furnace 100. According to the embodiment, non-volatile data
storage is included in the monitoring and control device 200 for
retaining key performance measures. By comparing key performance
data recorded during production testing with data gathered at
initial installation, installers can be warned about certain
installation problems that can lead to premature failure. By
monitoring the degradation of key performance measures and
recording run time, warnings can be issued on wear-out of key WAF
systems. By retaining all fault conditions over time, intermittent
problems can be more readily diagnosed.
[0025] As shown in FIG. 2, the monitoring and control device
includes a processor 202, a set of sensing devices 210, 212, 214,
216, 220, 222, 224, 226, 228, 230 communicatively coupled with the
processor 202, an analog-to-digital converter 208 to convert
signals from at one of the sensing devices from an analog signal to
a digital signal, data storage 204, an input/output (I/O) port 206,
and furnace control switches 234. The various elements of the
monitoring and control device 200 are inter-coupled via a data bus
232. In the exemplary embodiment, the data storage 204 stores
program code such as machine readable instructions for execution by
the processor 202, stored parameters that provide guidance and user
preferences for execution of the program code, and measured data
such as indicia received from the sensing devices or calculated by
the processor 202. The processor 202 may be one or more processing
units, such as a general-purpose processor and/or a digital signal
processor.
[0026] The plurality of sensing devices are now described. A flame
current sensor 210 provides an indication of the presence of flame
in the furnace. Several types of flame current sensors may be used
including A/C flame ionization sensors and photocell flame sensors.
A low flame current at initial installation may indicate poor earth
ground connection, flame rod movement due to shipping, low AC
voltage, or incorrect AC voltage polarity. High flame current at
initial installation may indicate over-fire, high AC line, or flame
rod movement during shipping. At later points, variance in flame
current may be indicative of other problems such as low flame
level, damaged flame current sensor 210, and/or a need for furnace
maintenance.
[0027] An inducer current sensor 212 provides an indication of
whether the inducer 116 is operating properly. According to an
exemplary embodiment, the inducer current sensor 212 measures the
current used by the inducer 116. Likewise, a fan current sensor 214
provides an indication of whether the fan 112 is operating
properly. According to the embodiment, the fan current sensor 213
measures the current used by the inducer 116. In a preferred
embodiment, a single sensor may comprise the fan current sensor
214, inducer current sensor 212, etc. This may allow a system to be
configured with just one current sensor yet obtain a variety of
data.
[0028] In the presently described embodiment, the flame current
sensor 210, inducer current sensor 212, and fan current sensor 214
each measure current level as an analog signal. The A/D converter
208 is used to convert the analog signals from the three current
sensors 210, 212, 214 to digital signals for the processor 202 and
data storage 204. In furnaces using a pressure switch, a pressure
switch sensor 216 indicates whether the pressure switch is open or
closed. The pressure switch is used as a safety feature to
automatically sense change in pressure and open or close an
electrical switching element when a predetermined pressure point is
reached. The pressure switch sensor 216 may further be used to
indicate pressure switch open time and pressure switch close time.
A heat exchanger temperature sensor 220 measures a temperature in
the heat exchanger 114. The sensor 220 may further be used to
obtain a rate of temperature change in the heat exchanger. An
increased temperature rise rate can, for instance, indicate a dirty
air filter, excessive duct restriction, fan motor failure, or over
fire condition.
[0029] Some elements of a furnace tend to wear out according to the
run-time of specific portions of the furnace cycle. For example,
elements associated with heating will need maintenance much less
often if the furnace system is only used as a fan and/or air
conditioner. Thus, several devices are provided for determining the
run-time of portions of the furnace cycle. For instance, a heating
switch 222 indicates whether the furnace is operating in a heating
mode, a cooling switch 224 indicates whether the furnace is
operating in a cooling (A/C) mode, a fan switch 226 indicates
whether the furnace is operating in a fan-only mode, an igniter
switch 228 indicates whether the furnace is operating with the
igniter on, and a pressure switch indicates whether the motor
and/or ductwork is operating properly. A counter 230 provides
timing information for each portion of the cycle. Thus, according
to an embodiment, the measurement and control device 200 may
determine, using the heating switch 222 and counter 230, that the
furnace has been operating in a heating mode for a specified number
of hours, such as 3,000 hours, for instance.
[0030] Alternatively/additionally, the counter 230, may be
configured to keep track of the number of run-cycles that have
taken place for each portion of the cycle. Thus, according to an
embodiment, the measurement and control device 200 may determine,
using heating switch 222 and counter 230, that the furnace has
operated in a heating mode for a specified number of cycles, such
as 30,000 cycles. As with run-time, the number of cycles can be
coupled with other measurements to determine or indicate a rate of
degradation of elements of the furnace system, and thus to predict
future failure or indicate present failure.
[0031] The I/O port 206 may allow the monitoring and control device
200 to communicate with a user and/or technician by, for instance,
warning the user that the furnace is not functioning correctly or
by indicating that the maintenance schedule has been updated. As
such, the port 206 may include a speaker, display (LCD) or lights
to provide a audible or visual output to the user. Further, the I/O
port 206 may provide connectivity for a technician to obtain stored
data and alter stored parameters. In an alternative embodiment,
data storage 204 includes a removable memory device such as a flash
memory microcontroller or EEPROM memory with a microcontroller. In
that case, the technician may transfer data to and from the
monitoring and control device 200 using the removable memory
device. Further, the system may be configured so that a technician
may obtain data via a hand-held tool, such as a portable data
device or personal data assistant (PDA). It is contemplated that
the hand-held tool may be connected via a Honeywell EnviroCOM
thermostat or via a wireless interface, for instance.
[0032] The furnace control switches 234 allow the processor 202 to
control activity of the furnace. For example, in an embodiment, the
processor 202 executes a standard test cycle through the furnace
control switches 234. In the test cycle, the furnace may be placed
in various modes such as heating and cooling modes. During the test
cycle, performance indicia are measured through the various sensing
devices and may be further calculated by the processors 202 and
stored in data storage 204.
Exemplary Operation
[0033] FIG. 3 provides a flow chart illustrating a method of
operation that may be used to modify a maintenance schedule of the
warm air furnace 100. The method measures current consumption and
other indicia at several points in the warm air furnace 100
operating sequence. The measured indicia are then compared with
baseline measures obtained before shipment of the furnace from a
factory setting. Depending upon the results of the comparison, a
maintenance schedule for the furnace 100 may be modified and/or
immediate maintenance recommended.
[0034] Initial installation data can be used to predict wear-out of
key system components and to help in diagnosis of fault conditions.
For example, increased temperature rate of rise can indicate dirty
air filter, excessive duct restriction, over fire condition, or fan
motor failure. Decreased HSI current can indicate a failing igniter
element. Increased motor currents can indicate bearing wear,
winding fault or locked rotor conditions. Pressure switch close or
open time increase can indicate increased vent restriction, or
inducer motor performance change.
[0035] Before installation, a baseline performance metric for the
furnace 100 is obtained 302. This metric may be obtained in the
factory where the furnace is manufactured, for instance. The
baseline performance metric is preferably a set of indicia measured
by the measurement and control device 200. These indicia may
include, for instance, factory test values for flame current, HSI
current, inducer current, fan current, pressure switch open and
close times, and heat exchanger rate of temperature rise. The
furnace is then installed at a customer premises at 304. During
installation, the measurement and control device 200 is used to
determine an installed performance metric at 306. As with the
baseline performance metric, the installed performance metric may
include a set of indicia measured by the measurement and control
device 200. In order to obtain the indicia, the measurement and
control device 200 may initiate a furnace test cycle. At
predetermined portions during the test cycle, the measurement and
control device 200 may obtain and record the indicia.
[0036] The test cycle may include passing the current through an
idle mode, safety check mode, inducer start mode, inducer run mode,
ignition mode, and burn mode for instance. When the warm air
furnace 100 is in the idle mode, the ignition element 108, the fan
112, and the inducer 116 may be deactivated. During the idle mode
302, a low current value may be supplied to the warm air furnace
100 due to the lack of current consumption by the ignition element
108, the fan 112, and the inducer 116. The measurement and control
device 200 may take an "Idle" current reading during the Idle mode.
Alternatively, the current sensing circuit 200 may take periodic
Idle current readings during the Idle mode. If the Idle current
reading is above a baseline amount, there may be a problem with the
warm air furnace 100. A fault may be caused by shorted or damaged
low voltage transformer in the AC power supply 202. Following the
idle mode, the furnace may pass through a safety check mode. In the
safety check mode, the pressure switch may be checked to ensure
that it is operating properly. If the pressure switch open and
close times vary from a baseline measure, then there may be a need
for immediate maintenance.
[0037] Next, the furnace may be placed in the inducer start mode,
and an inducer current is read during a first period after the
inducer motor begins operation. If the inducer start current
reading at installation is above a baseline reading, there may be a
problem with the warm air furnace 100. For example, either shorted
wiring or motor windings in the inducer 116 may have caused the
fault. After a wait period, an inducer run mode may be entered and
another inducer current may be read. This second inducer period may
be several seconds after the inducer start mode. If the
installation inducer run current reading is above or below the
corresponding baseline value, there may be a problem with the warm
air furnace 100. For instance, if the inducer run current reading
is well above the baseline reading, motor windings may be beginning
to short, motor bearings may be beginning to seize, or a rotor in
the AC shaded-pole motor may be locked due to an obstruction. If
the inducer run current is below the baseline amount, an excessive
vent restriction, deteriorating wiring connections, failing or
failed motor windings, or a damaged controller 102 may have caused
the fault.
[0038] The furnace may then be placed in an ignition mode by
activating the ignition element 108. At that point, an ignition
current reading may be taken. If the reading is above or below the
baseline amount, there may be a problem with the warm air furnace
100. If the ignition current reading is above the baseline amount,
shorted wiring or ignition element 108 may have caused the fault.
If the ignition current reading is below the baseline amount,
deteriorating wiring connections or ignition element 108, an open
ignition element 108, or a damaged controller 102 may have caused
the fault.
[0039] The controller 102 may then open the gas valve 104 after a
warm-up period following activation of the ignition element 108.
Once ignition element 108 has ignited the flame 110, the ignition
element 108 may be deactivated. A third inducer current reading may
be taken at this point. After a delay period to allow the heat
exchanger 114 to begin heating, the controller 102 may activate the
fan 112, as depicted in box, and a fan start current reading may be
taken soon after the fan motor begins operation. If the fan start
current reading is above a baseline amount, there may be a problem
with the warm air furnace 100. For instance, either shorted wiring
or motor windings in the fan 112 may have caused a fault.
[0040] After a wait period, the furnace may take a fan run current
reading during a second period after the fan motor begins
operation. The second period may be substantially 30 seconds after
the first fan run current reading. If the second fan run current
reading is above or below the corresponding baseline amount, there
may be a problem with the warm air furnace 100. If the fan run
current reading is above the baseline amount, motor windings in the
fan motor may be beginning to short, motor bearings in the fan
motor may be beginning to seize, or a fan cage may be locked or
obstructed. If the fan run current reading is below the baseline
amount, a duct restriction, deteriorating wiring connections,
failing or failed motor windings, or a damaged controller 102 may
have caused the fault.
[0041] The controller 102 may close the gas valve 104 when the
thermostat setting has been reached. The inducer 116 may be
deactivated after a predetermined time period, such as 30 seconds,
to ensure that the exhaust gasses have been removed from the heat
exchanger 114. The fan 112 may be deactivated after a predetermined
time period, such as 120 seconds, to ensure the heat from the heat
exchanger 114 is delivered to the warm air ducts. The warm air
furnace 100 may return to the idle mode 302 another idle current
reading may be taken.
[0042] In this embodiment, the installed performance metric
comprises the set of indicia obtained during the test cycle. Once
the installation performance metric is determined, the processor
202 is used to compare the installation performance metric with the
baseline performance metric.
[0043] According to the exemplary embodiment, the results of the
comparison may fall into three categories: limited variance;
significant variance, but within threshold; and variance outside
threshold. If there is only a limited variance between the metrics
310, then there will be no modification of a furnace maintenance
schedule. If there is a significant variance, but the variance
remains within a threshold (such as within 50% of the baseline) 312
then the processor 202 may modify the maintenance schedule to
account for the difference between the baseline metric and the
installed metric. If instead, the variance is outside of the
threshold, then immediate maintenance should be required.
Preferably, an installation technician is notified of the need for
immediate maintenance. In a further embodiment, the processor is
configured it identify at least one component in the warm air
furnace that may have caused the fault.
[0044] In some cases, a factory baseline metric may be unavailable.
In those cases, recommended operational values for the furnace may
be used in place of a measured baseline.
[0045] Although the method outlined by FIG. 3 uses a comparison
between a factory baseline metric and an installed metric. In a
further embodiment, a similar test cycle can be performed on a
regular basis such as for each operating cycle of the warm air
furnace 100. Alternatively, the testing may be performed on a
periodic basis such as daily. In that case, the new readings may be
compared to the baseline metric as well as other, previously
measured metrics. Further, some tests may be performed more than
others based on failure rates of the warm air furnace components.
It is also understood that additional current readings may be taken
during the operation of the warm air furnace 100. While the most
likely causes of the faults are provided in method 300, additional
warm air furnace components may cause a fault.
[0046] Not every test described in the method 300 needs to be run
during every operational cycle of the warm air furnace 100. For
example, some tests may be performed each time the warm air furnace
100 completes an operational cycle, while other tests may be
performed less frequently. Additional tests may also be included in
the method.
[0047] By maintaining a run-time counter, periodic maintenance
intervals can be established. The home-owner can then be notified
when a system component has reached a service interval and should
be checked. In a further embodiment, the system may be configured
to allow a home-owner to trigger a test cycle to diagnose any
suspected problems.
[0048] In a further embodiment, error codes that have occurred
since a reset of memory are stored in the data storage. Retaining
all error code conditions seen by the WAF greatly improves
troubleshooting; especially for intermittent faults. The control
provides a means to read-out and clear all stored error codes and
may have a plug to download data onto handheld device or use
wireless communication such as Bluetooth, for instance.
[0049] It should be understood that the illustrated embodiments are
exemplary only and should not be taken as limiting the scope of the
present invention. For example, the invention may be used to detect
faults in other ignition-controlled appliances, such as a water
heater. The claims should not be read as limited to the described
order or elements unless stated to that effect. Therefore, all
embodiments that come within the scope and spirit of the following
claims and equivalents thereto are claimed as the invention.
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