U.S. patent application number 14/603073 was filed with the patent office on 2015-07-30 for system and method of protecting an hvac system.
The applicant listed for this patent is Trane International Inc.. Invention is credited to George William Brandt, Darryl Elliott Denton.
Application Number | 20150211779 14/603073 |
Document ID | / |
Family ID | 53678698 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150211779 |
Kind Code |
A1 |
Brandt; George William ; et
al. |
July 30, 2015 |
System and Method of Protecting an HVAC System
Abstract
Systems and methods are provided for operating a heating,
ventilation, and/or air conditioning (HVAC) system that include
recording a number of consecutive occasions in which a defrost mode
is entered within a first predefined length of time after a heating
cycle is entered, preventing operation of at least one component of
the HVAC system for a second predefined length of time in response
to entering the defrost mode a first predetermined consecutive
number of occurrences within the first predefined length of time
after a heating cycle is entered, recording a number of consecutive
preventions of operation of the component of the HVAC system, and
determining that a fault condition exists in the HVAC system in
response to the number of consecutive temporary preventions of
operation of the component of the HVAC system exceeding a second
predefined number of occurrences.
Inventors: |
Brandt; George William;
(Tyler, TX) ; Denton; Darryl Elliott; (Tyler,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Trane International Inc. |
Piscataway |
NJ |
US |
|
|
Family ID: |
53678698 |
Appl. No.: |
14/603073 |
Filed: |
January 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61933748 |
Jan 30, 2014 |
|
|
|
Current U.S.
Class: |
62/80 ;
62/129 |
Current CPC
Class: |
F24F 11/32 20180101;
F24F 11/30 20180101; F25D 21/006 20130101; F24F 11/41 20180101 |
International
Class: |
F25D 21/00 20060101
F25D021/00 |
Claims
1. A method of operating a heating, ventilation, and/or air
conditioning (HVAC) system, comprising: detecting a fault condition
in response to the HVAC system to entering a defrost mode before a
predefined threshold is reached for a predefined number of
consecutive occasions; and preventing operation of at least one
component of the HVAC system for a predefined length of time in
response to detecting the fault condition.
2. The method of claim 1, further comprising: preventing operation
of at least one component of the HVAC system until the fault
condition is alleviated in response to detecting the fault
condition a predefined number of fault condition occurrences.
3. The method of claim 1, further comprising: incrementing a first
counter in response to the HVAC system entering the defrost mode
before the predefined threshold time.
4. The method of claim 3, further comprising: incrementing a second
counter in response to detecting the fault condition.
5. The method of claim 4, further comprising: preventing operation
of at least one component of the HVAC system in response to
incrementing the second counter a predetermined number of
times.
6. The method of claim 5, wherein the predefined threshold
comprises a predefined length of time after entering a heating
cycle.
7. The method of claim 1, wherein the predefined threshold
comprises a rate of change of a difference between an ambient air
temperature and an outdoor heat exchanger temperature.
8. The method of claim 1, wherein the fault condition comprises at
least one of: an air pressure drop across the outdoor heat
exchanger; a suction pressure; and an outdoor fan power or
current.
9. The method of claim 1, further comprising: providing a
notification of the fault condition.
10. A heating, ventilation, and/or air conditioning (HVAC) system,
comprising: a system controller configured to: detect a fault
condition in response to the HVAC system to entering a defrost mode
before a predefined threshold is reached for a predefined number of
consecutive occasions; and prevent operation of at least one
component of the HVAC system for a predefined length of time in
response to detecting the fault condition.
11. The HVAC system of claim 10, wherein the controller is further
configured to prevent operation of at least one component of the
HVAC system until the fault condition is alleviated in response to
detecting the fault condition a predefined number of fault
condition occurrences.
12. The HVAC system of claim 10, wherein the controller comprises a
first counter configured to increment each time the HVAC system
enters the defrost mode before the predefined threshold time.
13. The HVAC system of claim 10, wherein the controller comprises a
second counter configured to increment each time the controller
detects a fault condition.
14. The HVAC system of claim 13, wherein the controller is
configured to prevent operation of at least one component of the
HVAC system in response to incrementing the second counter a
predetermined number of times.
15. The HVAC system of claim 10, wherein the predefined threshold
comprises at least one of: a predefined length of time after
entering a heating cycle; a rate of change of a difference between
an ambient air temperature and an outdoor heat exchanger
temperature; an air pressure drop across the outdoor heat
exchanger; a suction pressure; and an outdoor fan power or
current.
16. The HVAC system of claim 10, wherein the controller is further
configured to provide a notification of the fault condition.
17. A method for operating a heating, ventilation, and/or air
conditioning (HVAC) system, comprising: recording a number of
consecutive occasions in which a defrost mode is entered within a
first predefined length of time after a heating cycle is entered;
preventing operation of at least one component of the HVAC system
for a second predefined length of time in response to entering the
defrost mode a first predetermined consecutive number of
occurrences within the first predefined length of time after a
heating cycle is entered; recording a number of consecutive
preventions of operation of the component of the HVAC system; and
determining that a fault condition exists in the HVAC system in
response to the number of consecutive temporary preventions of
operation of the component of the HVAC system exceeding a second
predefined number of occurrences.
18. The method of claim 17, further comprising: preventing
operation of at least one component of the HVAC system down until
the fault condition is alleviated.
19. The method of claim 17, further comprising: providing a
notification of the fault condition.
20. The method of claim 17, wherein the predetermined consecutive
number of occurrences and the second predefined number of
occurrences is three.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
119(e) to U.S. Provisional Patent Application No. 61/933,748 filed
on Jan. 30, 2014 by George William Brandt, et al., and entitled
"System and Method of Protecting an HVAC System," the disclosure of
which is hereby incorporated by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not applicable.
BACKGROUND
[0004] Heating, ventilation, and air conditioning systems (HVAC
systems) may be used to heat and/or cool comfort zones to
comfortable temperatures. Comfort zones are often the occupiable
portions of residential and/or commercial areas and may be subject
to variable zone conditions, such as temperature and humidity. A
portion of an HVAC system may be installed outdoors or in some
other location remote from the comfort zone for the purpose of
performing heat exchange. Such a location may be referred to as an
ambient zone and may also have variable temperature and humidity
conditions.
[0005] Some HVAC systems are heat pump systems. Heat pump systems
are generally capable of operating in a cooling mode in which a
comfort zone is cooled by transferring heat from the comfort zone
to an ambient zone using a refrigeration cycle (e.g., the Rankine
cycle). Heat pump systems are also generally capable of operating
in a heating mode in which the direction of refrigerant flow
through the components of the HVAC system is reversed so that heat
is transferred from the ambient zone to the comfort zone, thereby
heating the comfort zone. Heat pump systems generally use a
reversing valve for rerouting the direction of refrigerant flow
between the compressor and the heat exchangers associated with the
comfort zone and the ambient zone.
[0006] If moisture is present in an ambient zone, the moisture may
condense on the ambient zone components of an HVAC system.
Accordingly, when the temperature in the ambient zone is
sufficiently low, frost and/or ice may accumulate on the outdoor
components of the HVAC system, sometimes necessitating a defrosting
of the components of the HVAC system on which frost and/or ice have
accumulated. In a heat pump system, the defrosting may be achieved
by reversing the direction of refrigerant flow from the direction
of flow used in the heating mode. Specifically, the refrigerant
flow is such that heat is transferred from the comfort zone to the
ambient zone during the defrosting of the HVAC system
components.
SUMMARY
[0007] In some embodiments, a method of operating a heating,
ventilation, and/or air conditioning (HVAC) system is disclosed as
comprising: detecting a fault condition in response to the HVAC
system to entering a defrost mode before a predefined threshold is
reached for a predefined number of consecutive occasions; and
preventing operation of at least one component of the HVAC system
for a predefined length of time in response to detecting the fault
condition.
[0008] In other embodiments, a heating, ventilation, and/or air
conditioning (HVAC) system is disclosed as comprising: a system
controller configured to: detect a fault condition in response to
the HVAC system to entering a defrost mode before a predefined
threshold is reached for a predefined number of consecutive
occasions; and prevent operation of at least one component of the
HVAC system for a predefined length of time in response to
detecting the fault condition.
[0009] In yet other embodiments, a method for operating a heating,
ventilation, and/or air conditioning (HVAC) system is disclosed as
comprising: recording a number of consecutive occasions in which a
defrost mode is entered within a first predefined length of time
after a heating cycle is entered; preventing operation of at least
one component of the HVAC system for a second predefined length of
time in response to entering the defrost mode a first predetermined
consecutive number of occurrences within the first predefined
length of time after a heating cycle is entered; recording a number
of consecutive preventions of operation of the component of the
HVAC system; and determining that a fault condition exists in the
HVAC system in response to the number of consecutive temporary
preventions of operation of the component of the HVAC system
exceeding a second predefined number of occurrences.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of the present disclosure
and the advantages thereof, reference is now made to the following
brief description, taken in connection with the accompanying
drawings and detailed description:
[0011] FIG. 1 is a schematic diagram of an HVAC system according to
an embodiment of the disclosure;
[0012] FIG. 2 is a schematic diagram of the air circulation paths
of the HVAC system of FIG. 1;
[0013] FIG. 3 is a flowchart of a method for shutting down an HVAC
system; and
[0014] FIG. 4 is a representation of a general-purpose processor
(e.g., electronic controller or computer) system suitable for
implementing the embodiments of the disclosure.
DETAILED DESCRIPTION
[0015] FIG. 1 is a schematic diagram of an HVAC system 100
according to an embodiment of this disclosure. HVAC system 100
comprises an indoor unit 102, an outdoor unit 104, and a system
controller 106. In some embodiments, the system controller 106 may
operate to control operation of the indoor unit 102 and/or the
outdoor unit 104. As shown, the HVAC system 100 is a so-called heat
pump system that may be selectively operated to implement one or
more substantially closed thermodynamic refrigeration cycles to
provide a cooling functionality and/or a heating functionality. In
other embodiments, the HVAC system 100 may be some other type of
heating, ventilation, and/or air conditioning system.
[0016] The indoor unit 102 comprises an indoor heat exchanger 108,
an indoor fan 110, and an indoor metering device 112. The indoor
heat exchanger 108 may be a plate fin heat exchanger configured to
allow heat exchange between refrigerant carried within internal
tubing of the indoor heat exchanger 108 and fluids that contact the
indoor heat exchanger 108 but that are kept segregated from the
refrigerant. In other embodiments, the indoor heat exchanger 108
may comprise a spine fin heat exchanger, a microchannel heat
exchanger, or any other suitable type of heat exchanger.
[0017] The indoor fan 110 may be a centrifugal blower comprising a
blower housing, a blower impeller at least partially disposed
within the blower housing, and a blower motor configured to
selectively rotate the blower impeller. In other embodiments, the
indoor fan 110 may comprise a mixed-flow fan and/or any other
suitable type of fan. The indoor fan 110 may be configured as a
modulating and/or variable speed fan capable of being operated at
many speeds over one or more ranges of speeds. In other
embodiments, the indoor fan 110 may be configured as a multiple
speed fan capable of being operated at a plurality of operating
speeds by selectively electrically powering different ones of
multiple electromagnetic windings of a motor of the indoor fan 110.
In yet other embodiments, the indoor fan 110 may be a single speed
fan.
[0018] The indoor metering device 112 may be an electronically
controlled motor driven electronic expansion valve (EEV). In
alternative embodiments, the indoor metering device 112 may
comprise a thermostatic expansion valve, a capillary tube assembly,
and/or any other suitable metering device. The indoor metering
device 112 may comprise and/or be associated with a refrigerant
check valve and/or refrigerant bypass for use when a direction of
refrigerant flow through the indoor metering device 112 is such
that the indoor metering device 112 is not intended to meter or
otherwise substantially restrict flow of refrigerant through the
indoor metering device 112.
[0019] The outdoor unit 104 comprises an outdoor heat exchanger
114, a compressor 116, an outdoor fan 118, an outdoor metering
device 120, and a reversing valve 122. The outdoor heat exchanger
114 may be a spine fin heat exchanger configured to allow heat
exchange between refrigerant carried within internal passages of
the outdoor heat exchanger 114 and fluids that contact the outdoor
heat exchanger 114 but that are kept segregated from the
refrigerant. In other embodiments, the outdoor heat exchanger 114
may comprise a plate fin heat exchanger, a microchannel heat
exchanger, or any other suitable type of heat exchanger.
[0020] The compressor 116 may be a multiple speed scroll type
compressor configured to selectively pump refrigerant at a
plurality of mass flow rates. In alternative embodiments, the
compressor 116 may be a modulating compressor capable of operation
over one or more speed ranges, a reciprocating type compressor, a
single speed compressor, and/or any other suitable refrigerant
compressor and/or refrigerant pump.
[0021] The outdoor fan 118 may be an axial fan comprising a fan
blade assembly and fan motor configured to selectively rotate the
fan blade assembly. In other embodiments, the outdoor fan 118 may
comprise a mixed-flow fan, a centrifugal blower, and/or any other
suitable type of fan and/or blower. The outdoor fan 118 may be
configured as a modulating and/or variable speed fan capable of
being operated at many speeds over one or more ranges of speeds. In
other embodiments, the outdoor fan 118 may be configured as a
multiple speed fan capable of being operated at a plurality of
operating speeds by selectively electrically powering different
ones of multiple electromagnetic windings of a motor of the outdoor
fan 118. In yet other embodiments, the outdoor fan 118 may be a
single speed fan.
[0022] The outdoor metering device 120 may be a thermostatic
expansion valve. In alternative embodiments, the outdoor metering
device 120 may comprise an electronically controlled motor driven
EEV, a capillary tube assembly, and/or any other suitable metering
device. The outdoor metering device 120 may comprise and/or be
associated with a refrigerant check valve and/or refrigerant bypass
for use when a direction of refrigerant flow through the outdoor
metering device 120 is such that the outdoor metering device 120 is
not intended to meter or otherwise substantially restrict flow of
refrigerant through the outdoor metering device 120.
[0023] The reversing valve 122 may be a so-called four-way
reversing valve. The reversing valve 122 may be selectively
controlled to alter a flow path of refrigerant in the HVAC system
100 as described in greater detail below. The reversing valve 122
may comprise an electrical solenoid or other device configured to
selectively move a component of the reversing valve 122 between
operational positions.
[0024] The system controller 106 may comprise a touchscreen
interface for displaying information and for receiving user inputs.
The system controller 106 may display information related to the
operation of the HVAC system 100 and may receive user inputs
related to operation of the HVAC system 100. The system controller
106 may further be operable to display information and receive user
inputs tangentially related and/or unrelated to operation of the
HVAC system 100. In some embodiments, the system controller 106 may
comprise a temperature sensor and may further be configured to
control heating and/or cooling of zones associated with the HVAC
system 100. In some embodiments, the system controller 106 may be
configured as a thermostat for controlling the supply of
conditioned air to zones associated with the HVAC system 100.
[0025] In some embodiments, the system controller 106 may
selectively communicate with an indoor controller 124 of the indoor
unit 102, with an outdoor controller 126 of the outdoor unit 104,
and/or with other components of the HVAC system 100. In some
embodiments, the system controller 106 may be configured for
selective bidirectional communication over a communication bus 128.
In some embodiments, portions of the communication bus 128 may
comprise a three-wire connection suitable for communicating
messages between the system controller 106 and one or more of the
HVAC system components configured for interfacing with the
communication bus 128.
[0026] Still further, the system controller 106 may be configured
to selectively communicate with HVAC system components and/or
another device 130 via a communication network 132. In some
embodiments, the communication network 132 may comprise a telephone
network and the other device 130 may comprise a telephone. In some
embodiments, the communication network 132 may comprise the
Internet and the other device 130 may comprise a so-called
smartphone and/or other Internet-enabled mobile telecommunication
device.
[0027] The indoor controller 124 may be carried by the indoor unit
102 and may be configured to receive information inputs, transmit
information outputs, and otherwise communicate with the system
controller 106, the outdoor controller 126, and/or any other device
via the communication bus 128 and/or any other suitable medium of
communication. In some embodiments, the indoor controller 124 may
be configured to communicate with an indoor personality module 134,
receive information related to a speed of the indoor fan 110,
transmit a control output to an electric heat relay, transmit
information regarding an indoor fan volumetric flow rate,
communicate with and/or otherwise affect control over an air
cleaner 136, and communicate with an indoor EEV controller 138. In
some embodiments, the indoor controller 124 may be configured to
communicate with an indoor fan controller 142 and/or otherwise
affect control over operation of the indoor fan 110. In some
embodiments, the indoor personality module 134 may comprise
information related to the identification and/or operation of the
indoor unit 102 and/or a position of the outdoor metering device
120.
[0028] In some embodiments, the indoor EEV controller 138 may be
configured to receive information regarding temperatures and
pressures of the refrigerant in the indoor unit 102. More
specifically, the indoor EEV controller 138 may be configured to
receive information regarding temperatures and pressures of
refrigerant entering, exiting, and/or within the indoor heat
exchanger 108. Further, the indoor EEV controller 138 may be
configured to communicate with the indoor metering device 112
and/or otherwise affect control over the indoor metering device
112.
[0029] The outdoor controller 126 may be carried by the outdoor
unit 104 and may be configured to receive information inputs,
transmit information outputs, and otherwise communicate with the
system controller 106, the indoor controller 124, and/or any other
device via the communication bus 128 and/or any other suitable
medium of communication. In some embodiments, the outdoor
controller 126 may be configured to communicate with an outdoor
personality module 140 that may comprise information related to the
identification and/or operation of the outdoor unit 104. In some
embodiments, the outdoor controller 126 may be configured to
receive information related to an ambient temperature associated
with the outdoor unit 104, information related to a temperature of
the outdoor heat exchanger 114, and/or information related to
refrigerant temperatures and/or pressures of refrigerant entering,
exiting, and/or within the outdoor heat exchanger 114 and/or the
compressor 116. In some embodiments, the outdoor controller 126 may
be configured to transmit information related to monitoring,
communicating with, and/or otherwise affecting control over the
outdoor fan 118, a compressor sump heater, a solenoid of the
reversing valve 122, a relay associated with adjusting and/or
monitoring a refrigerant charge of the HVAC system 100, a position
of the indoor metering device 112, and/or a position of the outdoor
metering device 120. The outdoor controller 126 may further be
configured to communicate with a compressor drive controller 144
that is configured to electrically power and/or control the
compressor 116.
[0030] The HVAC system 100 is shown configured for operating in a
so-called cooling mode in which heat is absorbed by refrigerant at
the indoor heat exchanger 108 and heat is rejected from the
refrigerant at the outdoor heat exchanger 114. In some embodiments,
the compressor 116 may be operated to compress refrigerant and pump
the relatively high temperature and high pressure compressed
refrigerant from the compressor 116 through the reversing valve 122
to the outdoor heat exchanger 114. As the refrigerant is passed
through the outdoor heat exchanger 114, the outdoor fan 118 may be
operated to move air into contact with the outdoor heat exchanger
114, thereby transferring heat from the refrigerant to the air
surrounding the outdoor heat exchanger 114. The refrigerant may
primarily comprise liquid phase refrigerant and the refrigerant may
be pumped from the outdoor heat exchanger 114 to the indoor
metering device 112 through and/or around the outdoor metering
device 120, which does not substantially impede flow of the
refrigerant in the cooling mode. The indoor metering device 112 may
meter passage of the refrigerant through the indoor metering device
112 so that the refrigerant downstream of the indoor metering
device 112 is at a lower pressure than the refrigerant upstream of
the indoor metering device 112. The pressure differential across
the indoor metering device 112 allows the refrigerant downstream of
the indoor metering device 112 to expand and/or at least partially
convert to a gaseous phase. The gaseous phase refrigerant may enter
the indoor heat exchanger 108. As the refrigerant is passed through
the indoor heat exchanger 108, the indoor fan 110 may be operated
to move air into contact with the indoor heat exchanger 108,
thereby transferring heat to the refrigerant from the air
surrounding the indoor heat exchanger 108. The refrigerant may
thereafter reenter the compressor 116 after passing through the
reversing valve 122.
[0031] To operate the HVAC system 100 in the so-called heating
mode, the reversing valve 122 may be controlled to alter the flow
path of the refrigerant, the indoor metering device 112 may be
disabled and/or bypassed, and the outdoor metering device 120 may
be enabled. In the heating mode, refrigerant may flow from the
compressor 116 to the indoor heat exchanger 108 through the
reversing valve 122. The refrigerant may be substantially
unaffected by the indoor metering device 112 and may experience a
pressure differential across the outdoor metering device 120. The
refrigerant may pass through the outdoor heat exchanger 114 and
reenter the compressor 116 after passing through the reversing
valve 122. In general, operation of the HVAC system 100 in the
heating mode reverses the roles of the indoor heat exchanger 108
and the outdoor heat exchanger 114 as compared to their operation
in the cooling mode.
[0032] The HVAC system 100 is shown as a so-called split system,
wherein the indoor unit 102 is located separately from the outdoor
unit 104. Alternative embodiments of an HVAC system may comprise a
so-called package system in which one or more of the components of
the indoor unit 102 and one or more of the components of the
outdoor unit 104 are carried together in a common housing or
package. The HVAC system 100 is shown as a so-called ducted system
where the indoor unit 102 is located remote from the conditioned
zones, thereby requiring air ducts to route the circulating air.
However, in alternative embodiments, an HVAC system may be
configured as a non-ducted system in which the indoor unit 102
and/or multiple indoor units 102 associated with an outdoor unit
104 are located substantially in the space and/or zone to be
conditioned by the respective indoor units 102, thereby not
requiring air ducts to route the air conditioned by the indoor
units 102.
[0033] Referring now to FIG. 2, a schematic diagram of the air
circulation paths for a structure 200 conditioned by two HVAC
systems 100 is shown. In this embodiment, the structure 200 is
conceptualized as comprising a lower floor 202 and an upper floor
204. The lower floor 202 comprises zones 206, 208, and 210, while
the upper floor 204 comprises zones 212, 214, and 216. The HVAC
system 100 associated with the lower floor 202 is configured to
circulate and/or condition air of lower zones 206, 208, and 210,
while the HVAC system 100 associated with the upper floor 204 is
configured to circulate and/or condition air of upper zones 212,
214, and 216.
[0034] In addition to the components of the HVAC system 100
described above, in this embodiment, each HVAC system 100 further
comprises a ventilator 146, a prefilter 148, a humidifier 150, and
a bypass duct 152. The ventilator 146 may be operated to
selectively exhaust circulating air to the environment and/or
introduce environmental air into the circulating air. The prefilter
148 may generally comprise a filter medium selected to catch and/or
retain relatively large particulate matter prior to air exiting the
prefilter 148 and entering the air cleaner 136. The humidifier 150
may be operated to adjust the humidity of the circulating air. The
bypass duct 152 may be utilized to regulate air pressures within
the ducts that form the circulating air flow paths. In some
embodiments, air flow through the bypass duct 152 may be regulated
by a bypass damper 154, while air flow delivered to the zones 206,
208, 210, 212, 214, and 216 may be regulated by zone dampers
156.
[0035] Each HVAC system 100 may further comprise a zone thermostat
158 and a zone sensor 160. In some embodiments, a zone thermostat
158 may communicate with the system controller 106 and may allow a
user to control a temperature, humidity, and/or other environmental
setting for the zone in which the zone thermostat 158 is located.
Further, the zone thermostat 158 may communicate with the system
controller 106 to provide temperature, humidity, and/or other
environmental feedback regarding the zone in which the zone
thermostat 158 is located. In some embodiments, a zone sensor 160
may communicate with the system controller 106 to provide
temperature, humidity, and/or other environmental feedback
regarding the zone in which the zone sensor 160 is located.
[0036] The system controllers 106 may be configured for
bidirectional communication with each other and may further be
configured so that a user may, using either of the system
controllers 106, monitor and/or control any of the HVAC system
components regardless of which zones the components may be
associated with. Further, each system controller 106, each zone
thermostat 158, and each zone sensor 160 may comprise a humidity
sensor. As such, it will be appreciated that structure 200 may be
equipped with a plurality of humidity sensors in a plurality of
different locations. In some embodiments, a user may effectively
select which of the plurality of humidity sensors is used to
control operation of one or more of the HVAC systems 100.
[0037] If the outdoor temperature is sufficiently low, ice or frost
may form on the outdoor components of outdoor unit 104 of the HVAC
system 100, such as the coils in the outdoor heat exchanger 114. To
prevent or mitigate the formation of ice or frost on the outdoor
components of the HVAC system 100, the HVAC system 100 may enter a
defrost mode, wherein the HVAC system 100 heats the outdoor
components of the HVAC system 100 by entering the cooling mode.
That is, refrigerant flow is directed such that heat is removed
from indoor zones (such as the zones 206, 208, 210, 212, 214, and
216) and is transferred to the portions of the outdoor unit 104
that may be subjected to frosting. For example, heat may be removed
from the indoor zones and transferred to the outdoor heat exchanger
114 of the outdoor unit 104 to melt any accumulated frozen
condensation on the outdoor heat exchanger 114. Supplemental heat
may be added to the air supplied to the indoor zones while the
defrost mode is active to prevent the supplied air from becoming
uncomfortably cool at a time when warm air may be expected to be
provided.
[0038] Entry into a defrost mode may be triggered by several
different parameters, such as the ambient air temperature, the
temperature of the outdoor heat exchanger 114, the difference
between the ambient air temperature and the outdoor heat exchanger
114 temperature (which may be referred to as the delta T), the air
pressure drop across the outdoor heat exchanger 114, the suction
pressure, and/or the outdoor fan 118 power or current. A defrost
mode may be terminated based on an outdoor heat exchanger 114
temperature threshold or another related parameter.
[0039] Such a defrost mode is typically sufficient to remove frost
formed when water vapor in the ambient air freezes on the outdoor
heat exchanger 114. However, in cases where there is a heavier
buildup of ice on the outdoor heat exchanger 114, additional
defrosting may be needed. Such cases may be indicated by an
exceptionally high or exceptionally low delta T. When a heavy
buildup of ice is indicated, a timed defrost mode may be entered,
wherein a defrost mode is entered for a first predetermined length
of time, stopped for a second predetermined length of time, and
then re-entered for the first predetermined length of time. Such
timed cycles of starting and stopping a defrost mode may continue
for a predetermined number of cycles or may terminate when there is
an indication that the ice buildup on the outdoor heat exchanger
114 has been alleviated.
[0040] In some cases, the ice buildup on the components of the
outdoor unit 104 or other components of the HVAC system 100 may be
exceptionally heavy. For instance, an ice storm may cause the
outdoor heat exchanger 114 to become totally encapsulated in a
thick layer of ice. As another example, melting ice dripping from a
roof may fall on the outdoor heat exchanger 114 and then refreeze,
causing an ice bridge to form between the outdoor fan 118 and other
portions of the outdoor unit 104. The ice bridge may prevent
operation of the outdoor fan 118, thereby potentially allowing
greater ice formation. The timed defrost mode may not be sufficient
to remove the ice when such extreme conditions occur, and the ice
may not be removed until it melts naturally. If the timed defrost
mode is terminated by an indication that the ice has been
substantially eliminated from the outdoor heat exchanger 114, the
indication may not occur for an extended period of time. Timed
defrost cycles may continue throughout that time with little
effect.
[0041] Cycling in and out of a defrost mode for an extended length
of time may be detrimental to the compressor 116 and other
components of an HVAC system 100. That is, initiation or
termination of a defrost cycle of a heat pump system, such as HVAC
system 100, may instantaneously reverse the pressures across the
compressor 116. When such reversals occur and for a period of time
afterwards, the compressor 116 may be exposed to liquid
refrigerant, which increases the stress on the compressor 116. In
addition, oil viscosity is diluted, which can lead to bearing
damage. Further, liquid refrigerant is incompressible, and very
high impact pressures may result if liquid refrigerant enters the
compression mechanism of the compressor 116. Thus, it may be
undesirable to repeatedly cycle in and out of a defrost mode for an
extended period of time, particularly when it is unlikely that
lengthy operation in the defrost mode will remove enough ice to
allow a return to operation in the heating mode.
[0042] In an embodiment, techniques are provided for determining
when an ice buildup on the outdoor components of an HVAC system 100
are so heavy that multiple cycles of a timed defrost mode are
unlikely to sufficiently remove the ice. In an embodiment, the HVAC
system 100 may be shut down when such circumstances occur. As used
herein, terms such as "shut down" and the like may refer to
preventing operation at least one major HVAC system component, such
as a compressor 116 or an outdoor fan 118, that may be damaged by
repeated cycles of a timed defrost mode. Some components, such as
indoor fans, backup heaters, electronic processors, or fault
notification systems, may continue to operate during the shut-down.
As described in more detail below, the techniques for shutting down
an HVAC system under extreme icing conditions may also be applied
to other types of fault conditions, but the discussion herein
focuses mainly on icing as the fault condition.
[0043] One parameter that may be used to indicate that an excessive
coating of ice is present on the outdoor components of an HVAC
system 100 is the rate of change of the delta T, that is, how
quickly the difference between the ambient air temperature and the
outdoor heat exchanger 114 temperature is changing. It is known
that the rate of change of delta T for a normally operating system
in a heavy frosting condition is approximately 0.002
degrees/degree/second. Under heavy icing conditions, there may be
no airflow across the outdoor heat exchanger 114. In such
conditions, the rate of change of delta T is approximately 0.040
degrees/degree/second, or a 20 times higher rate than under more
typical conditions. Thus, in an embodiment, a rate of change of the
delta T that exceeds a predefined threshold may be used to indicate
that an ice coating on the outdoor components of an HVAC system 100
is heavier than is likely to be sufficiently removed by a timed
defrost mode.
[0044] Other parameters that may be used to indicate that a heavy
coating of ice is present on the outdoor components of an HVAC
system 100 include the air pressure drop across the outdoor heat
exchanger 114, the suction pressure, and/or the outdoor fan 118
power or current. For any such parameter, a threshold may be
defined which, when crossed, indicates that a heavy buildup of ice
exists on the outdoor components of an HVAC system 100 or that some
other type of fault condition exists.
[0045] In another embodiment, a time-based procedure may be used to
indicate that an outdoor component of the HVAC system 100 is
covered with so much ice that a timed defrost mode is unlikely to
sufficiently remove the ice. More specifically, when a heating
cycle on a heat pump system begins, the system will typically enter
the defrost mode more quickly when a heavy coating of ice is
present on the outdoor components of the HVAC system 100 than when
little or no frost is present. The timing of how soon the system
enters the defrost mode after a heating cycle begins can thus be
used as an indication that the outdoor components are heavily
coated with ice. When a heavy buildup of ice is indicated in such a
manner, it may be preferable to shut the system down rather than
subject the system to multiple cycles of defrosting that are
unlikely to be effective.
[0046] In an embodiment, the start of a defrost mode less than a
predefined length of time, such as 15 minutes, after the start of a
heating cycle may be taken as a preliminary indication that a heavy
coating of ice is present on the outdoor components of an HVAC
system 100. Since there may be other reasons for a defrost mode to
start shortly after the beginning of a heating cycle, it may be
preferable for a plurality of such preliminary indications to occur
consecutively before a more definitive indication is assumed. In an
embodiment, a count is kept of how many consecutive times a defrost
mode begins less than the threshold time after the start of a
heating cycle. When the count reaches a threshold count, such as
three consecutive times, the HVAC system is temporarily shut down
for a predefined length of time, such as 15 minutes. That is, at
least one of the major outdoor components of the system, such as
the compressor 116 or the outdoor fan 118, is temporarily not
allowed to operate. If the threshold count has not yet been reached
and a defrost mode begins longer than the threshold time after the
start of a heating cycle, the threshold count is reset to zero.
This ensures that a plurality of preliminary indications of an ice
buildup must occur consecutively in order for the more definitive
indication to be assumed.
[0047] In some cases, the temporary shutdown may alleviate the
situation that was causing a defrost mode to repeatedly begin less
than the threshold time after the start of a heating cycle. Thus,
it may be preferable for a plurality of such temporary shutdowns to
occur consecutively before a final indication of excessive icing on
the outdoor components of the HVAC system 100 is assumed. In an
embodiment, a count is kept of how many temporary shutdowns occur.
When the count reaches a threshold count, such as three consecutive
temporary shutdowns, a final indication is assumed that the outdoor
components of the HVAC system 100 are so heavily iced over that
further defrost cycles are unlikely to be effective.
[0048] In such a case, the HVAC system 100 is unlikely to function
properly, so there may be no point in continuing to operate the
system. Thus, in an embodiment, when the number of temporary
shutdowns reaches the shutdown threshold, the HVAC system 100 is
shut down completely to prevent the stress that would be placed on
the compressor 116 and other components in performing futile
defrosts. Shutting the HVAC system 100 down completely may refer to
preventing at least one of the major outdoor components of the
system, such as the compressor 116 or the outdoor fan 118, from
operating until the ice buildup is alleviated enough for a defrost
mode to produce a typical level of effectiveness. The ice may be
removed by an owner or operator of the HVAC system 100, by a
technician, by natural melting, or in some other manner. If the
fault condition was caused by something other than an ice buildup,
then the fault condition may need to be alleviated before the HVAC
system 100 is allowed to restart. In an embodiment, the HVAC system
100 may provide some indication that it has locked itself out and
that a technician may need to be called or some other action may
need to be taken to alleviate the fault condition.
[0049] FIG. 3 is a flowchart of a method 300 for operating an HVAC
system, such as HVAC system 100. At block 310, a timer is started
when a heating cycle begins. At block 320, the system enters a
defrost mode some length of time after the heating cycle begins,
and the timer is stopped. At block 330, the value of the timer is
read to determine if the defrost mode began less than 15 minutes
after the heating cycle began. In other embodiments, other
threshold values for the timer could be used. If the defrost mode
began less than 15 minutes after the heating cycle began, then at
block 340, a first counter that keeps track of how many consecutive
times the defrost mode began less than 15 minutes after the heating
cycle began is incremented. If the defrost mode began 15 minutes or
more after the heating cycle began, then at block 345, the first
counter and a second counter described below are reset to zero. The
procedure then returns to block 310, and additional values are
recorded for the time between the beginning of a heating cycle and
the beginning of a defrost mode.
[0050] After the first counter is incremented at block 340, a
determination is made at block 350 whether the first counter is
equal to three. That is, it is determined whether three consecutive
occasions have occurred in which a defrost mode began less than 15
minutes after a heating cycle began. In other embodiments, other
values could be used for the threshold for the first counter. If
the first counter does not equal three, the procedure returns to
block 310, and additional values are recorded for the time between
the beginning of a heating cycle and the beginning of a defrost
mode. If the first counter does equal three, the HVAC system is
shut down for 15 minutes at block 360. In other embodiments, other
lengths of time could be used for the temporary shutdown.
[0051] At block 370, after the temporary shutdown ends, a second
counter that keeps track of how many temporary shutdowns have
occurred is incremented. The first counter is reset to zero so that
it will again be ready to start counting how many times the timer
threshold is reached. Alternatively, the procedures at block 370
may occur before the procedures at block 360. At block 380, a
determination is made whether the second counter is equal to three,
indicating that three consecutive temporary shutdowns have
occurred. In other embodiments, other values could be used for the
threshold for the second counter. If the second counter does not
equal three, the procedure returns to block 310, and additional
values are recorded for the time between the beginning of a heating
cycle and the beginning of a defrost mode.
[0052] If the second counter does equal three, the typical heating
mode and cooling mode of the HVAC system are shut down completely
at block 390. That is, at least one of the major outdoor components
of the HVAC system 100 that may be damaged by continued use, such
as the compressor 116 or the outdoor fan 118, are no longer allowed
to operate at all. Some components, such as indoor fans or backup
heaters, may be allowed to continue to operate. The HVAC system 100
may not be allowed to re-enter the typical heating mode or cooling
mode until a technician repairs the problem or some other procedure
is performed to alleviate the fault condition.
[0053] In other embodiments, a similar shutdown procedure may be
used to shut an HVAC system 100 down when other major fault
conditions occur, such as a high rate of change of delta T, a loss
of airflow across the outdoor unit for a reason other than a
buildup of ice, a loss of refrigerant, a low suction pressure, or a
failure of the outdoor fan 118. In such embodiments, the procedures
at blocks 310, 320, and 330 in FIG. 3 may be replaced by the
detection of the relevant fault condition. The remaining procedures
in FIG. 3 may then be followed, wherein the HVAC system 100 is shut
down temporarily when a fault condition is detected a plurality of
times consecutively, a count is maintained of how many consecutive
times the system is temporarily shut down, and after a plurality of
consecutive temporary shutdowns, the system is completely shut
down. That is, components of the system that may be damaged by
continued use are prevented from operating until the fault
condition is alleviated.
[0054] As an example, if the rate of change of delta T exceeds a
predefined threshold in a predefined number of consecutive
measurements, the HVAC system 100 may be shut down temporarily. If
a predefined number of consecutive temporary shutdowns occur, the
HVAC system may be shut down completely.
[0055] FIG. 4 illustrates a typical, general-purpose processor
(e.g., electronic controller or computer) system 1300 that includes
a processing component 1310 suitable for implementing one or more
embodiments disclosed herein. In some embodiments, system
controller 106 may comprise the general-purpose processor system
1300. In addition to the processor 1310 (which may be referred to
as a central processor unit or CPU), the system 1300 might include
network connectivity devices 1320, random access memory (RAM) 1330,
read only memory (ROM) 1340, secondary storage 1350, and
input/output (I/O) devices 1360. In some cases, some of these
components may not be present or may be combined in various
combinations with one another or with other components not shown.
These components might be located in a single physical entity or in
more than one physical entity. Any actions described herein as
being taken by the processor 1310 might be taken by the processor
1310 alone or by the processor 1310 in conjunction with one or more
components shown or not shown in the drawing.
[0056] The processor 1310 executes instructions, codes, computer
programs, or scripts that it might access from the network
connectivity devices 1320, RAM 1330, ROM 1340, or secondary storage
1350 (which might include various disk-based systems such as hard
disk, floppy disk, optical disk, or other drive). While only one
processor 1310 is shown, multiple processors may be present. Thus,
while instructions may be discussed as being executed by a
processor, the instructions may be executed simultaneously,
serially, or otherwise by one or multiple processors. The processor
1310 may be implemented as one or more CPU chips.
[0057] The network connectivity devices 1320 may take the form of
modems, modem banks, Ethernet devices, universal serial bus (USB)
interface devices, serial interfaces, token ring devices, fiber
distributed data interface (FDDI) devices, wireless local area
network (WLAN) devices, radio transceiver devices such as code
division multiple access (CDMA) devices, global system for mobile
communications (GSM) radio transceiver devices, worldwide
interoperability for microwave access (WiMAX) devices, and/or other
well-known devices for connecting to networks. These network
connectivity devices 1320 may enable the processor 1310 to
communicate with the Internet or one or more telecommunications
networks or other networks from which the processor 1310 might
receive information or to which the processor 1310 might output
information.
[0058] The network connectivity devices 1320 might also include one
or more transceiver components 1325 capable of transmitting and/or
receiving data wirelessly in the form of electromagnetic waves,
such as radio frequency signals or microwave frequency signals.
Alternatively, the data may propagate in or on the surface of
electrical conductors, in coaxial cables, in waveguides, in optical
media such as optical fiber, or in other media. The transceiver
component 1325 might include separate receiving and transmitting
units or a single transceiver. Information transmitted or received
by the transceiver 1325 may include data that has been processed by
the processor 1310 or instructions that are to be executed by
processor 1310. Such information may be received from and outputted
to a network in the form of, for example, a computer data baseband
signal or a signal embedded in a carrier wave. The data may be
ordered according to different sequences as may be desirable for
either processing or generating the data or transmitting or
receiving the data. The baseband signal, the signal embedded in the
carrier wave, or other types of signals currently used or hereafter
developed may be referred to as the transmission medium and may be
generated according to several methods well known to one skilled in
the art.
[0059] The RAM 1330 might be used to store volatile data and
perhaps to store instructions that are executed by the processor
1310. The ROM 1340 is a non-volatile memory device that typically
has a smaller memory capacity than the memory capacity of the
secondary storage 1350. ROM 1340 might be used to store
instructions and perhaps data that are read during execution of the
instructions. Access to both RAM 1330 and ROM 1340 is typically
faster than to secondary storage 1350. The secondary storage 1350
is typically comprised of one or more disk drives or tape drives
and might be used for non-volatile storage of data or as an
over-flow data storage device if RAM 1330 is not large enough to
hold all working data. Secondary storage 1350 may be used to store
programs or instructions that are loaded into RAM 1330 when such
programs are selected for execution or information is needed.
[0060] The I/O devices 1360 may include liquid crystal displays
(LCDs), touch screen displays, keyboards, keypads, switches, dials,
mice, track balls, voice recognizers, card readers, paper tape
readers, printers, video monitors, transducers, sensors, or other
well-known input or output devices. Also, the transceiver 1325
might be considered a component of the I/O devices 1360 instead of
or in addition to being a component of the network connectivity
devices 1320.
[0061] At least one embodiment is disclosed and variations,
combinations, and/or modifications of the embodiment(s) and/or
features of the embodiment(s) made by a person having ordinary
skill in the art are within the scope of the disclosure.
Alternative embodiments that result from combining, integrating,
and/or omitting features of the embodiment(s) are also within the
scope of the disclosure. Where numerical ranges or limitations are
expressly stated, such express ranges or limitations should be
understood to include iterative ranges or limitations of like
magnitude falling within the expressly stated ranges or limitations
(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater
than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a
numerical range with a lower limit, R.sub.l, and an upper limit,
R.sub.u, is disclosed, any number falling within the range is
specifically disclosed. In particular, the following numbers within
the range are specifically disclosed:
R=R.sub.l+k*(R.sub.u-R.sub.l), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50
percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed. Use of the term "optionally" with
respect to any element of a claim means that the element is
required, or alternatively, the element is not required, both
alternatives being within the scope of the claim. Use of broader
terms such as "comprises", "includes", and "having" should be
understood to provide support for narrower terms such as
"consisting of", "consisting essentially of", and "comprised
substantially of". Accordingly, the scope of protection is not
limited by the description set out above but is defined by the
claims that follow, that scope including all equivalents of the
subject matter of the claims. Each and every claim is incorporated
as further disclosure into the specification and the claims are
embodiment(s) of the present invention.
* * * * *